Bulletin of the American Physical Society
APS April Meeting 2012
Volume 57, Number 3
Saturday–Tuesday, March 31–April 3 2012; Atlanta, Georgia
Session R9: New Particle Searches II |
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Sponsoring Units: DPF Chair: Yuri Gershtein, Rutgers University Room: Embassy E |
Monday, April 2, 2012 1:30PM - 1:42PM |
R9.00001: Search for Long-Lived Massive Particles at CMS Seth Cooper Several models of new physics, including split supersymmetry, predict the existence of a heavy particle, which is long-lived on timescales of the bunch spacing of the LHC. Such a particle would be observable using the Compact Muon Solenoid (CMS) at the Large Hadron Collider (LHC), and although produced at high momentum, it would travel slowly due to its large mass. We describe a search for these particles, using the experimental techniques of time of flight and dE/dx measurement. Results are presented based on data recorded with CMS in 2011. [Preview Abstract] |
Monday, April 2, 2012 1:42PM - 1:54PM |
R9.00002: Search for Multiply-Charged Heavy Stable Charged Particles at CMS Venkatesh Veeraraghavan We present searches for heavy, long-lived particles with charge $\pm Ne$ (N $>$ 1) in proton-proton collisions at a center of mass energy of 7 TeV at the Large Hadron Collider (LHC) using data collected with the Compact Muon Solenoid (CMS) detector. We consider a stable, multiply-charged fermion produced via the Drell-Yan process as our signal. The slow velocity and large charge of such particles yields an unambiguously amplified ionisation energy loss. Velocity measurement is made using the muon system and the energy deposition in the inner tracker is used to compute the average energy loss per path length. We present results from the 2011 run of the LHC. [Preview Abstract] |
Monday, April 2, 2012 1:54PM - 2:06PM |
R9.00003: A search for leptoquarks with the ATLAS detector Burton DeWilde Leptoquarks are hypothetical bosons that couple directly to both quarks and leptons, assumed to be of the same generation. They appear in a variety of theories beyond the Standard Model. The results of a search for pair production of scalar leptoquarks are presented for final states consisting of either two oppositely charged leptons (electrons or muons) and at least two jets, or a lepton plus missing transverse energy and at least two jets. A total of 1.0/fb of data recorded by the ATLAS detector at $\sqrt{s}$ = 7 TeV is used for the search. Event yields in the signal regions are checked for consistency with Standard Model background expectations, and limits are derived for leptoquark production cross-sections as a function of the branching fraction of a leptoquark decaying to a lepton and a quark. [Preview Abstract] |
Monday, April 2, 2012 2:06PM - 2:18PM |
R9.00004: Search for Anomalous Production of Multilepton Events and $R$-Parity-Violating Supersymmetry in $\sqrt{s} = 7$ TeV $pp$ Collisions Emmanuel Contreras-Campana, Richard Gray, Sunil Somalwar, Amitabh Lath, Scott Thomas, John Paul Chou, Matthew Walker, Sanjay Arora, Shruti Panwalkar, Peter Thomassen, Patrick Zywicki, Michael Park, Kin Chan, Kelvin Mei, Eric Williams We present a search for anomalous production of events with three or more isolated leptons produced in pp collisions at $\sqrt{s} = 7$ TeV collected by the CMS experiment at the LHC. We analyze $4.7 fb^{-1}$ of data collected by the CMS experiment during the 2011 LHC run. The search is applicable to any model of new physics that produces multiple leptons in the final state. We categorize observed multilepton events into exclusive search channels based on the identity and kinematics of the objects in the events. The channels are then ordered by the amount of expected standard-model background. We emphasize a data-based estimation of the standard-model backgrounds but also use simulation to estimate some of the backgrounds when appropriate. We interpret search results in the context of $R$-parity-violating models, for which the presence of missing transverse energy is not guaranteed due to the absence of stable supersymmetric particles. We derive exclusion limits as a function of squark and gluino masses for several $R$-parity-violating couplings. [Preview Abstract] |
Monday, April 2, 2012 2:18PM - 2:30PM |
R9.00005: Search for anomalous production of like-sign lepton pairs with the ATLAS detector Louise Skinnari We present a search for anomalous production of two prompt like-sign leptons and constraints on physics beyond the Standard Model. The search is performed using a data sample corresponding to an integrated luminosity of 5 fb$^{-1}$, collected in 2011 at $\sqrt{s} = 7$~TeV by the ATLAS detector at the LHC. Lepton pairs are selected inclusively by requiring two isolated leptons of the same electric charge with $p_T > 20$~GeV. The invariant mass distribution is examined and limits are placed on the anomalous production cross section as function of invariant mass with respect to a fiducial region close to that of the experimental selection. The inclusive search is also interpreted within a few different models of physics beyond the Standard Model. [Preview Abstract] |
Monday, April 2, 2012 2:30PM - 2:42PM |
R9.00006: Search for TeV-Scale Gravity Signatures in Final States with Leptons and Jets with the ATLAS Detector at sqrt(s) = 7 TeV German Colon Results are presented from a search for physics beyond the Standard Model in events with leptons and jets with large transverse momentum, using data collected by the ATLAS detector in 2011. Using models for strong gravitational states in extra-dimensional theories, such as black holes and string balls, we interpret the results in terms of the fundamental gravitational scale and the mass threshold for production of the aforementioned states. [Preview Abstract] |
Monday, April 2, 2012 2:42PM - 2:54PM |
R9.00007: Comparison of fourth generation charged leptons various models with 1 or 2 extra dimensions Christine DiMenna, Erin DePree, Elliot Russell Extra dimensions provide possible solutions to the hierarchy problem and other issues with the Standard Model (SM). The potential for discovery at the Large Hadron Collider (LHC) is huge, but it is essential to know which models can be eliminated based on the observation or lack of observation of various processes. We focus on the production of fourth-generation charged leptons. We compare the cross-sectional areas for heavy charged lepton production in several models: including the Standard Model, warped extra dimensions or Randall-Sundrum (RS) model, and the RS6 model with two extra dimensions. This analysis will help understand the implications of future data from the LHC. [Preview Abstract] |
Monday, April 2, 2012 2:54PM - 3:06PM |
R9.00008: Discriminating between fourth generation and Kaluza-Klein charged lepton decays Ian Morgan, Jeremy Perrin, Pasquale Raico, Kevin Tennyson Heavy charged leptons appear in many models. Sequential 4th generation leptons and Kaluza-Klein tau particles may have similar masses and can both decay to massive, rarely interacting particles. We explore the parameter space to determine under which circumstances they are indistinguishable. [Preview Abstract] |
Monday, April 2, 2012 3:06PM - 3:18PM |
R9.00009: Supersymmetric minimal B-L model at the TeV scale with right-handed Majorana neutrino dark matter. arXiv:1111.1789v2 [hep-ph] Zachary Burell We propose a supersymmetric extension of the minimal B-L model where we consider a new Z$_2$-parity under which one RH neutrino is assigned odd parity. When the Majorana Yukawa coupling of a Z$_2$-even RH neutrino is large, radiative corrections will drive the mass squared of the corresponding RH sneutrino to negative values, breaking the B-L gauge symmetry at the TeV scale in a natural way. Additionally, R-parity is broken and thus the conventional supersymmetric dark matter candidate, the neutralino, is no longer viable. Thanks to the Z$_2$-parity, the Z$_2$-odd RH neutrino remains a stable dark matter candidate even in the presence of R-parity violation. We demonstrate that the dark matter relic abundance with an enhanced annihilation cross section by the B-L gauge boson (Z') resonance is in accord with the current observations. Therefore, it follows that the mass of this dark matter particle is close to half of the Z' boson mass. If the Z' boson is discovered at the Large Hadron Collider, it will give rise to novel probes of dark matter: The observed Z' boson mass will delineate a narrow range of allowed dark matter mass. If the Z' boson decays to a pair of dark matter particles, a precise measurement of the invisible decay width can reveal the existence of the dark matter particle. [Preview Abstract] |
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