Section de physique
Département de physique nucléaire et corpusculaire



Séminaires de physique corpusculaire

Les séminaires du DPNC ont lieu les mercredis à 17.00 heures (chaques deux semaines) dans l'auditoire Stückelberg, Ecole de physique, 24, quai Ernest-Ansermet, Genève.

Semestre d'Hiver 2001-2002 - Semestre d'Été 2001-2002

Séminaires des années précédentes: <1998, 1998-1999, 1999-2000, 2000-2001

Retour DPNC

Semestre d'été 2001-2002

13 Mars 2002 Prof. Ralph Eichler - PSI The Particle Physics Programm at the Paul Scherrer Institut
17 Avril 2002 Dr. X. Wu - Université de Genève CDF-II Startup
15 Mai 2002 Dr. Ph. Chomaz - GANIL Atomic Nuclei in 2002: Surprises, discoveries and evolutions
28 Mai 2002 Dr. Christian Spiering - DESY-Zeuthen High energy neutrino astronomy - status and prospects
5 Juin 2002 Dr. Monika Grothe - CERN Mixing in the D0 system at BaBar
12 juin 2002 Dr. Volker Beckmann - Observatoire de Genève Blazars - The extreme Active Galaxies
19 juin 2002 Prof. Jean-Luc Vuilleumier - U.Neuchâtel Neutrino properties from experiments at low energy
26 juin 2002 Dr. K. Ragan - McGill University Ground-based gamma-ray astrophysics



Semestre d'été 2001-2002


Prof. Ralph Eichler: The Particle Physics Programm at the Paul Scherrer Institut

Precision experiments using high intensity pion, muon or neutron beams are sensitive to new forces or particles. Three examples will be given: i) pion beta decay, ii) rare muon decays and iii) search for an electric dipole moment of the neutron.


Dr. Xin Wu - U. Geneva: CDF Startup

The RunII of the Fermilab Tevatron Collider began in 2001, after extensive upgrades to both the machine and the CDF and D0 detectors. An overview to the CDF detector upgrades and performeance will be described, in particular the unique L2 impact parameter track trigger (SVT). The current data-taking status, as well as a fisrt glimpse of CDF data will be presented.

Dr. Philippe Chomaz - GANIL: Atomic Nuclei in 2002: Surprises, discoveries and evolutions

In this talk we will show how the study of nuclei under extreme conditions have changed our understanding of atomic nuclei. Indeed in the past 10 years unexpected results and important discoveries have shown how far nuclear models are from a realistic picture. Hot nuclei have renewed our understanding of phase transitions in finite systems in particular with the observation of negative heat capacities. This anomalous behavior has now been observed in other mesoscopic systems such as metallic cluster. Exotic nuclei have contradicted the paradigm of the nucleus as a homogeneous quantum drop of nucleons. The discovery of halo and molecular nuclei as well as the observation of the disappearance of magic number in neutron rich regions of the nuclear chart are some example of the actual "nuclear structure crisis".

Dr. Christian Spiering - DESY-Zeuthen: High energy neutrino astronomy - status and prospects

After a long period of development, high energy neutrino astrophysics is approaching a level of sensitivity which reaches below the upper bounds on extraterrestrial neutrino fluxes derived from the observed fluxes of cosmic rays and gamma rays. The day when first positive observations will start to populate the neutrino sky could therefore be close. The talk reviews physics goals and experimental status of high energy neutrino astronomy, with emphasis on results from the Amanda neutrino telescope at the South Pole.

Dr. Monika Grothe - CERN: Mixing in the D0 system at BaBar

Mixing in the D0 system may provide a sensitive probe for new physics beyond the Standard Model (SM). The SM predictions are small (<10-3) for the mixing parameters x, y which, in the absence of CP-violation, measure the difference in mass (x = DeltaMass/Gamma) and lifetime (y = DeltaGamma/2Gamma) of the CP-eigenstates in the D0 system. New physics may significantly enhance x while y is expected to be dominated by SM processes. The BaBar detector at the e+e- storage ring PEP-II provides the opportunity of studying charm decays with unprecedented statistics and purities. Two experimental methods will be described in detail: The determination of y from the D0 lifetime difference in the decays K-pi+ and K-K+, pi-pi+, and the extraction of y, x^2 and the wrong-sign (D0 ->K+pi-) decay rate from the time evolution of the D0 decay rate. Preliminary BaBar results for y and the wrong-sign decay rate will be presented.

Dr. Volker Beckmann - Observatoire de Genève: Blazars - The extreme Active Galaxies

Blazars mark the extreme end of the AGN (Active Galactic Nuclei) population. These galaxies are thought to host a supper massive black hole. Accretion onto this mass forms a disk of matter around the central engine. This process is accompagnied by forming a jet perpendicular to the disk, which transports electrons and/or positrons at relativistic speed away from the black hole. In the case of Blazars we look directly into this jet. The interaction of the particles which form the jet and the magnetic field surrounding it, leads to synchrotron radiation, and photons are up-scattered by relativistic electrons in inverse Compton processes. This leads to the observed properties of these AGNs: high variability, strong polarization, non-thermal emission, and a characteristic spectral energy distribution. The violent processes in the jet make Blazars observable up to the TeV domain. This talk will focus on the appearance of Blazars and especially what is observable at high energies.

Prof. Prof. Jean-Luc Vuilleumier - U.Neuchâtel: Neutrino properties from experiments at low energy

The study of solar and atmospheric neutrinos  has brought new insight on neutrino properties. Neutrinos have been shown to oscillate, and thus have masses. But the mass scale is still unknown. Next generation searches for neutrinoless double beta decay may give an answer. Some projects will be discussed.  Also neutrinos may have magnetic moments, which may have an impact on oscillation patterns. Searches for magnetic moments with sources or at nuclear reactors will be presented.

Dr. K. Ragan - McGill University: Ground-based gamma-ray astrophysics

Some of the most enigmatic phenomena in the Universe -- black-hole driven Active Galactic Nuclei, pulsar-driven Supernova Remnants, and perhaps even Gamma-Ray Bursts -- are now known to be strong gamma-ray emitters. Many have been seen and studied from orbiting satellite-based detectors, and a few from the ground. Unfortunately, these two techniques have, until now, left an 'unexplored window' in gamma-ray energy between approximately 10 GeV and 250 GeV. There is good reason to expect that this energy range is crucial to understanding these sources and the propagation of gamma-rays across the Universe. A number of new techniques and detectors are addressing this energy range; this talk will briefly introduce the scientific motivation for these detectors and talk about the different experimental approaches.


Semestre d'hiver 2001-2002

24 Oct. 2001 Dr. Pierre Antilogus - IPN Lyon La constante cosmologique : mesure et perspectives
14 Nov. 2001 Dr. Juan Alcaraz CIEMAT/CERN What have we learned from LEP2?
21 Nov. 2001 Dr. Jose Ocariz LPNHE-Paris VI et VII Recent results on CP violation from BaBar
28 Nov. 2001 Dr. Anne Ealet CPPM-Marseille Vers une mesure precise de l'energie noire: Le projet SNAP(SuperNova Acceleration Probe)
16 Jan. 2002 Dr. Achille Stocchi LAL-Orsay 10 Years of B Physics at LEP
30 Jan. 2002 Dr. Pierre Jarron CERN
Dr. Marc Winter IReS-Strasbourg
New developments in silicon detectors


Semestre d'hiver 2001-2002


Dr. Pierre Antilogus, IPN - Lyon: La constante cosmologique : mesure et perspectives

Les SuperNovae de type Ia (SN Ia) ont fourni la 1ère indication tangible de la présence d'une constante cosmologique non nulle. Les SNIa vont être amenées à jouer un rôle clef dans la mesure de l'énergie du vide ou plus généralement dans l'étude de l'Energie Noire. Au cours de ce séminaire, après avoir introduit le contexte scientifique, l'état actuel de la mesure de la constante cosmologique sera revu. Les perspectives d'une cosmologie de précision à l'aide des SN Ia sera présenté. Les programmes "nearby SuperNova Factory" (SNFactory) et "SuperNova Accelerating Probe satelite" (SNAP) seront introduits.


Dr. J. Alcaraz, CIEMAT/CERN: What have we learned from LEP2?

In this talk we will try to discuss LEP2 results from a non-standard point of view. It is well known that LEP collaborations have searched for the Higgs particle and for new physis beyond the Standard Model. Precise measurements of the W mass and the triple gauge coupling structure predicted by the theory are also underway. What is not so well known is that LEP2 physics presents many unique features when compared to LEP1 and e+e- interactions at lower energies. This new high energy domain is somehow comparable to the electroweak environment that will be found a future e+e- colliders.


Dr. J. Ocariz, LPNHE Paris VI-VII: Recent results on CP violation from BaBar

Following the spectacular turn-on of both the SLAC and KEK B factories, results from BaBar and Belle on CP violation have recently been published. I will review the analysis of time-dependent CP violating asymmetries in BaBar, together with a few other topics on B physics, and discuss future prospects.


Dr. A. Ealet, CPPM-Marseille: Vers une mesure precise de l'energie noire: Le projet SNAP(SuperNova Acceleration Probe)

Les supernovae de type Ia (Sn Ia) sont un outil simple et direct pour connaitre l'histoire de notre univers. Apres un rappel rapide du contexte scientifique, nous examinerons comment les supernovae peuvent donner des mesures de precision et montrerons qu'un echantillon important de SN avec des systematics bien controlees permet, au dela de la mesure precise de la constante cosmologique, une determination sans ambiguite de la nature de l'energie noire. Le projet de satellite SNAP est concu et dedie pour repondre a cette attente. Avec quelques milliers de SN Ia par an, il permettra de separer les modeles d'energie noire par la mesure du parametre w avec une precision meilleure que 0.05.


Dr. A.Stocchi LAL-Orsay/CERN

  10 Years of B Physics at LEP

In this seminar I'll show how, in the past 10 years, some measurements and theoretical results, have improved our knowledge of the Flavour Sector of the Standard Model. I'll put more emphasis in the central role played by the LEP experiments in most of these measurements and their impact in the determination of the Unitarity Triangle parameters.


Dr. P. Jarron (CERN) , Dr. M. Winter (IReS-Strasbourg)

  New developments in silicon detectors

In this seminar two projects of new pixel silicon for charged particle tracking will presented: the deposition of hydrogenated amorphous silicon above integrated circuits and the Monolithic Active Pixel Sensors
Hydrogenated amorphous silicon - a-Si:H - has been considered for a long time as a potential semiconductor material candidate to build low cost radiation sensors. Poor charge collection and insufficient signal to noise ratio have been the main issues preventing successful results. The deposition of hydrogenated amorphous silicon films above the readout integrated circuits is an attractive approach to overcome these issues and could allow to build radiation hard and low cost pixel detectors for tracking applications. Properties and fabrication of thin film a-Si:H detector will be discussed, and very preliminary results of a-Si:H deposition on ASICs will be presented.
Monolithic Active Pixel Sensors are new type of semi-conducting pixel which is expected to combine specific advantages of Charged Coupled Devices and Hybrid Pixel Sensors in a fully integrated architecture, where the read-out micro-circuits are implemented on the sensor substrate. Tests of the first prototypes demonstrate that this technology allows to detect m.i.p.s with high performances and is already adapted to rather sizeable radiation fluxes. The main results obtained will be discussed and the current and planned developments will be presented.


Last updated: 23 April 2002, Eduardo Cortina