Showing papers by "Claude Leroy published in 2004"

Hadronic calibration of the ATLAS liquid argon end-cap calorimeter in the pseudorapidity region 1.6 < |$\eta$| < 1.8 in beam tests

Abstract: A full azimuthal φ -wedge of the ATLAS liquid argon end-cap calorimeter has been exposed to beams of electrons, muons and pions in the energy range 6 GeV ⩽ E ⩽ 200 GeV at the CERN SPS. The angular region studied corresponds to the ATLAS impact position around the pseudorapidity interval 1.6 | η | 1.8 . The beam test setup is described. A detailed study of the performance is given as well as the related intercalibration constants obtained. Following the ATLAS hadronic calibration proposal, a first study of the hadron calibration using a weighting ansatz is presented. The results are compared to predictions from Monte Carlo simulations, based on GEANT 3 and GEANT 4 models.

Production and decay of excited electrons at the LHC

Abstract: We study single production of excited electrons at the CERN LHC through contact interactions of fermions. Subsequent decays of excited electrons to ordinary electrons and light fermions via gauge and contact interactions are examined. The mass range accessible with the ATLAS detector is obtained. PACS: 12.60.Rc, 13.85.Rm

Production of Excited Neutrino at LHC

Abstract: We study the potential of the CERN LHC in the search for the single production of excited neutrino through gauge interactions. Subsequent decays of excited neutrino via gauge interactions are examined. The mass range accessible with the ATLAS detector is obtained.

Signals from R-parity violating top quark decays at LHC

Abstract: We evaluate the potential of the CERN LHC collider to observe rare decays of the top quark in channels involving R-parity violating ( ) interactions. We stress the importance of calculating top quark production and decay simultaneously as a true 2→4 process. The process of t pair production followed by decay of one of the top quarks is analyzed with fast detector simulation. We show that intermediate supersymmetric particles can be observed as resonances even if they are heavier than the top quark due to the significant off-shell top quark mass effects. The approach where the top quark is produced on-mass-shell and then decays into 2- or 3-body final state would in general lead to incorrect kinematical distributions and rates. The rates of the 2→4 process with top quark production and 3-body decay depend on the total width of the heavy intermediate sfermion which could, therefore, be measured indirectly. We find that the LHC collider offers a unique potential to study rare top quark decays in the framework of supersymmetry with broken R-parity for branching fractions of top decays as low as 10−6.

Signals from R-parity violating top quark decays at LHC

Abstract: We evaluate the potential of the CERN LHC collider to observe rare decays of the top quark in channels involving R-parity violating (RPV) interactions. We stress the importance of calculating top quark production and decay simultaneously as a true 2->4 process. The process of tt-bar pair production followed by RPV decay of one of the top quarks is analyzed with fast detector simulation. We show that intermediate supersymmetric particles can be observed as resonances even if they are heavier than the top quark due to the significant off-shell top-quark mass effects. The approach where the top quark is produced on-mass-shell and then decays into 2- or 3-body final state would in general lead to incorrect kinematical distributions and rates. The rates of the 2 -> 4 process with top quark production and RPV 3-body decay depend on the total width of the heavy intermediate sfermion which could,therefore, be measured indirectly. We find that the LHC collider offers a unique potential to study rare top quark decays in the framework of supersymmetry with broken R-parity for branching fractions of RPV top decays as low as 10^{-6}

Characterization of the Response of Superheated Droplet (bubble) Detectors

Abstract: The PICASSO project is a cold dark matter (CDM) search experiment relying on the superheated droplet technique. The detectors use superheated freon liquid droplets (active material) dispersed and trapped in a polymerized gel. This detection technique is based on the phase transition of superheated droplets at room or moderate temperatures. The phase transitions are induced by nuclear recoils when undergoing interactions with particles, including CDM candidates such as the neutralinos predicted by supersymmetric models. The suitability of the technique for this purpose has been demonstrated by R&D studies performed over several years on detectors of various composition and volume. Simulations performed to understand the detector response to neutrons and alpha particles are presented along with corresponding data obtained at the Montreal Laboratory.