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Past seminars year 2008-2009 |
| 4thSept 2008 |
High precision measurement of the strong coupling constant αS
with high pT jets in DIS
| talk in pdf
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| 14:30 |
Maxime Gouzevitch (Ecole Polytechnique, Paris) |
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Abstract:
High pT jet production is a well established tool to explore the
perturbative QCD and measure the strong coupling αS. In comparison to
the other standard model couplings parameters, αS is poorly known within
a percent precision, but it plays a fundamental role in high energy
hadron-hadron collisions where the cross section is dominated by the
gluon-gluon interactions.
In ep collisions at HERA the events with at least two jets, in addition
to the proton remnant, in final state are directly sensitive to the
strong coupling intensity and give a handle to the αS(Q) running over
two orders of magnitude in transfer momentum Q. We would show a
preliminary result for an αS measurement from multi-jet rates, where for
the first time in DIS an experimental precision below 1% was achieved.
The analysis is based on the full data sample of nearly 400 pb-1
collected by the H1 experiment between 1999 and 2007.
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| 5thNov. 2008 |
The Relativistic Corrections of Exclusive and Inclusive J/psi production
at B-factories and QCD correction of D-wave Quarkonium Decay
| talk in pdf
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| 14:30 |
Zhiguo He (Peking Univ.) |
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Abstract:
The production and decay of heavy quarkonium are important topics in
heavy quarkonium physics. In recent years, there are two big puzzles about
the double charmonia production and inclusive $J/\psi$ prouction at two
B-factories Babar and Belle. To resolve them, the relativistic effect is
considered in the framework of Non-Relativisitic QCD(NRQCD) effective theory
method. There is also a long-standing problem in the non-$D\bar{D}$ decay of
D-wave dominate charmonium state $\psi(3770)$ measurement by CLEO and BES
collaborations seperately. To clarify this, the light hadron decay channel
is considered at next-to-leading order of $\alpha_{s}$ in the framework of
NRQCD factorization method.
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| 13thNov. 2008 |
High energy scattering processes in QCD
| talk in pdf
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| 11:00 |
Dr. Francesco Caporale (Universita della Calabria, Italy) |
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Abstract:
The BFKL approach in perturbative QCD is the general framework for the
description of hadronic hard processes at high-energy, i.e. in the so called
Regge limit of QCD. The first important success of this theory is the
prediction of the growth of the gluon density in the proton with decreasing
of the fraction of the proton momentum carried by gluons.
In this talk I discuss two physical processes studied entirely within
perturbative QCD in the BFKL approach.
The first analysis concerns the total hadronic cross section for the
collision of two virtual photons for energies in the range of LEP2 and in
the range of future linear colliders. Then I discuss some problems about the
convergence of the BFKL series at the next-to-leading order and I show an
improvement that comes from the collinear factorization approach, that we
tested in the determination of the amplitude of the electroproduction of two
light vector mesons.
A natural development of this works is the study the Mueller-Navelet jets
production amplitude at NLO in BFKL approach.
An other very active field of research is the diffractive production of
vector mesons.
In particular I will talk very briefly about the study of excitated states
and of higher spin states (spin-3 mesons) analysed in the k_t -
factorization approach.
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| 14thNov. 2008 |
Signals from the Universe: from DAMA/NaI to DAMA/LIBRA
| talk in pdf
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| 15:30 |
Dr. Pierluigi Belli (Roma) |
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Abstract:
The highly radiopure about 250 kg NaI(Tl) DAMA/LIBRA set-up is
running at the Gran Sasso National Laboratory of the I.N.F.N..
Results exploiting the model independent annual modulation
signature for Dark Matter particles in the galactic halo are
presented (exposure of 0.53 ton x yr). The DAMA/LIBRA data
confirm the evidence for the presence of Dark Matter particles
in the galactic halo as observed by the former DAMA/NaI experiment.
The combined analysis of the data of the two experiments
(total exposure 0.82 ton x yr) gives a C.L. at 8.2 sigma.
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| 25thNov. 2008 |
Towards the start-up of CMS detector
| talk in pdf
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| 11:00 |
Stephanie Beauceron (CERN) |
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Abstract:
The main current proton collider running so far is the TeVatron at
Fermilab. CDF and D0 detectors are recording events since 2001. D0
took up to 2 years to fully commission the detector. Despite small
changes in the detector itself between RunI and RunII, numerous new
challenges appeared. The lessons learn from the start-up phase of such
detectors are important in order to prepare the start-up of CMS
detector.
In a first part, a quick description of detector problems emerging at
the start-up of D0 detector will be presented. Then, in a second
part, a overview of the status of CMS will be given. CMS has been
design with the purpose of discovering the Higgs via two main
channels: H-->gamma gamma or H-->ZZ*--> 4l. These require a very good
electromagnetic calorimeter. Part of the detector have been exercised
over test beam and allow us to validate calibration methods. Results
from the campaign and its strategy for calibration will be exposed.
Preparation of a detector is not only checking hardware, it is also
preparing tools to perform analysis with the first data. As an
example, identification of electron candidate within a non perfectly
aligned and calibrated CMS detector will be exposed.
The first steps towards discoveries will be to established at 14 TeV
cross section measurement of different Standard Model processes. A
study of diboson production (pp--> WZ -->3lnu) will be presented
with an emphasize on techniques to measure background from data.
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| 16thJan. 2009 |
Building up the HERA legacy: impact on LHC
| talk in pdf
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| 14:30 |
Claude Vallee (CPPM Marseille) |
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Abstract:
The probe of the proton structure and dynamics at the electron-proton
collider HERA is of crucial interest for the predictions of proton-proton
processes at the LHC. The H1 and ZEUS experiments are now in the final
analysis phase of their full data sets and reaching their ultimate
precision to many respects. After a brief summary of the most relevant
investigations of new physics performed at HERA at the high energy
frontier,
the presentation will focus on the latest high-precision measurements
of the proton structure and dynamics and their implications for LHC.
A review of the present limitations on LHC predictions associated to the
parton distributions will be given. The recent breakthrough in precision
on the low-x proton structure, resulting from the combination of ZEUS and
H1 data, will be presented together with its impact on LHC predictions.
Detailed studies of the proton dynamics, especially in the very low-x
regime
where new QCD effects could appear at LHC, will also be addressed.
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| 29thJan. 2009 |
The study of Generalized Parton Distributions
with the CLAS(12) detector of Jefferson Lab.
| talk in pdf
or ppt
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| 14:30 |
Michel Guidal (IPN - Orsay) |
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Abstract:
We will first give an overview of the field of Generalized Parton
Distributions (GPDs) which allow to describe the structure of the nucleon in
a very rich and unprecedented way: they contain the correlations between the
(transverse) position and (longitudinal) momentum distributions of the
partons in the nucleon, they allow to derive the orbital momentum
contribution of partons to the nucleon'spin, they provide an access
to the nucleon's (q\bar{q}) content, etc...
Then, we will present the associated experimental program currently ongoing
with the 6 GeV electron beam of Jefferson Lab (JLab), with its recently
published results on Deep Virtual Compton Scattering, the cleanest
process which allows to access GPDs. We will focus particularly on the program
of the Hall B/CLAS detector and will present its perspectives with respect to
the 12GeV upgrade of JLab, scheduled around 2013/14.
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| 30thJan. 2009 |
Searching for Astrophysical Neutrinos from Gamma-Ray Bursts
| talk in pdf
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| 10:30 |
Dr. Erik Strahler (UW-Madison) |
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Abstract:
Gamma-ray bursts are a leading candidate for the acceleration of the highest
energy cosmic rays. In the case of hadronic acceleration, neutrinos in the TeV
to PeV energy range will be produced through pion and kaon decay and should be
detectable at Earth with an appropriate instrument. IceCube and its
predecessor AMANDA-II are such instruments, designed to collect the Cherenkov
light emitted by daughter particles produced through neutrino interaction in
the deep antarctic ice.
Since December of 2004, the Swift satellite has observed GRBs at an average
rate of one per four days. We present analysis methods and results of searches
for muon neutrinos from 126 of these bursts using the AMANDA-II and IceCube
Telescopes. We place these results in the context of previous searches for
neutrinos from GRBs.
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| 19thFeb. 2009 |
Status and perspectives of gamma-ray astroparticles physics
| talk in pdf
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| 14:30 |
Dr. Bruno Khelifi (LLR - Ecole Polytechnique - Paris) |
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Abstract:
Astroparticle physics is by essence an interdisciplinary field at the
intersection of particle physics and astrophysics. Numerous theoretical
studies and recent technological developments have led to new
generations of detectors and more interestingly new observational
results. Given the broad field of astroparticles, we will focus on
high-energy gamma-ray astrophysics that illustrates well the
astroparticle maturity with tremendous results in astrophysics. A brief
review of this field will be presented with its astrophysics dependency
with other observational probes and we will summarize the future
(European) projects to study key astroparticles topics.
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| 26thFeb. 2009 |
The Double Chooz Experiment and Beyond
| talk in pdf
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| 14:30 |
Mark Dierckxsens (Univ. Chicago) |
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Abstract:
The Double Chooz experiment is designed to search for the last unknown
neutrino mixing angle theta13 using reactor neutrinos. A significant
improvement over the previous experiments is obtained by comparing event
recorded in two identical detectors at different distances from the
reactor cores. The design, physics potential and status of the
experiment which is currently under construction will be discussed. An
observation of a non-zero value of theta13 opens the path to an
ambitious program to study CP violation in the lepton sector and the
mass hierarchy of the neutrinos. One proposal wants to send a neutrino
beam from Fermilab to a large detector at the Homestake mine in South
Dakota. The concept behind such an experiment as well as the expected
sensitivities will be reviewed.
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| 27thMarch 2009 |
Multi parton interactions and underlying events at HERA and LHC
| talk in pdf
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| 14:30 |
Hannes Jung (DESY) |
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Abstract:
The idea behind multiparton interaction is discussed. Experimental
results, which show evidence
for multiparton interaction will be presented and attempts to model
these processes will be discussed.
I will also put emphasis on the impact of HERA results for the
understanding of multiparton interaction .
Prospects of what can be expected at the LHC will be given.
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| 2thApril 2009 |
Preparing ttbar cross section measurement at LHC with CMS
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| 10:30 |
Jeremy Andrea (Universite Louis Pasteur - Strasbourg) |
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Abstract:
The LHC will produce the firsts proton-proton collisions during 2009. In
this context, I'll talk about the preparation of a ttbar cross section
measurement for an integrated luminosity of 100pb-1. In this analysis,
we have taken care of detector effects such as misalignment and
miscalibration. Data driven methods to estimate instrumental backgrounds
were also developed.
The top event selection is finalized with the use of a b-tagging
algorithm which will be briefly presented as well as the methods to
estimate btagging performance from data themself. B-tagging is strongly
related to tracks reconstruction. I'll finally present first results of
track efficiency estimate from (real) cosmic data.
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| 9thApril 2009 |
New detectors for the direct dark matter search EDELWEISS
| talk in pdf
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| 14:30 |
Xavier Defay (CSNSM - Orsay) |
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Abstract:
Understanding the nature of non-baryonic dark matter is one of the most
fascinating and challenging goals of modern physics. WIMP (Weak Interactive
Massive Particle) direct detection experiments such as EDELWEISS test the
hypothesis that dark matter is made up of particles (neutralino) predicted by
the supersymmetry and having an interaction cross-section with the nucleon of
about 10-8 picobarn. For that purpose, EDELWEISS uses ultrapure cryogenic
germanium detectors combining ionisation and heat measurements. This allows the
discrimination between nuclear recoils as expected for WIMPs and the electronic
recoils induced by the particles of the radioactive background. The main
limitation of this technique comes from events close to the detector surface
that mimic nuclear recoils. The solution presented here is based on a coplanar
grid technique for surface event identification with ionization signals. I will
present the principle of this type of detector
and its study: tests with different radioactive sources in a surface
laboratory and in the site of the experiment in the Modane underground
laboratory (LSM). The obtained gamma and surface event (beta) rejection
demonstrates the possibility to reach at least 10-8 picobarn in the frame of
the EDELWEISS II experiment which chose to use this type of detector for the
future
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| 23thApril 2009 |
Accelerator physics and the LHC
| talk in part1-pdf, part2-pdf
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| 15:00 - 17:30 |
Dr. Django Manglunki (CERN) |
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Abstract: The lecture is given in two parts:
1) Introduction to accelerator physics: a few selected notions (transverse & longitudinal stability,
emittance, beta functions, transition energy)
2) The LHC injector chain
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| 18thJune 2009 |
Search for a standard Higgs boson in the WH channel in the D0 experiment
AND
Preparing ATLAS for the SuperLHC: studies for the pixel vertex detector
| talk in pdf
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| 14:30 |
Dr. Jeremie Lellouch (LPNHE, Paris) |
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Abstract:
The first part of this seminar will start with a brief theoretical and
phenomenological introduction to the Higgs boson, showing that Higgs
production along with a W boson is the most sensitive channel at the
Tevatron. It is therefore the analysis strategy in this channel that will
be detailed. Recent developments will be shown, with emphasis on the use
of high-sensitivity-bringing optimisations and advanced analysis
techniques, and the current sensivity of this particular channel will be
discussed. The latest Tevatron Higgs combination, resulting in the first
95% confidence-level exclusion of a Higgs boson since the LEP era, will beshown, along with future prospects as regards its capabilities in
excluding and evidencing a standard Higgs boson.
The second part of the seminar will address the ATLAS detector and the
on-going upgrade program targetting the SuperLHC era. ATLAS in one of the
two general physics detectors present at the LHC. Once in operation, the
LHC will deliver high-energy, high-luminosity collisions, making it a tool
of choice for such various domains as Higgs searches, Standard Model
precision measurements and new physics searches. It will be superseded
around 2020 by the SuperLHC, a higher-luminosity upgrade of the collider.
Detectors have to be upgraded accordingly to accommodate the higher
luminosity and deliver optimum performance. The focus of this presentation
will be the pixel vertex detector. First, studies on the future
sub-system's geometry and its performance in terms of track resolution and
b-tagging will be presented. Other studies on thermal characterisation of
future detector elements will also be shown.
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| 29thJune 2009 |
Study of Very High Energy Gamma Ray Emission from TeV Blazars
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| 14:30 |
Dr. Debajan Bose (Universidad Complutense, Madrid) |
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Abstract:
I will talk about VHE gamma ray observations of blazars. I will briefly
describe Pachmarhi array of Cherenkov telescope (PACT). After that I will
talk about simulations which were carried out for PACT. Then I will show
the results of 4 blazars, which were observed using PACT. I will also
present results of a multiwavelength campaign for Mkn 421, involving
gamma-ray,X-ray and optical telescope. I will also talk about our work
on comparison of variability of AGN in soft and hard X-ray bands.
Finally I will talk about
AGN analysis I am doing in Madrid group for the MAGIC collaboration.
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Past seminars in:
[2003-2004]
[2004-2005]
[2005-2006]
[2006-2007]
[2007-2008]
[2008-2009]
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