Guy Wilkinson

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.

Abstract:

A combination of three LHCb measurements of the CKM angle γ is presented. The decays B±→DK± and B±→Dπ± are used, where D denotes an admixture of D0 and D-0 mesons, decaying into K+K-, π+π-, K±π∓, K±π∓π±π∓, KS0π+π-, or KS0K+K- final states. All measurements use a dataset corresponding to 1.0 fb-1 of integrated luminosity. Combining results from B±→DK± decays alone a best-fit value of γ=72.0° is found, and confidence intervals are setγ∈[56.4,86.7]°at 68% CL,γ∈[42.6,99.6]°at 95% CL. The best-fit value of γ found from a combination of results from B±→Dπ± decays alone, is γ=18.9°, and the confidence intervalsγ∈[7.4,99.2]°∪[167.9,176.4]°at 68% CL are set, without constraint at 95% CL. The combination of results from B±→DK± and B±→Dπ± decays gives a best-fit value of γ=72.6° and the confidence intervalsγ∈[55.4,82.3]°at 68% CL,γ∈[40.2,92.7]°at 95% CL are set. All values are expressed modulo 180°, and are obtained taking into account the effect of D0-D-0 mixing. © 2013 CERN.

Abstract:

A search for CP violation in the phase-space structures of D0 and D-0 decays to the final states K-K+π-π+ and π-π+π+π- is presented. The search is carried out with a data set corresponding to an integrated luminosity of 1.0 fb-1 collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. For the K-K+π-π+ final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the π-π+π+π- final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity. © 2013 CERN.