Bulletin of the American Physical Society
APS April Meeting 2015
Volume 60, Number 4
Saturday–Tuesday, April 11–14, 2015; Baltimore, Maryland
Session B16: Higgs Physics I |
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Sponsoring Units: DPF Chair: Robin Erbacher, University of California, Davis Room: Key 12 |
Saturday, April 11, 2015 10:45AM - 10:57AM |
B16.00001: Search for the standard model Higgs boson with mass $\sim$ 125 GeV in the H $\to$ WW $\to$ lvjj channel at CMS Joseph Goodell One of the biggest recent successes of the standard model (SM) was the 2012 discovery of a new scalar particle consistent with a SM-like Higgs boson by the CMS and ATLAS experiments at the Large Hadron Collider (LHC). The production of Higgs particles and their subsequent decay allows many distinct final states to be observed. Presented here is a search for a SM Higgs boson with mass $\sim$ 125 GeV that decays through two W bosons, where one W decays hadronically and the other leptonically. While H $\to$ WW has been observed at the LHC in the fully-leptonic final state, analyses in the lvjj channel have not yet achieved sufficient sensitivity to a low-mass Higgs. This analysis was optimized directly for a low-mass Higgs boson and aims to complement the observations of the Higgs in this regime. The decay chain H $\to$ WW $\to$ lvjj requires one W boson to have an off-shell mass; further, the presence of a neutrino in the final state makes Higgs mass reconstruction difficult. Lastly, this decay channel suffers from a large irreducible background from W$+$jets production. Multivariate techniques have been explored for signal extraction. This talk describes a boosted decision tree approach, focusing on the 2012 8 TeV proton-proton collision data collected at CMS. [Preview Abstract] |
Saturday, April 11, 2015 10:57AM - 11:09AM |
B16.00002: Observation and Measurement of the Higgs Boson with the $H\rightarrow WW^{(*)}\rightarrow \ell\nu\ell\nu$ Channel Jonathan Long We present the observation and measurement of the Higgs boson decaying to $WW^{(*)}$ in the leptonic final state using 25 fb$^{-1}$ of data collected with the ATLAS detector at the LHC in 2011 and 2012. We find an excess over the background expectation for $m_H=125.36$ GeV corresponding to 6.1 standard deviations, while the expectation is 5.8. This is the first discovery level sensitivity to the $H\rightarrow WW$ process. The ratio of the observed to expected number of signal-like events is $1.09^{+0.23}_{-0.21}$, the most precise such single-channel measurement with ATLAS. These are the final Run I ATLAS $H\rightarrow WW^{(*)}\rightarrow \ell\nu\ell\nu$ results. [Preview Abstract] |
Saturday, April 11, 2015 11:09AM - 11:21AM |
B16.00003: Bounds on the Higgs boson lifetime with H$\to $4l events Ulascan Sarica Constraints on the width of the Higgs boson, or equivalently its lifetime, are set using the H$\to $ZZ$\to $4l decay channel and the full dataset recorded by the CMS experiment during the LHC Run 1, corresponding to an integrated luminosity of 5.1 fb-1 at a center-of-mass energy of 7 TeV and up to 19.7 fb-1 at 8 TeV. The upper bound on the width is set using the off-shell production technique. [Preview Abstract] |
Saturday, April 11, 2015 11:21AM - 11:33AM |
B16.00004: Evidence for vector-boson fusion production of $H\rightarrow WW^\ast \rightarrow \ell\nu\ell\nu$ Philip Chang Evidence for the vector-boson fusion (VBF) production of the Higgs boson in its $WW^\ast$ decay channel in the dilepton final state is reported. The analysis was performed on 7 and 8~TeV pp collisions recorded by the ATLAS detector with an integrated luminosity of $25\, \mathrm{fb}^{-1}$. One of the main improvements over the previous result is the adoption of multivariate technique for an improved sensitivity to the VBF signal. For a Higgs boson mass of 125.36 GeV, the best-fit value for the ratio of the signal strength for gluon fusion (ggF) and VBF production, $\mu_{math{VBF}}/\mu_{\mathrm{ggF}}$, is measured to be $1.26\,^{+0.61}_{-0.45} \mathrm{(stat.)}\,^{+0.50}_{-0.26} \mathrm{(syst.)}$. The observed significance of the VBF production is 3.2 standard deviations; the expected is 2.7 standard deviations. This marks the final run~1 measurement in this channel; the inclusion of the upcoming run~2 data will improve the precision further and take us to the next step towards the Higgs boson precision era. [Preview Abstract] |
Saturday, April 11, 2015 11:33AM - 11:45AM |
B16.00005: Dark matter in new regions of the NMSSM with a 125 GeV Higgs Augusto Medeiros da Rosa, Francesc Ferrer, Roberto Franceschini The large higgs mass and the null results of the searches for supersymmetric particles at the LHC, are more easily accomodated in non-minimal extensions of the Standard Model, such as the NMSSM. We outline the dark matter properties in a very interesting region of the NMSSM, where the large $\sim 125$ GeV higgs mass is the result of mixings between the SM-like higgs and the singlet higgs. At variance with the usual large $\lambda$ NMSSM, the higgs sector is weakly self-coupled, and the reduced higgsino/singlino coupling assists in attaining the observed relic abundance from thermal decoupling. [Preview Abstract] |
Saturday, April 11, 2015 11:45AM - 11:57AM |
B16.00006: Search for a Standard Model-like Higgs boson decaying into WW to lnu qqbar in pp collisions at sqrt s $=$ 8 TeV Bibhuti Parida A search for a Standard Model-like Higgs boson decaying into the W$+$W- final state is performed with an integrated luminosity of 19.3 inverse femtobarn of pp collisions data recorded with the CMS detector at sqrt s $=$ 8 TeV. The search is performed in the semileptonic channel in the high mass region 600 \textless m\textunderscore H \textless 1000 GeV, where the hadronically decaying W boson is highly boosted and its decay products are contained in one jet. Advanced jet substructure techniques are used in identifying the hadronically decaying W. No evidence for an SM-like Higgs boson has been found in the investigated mass region. [Preview Abstract] |
Saturday, April 11, 2015 11:57AM - 12:09PM |
B16.00007: Constraints on anomalous $HVV$ couplings of the Higgs boson in proton collisions at $7$ and $8\mathrm{TeV}$ Christopher Martin Under the hypothesis that the resonance is a spin-zero boson, the tensor structure of the interactions of the recently discovered Higgs boson is performed using the $H \to ZZ,Z\gamma^*,\gamma^*\gamma^*\to 4\ell$ and $H \to WW \to \ell\nu\ell\nu$ decay modes. The full dataset recorded by the CMS experiment during the LHC Run 1 is used, corresponding to an integrated luminosity of up to $5.1\mathrm{fb}^{-1}$ at a center-of-mass energy of $7\mathrm{TeV}$ and up to $19.7\mathrm{fb}^{-1}$ at $8\mathrm{TeV}$. Limits on eleven anomalous contributions are set. Tighter constraints on anomalous $HVV$ interactions are obtained by combining the $HZZ$ and $HWW$ measurements. All observations are consistent with the expectations for the standard model Higgs boson with the quantum numbers $J^{PC}=0^{++}$. [Preview Abstract] |
Saturday, April 11, 2015 12:09PM - 12:21PM |
B16.00008: ABSTRACT WITHDRAWN |
Saturday, April 11, 2015 12:21PM - 12:33PM |
B16.00009: Search for Standard Model Higgs in ttbar-H, H$\rightarrow$$b\bar{b}$ decay channel at $\sqrt{s}$ = 8 TeV John Wood The most important goal of the Large Hadron Collider (LHC) is to elucidate the mechanism of electroweak symmetry breaking (EWSB). The Higgs boson of the Standard Model (SMH) is a prime candidate for EWSB. The newly discovered boson of July 4th, 2012, with a mass of ~125GeV, has so far been consistent with a SM Higgs. The final confirmation of this new particle as the SMH - or a Higgs boson of another exotic EWSB mechanism - depends on future measurements of all of its properties. The observation of this new particle in association with top-quark pairs would allow the couplings of this particle to top and bottom quarks to be directly measured. Higgs boson production in association with top-quark pairs (ttH), with subsequent decay H$\rightarrow$$b\bar{b}$, is an excellent channel to explore due to the dominant branching ratio of Higgs to $b\bar{b}$ and the kinematic handle the $t\bar{t}$ system offers in the event. However, it presents a plethora of difficult challenges due to a low signal to background ratio and uncertainties on kinematically similar SM backgrounds. This talk describes a search for the SMH in association with top-quark pairs. An analysis of the full 19.4 fb$^{-1}$ 2012 dataset collected by the CMS detector and optimization of the latest results will be presented. [Preview Abstract] |
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