Expected Sensitivity in Light Charged Higgs Boson Searches for H+ to tau+nu and H+ to c+sbar with Early LHC Data at the ATLAS Experiment

In many particle physics models beyond the Standard Model, the top quark can decay to a bottom quark and a light charged Higgs boson in the reaction top to bH+. In the Minimal Super-Symmetric Model (MSSM), the decays H+ to tau+nu can dominate other decays, depending on the parameter space, while H+ to c sbar can have a significant branching ratio for low tan(beta). In the early data-taking period, the ATLAS detector at the Large Hadron Collider (LHC) could either discover the light H+ or substantially improve the current Tevatron upper limits on the branching ratio of top to b H+. We assume an integrated luminosity of 200/pb and a center of mass energy 10 TeV, and evaluate expected upper limits for the branching ratio top to b H+ separately assuming the branching ratio of H+ to tau+ nu is 1 and the branching ratio of H+ to c sbar is 1

Combined search for the Standard Model Higgs boson in pp collisions at sv=7 TeV with the ATLAS detector.

A combined search for the Standard Model Higgs boson with the ATLAS detector at the LHC is presented. The datasets used correspond to integrated luminosities from 4.6 fb^-1 to 4.9 fb^-1 of proton-proton collisions collected at sqrt(s) = 7 TeV in 2011. The Higgs boson mass ranges of 111.4 GeV to 116.6 GeV, 119.4 GeV to 122.1 GeV, and 129.2 GeV to 541 GeV are excluded at the 95% confidence level, while the range 120 GeV to 560 GeV is expected to be excluded in the absence of a signal. An excess of events is observed at Higgs boson mass hypotheses around 126 GeV with a local significance of 2.9 standard deviations (sigma). The global probability for the background to produce an excess at least as significant anywhere in the entire explored Higgs boson mass range of 110-600 GeV is estimated to be ~15%, corresponding to a significance of approximately one sigma

The b-hadron production cross section is measured with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV, using 3.3 pb^-1 of integrated luminosity, collected during the 2010 LHC run. The b-hadrons are selected by partially reconstructing D*muX final states. Differential cross sections are measured as functions of the transverse momentum and pseudorapidity. The measured production cross section for a b-hadron with pT>9 GeV and |eta|<2.5 is 32.7 pm 0.8 (stat) ^{+4.5}_{-6.8} (syst) ub, higher than the next-to-leading-order QCD predictions but consistent within the experimental and theoretical uncertainties.

Results are presented of a search for new particles decaying to large numbers of jets in association with missing transverse momentum, using 4.7 fb^-1 of pp collision data at sqrt(s) = 7 TeV collected by the ATLAS experiment at the Large Hadron Collider in 2011. The event selection requires missing transverse momentum, no isolated electrons or muons, and from >=6 to >=9 jets. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a MSUGRA/CMSSM supersymmetric model, where, for large universal scalar mass m_0, gluino masses smaller than 840 GeV are excluded at the 95% confidence level, extending previously published limits. Within a simplified model containing only a gluino octet and a neutralino, gluino masses smaller than 870 GeV are similarly excluded for neutralino masses below 100 GeV

Measurement of the b-hadron production cross section using decays to D*µ-X final states in pp collisions at sqrt(s) = 7 TeV with the ATLAS detector.

The b-hadron production cross section is measured with the ATLAS detector in pp collisions at sqrt(s) = 7 TeV, using 3.3 pb^-1 of integrated luminosity, collected during the 2010 LHC run. The b-hadrons are selected by partially reconstructing D*muX final states. Differential cross sections are measured as functions of the transverse momentum and pseudorapidity. The measured production cross section for a b-hadron with pT>9 GeV and |eta|<2.5 is 32.7 pm 0.8 (stat) ^{+4.5}_{-6.8} (syst) ub, higher than the next-to-leading-order QCD predictions but consistent within the experimental and theoretical uncertainties

Observation of Associated Near-Side and Away-Side Long-Range Correlations in √s(NN)=5.02 TeV Proton-Lead Collisions with the ATLAS Detector

Two-particle correlations in relative azimuthal angle () and pseudorapidity () are measured in √s(NN)= 5.02 TeV p þ Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1 b1 of data as a function of transverse momentum (pT) and the transverse energy (EPb T ) summed over 3:1<<4:9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2 < jj < 5) ‘‘near-side’’ ( 0) correlation that grows rapidly with increasing EPb T . A long-range ‘‘away-side’’ ( ) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small EPb T , is found to match the near-side correlation in magnitude, shape (in and ) and EPb T dependence. The resultant correlation is approximately symmetric about =2, and is consistent with a dominant cos2 modulation for all EPb T ranges and particle pT

Search for microscopic black holes in a like-sign dimuon final state using large track multiplicity with the ATLAS detector

A search is presented for microscopic black holes in a like-sign dimuon final state in proton–proton collisions at √s=8 TeV. The data were collected with the ATLAS detector at the Large Hadron Collider in 2012 and correspond to an integrated luminosity of 20.3 fb-1. Using a high track multiplicity requirement, 0.6+- 0.2 background events from Standard Model processes are predicted and none observed. This result is interpreted in the context of low-scale gravity models and 95% C.L. lower limits on microscopic black hole masses are set for different model assumptions

Search for dark matter pair production in events with a hadronically decaying W or Z boson and missing transverse momentum in pp collisions at √s = 8 TeV with the ATLAS detector

A search is presented for dark matter pair production in association with a W or Z boson in pp collisions representing 20.3 fb−1 of integrated luminosity at √s=8 TeV using data recorded with the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet with the jet mass consistent with a W or Z boson, and with large missing transverse momentum are analyzed. The data are consistent with the standard model expectations. Limits are set on the mass scale in effective field theories that describe the interaction of dark matter and standard model particles, and on the cross section of Higgs production and decay to invisible particles. In addition, cross section limits on the anomalous production of W or Z bosons with large missing transverse momentum are set in two fiducial regions