Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session Y12: Searches III |
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Sponsoring Units: DPF Chair: Bob Bernstein, Fermi National Accelerator Laboratory Room: Plaza Court 1 |
Tuesday, April 16, 2013 1:30PM - 1:42PM |
Y12.00001: Measurement of $Z$ boson production in association with heavy flavor jets at D0 Joseph Zennamo Associated production of a $Z$ boson with a charm or bottom quark can serve as an important test of perturbative quantum chromodynamic calculations. The ratios of cross sections, $\sigma(Z+c \thinspace {\mathrm{jet}})/\sigma(Z+{\mathrm{jet}})$ and $\sigma(Z+c \thinspace {\mathrm{jet}})/\sigma(Z+b \thinspace {\mathrm{jet}})$ are measured for associated production of a $Z$ boson with jets as a function of the jet and $Z$ boson transverse momentum. Measurements use data collected by the D0 detector in Run~II of the Tevatron $p\bar{p}$ collider at a center-of-mass energy of 1.96 TeV, and correspond to an integrated luminosity of 9.7 fb$^{-1}$. Results are compared to predictions from next-to-leading order calculations and various Monte Carlo event generators. [Preview Abstract] |
Tuesday, April 16, 2013 1:42PM - 1:54PM |
Y12.00002: Helicity-Based Parton Shower for Matching with QCD Matrix Elements Kassahun Betre The search for new physics at the LHC requires ever better understanding of the QCD backgrounds of the Standard Model at high jet multiplicity. For this, event generators with the capacity to accurately handle the large phase space of high jet multiplicity events are needed. These event generators must also be able to match showered events with exact QCD matrix element calculations for improved accuracy. Antenna based showering algorithms have been developed that are capable of handling the large phase space of high multiplicity events efficiently. On the other hand, the exact leading-order QCD matrix element of high multiplicity events can be calculated efficiently using the BCFW recursion formula. In this talk I present a new event generator that implements BCFW for fast QCD matrix element calculation with antenna based, helicity-dependent showering algorithms. The showering produces helicity and color states at each step that are matched to the corresponding QCD matrix elements. [Preview Abstract] |
Tuesday, April 16, 2013 1:54PM - 2:06PM |
Y12.00003: Search for top quark pair resonances with ATLAS Venkatesh Kaushik Several Beyond the Standard Model (BSM) theories predict the existence of new resonances that decay into top-antitop quark pairs. We describe a search for such resonances using ATLAS data in the lepton plus jets decay channel produced in pp collisions at $\sqrt{s}$ = 8 TeV. The selection criteria and search method are presented. In the absence of signal we will produce 95\% CL limits on the production cross section times branching ratio of resonances predicted by a number of benchmark BSM models. [Preview Abstract] |
Tuesday, April 16, 2013 2:06PM - 2:18PM |
Y12.00004: Search for exotic same sign dilepton signatures in p-p collisions at $\sqrt{s}$ = 8TeV with the ATLAS detector Fionnbarr O'Grady We present the results of a search for exotic processes involving a final state containing a same sign dilepton pair using data from the ATLAS detector collected in 2012 at $\sqrt{s}$ = 8TeV. The analysis is optimized for a variety of beyond the standard model signals including pair production of down type heavy quarks (b$^{\prime}$) and single and pair production of heavy top quark partners ( T$_{5/3}$ ). Progress towards establishing a signal or producing 95\% CL limits on the production cross section are reported. [Preview Abstract] |
Tuesday, April 16, 2013 2:18PM - 2:30PM |
Y12.00005: Likelihood analysis in Compact Muon Solenoid search for physics beyond the standard model in events with bottom-quark jets Benjamin Kreis We present a search for physics beyond the standard model (BSM) in events with large missing energy, at least three jets, and at least one identified b-jet. The study is performed using a sample of proton-proton collisions collected with the Compact Muon Solenoid detector. We will describe in detail how control samples in the data are used to evaluate backgrounds arising from events with either one or two top quarks, a W boson produced in association with jets, or multiple jets produced through the strong interaction. The consistency of BSM models with the data is tested using a likelihood fit that accounts for BSM contributions to the control samples. [Preview Abstract] |
Tuesday, April 16, 2013 2:30PM - 2:42PM |
Y12.00006: Missing Transverse Energy Performance at CMS using Photon + Jet Events Brian Calvert, Ted Kolberg, Sarah Eno, Nick Hadley Missing Transverse Energy (MET) is an important variable in many searches for new physics at the LHC, as it can be used to infer the momentum carried by undetected particles such as neutrinos or the lightest supersymmetric particle in supersymmetry models with R-parity conservation. We present here a study of the performance of MET at the CMS detector, and compare to expectations based on detector simulation, using direct photon events. The study uses data collected in 2012 by the CMS detector at the LHC at $\sqrt{s} = 8$ TeV. [Preview Abstract] |
Tuesday, April 16, 2013 2:42PM - 2:54PM |
Y12.00007: Physics Beyond the Standard Model at a High-Luminosity LHC with the ATLAS Detector Chris Pollard The Phase 2 upgrade of the ATLAS detector will greatly increase its ability to probe physics beyond the Standard Model. Using parameterizations of detector performance, we present the expected gain in sensitivity to an extended electroweak symmetry-breaking sector and to new high-mass resonances with dilepton and ditop final states for the improved ATLAS detector and for the LHC delivering between 1 ab$^{-1}$ and 3 ab$^{-1}$ of data at a center-of-mass energy of 14 TeV. [Preview Abstract] |
Tuesday, April 16, 2013 2:54PM - 3:06PM |
Y12.00008: Electron Identification Studies for the ATLAS Level 1 Trigger Upgrade Last Feremenga, Marc-Andre Pleier, Francesco Lanni We study options available for achieving an efficient selection of electrons against an overwhelming background of neutral pions at the hardware-based trigger of the ATLAS trigger system. The lateral profiles of electrons and neutral pions are different when the interaction point of the colliding protons is at $z=0$ and an efficient selection is achieved. We show that this efficiency is lost for a more realistic model of the luminous profile of the proton beam. A variable used at the software-based trigger is also shown to be unstable against increasing pileup. [Preview Abstract] |
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