S?minaire de physique corpusculaire
Le s?minaire de DPNC tient lieu le mercredi a 17.00 heures (chaques
deux semaines) dans l'auditoire St?ckelberg
Semestre d' ete 1999-2000
Prof. Alan Litke, University of California Santa
Cruz: What Does the Eye Tell the Brain?: A High Energy Physicist
Enters the World of Neurobiology."
After a brief introduction to vision, I will describe a system we are developing
to study how the retina processes and encodes visual images. The "Retinal
Readout System" will allow the simultaneous detection of signals from hundreds
of output neurons in a living retina as it responds to a dynamic visual
image focused on the input neurons. The correspondence between these output
signals and the visual stimulus will help us understand the code that the
eye uses to send information about the visual world to the brain. This
system will be based, in part, on the silicon microstrip detector technology
and expertise developed for the study of short-lived particles in high
energy physics experiments.
Prof. Fyodor Tkachov: A Systematic Theory
of Jet Definition
The talk is an overview of the systematic theory of jet definition developed
recently (hep-ph/9901444, revision Jan. 2000) from first principles of
physical measurements and QCD. The resulting jet definitions are naturally
interpreted as cone algorithms with dynamically determined cone shapes
and entirely based on shape observables that generalize the venerable thrust,
thus being superbly ameanable to theoretical studies. Furthermore, the
proposed algorithms solve the fundamental problem with the conventional
algorithms (i.e. a vicious circle in the definition due to a lack of principles
to fix initial cone configuration/recombination order). A fast and robust
fortran code is available from http://www.inr.ac.ru/~ftkachov/projects/jets/index.htm.
The theory offers new options: a model independent tool for a quantitative
description of hadronization effects and the option of multiple jet configurations
(which physically corresponds to non-uniqueness of inversion of hadronization).
Dr. Szymon Gadomski, CERN-EP Division: Measurement
of the b-quark fragmentation fractions in p-pbar collisions at sqrt(s)
= 1.8 TeV
The CDF experiment has measured the probability of b quark to form B0s,
B0d or B+. This probabilities, known as the fragmentation fractions, have
not been measured in hadron collisions before. The measurement is also
interesting because of the new technique of reconstructing B mesons - using
sequential di-muon decays. The talk will present a brief overview of the
technique and the obtained result.
Dr. Alessandra Filippi,
INFN Torino: Experimental Results on Strangeness Production in Nucleon-Antinucleon
The latest generation of LEAR Experiments has provided
a wealth of high statistics data for the study of open and hidden strangeness
production in antinucleon-nucleon annihilation at rest and in flight a
low momenta. Many observations, performed in several final states and in
different experimental conditions, have shown the presence of anomalous
effects which cannot be accounted for by the simple naive Quark Model;
among them, an abundant production of phi meson evident in many annihilation
channels, which implies a dramatic OZI rule violation. For a more satisfactory
interpretation of the observed effects the formulation of new models
is required. One of the most appealing suggests the presence in the nucleon
wave function of a negatively strange quark condensate, whose effects could
be significant even at low energies. A review of the latest experimental
results from LEAR by will be reported,
and their possible interpretation in the frame
of some recently proposed models will be discussed.
Dr. Yannis Karyotakis,
LAPP Annecy: L'experience BaBar, Mesure de la Violation de CP
BaBar is running since a year now and has collected
more than 7 fm^-1 of data. The detector status and performances will be
presented together with preliminary analyses results, showing the capability
of the experiment to measure reliably sin(2 beta) in the very near future.
Plans for further CP measurements will be discussed and compared with expectations
of other experiments.
Prof. Andre Rubbia, ETH Zurich:
of the ICANOE Project
Semestre d' hiver 1999-2000
Dr. Lydia Fayard, LAL-Orsay: La mesure
de la Violation Directre de CP avec l' Experience NA48 au CERN
L'experience NA48 a annonce en Juin dernier son premier resultat concernant
la mesure de Re(epsilon'/epsilon). Lors de ce seminaire nous parlerons
des aspects experimentaux de NA48 ainsi que de l'analyse qui a conduit
a cette mesure.
Dr. G. Ambrossi, University of Geneva: Search
for anti-matter and geomagnetic effects on trapped particles with the AMS-01
The AMS experiment is a magnetic spectrometer designed and constructed
to measure charged particles in space. The detector used a permanent magnet
together with a precision silicon tracking detector, time-of-flight counters
and areogel counters. The first 10-day mission of AMS took place on June
2, 1998 on board the NASA space Shuttle Discovery. The construction of
the AMS detector, results on the anti-matter search and geomagnetic effects
on trapped particles will be presented.
Dr. Nikos Konstantinidis, University of California
Santa-Cruz: LEP up to 202 GeV - Anything new?
At the end of a very successful year, the four LEP experiments presented
last November the results from a first look at the data up to 202GeV. I
will review their findings, focussing on the issues left to be clarified
(with an "insider's" view for some of them), and discuss the implications
for HEP and the future prospects.
Prof. Jhon Carr, CPPM Marceille: ANTARES:
An Undersea Neutrino Telescope
The ANTARES Collaboration is in the process of building an Undersea Neutrino
Telescope in the Mediteranean Sea 40km offshore from Toulon, France. The
first R&D phase of the project is now finished and the construction
of a 0.1km2 surface area detector is started. The talk will report on results
from the site measurements of the first phase of the program and discuss
the scientific and technical aims of the second phase. The ultimate aims
of ANTARES are exploration of the universe using the new "messanger" of
neutrinos compared to the traditional messanger of photons of different
wavelengths. Indirect searchs of dark matter in the form of relic neutralinos
trapped in massive bodies will be possible with the same detector, as will
measurements of oscillations of atmospheric neutrinos.
Prof. Geoffrey Taylor, Melbourne: BELLE
- a search for CP violation in B-meson decays
Symmetries of nature have successfully guided our understanding of the
constituents of matter and their interactions. The symmetry between particles
and anti-particles is described by the CP invariance of their interaction.
CP invariance is known to be a very good symmetry of nature but not a perfect
one. CP violation, first seen in the decays of neutral K-mesons in the
early sixties, has only been seen in that process. An understanding of
the dominance of matter over anti-matter in our universe demands a more
significant violation of this symmetry than is seen in the Kaon system.
In the standard model of particle physics large CP violation is expected
in B-meson decays. This talk will give an overview and status of one of
the major efforts to discover and precisely measure CP violation in B-mesons.
The BELLE experiment at the Japanese KEK laboratory's KEKB colliding beam
was commissioned in 1999. This talk will describe the experiment and give
a progress report on its commissioning.
Dr. Manel Martinez, IFAE - Universitat Autonoma
de Barcelona: Gamma ray astronomy with the MAGIC telescope
MAGIC, which stands for a "Major Atmospheric Gamma Imaging Cherenkov" is
a telescope which will see its first light in summer 2001 in the "Roque
Muchachos" observatory in the "La Palma" Canary Island. The main aim
of this project is opening an unexplored window in Gamma Ray Astronomy.
The present status of this field as well as the physics motivation for
MAGIC, its observational principles and its main technical challenges will
Last updated: 25 November
1999, Ilias Efthymiopoulos