Bulletin of the American Physical Society
APS April Meeting 2010
Volume 55, Number 1
Saturday–Tuesday, February 13–16, 2010; Washington, DC
Session Q9: Higgs Searches III |
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Sponsoring Units: DPF Chair: Ritchie Patterson, Cornell University Room: Maryland A |
Monday, February 15, 2010 1:30PM - 1:42PM |
Q9.00001: Using tri-lepton events to improve SM Higgs search in $VH \rightarrow VWW$ decay channel at CDF Jason Nett We present an analysis designed to improve the sensitivity of the search for a standard model (SM) Higgs boson by more fully utilizing potential decay channels originating from associated production of a Higgs and a vector boson ($V = W,Z$). Potential Higgs decays via $H \rightarrow WW$ result in final state with three heavy vector bosons whose leptonic decays can result in events containing three and even four charged leptons. In the past CDF has incorporated same-sign dilpeton events, which also result from this production mode, within its SM higgs searches. By also incorporating tri-lepton events in the analysis, we can potentially improve the sensitivity of this search channel by roughly another 10\%. We also explore further expanding signal acceptance in this channel by incorporating events with small opening angle as well as those containing hadronic tau decays. [Preview Abstract] |
Monday, February 15, 2010 1:42PM - 1:54PM |
Q9.00002: Search for SM Higgs in $ZH \rightarrow ZWW$ incorporating hadronic decays of the $W$ boson at CDF Geumbong Yu We present a search for standard model (SM) Higgs production in association with a $Z$ boson at the Tevatron. We increase the signal acceptance for a potential Higgs boson by exploiting the large branching ratio for $W \rightarrow q\overline{q}$. The multi-jet backgrounds are highly suppressed by requiring that the $Z$ boson decays into a pair of charged leptons. The search is thus performed in two separate final states: $H \rightarrow WW$ decays resulting in four hadronic jets and $H \rightarrow WW$ decays leading to one charged lepton, missing transverse energy (from the neutrino), and two hadronic jets. Further discrimination between signal and backgrounds is obtained using an artificial neural network. Using 4.8fb$^{-1}$ of CDF data, we set 95\% C.L. upper limits on the production cross section for a potenital Higgs boson with masses between 110 and 200~GeV/$c^2$. [Preview Abstract] |
Monday, February 15, 2010 1:54PM - 2:06PM |
Q9.00003: Search for the SM Higgs in semi-leptonic $WW$* decays in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV Shannon Zelitch We present a search for the Standard Model Higgs boson produced via the H$\rightarrow$WW$^{(*)}\rightarrow$l+nu+j+j process at a center-of-mass energy of $\sqrt{s}=1.96$ TeV using up to 5 fb$^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron collider. We search in events with one lepton (electron or muon), two jets and missing transverse energy. A Higgs particle with a mass greater than 140 GeV primarily decays into a pair of $W$ bosons. While the di-lepton channels provide a cleaner signature, the semi-leptonic decay mode has a significantly larger cross section times branching ratio. Procedures used to identify signal-like events and to overcome the large $W$+jets background will be discussed. [Preview Abstract] |
Monday, February 15, 2010 2:06PM - 2:18PM |
Q9.00004: Search for the Higgs Boson in $WW^{(*)}\to \ell^+\ell^-$ Decays in $p\bar{p}$ Collisions at $\sqrt{s}=1.96$ TeV Davide Gerbaudo We present a search for the Standard Model Higgs boson produced via the $H\to WW^{(*)}\to l\nu l\nu$ process at a center-of-mass energy of $\sqrt{s}=1.96$ TeV, using 5.4~fb$^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron collider. We consider a final state where the Higgs boson decays into a pair of $W$ bosons which in turn decay leptonically; this channel, with its clear signature of two leptons and missing energy, provides the greatest sensitivity to the Higgs boson at the Tevatron in the high mass region. With the current dataset no excess above the Standard Model predictions is observed, and limits on the Higgs production cross-section are set for $m_{H}$ in the range $115-200$ GeV. [Preview Abstract] |
Monday, February 15, 2010 2:18PM - 2:30PM |
Q9.00005: Search for the Higgs boson in the four lepton final state Rachel Wilken The discovery potential for a Standard Model Higgs boson decaying to ZZ(*)-$>$4 leptons (electrons and muons) by the CMS detector at the LHC will be presented. The strategy for selecting signal and rejecting background using full simulation of the detector response will be discussed. The analysis has been performed for a Higgs mass range from 120 to 250 GeV/c2 . We will also give projections of how Higgs boson exclusion limits are effected by LHC center-of-mass collision energy changing from 14 to 10 TeV. [Preview Abstract] |
Monday, February 15, 2010 2:30PM - 2:42PM |
Q9.00006: Covariant Matrix based e/$\gamma$ Identification Algorithm for Higgs searches at the LHC H. Kim, J. Yu Discovery of the Higgs particle is one of the most important goals of the Large Hadron Collider (LHC) experiments. To detect the rare Higgs signal, the electromagnetic (EM) calorimeter must not only be able to precisely measure the energy of electrons and photons, but also identify them well. The discrimination against overwhelming background from jets can be achieved by measuring the detailed shapes of EM showers and by taking advantage of the correlations between shape variables. The covariant matrix technique, the H-matrix method, uses these correlations for electron and photon identifications. In this talk, we present construction of H-matrix e/$\gamma$ identification algorithm and its performance on single, isolated electron and $\gamma$ as well as on those from signal physics processes, along with the rejections on highly electromagnetic jets. In addition, prior to the LHC collisions, high-energy bremstraahlung photons produced by the cosmic ray muons passing through the ATLAS calorimeter provide valuable data that can used to validate the Monte Carlo modeling of the ATLAS detector and the performance of the photon identification algorithms. We will present the measurement of photon identification efficiency using cosmic data. [Preview Abstract] |
Monday, February 15, 2010 2:42PM - 2:54PM |
Q9.00007: Exploring exotic symmetry breaking scenarios in the di-boson (WZ) channel at the LHC Edgar Carrera An electroweak symmetry breaking mechanism, in which there is no elementary Higgs particle, is a possibility well worth exploring at the Large Hadron Collider (LHC). Theories such as the Minimal Higgsless Model (MHLM) or Technicolor (TC) predict the production of heavy resonant particles decaying into a pair of Standard Model gauge bosons ($WZ$), promising clean multi-lepton signatures. We present a study of such scenarios (MHLM and TC) in the electron- and muon-decay channels using the Compact Muon Solenoid detector for proton-proton collisions at $\sqrt s = 10{\rm TeV}$. [Preview Abstract] |
Monday, February 15, 2010 2:54PM - 3:06PM |
Q9.00008: Higgs Boson Exchange Effects in $l^+l^- \rightarrow W^+W^-$ at High Energy Elena Brewer, Ulrich Baur We consider the possibility for detecting effects due to the Higgs exchange diagram in high energy ${\mu}^+ {\mu}^-$, $e^+ e^-$, and ${\tau}^+ {\tau}^-$ collisions producing a pair of $W$ bosons. The processes $l^+l^- \rightarrow W^+W^-$ (with $l=\mu,e,\tau$) are analyzed, analytically and via numerical simulations, to determine the center of mass energy, ${\sqrt{s} _H}$, where the effects from Higgs exchange become relevant. The scaling of ${\sqrt{s}_H}$ with the mass of the incoming leptons is also studied. Special consideration is given to the $W^+W^- \rightarrow l^{\pm} {\nu}_l jj$ final state after experimental acceptance cuts are imposed. Angular cuts are shown to be able to significantly lower ${\sqrt{s}_H}$. The center of mass energy for which Higgs exchange effects become relevant in $l^+l^- \rightarrow W^+W^-$ is found to be much higher than that in $l^+l^- \rightarrow \bar{\nu} {\nu} W^+W^- $. Higgs boson exchange effects in $W$-pair production thus will not be relevant for the $e^+ e^-$ and ${\mu}^+ {\mu}^-$ colliders currently on the drawing board. [Preview Abstract] |
Monday, February 15, 2010 3:06PM - 3:18PM |
Q9.00009: Constraints on the Lee-Wick Higgs Sector Christopher Carone The Lee-Wick Standard Model has been proposed as a solution to the hierarchy problem. Lee-Wick partners to the Standard Model Higgs doublet may appear at a mass scale that is significantly lower than that of the remaining Lee-Wick partner states. In this case, the relevant effective theory is a two-Higgs doublet model in which one doublet has wrong-sign kinetic and mass terms. We determine bounds on this effective theory, including those from neutral B-meson mixing, $b \rightarrow X_s \gamma$, and $Z \rightarrow b \overline{b}$. The results differ from those of conventional two-Higgs doublet models and lead to meaningful constraints on the Lee-Wick Higgs sector. [Preview Abstract] |
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