Measurement of D0-D0bar mixing parameters and search for CP violation using D0->K+pi- decays
ArXiv 1309.6534 (2013)
Abstract:
Measurements of charm mixing parameters from the decay-time-dependent ratio of D0->K+pi- to D0->K-pi+ rates and the charge-conjugate ratio are reported. The analysis uses data, corresponding to 3 fb^{-1} of integrated luminosity, from proton-proton collisions at 7 and 8 TeV center-of-mass energies recorded by the LHCb experiment. In the limit of charge-parity (CP) symmetry, the mixing parameters are determined to be x'^2=(5.5 +- 4.9)x10^{-5}, y'= (4.8 +- 1.0)x10^{-3}, and R_D=(3.568 +- 0.066)x10^{-3}. Allowing for CP violation, the mixing parameters are determined separately for D0 and D0bar mesons yielding A_D = (-0.7 +- 1.9)%, for the direct CP-violating asymmetry, and 0.75 < |q/p|< 1.24 at the 68.3% confidence level, where q and p are parameters that describe the mass eigenstates of the neutral charm mesons in terms of the flavor eigenstates. This is the most precise determination of these parameters from a single experiment and shows no evidence for CP violation.Studies of the decays B+→pp̄h+ and observation of B+→Λ̄(1520)p
Physical Review D - Particles, Fields, Gravitation and Cosmology 88:5 (2013)
Abstract:
Dynamics and direct CP violation in three-body charmless decays of charged B mesons to a proton, an antiproton and a light meson (pion or kaon) are studied using data, corresponding to an integrated luminosity of 1.0 fb-1, collected by the LHCb experiment in pp collisions at a center-of-mass energy of 7 TeV. Production spectra are determined as a function of Dalitz-plot and helicity variables. The forward-backward asymmetry of the light meson in the pp̄ rest frame is measured. No significant CP asymmetry in B +→pp̄K+ decay is found in any region of the Dalitz plane. We present the first observation of the decay B +→Λ̄(1520)(→K+p̄)p near the K+p̄ threshold and measure B(B+→Λ̄ (1520)p)=(3.9-0.9+1.0(stat)±0.1(syst)±0.3(BF))×10 -7, where BF denotes the uncertainty on secondary branching fractions. © 2013 CERN. Published by the American Physical Society under the terms of the.Observation of a resonance in B+→K+μ +μ- decays at low recoil
Physical Review Letters 111:11 (2013)
Abstract:
A broad peaking structure is observed in the dimuon spectrum of B +→K+μ+μ- decays in the kinematic region where the kaon has a low recoil against the dimuon system. The structure is consistent with interference between the B+→K +μ+μ- decay and a resonance and has a statistical significance exceeding six standard deviations. The mean and width of the resonance are measured to be 4191-8+9 MeV/c2 and 65-16+22 MeV/c2, respectively, where the uncertainties include statistical and systematic contributions. These measurements are compatible with the properties of the ψ(4160) meson. First observations of both the decay B+→ψ (4160)K+ and the subsequent decay ψ(4160)→μ +μ- are reported. The resonant decay and the interference contribution make up 20% of the yield for dimuon masses above 3770 MeV/c2. This contribution is larger than theoretical estimates. © 2013 CERN, for the LHCb Collaboration Published by the American Physical Society under the terms of the http://creativecommons.org/licenses/by/3.0/ Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Measurement of cp violation in the phase space of B ±→K±π+π- and B±→K±K+K- Decays
Physical Review Letters 111:10 (2013)
Abstract:
The charmless decays B±→K±π +π- and B±→K ±K+K- are reconstructed using data, corresponding to an integrated luminosity of 1.0 fb-1, collected by LHCb in 2011. The inclusive charge asymmetries of these modes are measured as ACP(B±→K±π +π-)=0.032±0.008 (stat)±0.004 (syst)±0.007(J/ψK±) and ACP(B ±→K±K+K-)=-0. 043±0.009 (stat)±0.003 (syst)±0.007(J/ψK ±), where the third uncertainty is due to the CP asymmetry of the B±→J/ψK± reference mode. The significance of ACP(B±→K ±K+K-) exceeds three standard deviations and is the first evidence of an inclusive CP asymmetry in charmless three-body B decays. In addition to the inclusive CP asymmetries, larger asymmetries are observed in localized regions of phase space. © 2013 CERN.Measurement of the Bs(0)→μ+ μ- branching fraction and search for B(0)→μ+ μ- decays at the LHCb experiment.
Physical review letters 111:10 (2013) 101805