All future and past seminars

Autumn semester 2018


Sept. 19 :  Dr Philipp ELLER, Penn State University - Access to the talk
Title : Neutrino Oscillation Physics with IceCube


The Neutrino IceCube observatory, with its 5160 sensors submerged in Antarica's glacial ice, collects data from neutrino events over several orders of magnitude in energy. The DeepCore detector sub-array in the deepest clear ice of IceCube enables detection and reconstruction of neutrinos produced by the interaction of cosmic rays in the Earth’s atmosphere at energies and baselines suitable for the study of neutrino of oscillations.

We recently unblinded two different 3-year analyses using neutrinos with reconstructed energies between 5.6 and 56 GeV over a range of baselines up to the diameter of the Earth to simultaneously measure the muon neutrino disappearance and tau neutrino appearance. These new results are competitive in terms of precision with those of other, mainly long baseline accelerator experiments.


Sept. 26 : Prof. Martin KUNZ, Unige - Access to the talk
Title : Overview of the ESA Euclid satellite mission


I will give an overview of the Euclid satellite, first focusing on the
mission status and outlook, and on the consortium structure, including
the activities in Switzerland. I will then review the science goals and
place them into the current cosmological context.


Oct. 03  Dr Michael DOSER, CERN
Title :Experiments on antimatter at CERN


One and a half decades after the first production of “cold” antihydrogen, first precision measurements of the properties of antihydrogen have recently begun. Together with the start-up of an additional dedicated low energy antiproton decelerator (ELENA), and the development of a wide range of techniques that permit precise atomic measurements, the study of antihydrogen atoms has started in earnest. This presentation will provide an overview of the present status and outlook for fundamental physics with antihydrogen atoms. A special focus will be put on tests of gravity with antimatter and on the AEGIS experiment, which in a first step aims to measure the free fall of a pulsed beam of antihydrogen atoms over their parabolic trajectory, as well as on the technological developments from a variety of fields on which it relies.


Oct. 17 :   Dr. Mieczyslaw (Witold) KRASNY - Sorbonne University Paris and BE-ABP Division CERN - Access to the talk
Title :
The Gamma Factory for CERN:  conceptual foundation, feasibility studies and research opportunities


In this talk I shall discuss the initiative of broadening the present CERN research programme by including a new component exploiting a novel concept of the light source. The proposed, partially stripped ion beam driven, light source is the backbone of the Gamma Factory initiative. It could be realized at CERN by using the infrastructure of the already existing accelerators. It could push the intensity limits of the presently operating light-sources by at least 7 orders of magnitude, reaching the flux of the order of 10^17 photons/s, in the particularly interesting gamma-ray energy domain of  0.1 — 400  MeV. 

 The partially stripped ion beams, the unprecedented-intensity energy-tuned gamma beams, together with the gamma-beam-driven secondary beams of polarized positrons, polarized muons, neutrinos, neutrons and radioactive ions constitute the basic research tools of the Gamma Factory. A broad spectrum of new research opportunities, in a vast domain of uncharted fundamental and applied physics territories, could be opened by the Gamma Factory.

 Examples of new research opportunities and the recent progress in the project development will be presented in this talk. 


Oct. 31 : Dr Pasquale SERPICO, LAPTh (CNRS & Univ. of Savoie) Annecy, France - Access to the talk
Title : "Quo vadis, materia nigra?"


The main outcome of decades of efforts for the identification of dark matter (at colliders, direct detection underground, indirect detection via astrophysical signals) is a null result. What lessons have we learned, if any? Which models are still viable, and with what motivations? I will review some of the trends in the theoretical and phenomenological dark matter community and a few of the observational opportunities that will open up in the forthcoming years, in particular in indirect techniques. 


Nov. 07 :  Dr Stefan SCHLENSTEDT, DESY - Access to the talk
Title : Gamma-ray Astronomy - Recent Highlights from VERITAS


A short introduction to gamma-ray astronomy, a new field in astronomy and astroparticle physics, will be given. VERITAS is a ground-based gamma-ray observatory consisting of an array of four atmospheric Cherenkov telescopes located in southern Arizona, USA. VERITAS carries out an extensive observation program of the gamma-ray sky with a sensitivity in the energy range from 85 GeV to > 30 TeV. Recent highlights of the VERITAS observation program of extragalactic sources will be presented like active galactic nuclei and other extragalactic objects like radio galaxies and starburst galaxies. The studies of the extragalactic background light will be discussed. Also recent results on  galactic accelerators will be presented like supernova remnants with fast shocks, pulsars with powerful winds and intensely-interacting binary systems.


Nov 14 : Prof. Iwona GRABOWSKA-BOLD, AGH University of Science and Technology, Poland
Title : First direct measurement of light-by-light scattering


Light-by-light scattering is a process in which two photons interact with each other and in consequence change a direction of their motion. This phenomenon is forbidden in the classical physics. Only after the birth of quantum electrodynamics in the 30th of the XX century, Heisenberg and his student Euler realized that two photons may interact with each other. Unfortunately for decades that process has stayed elusive for direct measurements due to its tiny cross section. A breakthrough has occurred in 2017 when the ATLAS Collaboration at the LHC analysed data from lead-lead collisions collected at the center-of-mass energy of 5.02 TeV. A focus was given to a special class of events, so-called ultra-peripheral collisions (UPC), in which two lead nuclei do not collide but pass next to each other.  UPC events are considered a source of high-intensity electromagnetic fields, thus photons. In 4 billion analysed events, the ATLAS Collaboration found 13 event candidates with scattered photons, while about 2 were expected from background processes. This measurement established evidence for a first direct measurement of light-by-light scattering. In October 2018 also a result of light-by-light scattering from the CMS Collaboration was released. This talk will discuss the analysis, results of the measurements, and also prospects for future analyses of lead-lead data including the ongoing 2018 run.



Dec 05. : Prof. Ben KILMINSTER, Uni Zurich
Title : DAMIC


Dec. 12 : Dr. Florian BERNLOCHNER, University of Bonn, Germany
Title : Belle II: Status and prospect


Jan. 16 : Prof. Hugo ZBINDEN, Unige
Title : Quantum Cryptography

SPRING semester 2018


Feb. 7 : Dr. Zigfried Hampel-Arias, ULB, Brussels - Access to the talk
Title : Cosmic Ray Observations at the TeV Scale with the HAWC Observatory


Measurements of cosmic rays at TeV energies provide important probes to understanding the nature and distribution of galactic acceleration sites as well as the interstellar environment in which cosmic-ray particles propagate. Below ~10 TeV, direct detection experiments provide the most detailed measurements of the primary particle spectrum, whereas ground-based air-shower arrays typically access energies above ~100 TeV and can measure the anisotropy of the cosmic ray arrival distribution. With its high duty cycle and large field of view (~2 sr), the High-Altitude Water Cherenkov (HAWC) Observatory, an air-shower array located near Puebla, Mexico, continuously surveys the Northern cosmic ray sky at very high energies (100 GeV-1 PeV). We report on the all-particle cosmic ray energy spectrum from 10-500 TeV measured with a selection of 8.4 x 109 HAWC events, including evidence of a spectral break near 46 TeV. The measured spectrum exhibits agreement within systematic uncertainties with various experiments demonstrating that HAWC can bridge the energy region between direct detection and air-shower array techniques. With a large data set (12.3 x 1010 events) obtained from two years of continuous observation and a new statistical method, we also present HAWC results of the cosmic-ray anisotropy from 2-73 TeV, confirming the presence of previously observed energy-dependent angular features on both large and small scales.


Feb. 21 : Prof  Slava Voloshynovskiy, Department of Computer Science, UNIGE - Access to the talk
Title : Scalable and unsupervised classification : reality or myth ?


With the advent of deep network architectures many remarkable results have been reported in classification and hypothesis testing applications and estimation problems such as image restoration, denoising, super-resolution and compression. Most of these architectures benefit from the presence of a huge amount of training data per class.
The recent architectures assume end-to-end training where the entire architecture is optimized according to some loss function. Despite some obvious progress, interesting reported results, user-friendly ML libraries developed in TensorFlow, PyTorch and Keras and huge interest from the IT industry and research communities there are a number of questions that still remain either completely unsolved or weekly understood.
At the same time, partial solutions are advocated by unsupervised systems based on generative models such as GANs and VAEs. However, in the most cases the generative models have serious restrictions on the dimensionality of input and require accurate alignment. Additionally, in the most cases the validation of produced results in based on visual assessment.
Among the main difficulties towards large scale applications of these systems are: (a) complexity of training for large dimensional data, (b) need of labeled data for supervised classification, (c) limited amount of classes and trivial encoding methods of class labels, (d) vulnerability to perturbations in input and training data and lack of rejection options in classification space, (e) high sensitivity to geometrical deviations in the input data wrt training sets and (f) need of retraining of the entire network with the addition of new classes.
Not less important factors are security and privacy of data next to understanding what is learned by these systems and how the learned features are changed with the addition of new classes or training examples.

The last but not the least factor is a lack of solid information-theoretic foundations behind the design of deep architectures providing some estimates on the fundamental achievable limits of the performance in terms of accuracy, needed amount of training data, etc.. In this presentation, we will try to consider the existing deep architectures from common perspectives and advocate several solutions that partially address the above problems.


Feb 28 : Dr. Simone Campana, CERN - Access to the talk
Title : The Challenges of High Energy physics computing in the next decade


The experiments at the CERN Large Hadron Collider set the high end of the scale when considering the volume of resources for scientific computing in the last decade. The largest experiments collect tenths of Petabytes of RAW data every year and process more than on exabyte in the same period. The LHC physics program foresees a major upgrade in the middle of the 2020s and a High Luminosity phase after that. By that time the computing needs will have increased by up to 50 times. In the meanwhile, large other players in scientific computing are preparing to collect data: the Square Kilometre Array for example is expected to manage as much data as the LHC at the same time of its high luminosity phase. The HEP funding agencies are asking to keep the cost of computing under control and we cannot foresee an increase in hardware resources beyond what technology can provide. In this contribution I will explain the challenges of HEP computing in the next decade and indicate the areas of work where the HEP community foresees an evolution to cope with the future challenges.


Mar 14 : Prof. Anna Sfyrla, Université de Genève - Access to the talk
Title : Physics at ATLAS : How triggers define the experiment’s potential, now and in the future

 COLLOQUE : Procédure d’évaluation du Prof. Anna SFYRLA


The ATLAS experiment at the CERN's Large Hadron Collider (LHC) is collecting unprecedented amounts of data, enabling high energy physicists all over the world to unveil the hidden mysteries of our universe, by testing the predictions of the Standard Model, the theory that describes the building blocks of matter and how they interact. Sophisticated hardware and software systems are put in place to select detector data for analysis. This elaborate selection infrastructure, called "the trigger system", operates at extremely low latency and under stringent requirements in robustness and capacity.

 In this talk I will describe the ATLAS trigger system and its challenges. I will discuss how its performance defines the capability of the ATLAS experiment to realise its envisaged physics program. I will give particular focus to the ATLAS High-Luminosity LHC upgrade, anticipated for 2026 and for which the trigger architecture has recently been redesigned.


Mar. 21 : Dr Lorenzo Paolozzi, UNIGE - Access to the talk
Title : The TT-PET project: a 30 ps Time of Flight PET scanner in silicon pixel technology


The TT-PET collaboration is developing a small animal scanner for positron emission tomography based on silicon pixel detectors. The core element of the scanner is a full efficiency 1.1 × 2.4 cm2 monolithic silicon sensor in SiGe BiCMOS technology. The sensor, developed at the DPNC, will have a pixel size of 0.25 mm2, low-power consumption and 30 ps time-of-flight resolution. The scanner will be a layered structure, approximately 1.5 cm thick.

 Thanks to the sub-mm 3D detection granularity the scanner will have an unprecedented resolution for image reconstruction, while the compact structure will make it ready for insertion in a MRI machine.


Mar. 28 : Dr. Patrick Janot, CERN - Access to the talk
Title : Physics opportunities at the FCC


Prompted by the outcome of the 2013 European Strategy for Particle Physics, CERN has therefore undertaken a five-year study for a Future Circular Collider (FCC) facility built in a new 100 km-circumference tunnel. Such a tunnel could host an e+e- collider (FCC-ee) with an intensity up to five orders of magnitude higher than LEP and an energy exceeding the top-pair production threshold. It could also house a proton–proton collider (FCC-hh) operating at a centre-of-mass energy of 100 TeV, seven times that of the LHC, in view of collecting ten times more data than the HL-LHC. An electron–proton collider (FCC-eh) would allow the proton substructure to be measured with unmatchable precision. The FCC discovery potential would address many of the outstanding questions in modern particle physics and secure our exploration of the microscopic world for generations.


Apr. 11 : Dr Gaetano Barone, Brandeis University, USA - Access to the talk
Title : Study of the Higgs-boson properties with the ATLAS detector at LHC in Run 2

 The recent measurements of the Higgs boson properties in the diboson channels (ZZ*,γγ, and WW) with 36.1 fb⁻¹ of proton—proton collisions at √=13 TeV using the ATLAS detector are presented. The results include the Higgs boson mass measurement as well as inclusive, fiducial and differential cross section measurements, and constraints on Higgs boson production mode couplings. The results are interpreted within the Standard Model and its extensions.


Apr. 18 : Prof. Paris Sphicas, Univ. of Athens and CERN - Access to the talk
Title : Hadron Colliders Physics - a historical perspective


Experiments at hadron colliders have been a key driver of the establishment of the Standard Model of particle physics as one of the most powerful and successful scientific theories.  This has been possible by the development of a sequence of hadron accelerators and corresponding experiments that started with the advent of the ISR and has culminated with today's state of the art, the LHC and its four major experiments. We review the physics highlights of this period, which covers almost five decades, in an attempt to summarize some lessons learned and how we have arrived at today's ATLAS and CMS experiments that have already registered one major discovery and are out on the hunt for a deeper understanding of the Standard Theory and the hunt for physics beyond.


Apr. 25 : Dr Michel De Cian, EPFL - Access to the talk
Title : Anomalies in B decays


Flavour-changing neutral currents (FCNCs) only proceed via loop level in the Standard Model and therefore offer an excellent probe for new physics. In the last years, several measurements of rare B decays proceeding via FCNCs have shown deviations from the Standard Model predictions.

 After an introduction to the LHCb detector I will talk about the most important measurements of rare B decays and about the comparison with theoretical predictions. I will highlight the results from angular analyses and tests of lepton flavor universality in b -> s l l transitions from LHCb and other experiments, and the possible connection of all anomalies, including the puzzling deviations from the Standard Model seen in semileptonic B decays.


May 9 : Prof. Teresa Montaruli, UNIGE - Access to the talk
Title : Multi-messenger high-energy astrophysics with IceCube and CTA

Multi-messenger high-energy astrophysics is a rising domain thanks to the understood connection between high-energy cosmic-rays, gamma-rays and neutrinos and to therecent measurements that experiments are performing from ground and space.
The presentation focuses on the recent IceCube observations of cosmic neutrinos and on the future potential of CTA Observatory for these searches.


May 16 : Dr Francesco Riva, UNIGE, DPT - Access to the talk
Title : Precision Tests in the High Energy Era


With increasing integrated luminosity, precision tests of the SM are gaining importance as New Physics search tools at the LHC. 

 I focus on precision studies of SM processes at high-energy and on the challenges that this program faces from a BSM perspective. Using the language of Effective Field Theories, I will put particular emphasis on the implications of interesting BSM-SM non-interference rules.


May 30 : Dr Alexander Oh, Univ. of Manchester - Access to the talk
Title : Diamond Detectors - Status and Perspectives


Diamond is a promising material with remarkable mechanical and electronic properties to provide the basis for radiation resistant particle detectors for high energy particle physics (HEP). In the presentation the current state of diamond detectors in particle physics will be discussed, focussing on recent developments of 3D diamond detectors and test-beam results with prototype pixel devices.

Département de Physique Nucléaire et Corpusculaire | 2017 | Impressum.