Professor Chris Hays

Abstract:

A search for the Standard Model Higgs boson in the H→WW (⋆) →ℓνℓν (ℓ=e, μ) decay mode is presented. The search is performed using proton-proton collision data corresponding to an integrated luminosity of 4.7 fb -1 at a centre-of-mass energy of 7 TeV collected during 2011 with the ATLAS detector at the Large Hadron Collider. No significant excess of events over the expected background is observed. An upper bound is placed on the Higgs boson production cross section as a function of its mass. A Standard Model Higgs boson with mass in the range between 133 GeV and 261 GeV is excluded at 95% confidence level, while the expected exclusion range is from 127 GeV to 233 GeV. © 2012 CERN.

Abstract:

We report a measurement of the difference (ΔACP) between time-integrated CP-violating asymmetries in D0→K+K- and D0→π+π- decays reconstructed in the full data set of proton-antiproton collisions collected by the Collider Detector at Fermilab, corresponding to 9.7fb-1 of integrated luminosity. The strong decay D*+→D0π+ is used to identify the charm meson at production as D0 or D̄0. We measure ΔACP=[-0.62±0.21(stat)±0.10(syst)]%, which differs from zero by 2.7 Gaussian standard deviations. This result supports similar evidence for CP violation in charm-quark decays obtained in proton-proton collisions. © 2012 American Physical Society.

Abstract:

We present a search for the standard model Higgs boson produced in association with a W boson in √s=1.96TeV pp̄ collision data collected with the CDFA II detector at the Tevatron corresponding to an integrated luminosity of 9.45fb-1. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the W boson to an electron or muon and a neutrino, we set 95% credibility level upper limits on the WH production cross section times the H→bb̄ branching ratio as a function of Higgs boson mass. At a Higgs boson mass of 125GeV/c2, we observe (expect) a limit of 4.9 (2.8) times the standard model value. © 2012 American Physical Society.

Abstract:

We present a search for the standard model Higgs boson produced in association with a Z boson in data collected with the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.45fb-1. In events consistent with the decay of the Higgs boson to a bottom-quark pair and the Z boson to electron or muon pairs, we set 95% credibility level upper limits on the ZH production cross section times the H→bb̄ branching ratio as a function of Higgs boson mass. At a Higgs boson mass of 125GeV/c2, we observe (expect) a limit of 7.1 (3.9) times the standard model value. © 2012 American Physical Society.

Abstract:

We report on a search for the standard model Higgs boson produced in association with a vector boson in the full data set of proton-antiproton collisions at √s=1.96TeV recorded by the CDF II detector at the Tevatron, corresponding to an integrated luminosity of 9.45fb-1. We consider events having no identified charged lepton, a transverse energy imbalance, and two or three jets, of which at least one is consistent with originating from the decay of a b quark. We place 95% credibility level upper limits on the production cross section times standard model branching fraction for several mass hypotheses between 90 and 150GeV/c2. For a Higgs boson mass of 125GeV/c2, the observed (expected) limit is 6.7 (3.6) times the standard model prediction. © 2012 American Physical Society.