Abstract:

Measurements of b-hadron masses are performed with the exclusive decay modes B +→J/ψK +, B 0→J/ψK +, B0→J/ψKS0, Bs0→J/ψφ and Λb0→J/ψΛ using an integrated luminosity of 35pb -1 collected in pp collisions at a centre-of-mass energy of 7 TeV by the LHCb experiment. The momentum scale is calibrated with J/ψ→μ +μ - decays and verified to be known to a relative precision of 2 ×10 -4 using other two-body decays. The results are more precise than previous measurements, particularly in the case of the Bs0 and Λb0 masses. © 2012 CERN.

Abstract:

Measurements of b hadron production ratios in proton-proton collisions at a center-of-mass energy of 7 TeV with an integrated luminosity of 3pb -1 are presented. We study the ratios of strange B meson to light B meson production f s/(f u+f d) and Λb0 baryon to light B meson production f Λb/(f u+f d) as a function of the charmed hadron-muon pair transverse momentum p T and the b hadron pseudorapidity η, for p T between 0 and 14 GeV and η between 2 and 5. We find that f s/(f u+f d) is consistent with being independent of p T and η, and we determine f s/(f u+f d)=0.134±0.004-0.010+0.011, where the first error is statistical and the second systematic. The corresponding ratio f Λb/(f u+f d) is found to be dependent upon the transverse momentum of the charmed hadron-muon pair, f Λb/(f u+f d)=(0.404±0. 017(stat)±0.027(syst)±0.105(Br))×[1-(0.031±0. 004(stat)±0.003(syst))×p T(GeV)], where Br reflects an absolute scale uncertainty due to the poorly known branching fraction B(Λc+→pK -π +). We extract the ratio of strange B meson to light neutral B meson production f s/f d by averaging the result reported here with two previous measurements derived from the relative abundances of B̄s0→Ds+π - to B ̄0→D +K - and B ̄0→ D +π -. We obtain f s/f d=0.267-0. 020+0.021. © 2012 CERN.

Abstract:

A search for the decays Bs0→μ+μ- and B 0→μ +μ - is performed with 0.37 fb -1 of pp collisions at s=7 TeV collected by the LHCb experiment in 2011. The upper limits on the branching fractions are B(Bs0→μ+μ-)<1.6×10-8 and B(B0→μ+μ-)<3.6×10-9 at 95% confidence level. A combination of these results with the LHCb limits obtained with the 2010 dataset leads to B(Bs0→μ+μ-)<1.4×10-8 and B(B0→μ+μ-)<3.2×10-9 at 95% confidence level. © 2012 CERN.

Abstract:

Measurement of mixing-induced CP violation in B-s0 decays is of prime importance in probing new physics. So far only the channel B- s 0→J/ψφ has been used. Here we report on a measurement using an LHCb data sample of 0.41 fb -1, in the CP odd eigenstate J/ψf 0(980), where f 0(980)→π +π -. A time-dependent fit of the data with the B-s0 lifetime and the difference in widths of the heavy and light eigenstates constrained to the values obtained from B-s0→J/ψφ yields a value of the CP violating phase of -0.44±0.44±0.02 rad, consistent with the Standard Model expectation. © 2012 CERN.

Abstract:

A measurement of the effective Bs0→K+K- lifetime is presented using approximately 37pb -1 of data collected by LHCb during 2010. This quantity can be used to put constraints on contributions from processes beyond the Standard Model in the Bs0 meson system and is determined by two complementary approaches asτKK=1.440±0.096(stat)±0.008(syst)±0.003(model)ps. © 2011 CERN.