Bulletin of the American Physical Society
Annual Meeting of the Four Corners Section of the APS
Volume 59, Number 11
Friday–Saturday, October 17–18, 2014; Orem, Utah
Session D3: Particle Physics II |
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Chair: John Cumalat, University of Colorado - Boulder Room: Science Building 139 |
Friday, October 17, 2014 1:50PM - 2:02PM |
D3.00001: The Incredible Bulk Takahiro Yamamoto, Keita Fukushima, Chris Kelso, Jason Kumar, Pearl Sandick Recent results from the LHC have placed strong constraints on the masses of colored superpartners. The MSSM parameter space is also constrained by the measurement of the Higgs boson mass, and the requirement that the relic density of lightest neutralinos be consistent with observations. Although large regions of the MSSM parameter space can be excluded by these combined bounds, leptophilic versions of the MSSM can survive these constraints. In this paper we consider a scenario in which the requirements of minimal flavor violation, vanishing $CP$-violation, and mass universality are relaxed, specifically focusing on scenarios with light sleptons. We find a large region of parameter space, typically mass of bino and the lighter slepton around 100 GeV with maximal chiral mixing, which, analogous to the original bulk region, provides the efficient dark matter annihilation rate, allowing the s-wave contribution of which be as large as $\mathcal{O}$$(1)$pb. We find that the most relevant constraints on this scenario arise from collider bounds of direct slepton searches and from measurements of the magnetic and electric dipole moments of the electron and muon, and that these models have interesting signatures at a variety of indirect detection experiments. [Preview Abstract] |
Friday, October 17, 2014 2:02PM - 2:14PM |
D3.00002: A Higgs Discovery via Exotic Higgs Decays Felix Kling, Shufang Su, Barath Coleppa Models of electroweak symmetry breaking, with an extended Higgs sector, are theoretically well motivated. In this study, we focus on the Two Higgs Doublet Model, with a low energy spectrum containing scalars $H$, a pseudoscalar $A$ and charged scalars $H^\pm$. We look at exotic decays of those extra Higgses into a light Higgs and a gauge boson: $A/H \to HZ/AZ$ and $H^\pm \to HW/AW$. With detailed collider analyses, we obtain the exclusion bounds as well as the discovery reach at the 14 TeV LHC and interpret these bounds in the context of the Type II Two Higgs Doublet Model. [Preview Abstract] |
Friday, October 17, 2014 2:14PM - 2:26PM |
D3.00003: Light Charged Higgs Bosons in Single-Top Production Adarsh Pyarelal The Two Higgs Doublet Model (2HDM) is one of the simplest extensions to the Standard Model Higgs sector, and predicts the existence of additional Higgs bosons, including a pair of charged Higgs bosons $H^{\pm}$ and a pseudoscalar Higgs boson $A$. Existing searches for the charged Higgs mostly focus on the $H^{\pm}\rightarrow\tau\nu/cs$ decay channels. For light $A$'s, $H^{\pm}\rightarrow AW$ becomes kinematically accessible and competitive with the conventional channels. We examine the single top production channel with $t\rightarrow b H^\pm$, and the subsequent decay chain of $H^{\pm}\rightarrow AW^{\pm}\rightarrow \tau\tau \ell \nu$. We perform a collider analysis and obtain exclusion and discovery reach at the 14 TeV LHC with 100 fb$^{-1}$ integrated luminosity. We further study the implication of the search limits on the Type II 2HDM. [Preview Abstract] |
Friday, October 17, 2014 2:26PM - 2:38PM |
D3.00004: Observation of an Excited $B_c^\pm$ Meson State with the ATLAS Detector Aidan Grummer A search for excited states of the $B_c^\pm$ meson is performed using 4.9 $\mathrm{fb}^{-1}$ of 7 TeV and 19.2 $\mathrm{fb}^{-1}$ of 8 TeV \emph{pp} collision data collected by the ATLAS experiment at the LHC. A new state is observed through its hadronic transition to the ground state, with the latter detected in the decay $B_c^\pm$ $\rightarrow$ $J/\psi\pi^\pm$. The state appears in the $m(B_c^\pm{\pi^+\pi^-}) - m(B_c^\pm) - 2m(\pi^\pm)$ mass difference distribution with a significance of 5.2 standard deviations. The mass of the observed state is 6842 $\pm$ 4 $\pm$ 5 MeV, where the first error is statistical and the second is systematic. The mass and decay of this state are consistent with expectations for the second \emph{S}-wave state of the $B_c^\pm$ meson, $B_c^\pm(2S)$. [Preview Abstract] |
Friday, October 17, 2014 2:38PM - 2:50PM |
D3.00005: Measurement of the production of a W boson in association with a charm quark in pp collisions at sqrt(s) $=$ 7 TeV with the ATLAS detector Neil McFadden The production of a $W$ boson in association with a single charm quark is studied using 4.6 fb$^{\mathrm{-1}}$ of \textit{pp} collision data at sqrt(s) $=$ 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a $W$ boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the $W$-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be .96 $^{\mathrm{+0.26}}_{\mathrm{\thinspace -0.30}}$ at $Q^{2\thinspace }=$ 1.9 \textit{GeV }$^{\mathrm{2}}$, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio $\sigma $(W$^{\mathrm{+}}+$c-bar) / $\sigma $(W$^{\mathrm{-}}+$c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the $s-$s-bar quark asymmetry. [Preview Abstract] |
Friday, October 17, 2014 2:50PM - 3:02PM |
D3.00006: Measurement of the Lifetime of Cosmic Ray Muons Ian Brubaker, Darrel Smith In this experiment cosmic rays create scintillation light as they pass through a 5 gallon mineral oil/scintillator detector. Some of the low-energy cosmic muons come to rest in the detector and their subsequent decays ($\mu^+ \to e^+ \, \nu_{\mu} \, \bar{\nu}_e$ + \, $C.C.$) are observed as a second burst of light. The decay lifetime of 10,392 stopping muons were measured and the mean muon lifetime ($\tau_{\mu}$) was calculated. The composition of cosmic muons includes both positive and negative muons; however, a small fraction of the $\mu^-$ cosmic rays are captured by hydrogen atoms in the mineral oil ($CH_2$) thus affecting the accepted lifetime of muon decays (2.197 $\mu$s). The muon lifetime measured in this experiment $\tau_{\mu} = (2.092 \pm 0.019) \,\mu s$ does not differentiate between positive or negative muons and is consistent with the occurrence of $\mu^-$ capture on hydrogen. [Preview Abstract] |
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