Nov 30 : Dr Marco Fernandez Garcia - IFCA, Spain - Access to the talk
Title : 3D laser characterization of semiconductor devices
Abstract : The time-resolved analysis of the laser-induced currents on semiconductor detectors has been proven to be a chief and versatile tool for the understanding of the effects produced by the ionising radiation on such devices. So far, all these methods and techniques, known as Transient Current Techniques (TCT), are based on the single-photon absorption process where just one photon is required to create an electron-hole pair. We have developed a new TCT system based on a simultaneous Two-Photo-Absorption (TPA) for the creation of an electron-hole pair. This innovative TPA-TCT technique makes an important breakthrough with respect to the current state-of-the-art since it allows for the laser-induced generation of charge carriers on a very localised micrometric-scale voxel; opening a broad field of opportunities for the study of the current new generation of small-pixel devices where spatial resolution is a mandatory. The improved spatial resolution of this new measurement technique has allowed to resolve features like the Deep Implant of an HVCMOS, distinguish between drift and diffusion regions and calculate the effective doping concentration of the bulk. The technique can be used for 3D mapping of key properties of a detector, like the collected charge or electric field.
Dec 07 : Dr Lino Miceli - CAPP & KAIST, South Korea - Access to the talk
Title : Search for Relic Axions with the CAST Magnet at CERN
Abstract : There has been an increasing interest in searches for the axion, particularly over the past few years. Technology advances, and the development of new ideas, might in fact soon lead to experiments with unprecedented sensitivity over a mass range, roughly 1 to 100 μeV, where a discovery could solve two outstanding issues of modern physics, namely the so-called Strong CP problem and the nature of cold dark matter.
The IBS Center for Axion and Precision Physics Research (CAPP/IBS), based at the Korea Advanced Institute of Science and Technology (KAIST), was established with the goal to address the Strong CP problem, the axion resolution of it, and the proton electric dipole moment value. As part of its international collaborative efforts, the CAPP leads an experiment at CERN, the CAST-CAPP/IBS project, within the CERN Axion Solar Telescope (CAST)  collaboration.
Axions can couple to two photons in the presence of a strong magnetic field, B, as expressed by the Lagrangian term L= -gaγγ a(t)E(t)∙B . Where gaγγ is the coupling constant, a(t) is the axion field, and E(t) the electric field associated with the outgoing photon in this Primakov-like process. This coupling is the base of the CAPP axion search, in the version proposed by Sikivie  where a microwave cavity immersed in a strong magnetic field is tuned to resonate at the frequency of the axion mass (haloscope).
In the CAST-CAPP/IBS project, based on ideas suggested a few years ago , rectangular cavities are inserted in the 9T CAST dipole magnet, an LHC prototype, at CERN. The status and expected sensitivity of this experiment will be presented.
Dec 14 : Dr Federico Sanchez, IFAE Barcelona, Spain - Access to the talk
Title : Precision oscillation neutrino experiments, nuclear physics and the need of near detectors
Abstract : Neutrino oscillation physics have entered the era of precision physics. Next decade might see the first measurement of CP violation in neutrinos. But, this precision experiments requires to understand two main elements: neutrino flux and neutrino-Nucleus cross-sections. Near detectors, located few hundred meters from the neutrino production points, are in charge of these tasks. But, this enterprise is not trivial, our knowledge of neutrino-nucleus interaction model is lacking the precision and understanding of other fields of particle physics. Modern neutrino oscillation experiments focuses most of their efforts in this specific task. We will discuss neutrino oscillation experiment methodology, its challenges in the boundary between particle and nuclear physics and the need of near detectors in running and future experiments.
Spring semester 2016
March 2 : Dr Teng Jian Khoo, Université de Genève - Access to the talk
Title : Event reconstruction in SUSY searches at ATLAS and the LHC
Abstract: The LHC experiments have since 2010 dramatically transformed the landscape of supersymmetry, providing ever tighter constraints on how supersymmetric theories could be realised in nature. Central to most SUSY searches is the missing transverse momentum signature, signifying the presence of undetected particles such as stable neutralinos produced in cascade decays. This seminar will describe advances in the measurement of missing transverse momentum in ATLAS, and how we derive and employ transverse mass variables in the quest for supersymmetry at the LHC.
March 16 : Dr Stephan Zimmer, Université de Genève - Access to the talk
Title : Galaxy Clusters as unlike Cold Dark Matter candidates harboring complex astrophysics - 7+ years of Fermi-LAT observations and still no firm detection
Abstract: Galaxy clusters are the most massive virialized systems known in the Universe and are believed to have formed through large scale structure formation. They host relativistic cosmic-ray (CR) populations and are gravitationally bound by large amounts of Dark Matter (DM), both providing conditions in which high-energy gamma rays may be produced either via CR interactions with the intracluster medium or through the annihilation or decay of DM particles.
Prior to the launch of the Fermi satellite, predictions were optimistic that these sources would be established as gamma-ray-bright objects by observations through its prime instrument, the Large Area Telescope (LAT). Yet, despite numerous efforts, even a single firm cluster detection is still pending.
In my talk I will provide an overview and discuss recent studies carried out by the LAT collaboration aiming to discover these missing gamma rays and discuss detection prospects with planned observatories such as CTA and DAMPE.
April 6 : Dr Pier-Olivier Deviveiros, CERN - Access to the talk
Title : Tau Leptons at ATLAS: Reconstruction & Physics
Abstract: Tau leptons play a significant role in the ATLAS physics program. As the heaviest leptons, they offer the most sensitive probe into the properties of leptonic Higgs couplings. Additionally, they offer unique sensitivity to beyond the Standard Model physics scenarios where they are often produced preferentially. From the first observation of hadronically-decaying taus in W decays in 2010, to the recent evidence for Higgs decays to leptons, a lot of progress has been made in the reconstruction of tau leptons at ATLAS. In this seminar, a summary of the tau reconstruction, calibration and identification algorithms at ATLAS will be shown. Additionally, a review of the most recent ATLAS physics results in final states with hadronically-decaying tau leptons will be presented.
April 20: Dr Patrick Czodrowski, University of Alberta - Access to the talk
Title : Searches for strong gravity signatures produced in proton-proton collisions using the ATLAS detector at the CERN Large Hadron Collider
Abstract : Searches for new physics in using data from proton-proton collisions at √s = 8 TeV and 13 TeV taken at the CERN Large Hadron Collider with the ATLAS detector were conducted. The presented searches focus on signatures of new physics models of strong gravity that hypothesize additional space-time dimensions, as for example black holes and string-balls. After a summary of current results an outlook on the future search efforts by the ATLAS collaboration in this physics domain is given.
May 4 : Dr Elisabetta Pianori, University of Warwick - Access to the talk
Title : ATLAS and CMS Higgs coupling combination
Abstract : I will present the first combined ATLAS+CMS measurement of the Higgs boson production and decay rate based on the 5/fb of 7 TeV and 20/fb of 8 TeV data. Constraints on the Higgs boson’s couplings to other SM particles are presented as well. This is the most precise and comprehensive experimental results to date. I will also highlight how these measurements constrain the existence of new physics, and discuss the prospects for Higgs boson measurements and their interpretations in Run2.
Autumn semester 2015
Sept 23 : Dr Roland Horlsberger - PSI
Title : The CMS pixel detector in LS1: a surprising story has a good ending - Access to the talk
Abstract: The CMS pixel detector has proven to be a crucial in the track reconstruction of CMS. The installation of a new smaller radius beam pipe in LS1 required the removal in Spring 2013 and storage outside the CMS experiment. This has not been without surprises before its re-installation in Fall 2014 into CMS for Run2. The talk describes the detailed chain of events that required a successful repair of the barrel pixel prior to its re-installation into CMS. The talk will also briefly describe the status of the ongoing Phase I Pixel Upgrade that is planned to installed in 2017.
Sept 25 : Prof. Zhen CAO - Institute of High Energy Physics, Beijing
Title: A multi-purpose Cosmic Ray Experiment: The LHASSO Project
Abstract : In 21st century, one of the fundamental scientific problems is the origin of the cosmic rays which were discovered 103 years ago. One of successful approaches is the VHE gamma ray astronomy that was started with the discovery of the Crab Nebula as a source of the gamma rays above 1 TeV at 1989. More than 150 VHE gamma ray sources are discovered, mainly by using the pointing Cherenkov telescopes such as HESS, MAGIC and VERITAS. To keep the momentum of the discovery power, a full sky survey with wide field of view and full duty cycle is necessary. Struggling on developing a right survey technology, the Chinese group together with its Italian and Japanese collaborators has successfully carried out two experiments, ARGO-YBJ and ASγ in last 25 years and has proposed the LHAASO project now. In this presentation, the scientific achievements of ARGO-YBJ will be cited as indications of what will be possibly achieved by LHAASO that is a factor of 30 more sensitive at low energies and 300 more sensitive at high energies than ARGO-YBJ. Simultaneously, LHAASO will significantly boost the performance of cosmic ray measurements in the energy region of “knees”. The scientific prospects, detector performance and prototyping status will be summarized.
Oct 14: Dr Olaf NACKENHORST, Université de Genève, DPNC
Title: Search for the Higgs boson produced in association with top quark pairs at 8 TeV with the ATLAS detector using the Matrix Element Method - Access to the talk
Abstract : After the discovery of a Higgs boson in bosonic decays, it is important to confirm this particle in fermionic decays in order to gain more confidence in the Standard Model (SM) Higgs boson hypothesis of the observation.
The production of the Higgs boson in association with a pair of top quarks (ttH), is one of the four main production mechanisms of the Higgs boson predicted by the SM.
Despite the fact that many searches for this production mechanism have been performed during Run I of the LHC, it has not yet been observed.
Such an observation would not only verify the coupling of the Higgs boson to fermions, but would also allow for the most direct determination of the top quark Yukawa coupling, which is an important parameter of the SM.
The presented search is designed for the b-quark pair decay mode of the Higgs boson and makes use the Matrix Element Method (MEM) to better distinguish the signal from its main and irreducible background tt+bb.
The MEM uses the theoretical description of a process in order to assign a probability weight to each observed event.
This probability reflects how likely it is that the observed event is consistent with a certain hypothesis.
Powerful discriminants can be constructed from the signal and background probabilities to significantly enhance the search sensitivity.
Oct 16: Dr Arnaud JOLIVET - Procédure de nomination
Title:The role of brain energetics in information processing and immune surveillance
Abstract : The nervous system consumes a disproportionate fraction of the resting body’s energy production: in humans the brain is only 2% of the body’s mass, yet it uses ~20% of the oxygen consumed by the body. Expansion in the size of the brain relative to the body and an increase in the number of connections between neurons during evolution underpin our cognitive powers and are responsible for our brains’ high metabolic rate. The molecules at the center of cellular energy metabolism also act as signals to other cells and constitute an important communication pathway, coordinating for instance the immune surveillance of the brain. Despite the significance of energy consumption in the nervous system, how energy constrains and shapes brain function is often underappreciated. I will illustrate the importance of brain energetics and metabolism with two examples from my recent work. First, I will show how the brain trades information for energy savings in the visual pathway. Indeed, a significant fraction of the information those neurons could transmit in theory is not passed on to the next step in the visual processing hierarchy. I will discuss how this can be explained by considerations of energetic optimality. Second, I will show how adenosine triphosphate, the energy currency of cells, is critical in regulating immune surveillance of the brain by a specialised population of brain immune cells. I will also discuss a new mechanism that we recently identified, which plays a key role in regulating the patrolling of brain tissue by these cells. I will conclude by discussing future research directions in brain energetics.
Nov 4 : Dr Pierre BARRILLON, LAL, CNRS, Paris
Title: EUSO-BALLOON, the story of three adventurous years
Abstract : The night of the 24th of August 2014, EUSO-BALLOON instrument took off from the stratospheric balloons launching base of Timmins in Ontario (Canada). Supported by a 400000 m3 helium balloon, it flew for about 5 hours at an altitude of 38 km over forests. In total, around 100 Go of data were acquired. They are used to better know the UV background from sky and earth as well as the infra-red emission of the clouds.
This flight is the outcome of almost 3 years of work of a scientific and technical collaboration involving 50 people and supported by the CNES balloon division.
This seminar will relate the adventure of this project from the kick off meeting of the 14th of September 2011 until the recent results of the data analysis presented at ICRC conference.
Nov 11 : Dr Rolf BUEHLER, DESY
Title: The Universe observed in Gamma-rays
Abstract : Astronomical sources are able to accelerate particles to energies far beyond what accelerators at Earth can do. The study of these astrophysical accelerators takes one to some of the most extreme places in the Universe, such as Super Massive Black Holes, Neutron Stars or Super Novae explosions. The particle acceleration in these sources are best studied in gamma-rays. In this presentation I will give a tour through the gamma-ray sky and discuss the acceleration and emission mechanisms at work in high-energy sources.
Spring semester 2015
|Dr Avishek Chatterjee
Université de Genève, DPNC
|Fast Ion Instability at CESR-TA
||Dr Enrico Jr. Schioppa
Université de Genève, DPNC
|The color of X-rays
||Dr Steven Schramm
Université de Genève, DPNC
|Searching for Dark Matter at ATLAS
||Dr Andrea Coccaro,
Université de Genève, DPNC
|Looking for a hidden sector in exotic Higgs boson decays with the ATLAS experiment
||Dr Chiara Casella,
|The SAFIR project - Challenges of a novel detector for fast hybrid PET/MR imaging
||Dr Heather Gray,
|The Art of the Impossible: Probing challenging Higgs channels at the LHC
||Dr Felix Sefkow,
|Imaging calorimeters for particle flow reconstruction
Prof. Mark Hartz,
IPMU, University of Tokyo
|nuPRISM: A Novel Experiment for Studying Neutrino-Nucleus Interactions
Jan. 14: Dr Avishek Chatterjee, University of Geneva, DPNC
Title: Fast Ion Instability at CESR-TA - Access to the talk
Abstract:Fast Ion Instability can lead to deterioration of an electron beam (increasing emittance and instability of a train of bunches) in storage rings and linacs. An overview of the study done at at the Cornell Electron Storage Ring Test Accelerator using a 2.1 GeV low emittance beam will be presented. As the source of ions is residual gas, measurements are conducted at various pressures, including nominal vacuum as well as injected gas (Ar, Kr). We experiment with mitigation techniques, including changing the bunch pattern to have mini-trains instead of one long train, as well as increasing the initial vertical emittance of the beam. We also check to ensure that ion-trapping is not a substantial effect in our measurements. We measure turn-by-turn vertical bunch size and position, as well as the multi-bunch power spectrum. Our measurements confirm fast ion instability under all vacuum conditions. A detailed simulation is then used to compare theory with observations. Since Fast Ion Instability is likely to be a significant effect for beam conditions expected at CLIC and ILC, such studies are of great importance for a deeper understanding of design considerations for future accelerators.
Mar 04: Dr Enrico Jr. Schioppa, University of Geneva, DPNC
Title: The color of X-rays - Access to the talk
Abstract: We all are familiar with the definition of colors as related to the energy of visible light photons. What is the best way we can define colors also in other ranges of the electromagnetic spectrum?
The X-ray range is particularly interesting because X-rays are widely used for non-invasive imaging. The fact that radiography has always been a greyscale imaging technique is related to limitations on the X-ray detector technology: conventional detectors for imaging applications cannot measure energy, but only radiation intensity. The interest towards novel detectors that are capable of achieving spectral resolution together with spacial resolution is very high, because, as it turns out for X-rays, colors can be defined in terms of the materials contained in the imaged sample. This means that, among other advantages (such as dose reduction), spectral X-ray imaging would allow for direct material separation capability.
It will be discussed how the study of the charge transport properties in the sensor, together with an accurate calibration of individual pixels, can lead to the full knowledge of the detector energy response function. Furthermore, it will be shown how this information can be exploited to achieve color (i.e. material resolved) and artifact-free 3D X-ray imaging.
Apr. 1st: Dr Steven Schramm, University of Geneva, DPNC
Title: Searching for Dark Matter at ATLAS - Access to the talk
Abstract: Despite decades of studies, the nature of Dark Matter remains one of the largest open questions in physics. In particular, it is not known if elusive Dark Matter particles can interact with normal matter. If such an interaction exists, and if the Dark Matter particles are not too massive, then they can be produced in high-energy collisions at the LHC. Collisions producing only Dark Matter particles are invisible in ATLAS, as the Dark matter particles escape the detector without interacting. Instead, searches focus on events where invisible Dark Matter particles are balanced by visible objects.
One particularly sensitive topology at the LHC is where the visible objects are jets (the hadronization of quarks or gluons). This specific scenario is investigated, and results are interpreted in terms of several different Dark Matter models. The expected sensitivity to Dark Matter at an upgraded LHC is also briefly discussed.
Apr. 15: Dr Andrea Coccaro, University of Geneva, DPNC
Title: Looking for a hidden sector in exotic Higgs boson decays with the ATLAS experiment - Access to the talk
Abstract: The nature of dark matter is one of the most intriguing questions in particle physics. Dark matter can be postulated to be part of a hidden sector whose interactions with the visible matter are not completely decoupled. The discovery of a fundamental scalar particle compatible with the Higgs boson predicted by the Standard Model paves the way for looking for dark matter with novel methods. An overview of the searches looking for a hidden sector in exotic Higgs decays within the ATLAS experiment is presented. Prospects for searches with LHC data at a center-of-mass energy of 13 TeV are summarised .
May 06: Dr Chiara Casella, ETHZ
Title: The SAFIR project - Challenges of a novel detector for fast hybrid PET/MR imaging - Access to the talk
Abstract: SAFIR (Small Animal Fast Insert for mRi) is a novel, challenging project in instrumentation for Positron Emission Tomography (PET), recently initiated at ETH Zurich, as a collaboration between the Institute for Particle Physics (IPP) and the Institute for Biomedical Engineering (IBT).
Goal of SAFIR is to design, build, and characterize an innovative high counting rate PET insert for hybrid PET/MRI of small animals. SAFIR will be designed to cope with ultra short PET scan durations, of the order of a few seconds, at a high repetition rate, and simultaneously with the magnetic resonance imaging (MRI). In the rapidly evolving scenario of PET/MRI instrumentation, the peculiarity of SAFIR relies on its excellent achievable temporal resolution, which will allow for dynamic imaging on time scales precluded so far. To compensate the statistics losses related with the acquisition duration, the PET detector will be operated at high injected activities, up to ~ 500 MBq, one order of magnitude increase in the activities normally employed in pre-clinical scanners. Severe requirements are then imposed on the detector, which must be able to cope with such a high rate of decays without suffering significantly of event losses, due either to pileup or deadtime, and without being dominated by the randoms contribution.
SAFIR relies on LYSO scintillating crystals readout by SiPM arrays. Special emphasis right now is given to the choice of the readout solution. At present, two existing ASICs, the TOFPET and the STiC chips, are being investigated, with small scale setups tested with low activity sources (in the laboratory) and with high activity phantoms (at Zurich University hospital).
The SAFIR detector concept will be described, and its status in terms of hardware characterization measurement and simulation results will be summarized.
May 13: Dr Heather Gray, CERN
Title: The Art of the Impossible: Probing challenging Higgs channels at the LHC - Access to the talk
Abstract: Measurements of the Higgs coupling to top and bottom quarks and the width of the Higgs were not thought to be possible at the LHC Run 1. Yet, ATLAS and CMS have both produced promising results for all these channels. I will highlight selected aspects of these measurements to discuss what allowed ATLAS and CMS to probe the impossible.
May 27: Dr Felix Sefkow, DESY
Title: Imaging calorimeters for particle flow reconstruction - Access to the talk
Abstract: In the past decade, advances in particle detection technology and micro-electronics integration have led to the development of highly granular calorimeters, able to produce detailed images of electromagnetic and hadronic showers. These capabilities can be used to reconstruct charged and neutral particles individually even in the the dense environment of jets produced at present and future high energy collider experiments. The talk will give an overview on the concept, the technological developments and the results obtained in test beam experiments.
June 24: Prof. Mark Harz, IPMU, University of Tokyo
Title: nuPRISM: A Novel Experiment for Studying Neutrino-Nucleus Interactions
Abstract: Current and future neutrino oscillation experiments that will search for CP violation and determine the mass hierarchy are entering the era of precision measurements where uncertainties on neutrino interaction models will limit experimental sensitivities. Recent years have seen significant work to develop neutrino-nucleus interaction models that account for all scattering processes in the nuclear environment, but consistency between models and experimental data is still elusive. The proposed nuPRISM experiment will take advantage of the so-called off-axis effect in a neutrino beam from pion decays to measure the properties of neutrino interactions on water with neutrino spectra having peak energies ranging from 400-1200 MeV. By using measurements over a range of energies, nuPRISM can predict observed final states in neutrino oscillation measurements in a largely model independent way. Conversely the data from nuPRISM can be used to over-constrain neutrino interaction models with data from a single experiment. I will describe the nuPRISM detector concept and its potential application to oscillation experiments such as T2K and Hyper-K, as well as its unique capabilities to make measurements of neutrino interaction cross sections.
Autumn semester 2014
Sep 10: Dr Merlin Kole, KTH Stockholm
Title: Atmospheric Neutrons - a Background Study for the X-ray Polarimeter PoGOLite
Abstract: Polarimetry remains a relatively unexplored field of X- and gamma-ray astrophysics. The lack of polarimetric measurements in this energy range is partly a result of the typically low signal detection efficiencies of the detectors. A second reason, especially relevant for balloon-borne detectors, is the high radiation environment in which the measurements have to be performed. PoGOLite is a balloon-borne hard X-ray polarimeter which performed its first scientific, near circumpolar flight, during the summer of 2013. It is designed to measure the polarisation of X-rays coming from astrophysical point sources, such as the Crab nebula, using a segmented plastic scintillator array. To reduce the measurement background PoGOLite employs several dedicated background rejection systems. The background encountered during flight, which is mostly a result of fast neutrons scattering in the plastic scintillator array, remains however, significant. A detailed understanding of the background is therefore required, including an understanding of the variation of the background rate during the flight, and the ability of such a backgrounds to induce a fake polarisation signal. For this purpose, detailed Monte Carlo studies of the PoGOLite instrument were performed. The high altitude atmospheric neutron environment, responsible for the majority of the PoGOLite background, was furthermore studied using a dedicated balloon-borne detector called PoGOLino. This instrument uses a novel scintillator based technique to measure the neutron flux. PoGOLino was launched from the Esrange Space Centre in Northern Sweden in March 2013. The measurement results of this detector will be discussed, together with a new model describing the atmospheric neutron flux which was developed by members of the PoGOLite collaboration. Finally the results of the PoGOLite flight of 2013 will be discussed and compared to predictions made using the performed background study.
Sep 24: Dr Nicolo Cartiglia, INFN Torini
Title: Ultrafast silicon detector for Picosecond Tracking
Abstract: In this seminar I will review the progress towards the development of a new type of silicon detectors suited for picosecond tracking, the so called Ultra-Fast Silicon Detectors . UFSD are based on the concept of Low-Gain Avalanche Detectors, which are silicon detectors with an internal multiplication mechanism so that they exhibit a signal which is a factor of ~ 10 larger than standard silicon detectors. This increased signal makes LGAD ideal for many applications, ranging from experiments requiring very low material budgets, to very high radiation environment, to applications that need very precise timing.
I will report on first measurements and the plan for future productions.
Oct 8: Dr Nicola Pacifico, University of Bergen
Title: Weighting antimatter: The AEgIS experiment
Abstract: The AEgIS experiment at the CERN Antiproton Decelerator aims at testing the weak equivalence principle by directly measuring gravitational acceleration exerted by Earth on antihydrogen atoms.
The experiment will for the first time create a pulsed beam of antihydrogen atoms that will then be selected through a moire deflectometer. Downstream detection of the vertical acceleration is then performed through a position sensitive detector, combining silicon strips emulsions and scintillating fiber detectors.
We provide here an overview of the working principles of the experiment, with an insight on the antihydrogen production and detection system.
Norway, with the University of Bergen and Oslo, is developing one of the components of an hybrid annihilation detector. The sub-detector, based on silicon microstrip sensors, will be the first application of the technology to the detection of antihydrogen. In addition to the challenges defined by this new type of measurement, the detector will have to address technical constraints like cryogenic operation and a reduced physical thickness (50 um). This seminar will cover the aims and principles of the AEgIS experiment, with a final focus on the development of the silicon annihilation detector at Bergen and Oslo.
Oct 29 : Dr Alessandro Bravar, Université de Genève
Title: The Mu3e Experiment
Abstract: The Mu3e experiment will search for the lepton flavor violating neutrinoless muon decay μ → e+e-e+ with a sensitivity of 10-16, a four order of magnitude improvement over previous experiments, using the world most intense muon beam at the Paul Scherrer Institute. This decay is strongly suppressed in the Standard Model, whilst several BSM models predict observable effects accessible to the new generation of LFV experiments.
The search for the μ → e+e-e+ decay requires a large acceptance detector capable of coping with rates of up to 2 x 10-9 stopped muons per second with excellent momentum, spacial, and time resolution to suppress backgrounds to below the 1016 level. The required Mu3e detector performance is possible thanks to tracking detectors based on thin monolithic active silicon pixel sensors (HV-MAPS) in conjunction with an innovative tracking concept and very precise timing measurements using scintillating fibers and tiles coupled to silicon photo-multipliers. The recently approved Mu3e experiment is currently preparing for detector construction.
In this seminar I will breifly discuss the phenomenology of lepton flavor violation and the various models suggesting sizable LFV effects accessible to the next generation of muon experiments. I will overview the status of current LFV searches. Then I'll discuss in detail the principle and conceptual design of the Mu3e experiment and the experimental challenges associated with this search. Finally I will illustrate the various detector components and their expected performance.
Nov 19 : Dr Matt Noy, CERN
Title: TDCPix: A High Time Precision Pixel Chip for the NA62 GigaTracker
Abstract: The TDCPix is a hybrid pixel detector readout ASIC designed for the NA62 GigaTracker detector. The driving requirements are a single-hit timing resolution better than 200ps RMS and a hit loss of less than 1\% in the presence of a (highly non-uniform) beam rate up to 80MHz/cm^2. This hit rate leads to an expected data rate at the output of the chip which can reach 6Gb/s.
The TDCPix comprises an asynchronously operating pixel array with 1800 pixels organised as 40 columns of 45 pixels, each one 300 x 300 $\mu m^2$. The front end input stage has been optimised for a detector capacitance of 250fF and the predicted ENC with the fully depleted detector is better than 250$e^-$. The base-line detector is expected to be a standard P-in-N planar pixel detector 200$\mu m$ thick, although the front end remains programmable such that other detector technologies may be evaluated. The pre-amplifier was designed with a peaking time of 5ns to provide the required timing performance. Rather than distribute a high precision reference signal to the pixel array,
the discriminated hit signals are driven to the end of column region via dedicated transmission lines. There, each column is instrumented with a 720 channel Delay Locked Loop based time-to-digital converter (TDC) with a nominal bin size of 97ps. The TDC measures both the discriminator leading and trailing edge times permitting a time-over-threshold approach to the required discriminator time-walk correction. Hits from the TDCs are sent to data buffering and concentrating
logic. The read-out uses four 3.2Gb/s serialisers with the high speed clock being provided by a low-noise on-chip Phase Locked Loop. The high data rates negate the possibility of buffering the data stream whilst awaiting a trigger, thus a self triggering architecture with continuous data readout has been adopted.
All configuration and state logic in the design deemed critical for the correct operation of the chip has been triplicated to provide increased single event effect tolerance. On-chip digital-to-analogue converters provide threshold generation and trimming and are configurable through a single-signal configuration interface. The configuration and DAQ interfaces include a DC-balanced protocol layer permitting direct optical connections when the detector assembly is installed in the experiment. Dedicated calibration circuitry is included to enable the required timing resolution to be reached.
The chip was manufactured in a commercial 130nm process during the second half of 2013 and testing began at the start of 2014. Bump bonding of the TDCPix chip to a P-in-N detector is currently being scheduled. A detailed description of the ASIC architecture and performance will be presented alongside results from the single chip assembly, if it available in time.
Nov 26: Prof. Dieter H.H. Hoffmann, Technische Universität Darmstad
Title: TDCPix: Status and Perspectives of Search for Dark Matter with the CERN Axion Solar Telescope (CAST)
Abstract: The CAST experiment is designed to search for solar axions which are produced in the interior of the sun via the Primakoff effect. The central part of the experiment, the helioscope is an LHC prototype magnet that has attached different types of sensitive detectors for x-rays in the regime of 1-10 keV. The experiment has been taking data since 2003 and provided the most restrictive limits on the axion-photon coupling in a broad mass range. Beyond 0,02eV/c**2 the mass the sensitivity is degraded due to coherence loss. In order to restore coherence, the magnet can be filled with a buffer gas providing an effective mass to the photon. By changing the pressure of the buffer gas in steps, one can scan an entire range of axion mass values. The CAST experiment started this gas program entering its phase II at the end of 2005. From 2005 to 2007, the magnet bore was filled with 4He gas extending the sensitivity to masses up to 0.4 eV. From March 2008 onwards the magnet bore has been filled with 3He. With the end of the 2011 data taking in July, the CAST experiment has covered axion masses up to 1.18 eV surpassing the initial goal of the phase II which was to reach 1.16 eV. The results of the first part of the 3He, with a sensitivity up to 0.64 eV, have been finalized.
An overview on the current status of CAST and the future perspectives will be given.
Dec 17 : Dr Hans Dijkstra, CERN
Title: Search for Heavy Neutral Leptons at the SPS - Access to the talk
Abstract: A new fixed-target experiment at the CERN SPS accelerator is proposed that will use decays of charm mesons to search for Heavy Neutral Leptons (HNLs), which are right-handedpartners of the Standard Model neutrinos. The existence of such particles is strongly motivated by theory, as they can simultaneously explain the baryon asymmetry of the Universe, account for the pattern of neutrino masses and oscillations and provide a Dark Matter candidate. The experiment will be motivated, and previous searches will be reviewed. The experiment requires a 400 GeV proton beam from the SPS with a total of 2x10^20 protons on target. The proposed detector will reconstruct exclusive HNL decays and measure the HNL mass. The discovery of a HNL would have a great impact on our understanding of nature and open a new area for future research. In addition the experiment could accomodate a nu-tau detector, which could increase the statistics of nu-tau interactions by more than two orders of magnitude.
Colloque en vue de la nomination par appel d'un/e Professeur/e Assistant/e
Jeudi 4 décembre à 16h00 - Grand Auditoire A - Ecole de physique
Dr Anna Sfyrla
Seeking supersymmetry with jets at ATLAS
With the discovery of the Higgs boson, all particles that the Standard Model predicts have been experimentally confirmed. Despite its great success, the Standard Model leaves unanswered several questions: why is the Higgs boson a light particle, are the forces unified at very high energies and what is the dark matter that astrophysical and cosmological observations hypothesise. Several extensions to the Standard Model are proposing solutions to these open questions, with supersymmetry being one of the best motivated and studied. Supersymmetric particles have been extensively searched for at collider experiments, evading discovery so far. They decay dominantly to quarks, creating collimated sprays of particles that are reconstructed in the detector as hadronic jets. Final states with many jets have been thoroughly exploited in the ATLAS experiment at the LHC. A roadmap of how this final state provides a unique discovery potential in the searches for supersymmetry is outlined and prospects for the higher energy and luminosity LHC runs are given.
Spring semester 2014
Feb 26: Prof Gennaro Miele, University of Naples - ANNULÉ
Title: Neutrino physics in the Planck era
Abstract: I briefly summarize the status of art about the properties of relic neutrino distributions and the implications of different neutrino scenarios on cosmological observables after the first measurements by Planck. In particular I will pay particular attention to the effects due to neutrino-antineutrino asymmetry and to the presence of sterile degrees of freedom.
Mar 19: Prof Antonio Ereditato, Bern University
Title: Hunting for sterile neutrinos: short baseline neutrinos at FERMILAB - Access to the talk
Abstract : The "anomaly" constituted by the LSND/MiniBooNE neutrino signal is still there after many years. This points to the possible existence of sterile neutrinos.
An extensive short-mid term program aimed at solving the "puzzle" is being conducted at Fermilab in the Booster neutrino beam, centered on the use of new detectors based on the liquid Argon TPC technology. A multi-step strategy envisions at first the use of the MicroBooNE apparatus, being commissioned in the next months. In a second phase, MicroBooNE will be possibly complemented by the LAr1-ND near detector, being proposed to the Fermilab scientific committee.
This program and its prospects will be presented, as well as the parallel work being conducted on LAr TPCs by the MicroBooNE/LAr1-ND Bern group.
Apr 09 : Prof Francesca Di Lodovico, University of London
Title: A window to the future: the Hyper-Kamiokande project - Access to the talk
Abstract : In this talk we present the latest status of the Hyper-Kamiokande project. The experiment, based in Japan, has an extremely rich physics portfolio that spans from the study of the CP violation in the leptonic sector and neutrino mixing parameters to proton decay, atmospheric neutrinos and neutrinos of an astronomical origin.
In particular, thanks to an upgraded beam power, we will focus on the extremely high sensitivity to CP violation.
The project was recently selected as one of the top 27 projects by the Japanese Science Council in the "Japanese Master Plan of Large Research Projects" and is supported worldwide by the international community. It is currently in the design and R&D phase.
In this talk we will review both the physics potential of the experiment and the current design and R&D.
Apr 16: Dr Urs Baltensperger, Laboratory of Atmospheric Chemistry, Paul Scherrer Institute
Title: Aerosol particle formation in the atmosphere: the CLOUD experiment at CERN, the possible influence of galactic cosmic rays, and comparison to field observations - Access to the talk
Abstract : Atmospheric aerosol particles are liquid or solid particles suspended in the atmosphere, with a size of approximately 0.001 - 100 μm. Atmospheric aerosols are of interest mainly because of their effects on health and climate. Concerning health, many epidemiological studies have shown a link between increased mortality/morbidity and increased PM10 or PM2.5(particulate matter with an aerodynamic diameter Atmospheric aerosol particles are produced by a large variety of sources, and are either emitted as primary particles (i.e., they are directly emitted as particles into the atmosphere) or formed by secondary processes (i.e., by transformation of emitted precursor gases). Depending on the conditions, the latter may either result in homogeneous nucleation of new particles or condensation of species on the pre-existing aerosol. The mechanisms of new particle formation are still subject of debates, but with the CLOUD chamber at CERN a facility is now available where the relevant processes can be investigated without the artefacts of previous studies . Besides sulfuric acid, which for a long time has been known as an important driver of nucleation, several other components have been identified that increase nucleation rates by many orders of magnitude compared to a pure sulfuric acid/water system, including ammonia , amines , and organics . The possible influence of galactic cosmic rays is explored, and a comparison to field observations is made.
 J. Kirkby et al., Role of sulphuric acid, ammonia and galactic cosmic rays in atmospheric aerosol nucleation, Nature, 476, 429-433, 2011.
 J. Almedia et al., Molecular understanding of sulphuric acid-amine particle nucleation in the atmosphere, Nature, 502, 359-363, 2013.
 F. Riccobono et al., Oxidation products of biogenic emissions contribute to nucleation of atmospheric particles, (soon to be) accepted in Science, 2014.
Apr 30: Prof Dainis Dravins, Lund Observatory
Title: Astronomical Imaging a Thousand Times Sharper than Hubble: Optical Interferometry with the Cherenkov Telescope Array - Access to the talk
Abstract: Much of the progress in astronomy is led by improved imaging. In the optical, one tantalizing threshold will be two-dimensional imaging of stellar surfaces. With typical sizes of a few milliarcseconds, bright stars require interferometry over kilometer-long baselines. Although several concepts for such interferometer complexes on the ground and in space have been proposed, their realization is not imminent.
However, the availability of large optical flux collectors (air Cherenkov telescopes, in particular CTA – the Cherenkov Telescope Array – primarily erected for gamma-ray studies) enable a revival of the quantum-optical method of intensity interferometry, once developed for astronomy but recently mainly pursued as boson- or HBT-interferometry in high-energy particle physics.
The advantage of intensity interferometry is that it is insensitive to either atmospheric turbulence or to telescope optical imperfections, enabling very long baselines as well as observing at short optical wavelengths. Telescopes are connected only electronically (rather than optically), and the noise budget relates to electronic timescales of perhaps 10 nanoseconds (light-travel distances of meters), enabling the use of also optically imperfect telescopes.
CTA will cover an area of a few km^2, and with suitable software could already quite soon become the first kilometer-scale optical imager, reaching into novel microarcsecond parameter domains. It could reveal the surfaces of rotationally flattened stars with their circumstellar disks and winds, monitor a nova eruption, or possibly even visualize an exoplanet during its transit across some nearby star.
May 07: Dr Elisa Prandini, ISDC, University of Geneva
Title: The gamma ray sky as seen with two MAGIC eyes - Access to the talk
Abstract : In this talk I will review the most important results achieved by the MAGIC Collaboration, which operates two 17-m diameter imaging atmospheric Cherenkov telescopes in the Observatorio del Roque de los Muchachos, in the Canary island of La Palma at 2200 m asl. The MAGIC telescopes cover the energy range from 50 GeV to 50 TeV with focus on the energy range below 1 TeV.
I will present recent scientific highlights including detailed multi-wavelength studies of flaring blazars, detection of Crab pulsar bridge emission, and morphology studies of galactic sources.
May 14: Dr Daniel G. Figueroa, Theoretical Physics Dept, University of Geneva
Title: BICEP2: results and implications for cosmology - Access to the talk
Abstract : I will describe the physics behind the recently detected B-modes in the polarization of the Cosmic Microwave Background (CMB) by BICEP2. I will describe the implications of this detection for cosmology and for theoretical physics in general. Note: I'll keep the discussion at a level accessible to non-cosmologists.
May 21: Dr Nicoleta Dinu, LAL, Orsay
Title: Silicon Photomultiplier – characteristics and applications - Access to the talk
Abstract : The Silicon PhotoMultiplier (SiPM) is nowadays the latest generation of solid state detectors in silicon technology dedicated to visible light detection. In particular, it can be used when multi-photon detection is involved and where low voltage operation, low power consumption, insensibility to magnetic field, small spatial resolution and compactness are required.
In this seminar, the device working principle as well as its electro-optical characteristics will be reviewed. The application of SiPM arrays in building very compact hand-held radiation detector used in therapeutic purposes will be also presented.
May 28: Prof. Xin Wu, Department of particle physics, University of Geneva
Title: High Energy Astroparticle Physics in Space with DAMPE and HERD - Access to the talk
Abstract : High energy astroparticle physics in space is a very active and diverse field of research that is playing a crucial role to connect particle physics with astronomy and cosmology, and is complementary to ground base astroparticle experiments such as large area air-shower detectors, neutrino observatories and Cherenkov gamma-ray telescopes.
A large number of space missions have been successfully launched, including AMS-02, PAMELA, FERMI, with several more in the construction or planning phases, for example DAMPE, CALET, ISS-CREAM, JEM-EUSO, HERD. In this seminar I will give an overview to the current status of research in the field and discuss the science goals, detector concepts and status of two missions that the Département de physique nucléaire et corpusculaire of the University of Geneva is participating: the DArk Matter Particle Explorer (DAMPE) satellite mission and the High Energy Radiation Detection facility (HERD) facility on board the Chinese Space Station.
Autumn semester 2013
Oct 2: Dr Marco Cirelli, Saclay
Title: Dark Matter Indirect Detection: status circa 10/2013 - Access to the talk
Abstract: Dark Matter constitutes more that 80% of the total amount of matter in the Universe, yet almost nothing is known about its nature. A powerful investigation technique is that of searching for the products of annihilations of Dark Matter particles in the galactic halo, on top of the ordinary cosmic rays. Recent data from satellite and balloon experiments have reported unexpected excesses in the measured fluxes of charged cosmic rays, which have been interpreted as a possible first direct evidence for Dark Matter. If this is the case, which DM models and candidates can explain these anomalies and what do they imply for future searches? What are the constraints from other measurements (such as those in gamma rays or neutrinos) and from cosmology? And what is in store for the near future in this field ?
Oct 16: Dr Ugo Amaldi, Technische Universität München and TERA Foundation
Title: Particle Accelerators in Tumour Therapy - Access to the talk
Abstract : ‘Hadrontherapy’, or ‘particle therapy’, is a collective word which covers all cancer therapy modalities which irradiate patients with beams of hadrons.
The most used hadrons are protons and carbon ions. Protontherapy is developing very rapidly: more than 100'000 patients have been treated and eight companies offer turn-key centres. Carbon ions, used for about 8000 patients, have a larger radiobiological effectiveness and, being a qualitatively different radiation, require still radiobiological and, in particular, clinical studies to define the best tumour targets.
After a review of the rationale for hadrontherapy and of the accelerators used in protontherapy, the European centres for carbon ion therapy will be discussed. Finally the two challenges facing the physicists and the engineers developing the accelerators for hadrontherapy will be described: the construction of ‘single-room’ facilities for protons and of multi-room facilities, not based on synchrotrons, for carbon ions.
Oct 30: Dr Marco Durante, Darmstadt University
Title: Heavy Ions in Therapy and Space - Access to the talk
Abstract: Research in the field of biological effects of energetic charged particles is rapidly increasing. It is needed for both radiotherapy and protection from the exposure to galactic cosmic radiation in long-term manned space missions. Although the exposure conditions are different in therapy and space (e.g. low- vs. high-dose rate; total- vs. partial-body exposure), a substantial overlap exists in several research topics, such as: individual radiosensitivity, mixed radiation fields, normal tissue degenerative effects, biomarkers of risk, radioprotectors, non-targeted effects. Late effects of heavy ions are arguably the main health risk for human space exploration, and with the increasing number of cancer patients (including young adults and children) treated by protons and carbon ions, this issue is now becoming extremely important in particle therapy as well. Reducing uncertainty in both cancer and noncancer late risk estimates is therefore the first priority in heavy-ion radiobiology: it is necessary for a safe use of ion therapy in radiation oncology and for planning exploratory missions, especially the Mars exploration. In addition, researchers involved either in experimental studies on space radiation protection or particle therapy often use the same high-energy accelerator facilities. Several particle therapy facilities are now operating, under construction or planned in Europe, USA, and Asia. It is foreseeable that the availability of beamtime and the presence of many dedicated research programs will lead to great improvements in our knowledge of biological effects of heavy ions in the coming few years.
Nov 6:Dr Ivan Peric, Heidelberg University
Title: Particle Sensors in CMOS Technologies - Access to the talk
Abstract: The use of pixel sensors implemented in standard CMOS technologies has gained in popularity over the last decade. The most prominent application is consumer electronics – the sensors for digital cameras. CMOS sensors are also a promising option for high energy physics. An overview of existing CMOS detector structures for particle tracking will be given, and their properties compared.
Nov 13:Dr Carlos de Los Heros - Uppsala University
Title: Dark Matter searches in IceCube - Access to the talk
Abstract : The IceCube Neutrino Observatory at the South Pole is the world's largest neutrino telescope. It instruments a kilometer cube of ice with more than 5000 optical sensors that detect the Cherenkov light emitted by secondary particles produced in neutrino-nucleon interactions in the ice. Covering a wide range of neutrino energies, from 10s of GeVs to PeVs, its physics program is extremely rich. The talk will focus on dark matter searches. In many models, dark matter gravitationally concentrated at the center of the Sun or the galactic center can self-annihilate to standard model particles, producing a flux of neutrinos from the decays of the annihilation products. IceCube can look for such neutrino flux, and competitive limits on the dark matter-nucleon cross section and on the dark matter self-annihilation cross sections have been obtained.
Nov 20: Dr Michelangelo Mangano, CERN - Access to the talk
Title: Standard Model measurements at the LHC: importance and prospects
Abstract: The key missions of the LHC include the study of the Higgs boson and of electroweak symmetry, and the search for new physics phenomena. These goals, nevertheless, rely on the precise measurements of Standard Model (SM) particles, which are the ultimate measurable decay products of any phenomenon emerging from the LHC. The detailed and accurate study of the dynamics of SM interactions, therefore, becomes a crucial step in fulfilling the LHC's key missions. The dynamical regime exposed by the LHC, with the highest energies ever produced in the laboratory, and the precision required by the experimental measurements, challenge our ability to deliver accurate enough theoretical predictions, and limit the fullest exploitation of the LHC results. A global and coordinated campaign of SM measurements and comparisons to theory will however greatly enrich the outcome of LHC physics, increasing the sensitivity to anomalies and new phenomena, and better guiding the interpretation of the data.
Dec 04: Dr Andres Sandoval, Physics Institute, UNAM, Mexico
Title: Recent Results from the HAWC - High Altitude Water Cherenkov - Gamma Ray Observatory
Abstract: The High Altitude Water Cherenkov (HAWC) observatory, under construction in Central Mexico at an altitude of 4,100m, consist of 300 large light-tight water tanks instrumented with 4 photomultiplier tubes each. Ground level particles from showers produced by gamma rays and cosmic rays that collide with the upper atmosphere are detected with these tanks. HAWC differentiates gamma-ray and cosmic-ray primaries by their topology in the 100 GeV - 100 TeV energy range with 2 sr instantaneous field of view and >95% duty cycle. Since August of this year HAWC entered continuous operation with 1/3 of the array. I will discuss construction and operation status and the preliminary results. I will also summarize prospects for detections of supernovae remnants, diffuse galactic sources, active galactic nuclei, gamma-ray bursts, etc.
Spring semester 2013
Feb 06: Prof. Laura Baudis, University of Zurich
Title: Dark matter searches with liquid xenon - Access to the talk
Abstract: We have strong evidence that about 80% of matter in our Universe is dark, revealing its presence only by its gravitational attraction. If the dark matter is made of Weakly Interacting Massive Particles (WIMPs), it can be directly detected via elastic scattering from nuclei in ultra-low background, deep underground detectors. After a brief introduction to the direct detection method, I will review current techniques based on liquid xenon as target material to search for these hypothetical particles. The focus will be on recent results, including those of XENON100, and on the most promising ideas for the near future.
Feb 27: Dr Saverio Braccini, Albert Einstein Center for Fundamental Physics, University of Bern
Title: The new Bern cyclotron laboratory for PET radioisotope production and its beam line for multi-disciplinary research - Access to the talk
Abstract: The new Bern cyclotron laboratory is based on a 18 MeV proton cyclotron equipped with a specifically conceived 6 m long research beam line, terminated in a separate bunker. This particular configuration is designed for industrial Positron Emission Tomography (PET) radioisotope production as well as for novel detector, radiation biophysics, radiation protection, materials science, radiochemistry and radiopharmacy scientific activities. This project is the result of the successful collaboration among the University Hospital in Bern (Inselspital), the University of Bern, private investors and industrial partners. This new facility is now operational and open to national and international collaborations. The design, the construction, the commissioning and the first research activities will be presented.
Mar 20: Dr Vittorio Boccone, University of Geneva
Title: A new technique in gamma astronomy: an innovative camera for a high-energy gamma-ray telescope array - Access to the talk
Abstract: Solid-state detectors, in particular Geiger-mode Avalanche Photo-Diodes (G-APDs) represent a valuable alternative to substitute the Photomultipliers in many applications.
The Cherenkov Telescope Array (CTA) is the first open-access high energy (HE) gamma ray observatory and consists of many tens of telescopes of three different sizes (Small, Medium and Large) covering a large area on the ground.
We proposed a novel design for the Small Size Telescopes of CTA based on a 4 m Davies Cotton reflector focusing the light on a large area G-APD (developed by us together with Hamamatsu) array coupled to non-imaging light concentrators.
I’ll first introduce briefly the physics motivations of CTA with particular regards to the SST energy range and I’ll then give an overview of the 4-m DC SST project. I will focus my talk on the R&D necessary for the design and construction of the G-APD camera that was proposed by the University of Geneva. I will describe the measurements necessary to characterize the G-APD and I will discuss and compare our first results to the design requirements.
April 24: Dr Roberto Cardarelli, University Tor Vergata
Title: Ultra low-noise amplifiers for silicon and diamond detectors - Access to the talk
Abstract: Thanks to the SiGe heterojunction, in the last years the BJT transistor technology has been experiencing a great development for high frequency and low-noise operation. The performance of an ultra-low-noise preamplifier (500 e- RMS) with low frequency (100 MHz BW) will be shown. This amplifier, given the low dependence of the noise from the source capacitance (up to 1 nF), the very fast rise time (up to 100 ps) and the 50 Ohm input impedance, is particularly promising for silicon, diamond and high rate gas detectors.
May 08: Dr Francesco Cafagna, Bari University and INFN
Title: The PAMELA mission: more than six years of Cosmic Rays investigation - Access to the talk
Abstract: The PAMELA mission major scientific objective is the measurements of Cosmic Rays energy spectra, with special focus on the antiparticles, i.e. antiprotons and positrons, ones.
The PAMELA apparatus is a satellite borne magnetic spectrometer and comprises a time-of-flight system, a silicon-microstrip magnetic spectrometer, a silicon-tungsten electromagnetic calorimeter, an anticoincidence system, and shower tail catcher scintillator. It has been more than six years that the PAMELA mission is taking data in space, on board of the russian satellite Resurs-DK.
Important results have been obtained on the positron and antiproton abundance and spectra. Moreover new results have been obtained on the composition of the charged cosmic radiation that challenge our current understanding of the mechanisms of production, acceleration and propagation of cosmic rays in the Galaxy.
In this talk we will review the most recent scientific results obtained by PAMELA and the apparatus performances during its six year mission.
May 15: Dr Jiri Krepel, PSI Paul Scherrer Institut
Title: Thorium or Uranium fuel cycle for advanced nuclear reactors? Fuel recycling, multi-recycling, breeding and burning. - Access to the talk
Abstract: Thorium fuel cycle provides several advantages, which make it very attractive; e.g. lower waste production and possibly improved reactor safety. However, there are also some drawbacks if compared with Uranium cycle. The seminar will provide an overview of basic physical features of both Thorium and Uranium fuel cycles and comparison of their performance (criticality, breeding gain) and safety-related (Doppler effect, coolant density effect) parameters, with respect to the fuel recycling, multi-recycling, breeding and burning.
May 29: Dr Mercedes Paniccia, University of Geneva
Title: AMS - First results - Access to the talk
Precision measurement of the positron fraction in primary cosmic rays from 0.5 to 350 GeV with AMS02
Abstract : The Alpha Magnetic Spectrometer is a state-of-the-art particle physics detector operating as an external module on the International Space Station. It uses the unique environment of space to study the universe and its origin by searching for antimatter, dark matter while performing precision measurements of cosmic rays composition and flux. Since its installation on May 19, 2011 it has collected over 30 billion cosmic rays of energies ranging from several hundred MeV up to few TeV.
In this talk we will present the precision measurement of the positron fraction in cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 million positron and electron events collected in the initial 18 month period of operation in space.
Autumn semester 2012
Sept. 19: Dr Philipp Mertsch, University of Oxford and Kavli Fellow at the Kavli Institute of Particle Astrophysics and Cosmology, SLAC, Stanford University
Title: From radio halos to Fermi bubbles
Abstract : Diffuse radiation fields pervade the Galaxy from radio waves to gamma-rays and encode a plenitude of information about non-thermal processes. For other studies, e.g. dark matter searches, CMB analysis or even for faint point sources, they constitute an irreducible background and need to be subtracted off. I will focus on diffuse Galactic emission in the radio and in gamma-rays describing new ways to understand and model them. Particular mention will be made of the recently detected Fermi bubbles and I will suggest a theoretical picture that can explain both their energy spectrum and morphology.
Sept. 26: Dr. Bill Murray (RAL):
Title: Higgs boson properties and how to constrain them - Access to the talk
Abstract: The recently-discovered new boson at CERN seems to be a good candidate for the long-sought Higgs boson. This seminar explores what we need to learn about it to confirm that it is the Higgs boson and how we will obtain that information. Some progress should come rather rapidly at the LHC, but other information will be much harder. If it is the Higgs boson then its existence at this mass presents some interesting puzzles, and more detailed measurements may tell us something about the dark matter binding galaxies together and maybe the ultimate fate of the Universe.
Oct. 8: Prof. Subir Sarkar (Oxford)
Title: Alternatives to SUSY dark matter - Access to the talk
Abstract: Much effort has been devoted to the study of weak scale particles, e.g. supersymmeteric neutralinos, which have a relic abundance from thermal equilibrium in the early universe of order what is inferred for dark matter. This does not however provide any connection to the comparable abundance of baryonic matter, which *must* have a non-thermal origin. Candidate particles with such a connection are "dark baryons" with mass of order 10 GeV from a new strongly
interacting sector. Putative signals in experiments such as CoGeNT, CRESST and DAMA have also focussed attention on such particles. They can affect heat transport in the Solar interior so as to affect low energy neutrino fluxes and helio-seismology.
Oct. 31: Prof. Andrii Neronov (ISDC, University of Geneva)
Title: Gamma-ray astronomy in the 100 TeV band
Abstract: Small size telescopes (SST) sub-array of the next-generation ground-based gamma-ray observatory CTA will extend the energy "window" available for astronomical observations toward the 100 TeV energy band. Based on the experience of observations with the current-generation gamma-ray telescopes, HESS, MAGIC and VERITAS, we have some idea of what kinds of astronomical sources and what kinds of astrophysical phenomena we will observe in this new "extremely high energy" (EHE) band. However, future observations of the sky in the up-to-now unexplored EHE gamma-ray band might bring some surprising unexpected discoveries. In this talk I will review the perspectives and challenges of the new field of EHE gamma-ray astronomy which will be opened by the SST sub-array of CTA.
Nov. 7: Dr. Mario Campanelli (UCL)
Title: Jet substructure as a tool to reconstruct the decay of heavy boosted objects - Access to the talk
Abstract: The LHC is the first collider where particles with mass at the electroweak scale can be produced with momenta much higher than their mass. The decay products of these particles are very boosted, and Hadronic decays would be reconstructed as a single "fat" jet. In the last few years there has been a great wealth of studies in the field of hadronic jet substructure to reconstruct these final states. In this seminar i will review the main phenomenological ideas, as well as the first experimental results using jet substructure as a tool to explore new and old physics.
Nov. 21: Prof. Alain Blondel, Université de Genève
Title: Future possibilities for precise studies of the H(126) Higgs candidate - Access to the talk
Abstrac: We present a summary of the state-of-the-art comparison relevant to possible studies of the H(126) Higgs boson candidate. The machines considered are the LHC and its upgrades, Linear and circular e+e- colliders such as ILC/CLIC or LEP3/TLEP, gamma-gamma colliders and muon colliders. The conclusions of the recent ICFA beam dynamics HF2012 workshop in Fermilab will also be shown.
Dec. 5: Prof. Max Klein, University of Liverpool
Title: Physics and Realisation of the LHeC - Access to the talk
Abstract: The Large Hadron Electron Collider (LHeC) project involves upgrading the LHC with a new electron beam in order to build a luminous, TeV energy ep and eA collider at CERN. An introduction is given to the physics programme of the LHeC, and the design concepts are described of the 60 GeV electron accelerator and of a new detector for precision deep inelastic scattering.
Dec. 12: Dr Daniel Muenstermann, CERN
Title: Radiation-hard Active Silicon Sensors for the ATLAS Upgrade
Abstract: In the coming years, the LHC will be upgraded to provide much higher luminosity. This implies increased radiation damage, occupany and pile-up for ATLAS and requires the replacement of the current Inner Detector with an improved all-silicon Tracker. While the standard silicon sensor technology appears to be capable of fulfilling the demanding HL-LHC requirements, new innovative technologies might offer significant advantages.
Deep-submicron HV CMOS processes feature moderate bulk resistivity and HV capability and are therefore good candidates for drift-based radiation-hard monolithic active pixel sensors (MAPS). For the ATLAS Upgrade, the concept of using a deep-submicron HV CMOS process to produce a drop-in replacement for traditional radiation-hard silicon sensors is explored. Unlike fully integrated MAPS, such active sensors contain simple circuits, e.g. amplifiers and discriminators, but still require a traditional (pixel or strip) readout chip. This approach yields most of the advantages of MAPS (improved resolution, reduced cost and material budget, etc.), without the complication of full integration on a single chip.
After outlining the design of the HV2FEI4 test ASIC, characterization results and first experience obtained with pixel and strip readout will be shown before discussing future prospects of active sensors and CMOS-based detectors in general.
Dec. 19: Prof. Julien Lesgourges, EPFL, Lausanne
Title: Active and sterile neutrinos in cosmology - Access to the talk
Abstract: Review of status and prospects for constraining the neutrino sector using cosmological observables, with an emphasis on cosmic microwave background and large scale structure data.
Séminaires exceptionnels - Candidats au poste de MER
Mercredi 18 juillet 2012 dès 08h30 - Auditoire Stückelberg
Ecole de physique, 24, quai Ernest-Ansermet, Genève
08h30-09h20 :Dr Chiara Casella (ETZH) - From muon lifetime to positron emission tomography: Scintillators and photodetectors in precision measurements
The detection of scintillation light produced by ionizing radiation is certainly one of the oldest and still most widely adopted techniques in particle physics. Based on my personal experience, I will describe the experimental concepts and results of two different examples in this direction: the FAST and the AX-PET experiments.
FAST is a high precision muon lifetime measurement, aiming at a 2 ppm accuracy on the muon lifetime tµ. This is achieved with a DC p+ beam (170 MeV/c), stopped on a high granularity plastic scintillator target, viewed by position sensitive photomultipliers (PSPM).
AXPET is a prototype for a novel geometrical concept of positron emission tomography (PET), based on matrices of LYSO scintillating crystals read-out by Silicon Photomultipliers (SiPM), for the detection of 511 keV photons. It aims at a high spatial resolution (~ 1 mm3) in the reconstruction of the photons interaction point.
The working principle and the achieved results of the two experiments will be described.
09h20-10h10 : Dr Domenico della Volpe (Università di Napoli) - Unfolding the New Physics at LHC
The most recent results on the Higgs discovery with the ATLAS detector will be presented. The mechanisms to generate the masses of the particle in the frame of the Standard Model will be first introduced and then the recents observation will be presented and discussed.
The success of the measurement has depended strongly on the trigger system, which is fundamental to unfold the interesting physics process from the huge background from underlying collision events.
As this is is my current area of research activity, I will present the system's architecture and implementation and discuss the relevance for the measurement.
10h10-10h40 : Coffee break
10h40-11h30 : Dr Pedro Facal (U. of Chicago) - The microwave technique for the study of the highest energy cosmic rays
The origin and composition of the ultra high energy cosmic rays (UHECRs, those with energies above 1018 eV) have been studied for long. Recent results by the Pierre Auger Observatory, a 3000 square kilometers hybrid detector with unprecedented sensitivity, have shed a light in some of the most pressing questions of the field, like the anisotropy in the arrival directions and the mass composition. But these results show also some of the limitations of the current techniques used for UHECR detection. Recent laboratory measurements suggest that detection of cosmic rays using microwave radiation in the GHz band is possible, and would allow to cover large areas, as needed, with 100% duty cycle and virtually no atmospheric attenuation. I will review the most recent UHECR measurements and present the current efforts towards GHz detection, in particular MIDAS, a prototype radio telescope instrumented with 53 microwave receivers at the University of Chicago.
11h30-12h20 : Dr Gerd Pühlhofer (Tübingen University) - Hunting cosmic ray accelerators with TeV observations: Clues from dark TeV sources and Supernova remnants
TeV observations of the Galactic plane hold the promise of identifying the accelerators of Galactic cosmic rays. Indeed, current Cherenkov telescopes have found a rich population of Galactic TeV gamma-ray sources over the past few years. But identifying these gamma-ray sources with astrophysical objects often turned out to be challenging. I will report on lessons we learned throughout the identification process, with a particular emphasis on supernova remnants which are believed to be the main sources of Galactic cosmic ray particles.
12h20-13h10 : Dr Giulio Saracino (Naples University) - An application of Silicon Photomultipliers to a tracking detector for the muon radiography.
Silicon Photomultipliers have been developed about ten years ago and their use, as an alternative to traditional photomultiplier tubes, is increasing more and more. They have single photon response capability, high detection efficiency, high gain at low bias voltage, low power consumption and very good timing performance. In spite of their Geiger regime, they can work as linear devices. All these properties motivated their adoption for a tracker designed for the muon radiography of volcanoes (muography).
Muography is a novel technique based on the measurement of the absorption suffered by cosmic muons while traversing the volcano’s edifice. It can provide a density map of the upper part of a volcano with resolution better than 100 m. The detector is required to be able to work in harsh environment and to have low power consumption, good angular and time resolutions, large active area and modularity.
In this talk I will discuss the main properties of Silicon Photomultiplier and the design, construction and first measurements of the muon detector prototype developed for the MU-RAY project.