Sneha Malde

Abstract:

Direct and mixing-induced CP-violating asymmetries in B0s → K+K- decays are measured for the first time using a data sample of pp collisions, corresponding to an integrated luminosity of 1.0 fb-1, collected with the LHCb detector at a centre-of-mass energy of 7TeV. The results are CKK = 0.14 ± 0.11 ± 0.03 and SKK = 0.30 ± 0.12 ± 0.04, where the first uncertainties are statistical and the second systematic. The corresponding quantities are also determined for B0→π +π- decays to be Cππ = -0.38±0.15±0.02 and Sππ = -0.71±0. 13±0.02, in good agreement with existing measurements.

Abstract:

The decay Bc+to → J/ψ K+ is observed for the first time using a data sample, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. A yield of 46 ± 12 events is reported, with a significance of 5.0 standard deviations. The ratio of the branching fraction of Bc+to → J/ψ K+ to that of Bc+to → J/ψ K+ is measured to be 0.069 ± 0.019 ± 0.005, where the first uncertainty is statistical and the second is systematic. © 2013 Cern for the benefit of the LHCb collaboration.

Abstract:

The first observation of the decay Bs0 → φK̄*0 is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb-1 of pp collisions at √s = 7 TeV, collected with the LHCb detector. A yield of 30 ± 6 Bs0 → (K+K-)(K -π+) decays is found in the mass windows 1012:5 < M(K+K) < 1026:5MeV/c2 and 746 < M(K -π+) < 1046MeV/c2. The signal yield is found to be dominated by Bs0 → φK̄* 0 decays, and the corresponding branching fraction is measured to be B(Bs0 → φK̄*0) = (1:10 ± 0:24 (stat) ± 0:14 (syst) ± 0:08 (fd/f s)) × 10-6, where the uncertainties are statistical, systematic and from the ratio of fragmentation fractions fd/f s which accounts for the different production rate of B0 and Bs0 mesons. The significance of Bs0 → φK̄*0 signal is 6.1 standard deviations. The fraction of longitudinal polarization in Bs0 → φK̄*0 decays is found to be f 0 = 0:51 ± 0:15 (stat) ± 0:07 (syst). Copyright CERN.

Abstract:

Limits on the cross-section times branching fraction for neutral Higgs bosons, produced in pp collisions at √s = 7 TeV, and decaying to two tau leptons with pseudorapidities between 2.0 and 4.5, are presented. The result is based on a dataset, corresponding to an integrated luminosity of 1.0 fb -1, collected with the LHCb detector. Candidates are identified by reconstructing final states with two muons, a muon and an electron, a muon and a hadron, or an electron and a hadron. A model independent upper limit at the 95% confidence level is set on a neutral Higgs boson cross-section times branching fraction. It varies from 8.6 pb for a Higgs boson mass of 90 GeV to 0.7 pb for a Higgs boson mass of 250 GeV, and is compared to the Standard Model expectation. An upper limit on tan β in the Minimal Supersymmetric Model is set in the mh0max scenario. It ranges from 34 for a CP -odd Higgs boson mass of 90 GeV to 70 for a pseudo-scalar Higgs boson mass of 140 GeV. [Figure not available: see fulltext.] © 2013 Cern for the benefit of the LHCb collaboration.

Abstract:

The branching fraction of the rare decay B 0 → K *0 e + e - in the dilepton mass region from 30 to 1000 MeV/c 2 has been measured by the LHCb experiment, using pp collision data, corresponding to an integrated luminosity of 1.0 fb-1, at a centre-of-mass energy of 7 TeV. The decay mode B 0 → J/ψ (e + e -)K *0 is utilized as a normalization channel. The branching fraction B(B 0 → K *0 e + e -) is measured to be B(B 0 → K *0 e + e -)30-1000 MeV/c2=(3.1+0.9-0.80.2-0.3 ± 0.2) × 10 -7 where the first error is statistical, the second is systematic, and the third comes from the uncertainties on the B 0 → J/ψ K *0 and J/ψ → e + e - branching fractions. [Figure not available: see fulltext.] © 2013 Cern for the benefit of the LHCb collaboration.