First observation of Bs0 → D*s2+Xμ-ν decays

Using data collected with the LHCb detector in proton–proton collisions at a centre-of-mass energy of 7 TeV, the semileptonic decays B0s→D+sXμ−ν and B0s→D0K+Xμ−ν are detected. Two structures are observed in the D0K+ mass spectrum at masses consistent with the known Ds1(2536)+ and D∗s22573)+ mesons. The measured branching fractions relative to the total B0s semileptonic rate are B(B0s→D∗+s2Xμ−ν)/B(B0s→Xμ−ν) = (3.3±1.0±0.4)%, and B(B0s→D+s1Xμ−ν)/B(B0s→Xμ−ν) = (5.4±1.2±0.5)%, where the first uncertainty is statistical and the second is systematic. This is the first observation of the D∗+s2 state in B0s decays; we also measure its mass and width

Measurement of the Bs0-Bs0 oscillation frequency δms in Bs0→Ds-(3)π decays

The Bs0-Bs0 oscillation frequency δms is measured with 36 pb-1 of data collected in pp collisions at s=7TeV by the LHCb experiment at the Large Hadron Collider. A total of 1381 Bs0→Ds-π+ and Bs0→Ds-π+π-π + signal decays are reconstructed, with average decay time resolutions of 44 fs and 36 fs, respectively. An oscillation signal with a statistical significance of 4.6σ is observed. The measured oscillation frequency is δm s=17.63±0.11(stat)±0.02(syst)ps -1

Observation of the suppressed ADS modes B± → [π±K-/+ π+π-]D K± and B± → [π± K-/+π+π-]Dπ±

An analysis of and B± → DK± and B± → Dπ± decays is presented where the D meson is reconstructed in the four-body final state K± π-/+π+π-. Using LHCb data corresponding to an integrated luminosity of 1.0 fb-1, first observations are made of the suppressed ADS modes B± →[π± K-/+π+π-]DK± and B± → [π± K-/+π+π-]Dπ± with a significance of 5.1 sigma and greater than 10 sigma, respectively. Measurements of CP asymmetries and CP-conserving ratios of partial widths from this family of decays are also performed. The magnitude of the ratio between the suppressed and favoured B± → DK ± amplitudes is determined to be rKB = 0.097 ± 0.011

Study of beauty hadron decays into pairs of charm hadrons

First observations of the decays Λb 0 → Λc +D(s) - are reported using data corresponding to an integrated luminosity of 3fb-1 collected at 7 and 8 TeV center-of-mass energies in proton-proton collisions with the LHCb detector. In addition, the most precise measurement of the branching fraction B(Bs 0→D+Ds -) is made and a search is performed for the decays B(s) 0→Λc +Λc -. The results obtained are B(Λb 0→Λc +D-)/ B(Λb 0→Λc +D s -)=0.042±0.003(stat)±0.003(syst), [B(Λb 0→Λc +D s -)/B(B̄0→D+D s -)]/[B(Λb 0→Λ c +π-)/B(B̄0→D +π-)]=0.96±0.02(stat)±0.06(syst),B(B s 0→D+Ds -)/ B(B̄0→D+Ds -)=0. 038±0.004(stat)±0.003(syst),B(B̄0→Λ c +Λc -)/B(B̄ 0→D+Ds -)<0.0022[95%C.L.], B(Bs 0→Λc +Λ c -)/B(Bs 0→D+D s -)<0.30[95%C.L.]. Measurement of the mass of the Λb 0 baryon relative to the B̄0 meson gives M(Λb 0)-M(B̄0)=339. 72±0.24(stat)±0.18(syst)MeV/c2. This result provides the most precise measurement of the mass of the Λb 0 baryon to date

First observation of the decay B0s→ϕK∗0

The first observation of the decay B0s→ϕK∗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 B0s→(K+K−)(K−π+) decays is found in the mass windows 1012.5 < M (K + K −) < 1026.5 MeV/c 2 and 746 < M(K − π +) < 1046 MeV/c 2. The signal yield is found to be dominated by B0s→ϕK∗0 decays, and the corresponding branching fraction is measured to be B(B0s→ϕK∗0) = (1.10 ± 0.24 (stat) ± 0.14 (syst) ± 0.08 (f d /f s )) × 10−6, where the uncertainties are statistical, systematic and from the ratio of fragmentation fractions f d /f s which accounts for the different production rate of B 0 and B0s mesons. The significance of B0s→ϕK∗0 signal is 6.1 standard deviations. The fraction of longitudinal polarization in B0s→ϕK∗0 decays is found to be f 0 = 0.51 ± 0.15 (stat) ± 0.07 (syst)

Search for the rare decays B0s→μ+μ− and B0→μ+μ−

A search for the decays and B0→μ+μ− is performed with 0.37 fb−1 of pp collisions at collected by the LHCb experiment in 2011. The upper limits on the branching fractions are 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 and B(B0→μ+μ−)<3.2×10−9 at 95% confidence level

Effective lifetime measurements in the B-s(0) -> K+K-, B-0 -> K+pi(-) and B-s(0) -> pi K-+(-) decays

Measurements of the effective lifetimes in the View the MathML source, B0→K+π− and View the MathML source decays are presented using 1.0 fb−1 of pp collision data collected at a centre-of-mass energy of 7 TeV by the LHCb experiment. The analysis uses a data-driven approach to correct for the decay time acceptance. This is the most precise determination to date of the effective lifetime in the View the MathML source decay and provides constraints on contributions from physics beyond the Standard Model to the View the MathML source mixing phase and the width difference ΔΓs

Measurement of relative branching fractions of B decays to ψ(2S) and J/ψ mesons

The relative rates of B-meson decays into J/ψ and ψ(2S) mesons are measured for the three decay modes in pp collisions recorded with the LHCb detector. The ratios of branching fractions (B) are measured to be B(B +→ψ(2S)K + ) B(B+→J/ψK+) = 0.594±0.006(stat)±0.016(syst)±0.015(Rψ), B(B0→ψ(2S)K ∗0) B(B0→J/ψK∗0) = 0.476±0.014(stat)±0.010(syst)±0.012(Rψ), B(B0 s →ψ(2S)φ) B(B0 s →J/ψφ) = 0.489±0.026(stat)±0.021(syst)±0.012(Rψ), where the third uncertainty is from the ratio of the ψ(2S) and J/ψ branching fractions to μ + μ −. 1 Introductio

Search for the doubly charmed baryon Xi+cc

A search for the doubly charmed baryon Ξ+ cc in the decay mode Ξ+ cc→ Λ + c K−π + is performed with a data sample, corresponding to an integrated luminosity of 0.65 fb−1 , of pp collisions recorded at a centre-of-mass energy of 7 TeV. No significant signal is found in the mass range 3300–3800 MeV/c2 . Upper limits at the 95% confidence level on the ratio of the Ξ+ cc production cross-section times branching fraction to that of the Λ + c , R, are given as a function of the Ξ+ cc mass and lifetime. The largest upper limits range from R < 1.5×10−2 for a lifetime of 100 fs to R < 3.9 × 10−4 for a lifetime of 400 fs

Observation of B0s→χc1ϕ decay and study of B0→χc1,2K∗0 decays

The first observation of the decay View the MathML source and a study of B0→χc1,2K∗0 decays are presented. The analysis is performed using a dataset, 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. The following ratios of branching fractions are measured: B(B0s→χc1φ)/B(B0s→J/ψφ) = (18.9±1.8 (stat) ±1.3 (syst) ±0.8(B))×10−2, B(B0→χc1K∗0)/B(B0→J/ψK∗0) = (19.8±1.1 (stat) ±1.2 (syst) ±0.9(B)) ×10−2, B(B0→χc2K∗0)/B(B0→χc1K∗0) = (17.1 ±5.0 (stat)±1.7 (syst)±1.1(B)) ×10−2, where the third uncertainty is due to the limited knowledge of the branching fractions of χc→J/ψ