Rubin-LSST

Abstract:

A search for a Higgs boson decaying into a Z boson and a photon is described. The analysis is performed using proton-proton collision datasets recorded by the CMS detector at the LHC. Events were collected at center-of-mass energies of 7 TeV and 8 TeV, corresponding to integrated luminosities of 5.0fb-1 and 19.6fb-1, respectively. The selected events are required to have opposite-sign electron or muon pairs. No excess above standard model predictions has been found in the 120-160 GeV mass range and the first limits on the Higgs boson production cross section times the H→Zγ branching fraction at the LHC have been derived. The observed at 95% confidence level limits are between about 4 and 25 times the standard model cross section times the branching fraction. For a standard model Higgs boson mass of 125 GeV the expected limit at the 95% confidence level is 10 and the observed limit is 9.5. Models predicting the Higgs boson production cross section times the H→Zγ branching fraction to be larger than one order of magnitude of the standard model prediction are excluded for most of the 125-157 GeV mass range. © 2013 CERN.

Abstract:

Results are reported from a search for non-standard-model Higgs boson decays to pairs of new light bosons, each of which decays into the μ+μ- final state. The new bosons may be produced either promptly or via a decay chain. The data set corresponds to an integrated luminosity of 5.3 fb-1 of proton-proton collisions at s=7 TeV, recorded by the CMS experiment at the LHC in 2011. Such Higgs boson decays are predicted in several scenarios of new physics, including supersymmetric models with extended Higgs sectors or hidden valleys. Thus, the results of the search are relevant for establishing whether the new particle observed in Higgs boson searches at the LHC has the properties expected for a standard model Higgs boson. No excess of events is observed with respect to the yields expected from standard model processes. A model-independent upper limit of 0.86±0.06 fb on the product of the cross section times branching fraction times acceptance is obtained. The results, which are applicable to a broad spectrum of new physics scenarios, are compared with the predictions of two benchmark models as functions of a Higgs boson mass larger than 86 GeV/c2 and of a new light boson mass within the range 0.25-3.55 GeV/c2. © 2013 CERN.

Abstract:

In several extensions of the Standard Model, the top quark can decay into a bottom quark and a light charged Higgs boson H +, t → bH +, in addition to the Standard Model decay t → bW. Since W bosons decay to the three lepton generations equally, while H + maypredominantlydecayinto τν, charged Higgs bosons can be searched for using the violation of lepton universality in top quark decays. The analysis in this paper is based on 4.6 fb-1 of proton-proton collision data at √s=7 TeV collected by the ATLAS experiment at the Large Hadron Collider. Signatures containing leptons (e or μ) and/or a hadronically decaying τ (τ had) are used. Event yield ratios between e + τ had and e + μ, as well as between μ + τ had andμ + e, final states are measured in the data and compared to predictions from simulations. This ratio-based method reduces the impact of systematic uncertainties in the analysis. No significant deviation from the Standard Model predictions is observed. With the assumption that the branching fraction ℬ (H + → τν) is 100%, upper limits in the range 3.2%-4.4% can be placed on the branching fraction ℬ (t → bH +) for charged Higgs boson masses m H+ in the range 90-140 GeV. After combination with results from a search for charged Higgs bosons in t\overline{t} decays using the τ had + jets final state, upper limits on ℬ (t → bH +) can be set in the range 0.8%-3.4%, for m H+ in the range 90-160 GeV.[Figure not available: see fulltext.] © 2013 Cern for the benefit of the ATLAS collaboration.

Abstract:

A search is presented for direct chargino production based on a disappearing-track signature using 20:3 fb-1 of proton-proton collisions at √s = 8 TeV collected with the ATLAS experiment at the LHC. In anomaly-mediated supersymmetry breaking (AMSB) models, the lightest chargino is nearly mass degenerate with the lightest neutralino and its lifetime is long enough to be detected in the tracking detectors by identifying decays that result in tracks with no associated hits in the outer region of the tracking system. Some models with supersymmetry also predict charginos with a significant lifetime. This analysis attains sensitivity for charginos with a lifetime between 0.1 and 10 ns, and significantly surpasses the reach of the LEP experiments. No significant excess above the background expectation is observed for candidate tracks with large transverse momentum, and constraints on chargino properties are obtained. In the AMSB scenarios, a chargino mass below 270 GeV is excluded at 95% confidence level.

Abstract:

A search for the electroweak pair production of charged sleptons and weak gauginos decaying into final states with two leptons is performed using 4.7 fb-1of proton-proton collision data at √s = 7 TeV recorded with the ATLAS experiment at the Large Hadron Collider. No significant excesses are observed with respect to the prediction from Standard Model processes. In the scenario of direct slepton production, if the sleptons decay directly into the lightest neutralino, left-handed slepton masses between 85 and 195 GeV are excluded at 95% confidence level for a 20 GeV neutralino. Chargino masses between 110 and 340 GeV are excluded in the scenario of direct production of wino-like chargino pairs decaying into the lightest neutralino via an intermediate on-shell charged slepton for a 10 GeV neutralino. The results are also interpreted in the framework of the phenomenological minimal supersymmetric Standard Model.