Search for gluinos with ATLAS at LHC

Prospects for ATLAS observation of a SUSY-like signal from two gluinos are investigated within a certain region of the mSUGRA parameter space, where the cross section of the two gluinos production via gluon-gluon fusion is estimated at a rather high level of 13 pb. The event selection trigger uses a very clear signature of the process (4 jets + 4 muons + up to 4 secondary vertices topology) when final decay products of each gluino are b-anti-b and muon-anti-muon pairs and the lightest SUSY particle, the neutralino. Rather high transverse missing energy carried away by two neutralinos is an essential signature of the event and also allows the relevant Standard Model background to be reduced significantly. The generation and reconstruction processes are performed by means of the ATLAS common software framework ATHENA.Comment: LaTeX, 9 pages, 7 eps figure

Study of TileCal Sampling Fraction for Improvement of Monte-Carlo Data Reconstruction

In this work we made a detailed calculation of Tile Calorimeter Sampling Fraction parameter (TSF) using single electron and pion Geant4 Monte-Carlo simulation of ATLAS hadronic calorimeter (TileCal) within ATHENA --- common software framework of ATLAS. Our study was based on MC Truth data provided by special Geant4 MC simulation objects --- Calibration Hits, design which was implemented in TileCal simulation by our group. We used this TSF value for reconstruction of TileCal single pions simulation data. It was done for ATLAS Combined test beam 2004 (CTB2004) configuration setup. Results of the reconstruction were compared with MC Truth and CTB2004 reconstructed experimental data. Good agreement between them shows quite evident improvement in TileCal MC data reconstruction of hadronic shower energy in electromagnetic scale

Production of (super)heavy quarkonia and new Higgs physics at hadron colliders

Based on the two Higgs doublet model, we study the effect of Higgs-boson exchange on the (super)heavy quarkonium \bar QQ, which induces a strong attractive force between a (super)heavy quark Q and an antiquark \bar Q. An interesting application is the decay of (super)heavy quarkonia \bar QQ into a Higgs boson associated with gauge bosons. The criterion for making the \bar QQ bound state is studied. We also show that non-perturbative effects due to gluonic field fluctuations are rather small in such a heavy quark sector. Possible enhancement for productions and decays of \bar QQ bound states made from the fourth generation quark Q is discussed for \bar p p (at the Tevatron) and pp (at the LHC) collisions.Comment: 18 pages, REVTeX, 9 figures. V2: minor changes, references and acknowledgments adde

Study of the Transition Effect with the ATLAS Tile Calorimeter

With the aim to establish the electromagnetic energy scale of the ATLAS Tile calorimeter and understanding the performance of the calorimeter to electrons 12% of modules have been exposed in electron beams with various energies. On a basis of the obtained electromagnetic calibration constants we have determined the e/mip values in dependence of the absorber thickness using different beam incident angles. We have observed the transition effect (e/mip < 1) and, for the first time, its behaviour as a function of the absorber thickness --- the e/mip ratio decreases logarithmically when the absorber thickness increases this is well described by the GEANT4 version 6.2 Monte Carlo simulation. These results are important for precision electromagnetic energy scale determination for the ATLAS Tile calorimeter

Prospects for K+→π+ννˉK^+ \to \pi^+ \nu \bar{ \nu } at CERN in NA62

The NA62 experiment will begin taking data in 2015. Its primary purpose is a 10% measurement of the branching ratio of the ultrarare kaon decay $K^+ \to \pi^+ \nu \bar{ \nu }$, using the decay in flight of kaons in an unseparated beam with momentum 75 GeV/c.The detector and analysis technique are described here.Comment: 8 pages for proceedings of 50 Years of CP

Measurements of Higgs boson production and couplings in diboson final states with the ATLAS detector at the LHC

Measurements are presented of production properties and couplings of the recently discovered Higgs boson using the decays into boson pairs, H →γ γ, H → Z Z∗ →4l and H →W W∗ →lνlν. The results are based on the complete pp collision data sample recorded by the ATLAS experiment at the CERN Large Hadron Collider at centre-of-mass energies of √s = 7 TeV and √s = 8 TeV, corresponding to an integrated luminosity of about 25 fb−1. Evidence for Higgs boson production through vector-boson fusion is reported. Results of combined fits probing Higgs boson couplings to fermions and bosons, as well as anomalous contributions to loop-induced production and decay modes, are presented. All measurements are consistent with expectations for the Standard Model Higgs boson

Standalone vertex finding in the ATLAS muon spectrometer

A dedicated reconstruction algorithm to find decay vertices in the ATLAS muon spectrometer is presented. The algorithm searches the region just upstream of or inside the muon spectrometer volume for multi-particle vertices that originate from the decay of particles with long decay paths. The performance of the algorithm is evaluated using both a sample of simulated Higgs boson events, in which the Higgs boson decays to long-lived neutral particles that in turn decay to bbar b final states, and pp collision data at √s = 7 TeV collected with the ATLAS detector at the LHC during 2011

Single hadron response measurement and calorimeter jet energy scale uncertainty with the ATLAS detector at the LHC

The uncertainty on the calorimeter energy response to jets of particles is derived for the ATLAS experiment at the Large Hadron Collider (LHC). First, the calorimeter response to single isolated charged hadrons is measured and compared to the Monte Carlo simulation using proton-proton collisions at centre-of-mass energies of sqrt(s) = 900 GeV and 7 TeV collected during 2009 and 2010. Then, using the decay of K_s and Lambda particles, the calorimeter response to specific types of particles (positively and negatively charged pions, protons, and anti-protons) is measured and compared to the Monte Carlo predictions. Finally, the jet energy scale uncertainty is determined by propagating the response uncertainty for single charged and neutral particles to jets. The response uncertainty is 2-5% for central isolated hadrons and 1-3% for the final calorimeter jet energy scale.Comment: 24 pages plus author list (36 pages total), 23 figures, 1 table, submitted to European Physical Journal