4,557 research outputs found
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
Artificial Neural Networks for reconstruction of energy losses in dead materials between barrel LAr and Tile calorimeters: exploration and results
In the course of computational experiments with Monte-Carlo events for ATLAS Combined Test Beam 2004 setup Artificial Neural Networks (ANN) technique was applied for reconstruction of energy losses in dead materials between barrel LAr and Tile calorimeters (Edm). The constructed ANN procedures exploit as their input vectors the information content of different sets of variables (parameters) which describe particular features of the hadronic shower of an event in ATLAS calorimeters. It was shown that application of ANN procedures allows one to reach 40% reduction of the Edm reconstruction error compared to the conventional procedure used in ATLAS collaboration. Impact of various features of a shower on the precision of reconstruction is presented in detail. It was found that longitudinal shower profile information brings greater improvement in reconstruction accuracy than cell energies information in LAr3 and Tile1 samplings
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
Electromagnetic Cell Level Calibration for ATLAS Tile Calorimeter Modules
We have determined the electromagnetic calibration constants of 11% TileCal modules exposed to electron beams with incident angles of 20 and 90 degrees. The gain of all the calorimeter cells have been pre-equalized using the radioactive Cs-source that will be also used in situ. The average values for these modules are equal to: for the flat filter method 1.154+/-0.002 pC/GeV and 1.192+/-0.002 pC/GeV for 20 and 90 degrees, for the fit method 1.040+/-0.002 pC/GeV and 1.068+/-0.003 pC/GeV, respectively. These average values for all cells of calibrated modules agree with the weighted average calibration constants for separate modules within the errors. Using the individual calibration constants for every module the RMS spread value of constants will be 1.9+/-0.1 %. In the case of the global constant this value will be 2.6+/-0.1 %. Finally, we present the global constants which should be used for the electromagnetic calibration of the ATLAS Tile hadronic calorimeter data in the ATHENA framework. These constants are equal to 1.15 pC/GeV in the case of the flat filter method and 1.04 pC/GeV for the fit one
Design and construction of new central and forward muon counters for CDF II
New scintillation counters have been designed and constructed for the CDF
upgrade in order to complete the muon coverage of the central CDF detector, and
to extend this coverage to larger pseudorapidity. A novel light collection
technique using wavelength shifting fibers, together with high quality
polystyrene-based scintillator resulted in compact counters with good and
stable light collection efficiency over lengths extending up to 320 cm. Their
design and construction is described and results of their initial performance
are reported.Comment: 20 pages, 15 figure
Anomalously interacting new extra vector bosons and their first LHC constraints
In this review phenomenological consequences of the Standard Model extension
by means of new spin-1 chiral fields with the internal quantum numbers of the
electroweak Higgs doublets are summarized. The prospects for resonance
production and detection of the chiral vector and bosons at
the LHC energies are considered. The boson can be observed as a
Breit-Wigner resonance peak in the invariant dilepton mass distributions in the
same way as the well-known extra gauge bosons. However, the bosons
have unique signatures in transverse momentum, angular and pseudorapidity
distributions of the final leptons, which allow one to distinguish them from
other heavy neutral resonances. In 2010, with 40 pb of the LHC
proton-proton data at the energy 7 TeV, the ATLAS detector was used to search
for narrow resonances in the invariant mass spectrum of and
final states and high-mass charged states decaying to a charged
lepton and a neutrino. No statistically significant excess above the Standard
Model expectation was observed. The exclusion mass limits of 1.15 TeV and
1.35 TeV were obtained for the chiral neutral and charged
bosons, respectively. These are the first direct limits on the and
boson production. For almost all currently considered exotic models the
relevant signal is expected in the central dijet rapidity region. On the
contrary, the chiral bosons do not contribute to this region but produce an
excess of dijet events far away from it. For these bosons the appropriate
kinematic restrictions lead to a dip in the centrality ratio distribution over
the dijet invariant mass instead of a bump expected in the most exotic models.Comment: 24 pages, 34 figure, based on talk given by V.A.Bednyakov at 15th
Lomonosov conference, 22.08.201
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