Abstract:

The B+→D∗-K+π+ decay potentially provides an excellent way to investigate charm meson spectroscopy. The decay is searched for in a sample of proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV, corresponding to an integrated luminosity of 3 fb-1. A clear signal is observed, and the ratio of its branching fraction to that of the B+→D∗-π+π+ normalization channel is measured to be B(B+→D∗-K+π+)/B(B+→D∗-π+π+)=(6.39±0.27±0.48)×10-2, where the first uncertainty is statistical and the second is systematic. This is the first observation of the B+→D∗-K+π+ decay.

Abstract:

A study of Bs0 → ηcϕ and Bs0 → ηcπ+π− decays is performed using pp collision data corresponding to an integrated luminosity of 3.0 fb^−1 , collected with the LHCb detector in Run 1 of the LHC. The observation of the decay Bs0 → ηcϕ is reported, where the ηc meson is reconstructed in the pp, K+K−π+π−, π+π−π+π− and K+K−K+K decay modes and the ϕ(1020) in the K+K− decay mode. The decay Bs0→J/ψϕ is used as a normalisation channel. Evidence is also reported for the decay Bs0 → ηcπ+π− , where the ηc meson is reconstructed in the pp decay mode, using the decay Bs0 → J/ψπ+π− as a normalisation channel. The measured branching fractions are(Formula Presented.)where in each case the first uncertainty is statistical, the second systematic and the third uncertainty is due to the limited knowledge of the external branching fractions..

Abstract:

Asymmetries in the time-dependent rates of D0→K+K- and D0→π+π- decays are measured in a pp collision data sample collected with the LHCb detector during LHC Run 1, corresponding to an integrated luminosity of 3  fb^-1. The asymmetries in effective decay widths between D0 and D¯0 decays, sensitive to indirect CP violation, are measured to be AΓ(K+K-)=(-0.30±0.32±0.10)×10^-3 and AΓ(π+π-)=(0.46±0.58±0.12)×10^-3, where the first uncertainty is statistical and the second systematic. These measurements show no evidence for CP violation and improve on the precision of the previous best measurements by nearly a factor of two.

Abstract:

The production cross-section of J/ψ pairs is measured using a data sample of pp collisions collected by the LHCb experiment at a centre-of-mass energy of s=13 TeV, corresponding to an integrated luminosity of 279 ±11 pb −1 . The measurement is performed for J/ψ mesons with a transverse momentum of less than 10 GeV/c in the rapidity range 2.0 < y < 4.5. The production cross-section is measured to be 15.2 ± 1.0 ± 0.9 nb. The first uncertainty is statistical, and the second is systematic. The differential cross-sections as functions of several kinematic variables of the J/ψ pair are measured and compared to theoretical predictions.

Abstract:

Production cross-sections of prompt charm mesons are measured using data from pp collisions at the LHC at a centre-of-mass energy of 5TeV. The data sample corresponds to an integrated luminosity of 8:60 ± 0:33 pb^-1 collected by the LHCb experiment. The production cross-sections of D0, D+, D+s, and D*+ mesons are measured in bins of charm meson transverse momentum, pT, and rapidity, y. They cover the rapidity range 2:0 < y < 4:5 and transverse momentum ranges 0 < pT < 10 GeV=c for D0 and D+ and 1 < pT < 10 GeV=c for D+s and D*+ mesons. The inclusive cross-sections for the four mesons, including charge-conjugate states, within the range of 1 < pT < 8 GeV=c are determined to be

σ(pp → D0X) = 1004 ± 3 ± 54 μb;

σ(pp → D+X) = 402 ± 2 ± 30 μb;

σ(pp → D+s X) = 170 ± 4 ± 16 μb;

σ(pp → D*+X) = 421 ± 5 ± 36 μb

where the uncertainties are statistical and systematic, respectively.