Base de données PIC07

Table des POSTERS



University of Delhi

We present simulation results of $\gamma$ + Jet analysis using CMS (Compact Muon Solenoid) Object-Oriented software at the LHC center of mass energy ($\sqrt{s}$=14 TeV). The study of direct photon production helps in validating the perturbative quantum chromodynamics (pQCD) and constraining the gluon distribution of nucleons. Direct photon processes also represent a major contribution in estimating background to other Standard Model (SM) processes and signals of new physics. Thus these processes need to be understood precisely in the new energy regime mentioned above. In this work, we have done a detailed study of the complete GEANT4 simulated events of $\gamma$ + jet generated with Pythia and the related background processes at $\sqrt{s}$=14 TeV. Isolation cuts have been defined for the direct photon which improves the signal to background ratio by $\sim25\%$ as compared to previous studies done in CMS. This details of this work can be seen in CMS NOTE 2007/004.



LAPP/Université de Savoie/in2p3/CNRS

We present here the results of our first study on the determination of the effective weak mixing angle from the measurement of the Forward-Backward Asymmetry in Z-->e+e- events at LHC. The statistical precision (10^-4) on $\sin^{2}\theta^{lept}_{eff}$ found is better than the current results. To reach such a precision it will be necessary to identify the electrons in the forward region of the ATLAS detector with an efficiency better than 50% and an electron-jet rejection more than 100.



Institute of Nuclear Physics PAN

Title: Study of four-fermion neutral currents processes in the DELPHI experiment at LEP. Abstract: The four-fermion neutral currents processes were studied in the DELPHI experiment at LEP collider. The results are based on data collected in 1997-2000 at the energy range 183-209 GeV. The final results for ZZ pair production and single Z/$\gamma^*$ production were already published. The results of the analysis of $Z \gamma^*$ production and study of anomalous triple neutral bozon couplings are submitted and accepted for publication respectively. Within the expermental uncertainties, the results confirm the predictions of the electroweak theory.



Politecnico di Torino

Non-conventional statistical effects in high energy heavy-ion collisions Starting from the presence of non-ideal plasma effects due to strongly coupled plasma in the early stage of relativistic heavy-ion collisions, we investigate, from a phenomenological point of view, the relevance of non-conventional statistical mechanics effects on the interpretation of the experimental observables in relativistic heavy-ions collisions. We study the relativistic thermodynamics and the equation of state in the hadronic and in the quark-gluon plasma phase in the framework of the generalized non-extensive thermodynamics, strictly connected to the presence of long range forces, memory effects. In this context, we show that the broad rapidity shape measured at RHIC can be very well reproduced in the framework of a non-linear relativistic Fokker-Planck equation which incorporates non-extensive statistics and anomalous diffusion.


Duc Ninh


We consider the mechanism to produce the SM Higgs associated with a bottom-antibottom pair at the Large Hadron Collider (LHC), in particular we investigate the one loop electroweak correction to the process $gg\rightarrow b\bar{b}H$ in the SM. We find that the NLO electroweak correction to the total cross section at the tree level is small, about $-3\%$ if the Higgs mass is $120$GeV. In the limit of vanishing bottom Yukawa coupling the cross section is generated solely at the loop level. This contribution is very small at $M_H\sim 120$GeV and increases with growing Higgs mass, reaching about $+17\%$ of the total cross section when the Higgs mass is about $150$GeV.


Ana Amelia


In this work the S-wave component of the $K\pi$ amplitude from decay of $D^+\to K^-\pi^+\pi^+$ it is directly measured. The data come from the Fermilab E831/FOCUS experiment. The amplitude measurement is made using the partial wave analysis without any preliminary assumption about the nature of the S-wave component of the $K\pi$ system. The phase and magnitude of the S-wave amplitude are generic functions to be determined directly through the Dalitz plot fit. For the sake of comparison, our results the same decay is analised using the isobar model, which is the standard way to analise the Dalitz plot. The data fit obtained with the partial wave analysis is better than the data fit from the isobar model. The phase variation with respect to the invariant mass $K\pi$ is compared with the measurement of the phase $\delta_{I=1/2}^0 (m_{K\pi})$ from $K\pi\to K\pi$ scattering. The difference between both analysis is discussed considering: a difference in the composition of the isospin components I=1/2 and I=3/2 of the $K\pi $ system between $D^+$ decay and the $K\pi\to K\pi$ scattering; and the final state interaction involving all particles from decay.



ICEPP, The university of Tokyo

In the end cap region of the ATLAS muon detector, the technology of TGC (Thin Gap Chamber) is placed for triggering high momentum muons because of its high rate capability and fast response to identify the crossing bunch of LHC. TGC is assembled as 6 wheels having diameter of 25m, and each wheel consists of 12 sectors. In total 72 sectors are assembled on surface building at CERN and its scheme and summary of test results against 320k channels are presented. Also the the readiness of both detector and electronics to work as LVL1 muon trigger system is shown throught the result of TGC wheel commissioning with using cosmic-ray in the pit.



COMSATS Institute of Information Technology, Islamabad

Percolation cluster formation at ultrarelativistic heavy ion collisions. M. K. Suleymanov, E. U. Khan, K. Ahmed, M. Q .Haseeb, F. Tahir, Ya. H. Huseynaliyev Department of Physics COMSATS Institute of Information Technology We discuss that the experimental study of percolation cluster formation and appearance of the critical transparency of the strongly interacting matter can give the information about the onset state of the deconfinement.


Thi Nguyet

Centre de Physique des Particules de Marseille

Searches for New Physics at HERA The high energy program of the HERA ep collider ended in march 2007. Along the whole HERA program, a total integrated luminosity of around 0.5 fb-1 has been collected by the H1 experiment. In this context, the most recent results from H1 about searches for new phenomena will be presented. New searches for excited electrons and neutrinos have been performed using the complete HERA I and II data samples and the limits derived are presently the most stringent for high mass excited leptons, in good complementarity with Tevatron and LEP results. Isolated lepton and multi-leptons topologies have also been investigated using the full H1 luminosity. An excess of events containing isolated high transverse energy electrons or muons and large missing transverse momentum compared to the Standard Model prediction is observed in the $e^{+}$ data. At large hadronic transverse momentum $P_{T}^{X} >$ 25 GeV, it corresponds to a "3 $\sigma$" deviation. Finally, all event topologies involving isolated electrons, photons, muons, neutrinos and jets with high transverse momenta have been investigated in a model-independent search. Deviations from the Standard Model prediction have been looked for and quantified using a dedicated statistical algorithm. This is the broadest range signature based search done at a collider.



Soltan Institute for Nuclear Studies, Warsaw

"A study of angular correlations in H->ZZ->4l" This poster shows a study of a possible measurement at the CMS detector of the CP-parity of the Higgs boson coupling HZZ. The study is performed using angular correlations in the H->ZZ->2e2mu process, which is a "golden plated channel" for Higgs boson searches at LHC. It is shown that a measurement of the xi-parameter describing a generalized HZZ coupling will be feasible at CMS. The precision of the measurement is sufficient for determination of CP-parity of the Higgs boson, in particular to distinguish between the scalar and pseudoscalar Higgs bosons.



Centro de Física Teórico e Computacional da Universidade de Lisboa

We study the effects of dimension six effective operators on the flavour violating production and decay of leptons at the International Linear Collider. We present an analysis of the feasibility of their observation at the ILC.




Indirect searches for Dark Matter with AMS02 : AMS02 is a multi-purpose spectrometer with superconducting magnet, designed for 3 years of data taking abroad the international Space Station. Its high performance regarding particle identification and energy measurement will allow performing indirect searches for dark matter (DM) in different channel simultaneously: gamma rays, positrons, antiprotons and hopefully antideuterons. A new spectrum generator, based on the public package micrOMEGAs is being developed for the computation of those signals. It includes cross section computations, dark halo modelling and charged particles Galactic propagation handle. This tool is presented, together with a novel method for the quantitative prediction of boost factors. These are expected to be caused by DM substructures, a specific class of which is considered. We show that DM spike formation around intermediate mass black holes can lead to dramatic enhancement of the signals. These studies allow to determine the AMS02 sensitivity to new physics, which is eventually presented.



New Mexico State University

The data collected from the collision of polarized protons at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory is just beginning to yield results, particularly in constraining the gluon contribution to the spin of the proton. After a long program of commissioning the injection, storage, acceleration and manipulation of polarized protons in the two storage rings, the main course of physics results will now begin to become available in the next few years. The upcoming spin physics program at RHIC will explore: the polarization of glue in the proton via the production of pions, heavy flavor, jets and prompt photons, including di-jet and $\gamma$-jet correlations; the polarization of $u$, $\bar{u}$ $d$ and $\bar{d}$ quarks via $W$-production in $pp$ collisions at $\sqrt{s}=500$ GeV, as well as via the Drell-yan process and the production of prompt $\gamma\gamma$ pairs; and a wide range of transverse spin phenomena. This program of measurements, to be completed by 2012, will provide a wealth of data on polarized parton distribution functions and address other critical issues in nucleon structure.




"Implementation and performance of the Tau Trigger in the ATLAS experiment" Triggering with hadronic taus at the LHC is a difficult task due to the high rate and occupancy of the events. However, it is worth to trigger on taus. This trigger is used in many physics channels such as VBF H->tau tau, charged Higgs, etc. In order to select these events, the tau vertical trigger is organized in three trigger levels: first (LVL1), second (LVL2) and third (Event Filter -EF-) level triggers. The LVL1 trigger is hardware based and identifies a narrow jet in the calorimeter. It reduces the rate of accepted tau candidates from 40 MHz to about 1 kHz. Both LVL2 and EF are software based triggers which select tau candidates analyzing calorimeter clusters and tracks reconstructed in the inner detector. The goal of LVL2 and EF in the tau slice is to reduce the event rate to about 10 Hz. This contribution will present a detailed description of the algorithms used in the tau trigger and their performance in terms of event rates, signal efficiency and timing. Different run conditions will be considered, including luminosity and occupancy of the detector. The effects in relevant physics and background samples will be evaluated.



University of Cambridge

LHCb, one of the experiments of the Large Hadron Collider at CERN, has been designed for the purpose of high-precision measurements of the parameters of the CKM quark-mixing matrix, and for studies of rare B-hadron decays. An essential part of the experiment is an efficient system of particle identification, effective over a momentum range of ~1 to ~150 GeV/c. For this we use a set of two ring imaging Cherenkov detectors and three Cherenkov radiators: C4F10 and CF4 gases, and Silica aerogel. Cherenkov photons in a wavelength range of 200-600nm are to be detected by 484 Hybrid Photon Detectors (HPDs), each consisting of 1024 pixels and covering a total area of 2.6m**2, in four planes. The general status of the LHCb RICH detectors will be described, and the work in progress on commissioning and preparing for LHC beam and data-taking will be summarized.



On behalf of the ATLAS H->4l Analysis Group. Actual Speaker to be nominated.

The ATLAS detector, currently being installed at CERN, is designed to search for new physics and to make precise measurements, by colliding proton beams at the unprecedented center of mass energy of 14 TeV at the Large Hadron Collider (LHC). Central to these searches is the discovery of the Standard Model Higgs boson, one of the most striking experimental signatures of which is the production of four isolated prompt charged leptons. In this paper, the Standard Model Higgs boson discovery potential through its observation in the H->ZZ*->4-lepton (electron and muon) final state is investigated in a wide mass range, starting from 120 GeV/c2. The trigger, offline identification and precise momentum measurement of leptons are performed using the combined information from the inner tracker and the muon spectrometer, and of energy deposition measurements in the calorimeters. The performance of the relevant sub-detectors is studied through a Geant4 based simulation of the ATLAS detector, including samples of signal and background processes. The selection analysis is performed by exploiting various techniques, in order to obtain optimal discrimination between the signal and background processes. The impact of a misaligned/miscalibrated detector and the effects of pile-up and cavern background on the analysis performance are also investigated.

De La Cruz Burelo


University of Michigan

B Physics at Dzero We present the latest results on B physics from the D0 collaboration at the Tevatron collider. The large cross-section of b quark production and the diversity of b hadron species available at the Tevatron energy allow the D0 collaboration to perform exciting measurements such as lifetimes, mixing, and rare decay studies. In many cases these are either world's first or world's best measurements.




The CMS electromagnetic calorimeter (ECAL) comprises about 76000 Lead Tungstate scintillating crystals. The barrel part of ECAL consists of 36 supermodules, each containing 1700 crystals . During summer 2006, nine of these supermodules were exposed to an electron beam, allowing us to determine initial intercalibration coefficients for all their crystals. Different methods of intercalibration based either on single crystal response or on matrices of crystals (as will be used in CMS) have been used and compared. The calorimeter response and the energy resolution have been measured over the whole area of the supermodules. These measurements will be presented, showing that the calorimeter performance is in agreement with the design resolution.



Faculty of Nuclear Sciences and Physical Engineering

One of the many phenomena to be studied on the LHC is the proton-antiproton asymmetry in heavy-ion and pp collisions. We will be able to study proton stopping in the collision and their emission in plane perpendicular to the beam axis. Measurement of this observable will be possible with the upcoming ALICE detector at energies up to 14 TeV in pp and 5.5 ATeV in Pb-Pb collisions. Before the detector will be ready, simulations are done in the AliRoot framework. During this preparation for the real data, proper analysis tools have to be ready. Predictions of the value of proton-antiproton yields asymmetry can be made.



Technion, Israel Institute of Technology

We present a new measurement of the Lambda_b lifetime through the exclusive decay channel Lambda_b to J/psi(mu+ mu-)Lambda(p pi-) and a complementary measurement of the B0 lifetime in the decay B0 to J/psi(mu+mu-)K0_S(pi+pi-). We also present the lifetime ratio of tau(Lambda_b)/tau(B0) based on these results. The measurement was done in the D0 experiment, based on an integrated luminosity of 1.2 fb-1. The measurement of the b hadron lifetime is very important to understand the influence of the light quarks in b hadron decays. At the leading order, Heavy Quark Effective Theory predicts the lifetime of all b hadrons to be the same, since the light quarks are considered spectators. Including the interactions between the b quark and the light quark, the lifetime of b hadrons should satisfy the following relation: tau(B+)>=tau(B0)~tau(B_s)>tau(Lambda_b)>>tau(B_c). We found that the measurement of the Lambda_b lifetime is consistent with the world average and the ratio of Lambda_b and B0 lifetimes is consistent with the most recent theoretical predictions.



Faculty of nuclear sciences and physical engineering, Czech technical university

Currently, the most successful particle theory is Standard Model. It explains the basic phenomena of interactions between particles. Almost all particle physics experiments are dedicated to the verification or even extension of this model. The Standard Model will be tested in new energetic region in experiments at the LHC in near future. Very important process for such tests is Z boson production. Both components of Standard Model (QCD and GWS theory) will be tested. Mainly, we will insist on the Drell-Yan production of lepton pair via Z boson. Appropriate theoretic framework is also presented for better understanding of the whole process. This work is devoted to the study of kine- matic variables of Z boson created in pp interactions on kinematic cuts applied on its secondaries. The invariant mass, rapidity and transverse momentum were chosen as representative variables for this process. Decay channel Z-> e+e- is investigated.



Indiana University Cyclotron Facility

Dissecting the Proton's Spin with Polarized Proton Collisions at RHIC -- In addition to discovering a new form of matter in Au-Au collisions the Relativistic Heavy Ion Collider is also the world's first polarized proton collider. An important part of the program is to investigate the polarization of the partons in the proton via hard partonic scattering. Spin dependent inclusive jet yields from such scattering are sensitive to the gluon polarization via quark-gluon and gluon-gluon scattering. Results from 2005 at root(s)=200 GeV for inclusive jets from STAR and inclusive pi0s from Phenix are beginning to provide new significant constraints on deltaG, the first moment of the gluon helicity distribution. Increased luminosity, polarization and detector coverage in 2006 will allow a first glimpse of the x dependence of deltaG via particle correlation measurements such as di-jets and photon-jets. Results from 2005 and progress on 2006 analyses will be presented.



Queen's University

The Status of SNOLAB, a new international facility for underground science. A new facility for astroparticle physics, SNOLAB, is currently nearing completion. This new facility will provide the infrastructure support required for next generation solar neutrino detectors, dark matter search experiments and neutrinoless double beta decay detectors. The status of this facility, the physics scope being targeted, the infrastructure available, and the initial physics program under consideration will be presented.



LAPP, Annecy

We present the update of the Unitarity Triangle analysis in the Standard Model. Combining the direct measurements on sides and angles of the Unitarity Triangle, we determine the values of the CKM parameters rhobar and etabar. We discuss the agreement of the current measurements and the indirect determinations from the rest of the fit. Then we generalize the analysis to account for the presence of physics behyond the Standard Model. We discuss the current model-independent bounds on NP contributions to K-Kbar, D-Dbar and Bq-Bq bar (q=d,s) mixing processes. This information is then translated into a lower limit on the probed scale of New Physics. We consider several scenarios, such as a New Physics with generic flavour structure, NMFV, as well as MFV with low, moderate or large values of tanbeta.



LPHEA, Cadi-Ayyad University

Title: Charged Higgs Bosons decays H^\pm \to W^\pm (\gamma, Z) in MSSM. ************************************************************************************************************************ We study the complete one loop contribution to $H^\pm\to W^\pm V$, $V= Z, \gamma$, in the Minimal Supersymmetric Standard Model (MSSM). We evaluate the MSSM contributions taking into account $B\to X_s\gamma$ constraint as well as experimental constraints on the MSSM parameters. We found that in the intermediate range of $\tan\beta \la 10$ and for large $A_t$ and large $\mu$, where lightest stop becomes very light and hence squarks contribution is not decoupling, the branching ratio of $H^\pm \to W^{\pm} Z$ can be of the order $10^{-3}$, while the branching ratio of $H^\pm \to W^{\pm} \gamma$ is of the order $10^{-5}$. We also discuss the impact of the CP violating phases of Soft SUSY parameters and show that they can modify the branching ratio by about one order of magnitude. ***************************************************************