Bulletin of the American Physical Society
APS April Meeting 2011
Volume 56, Number 4
Saturday–Tuesday, April 30–May 3 2011; Anaheim, California
Session L8: Tevatron and LHC BSM Searches |
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Sponsoring Units: DPF Chair: Manfred Paulini, Carnegie Mellon University Room: Grand F |
Sunday, May 1, 2011 3:30PM - 3:42PM |
L8.00001: Searches for fourth generation top quark in dilepton channel at ATLAS Michael Werth, Daniel Whiteson A fourth generation of quarks is a natural and powerful extension to the Standard Model. It supports heavier Higgs models, provides additional CP Violation for $B_s$ decays, and addresses numerous other theoretical and experimental questions. We present a search for pair-produced heavy up-type fourth generation quarks, $t'\bar{t'} \to W^+ W^- b\bar{b}$, with the ATLAS detector at the LHC. We examine events where both $W$ bosons decay leptonically, and we reconstruct the $t'$ invariant mass using a collinear approximation to deduce the missing neutrino information from the lepton directions and $E_{\mathrm{T}}^{\mathrm{miss}}$ of each event. Our search encompasses a total recorded luminosity of 38 $pb^{-1}$ of pp collisions at center-of-mass energy of $\sqrt{s} = 7$ TeV. [Preview Abstract] |
Sunday, May 1, 2011 3:42PM - 3:54PM |
L8.00002: Search for a fourth generation $t'$ quark that decays to W boson + jet Jeong Ku Lim, Dookee Cho We present a search for pair-production of a fourth generation $t'$ quark with its antiparticle, followed by their decays to $Wq$, based on 5.3 fb$^{-1}$ of proton-antiproton collisions at $\sqrt{s}=1.96$ TeV collected by the D0 experiment at the Fermilab Tevatron. We compare the reconstructed mass of the $t'$ quark from lepton+jets final states and the scalar sum of the momenta of all observed objects in the event to Standard Model expectations to search for signals of new physics. We set upper limits on the $t'\bar{t}'$ production cross section. [Preview Abstract] |
Sunday, May 1, 2011 3:54PM - 4:06PM |
L8.00003: Search for Heavy Vector-Like Quarks Jordan Webster We search for singly-produced quarks above the top mass in events with a W or Z boson produced in association with two or three high transverse momentum jets. The vector boson is reconstructed in the W $\rightarrow$ $\ell\nu$ and Z $\rightarrow$ $\ell\ell$ modes, where $\ell$ is an electron or a muon. Using 35 pb$^{-1}$ of ATLAS data collected at a center-of-mass energy of 7 TeV, we fit the invariant mass of the system composed of the vector boson and the highest transverse momentum jet to set limits on the heavy quark production cross section. [Preview Abstract] |
Sunday, May 1, 2011 4:06PM - 4:18PM |
L8.00004: Search for First Generation Leptoquarks Regina Caputo Leptoquarks are hypothetical particles that carry both lepton and baryon number and are proposed to exist in several Grand Unification Theories (GUTs) and technicolor models. This work presents a search for first generation leptoquarks at the ATLAS detector using an integrated luminosity of 35 $pb^{-1}$ collected from the 2010 data set. The search is for pair production of leptoquarks in which one leptoquark would decay into an electron/quark pair, and the other into a neutrino/quark pair giving an event topology of one high energy electron, missing transverse energy and two high energy jets. The background, predominantly from associated production of W bosons with jets and of top quarks, is estimated using Standard Model simulated data, normalized to observations in control regions. [Preview Abstract] |
Sunday, May 1, 2011 4:18PM - 4:30PM |
L8.00005: Search for Pair Production of First-Generation Scalar Leptoquarks in pp Collisions at sqrt(s) = 7 TeV Dinko Ferencek A search for pair production of first-generation scalar leptoquarks is performed in the final state containing two electrons and two jets using proton-proton collision data at $\sqrt{s}=7$~TeV. The data sample used corresponds to an integrated luminosity of 33 pb$^{-1}$ collected with the CMS detector at the CERN LHC. The number of observed events is in good agreement with the predictions for the standard model background processes, and an upper limit is set on the leptoquark pair production cross section times $\beta^2$ as a function of the leptoquark mass, where $\beta$ is the branching fraction of the leptoquark decay to an electron and a quark. A 95\% confidence level lower limit is set on the mass of a first-generation scalar leptoquark at 384 GeV for $\beta=1$, which is the most stringent direct limit to date. [Preview Abstract] |
Sunday, May 1, 2011 4:30PM - 4:42PM |
L8.00006: The Search for Pair Production of Second Generation Scalar Leptoquarks in pp Collisions at sqrt(s) = 7 TeV Darin Baumgartel A search for pair production of second generation scalar leptoquarks is presented in the final states with two jets and either two muons or one muon and one neutrino. The data sample used corresponds to 34 pb$^{-1}$ of integrated luminosity collected at the CMS detector at the LHC. The number of observed events is in good agreement with standard model processes. An upper limit is set for beta as a function of leptoquark mass, where beta is the branching fraction of a leptoquark into a lepton and a quark. Leptoquarks with masses below 394 GeV are excluded for $\beta = 1$, and masses below 297 GeV are excluded for $\beta = 1/2$. These limits are the most stringent to date. [Preview Abstract] |
Sunday, May 1, 2011 4:42PM - 4:54PM |
L8.00007: Search for Randall-Sundrum Gravitons at CMS Yousi Ma We describe the search for Randall-Sundrum (RS) gravitons decaying in the diphoton channel at the CMS Experiment, with 33.9 pb$^{-1}$ of $\sqrt{s} = 7$~TeV proton-proton collision data. We find the spectrum to agree with our expectations based solely on the standard model, and find no evidence for a resonance. We therefore derive limits on the cross-section for the production of RS gravitons, and hence on the parameters of the warped extra dimension model. For values of the coupling parameter ranging from 0.01 to 0.1, we find that at 95\% confidence level, graviton masses below 330 to 850 GeV/$c^2$ are excluded. [Preview Abstract] |
Sunday, May 1, 2011 4:54PM - 5:06PM |
L8.00008: Search for the lepton-flavor-violating decays $B^{\pm} \to h^{\pm} \tau \ell$ $(h=K,\pi;\ell=e,\mu)$ at {\sc BaBar} Gil M. Vitug, Owen R. Long We present a search for the lepton-flavor-violating decays $B^{\pm} \to h^{\pm} \tau \ell$ ($h= K,\pi$; $\ell= e,\mu$) using the full {\sc BaBar} dataset, which corresponds to 471.9 million $B\bar{B}$ pairs. The search uses a sample of events where one $B$ meson (the ``tag'' $B$) is fully reconstructed in one of several hadronic final states. Using the tag-$B$ momentum and the reconstructed $h$ and $\ell$, we are able to fully reconstruct the $\tau$ 4-momentum. The reconstructed $\tau$ mass is our main discriminant against combinatoric background. [Preview Abstract] |
Sunday, May 1, 2011 5:06PM - 5:18PM |
L8.00009: Search for Heavy Massive Fourth-Generation Neutrinos at CDF Jared Vasquez Within the standard model of elementary particles we have dis- covered three generations of quarks and leptons. A natural extension would be the addition of a fourth generation, the lightest of which may be the neutrino. Using 4 fb$^{-1}$ of data from collisions recorded by the CDF detector in proton-antiproton collisions at the Tevatron with center-of-mass energy of 1.96 TeV, we present a search for such a fourth generation neutrino. We search for pair production of unstable massive fourth generation neutrinos each which decay to a heavy stable neutrino and a Z boson. We examine the mode in which one Z decays leptonically and the other hadronically, leading to a final state of two jets, two charged leptons and missing transverse momentum. [Preview Abstract] |
Sunday, May 1, 2011 5:18PM - 5:30PM |
L8.00010: Search for Heavy Majorana Neutrino in Same-Sign Dilepton Channel Matthew Relich Non-zero neutrino masses require the introduction of right-handed field components for the neutrino. Generating sub-eV neutrino masses through Yukawa interactions requires extremely small coupling constants, thus leading to an aesthetically unpleasing theory. Using Type-I seesaw mechanism, light neutrino masses and mixings are generated naturally by introducing heavy Majorana neutrino (HMN) terms. We study the production and decay of HMN using a Lagrangian of effective operators in LHC ${\it pp}$ collisions at ${\sqrt s}$ = 7 TeV. This model independent approach allows for a broader and more reliable view of expected physics for TeV-scale Majorana neutrinos. We present a search for HMN with a total integrated luminosity of 35 $\it pb$${^{-1}}$ recorded with the ATLAS detector. [Preview Abstract] |
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