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Indiana University Bloomington
ATLAS Experiment

IU Collaborators: Brunet, Egorov, Evans, Gagnon, Jain, Lammers, Luehring, Ogren, Penwell, Price, Whittington, Yang, Zieminska

Beam Splash event in ATLAS

ATLAS is one of four new experiments that will begin taking data this fall when the LHC begins colliding beams. The scientific community has been anticipating these new generation of experiments because we believe new discoveries into the fundamental nature of matter will occur. Our group has had a leading role in the construction, commissioning and calibration of the Transition Radiation Tracker (TRT). Harold Ogren led the Barrel TRT design and construction phases, and several modules were assembled in Bloomington. Because we don't know exactly what will be discovered at the LHC, our analysis interests cross a broad range of topics. The LHC was built to investigate the nature of electroweak symmetry breaking, and we have interests in both Standard Model and Beyond the Standard Model (BSM) searches for the Higgs Boson. Supersymmetry has been touted as the likely explanation for TeV-scale new physics, and we are developing analysis techniques for observing heavily ionizing massive particles and heavy resonances.

Transition Radiation Tracker

The TRT detector observed from the beamline axis. Tracks observed are from a beam-splash event during single-beam running in September, 2008. Turn on of transition radiation (high threshold hits) from cosmic ray muons measured in the barrel TRT in October, 2008. The turnon agrees well with predictions from testbeam data.

Recent Physics Results

R-hadron search:Distribution of the fraction of TRT high-threshold hits for candidates satisfying the loose selection. Data (dots) are compared with area-normalised signal ($|q|=10e$ and $m=500$~GeV, dashed line) and Standard Model background (shaded area) simulations. The dotted line shows the selection cut value. Details are at this link Upsilon(1S) cross-section for the |y| < 1.2 as function of pT Upsilon(1S) for pT > 4 GeV and |eta| < 2.5 on both muons. Also shown is the colour-singlet NLO (CSM) prediction using mT for the renormalisation and factorisation scales. The shaded area shows the change in the theoretical prediction when varying the renormalisation and factorisation scales by a factor of two. The CSM NLO calculation accounts only for direct production of ?(1S) mesons and not for any feed-down from excited states. The NRQCD prediction as implemented in PYTHIA8 is also shown for a particular choice of parameters. Details are at this link

R-parity violating decays (in SUSY): 95% C.L. upper limits on the production cross section times branching ratio vs. the neutralino lifetime times the speed of light for different combinations of squark and neutralino masses, based on the observation of zero events in a 33 pb^-1 data sample. The curves show the expected limits, and the points are the observed limits. Details are at this link Higgs search Exclusion plot for Higgs using the Higgs->WW->llnunu decay mode. This is one of the decay modes that was in the combination plot that was recently made public. See combined result here


  • ATLAS Experiment
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  • Last updated: 22 April 2014
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