Sneha Malde

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:

A search for CP violation in the decay Λb0 → pK−μ+μ− is presented. This decay is mediated by flavour-changing neutral-current transitions in the Standard Model and is potentially sensitive to new sources of CP violation. The study is based on a data sample of proton-proton collisions recorded with the LHCb experiment, corresponding to an integrated luminosity of 3 fb^−1. The Λb0 → pK−μ+μ− decay is observed for the first time, and two observables that are sensitive to different manifestations of CP violation are measured, ΔACP ≡ ACP(Λ0b→pK−μ+μ−) − ACP(Λ0b→pK−J/ψ) and a aT-odd/CP, where the latter is based on asymmetries in the angle between the μ+μ− and pK− decay planes. These are measured to be ΔACP = (−3.5 ±5.0(stat) ±0.2(syst))×10^−2, aT-odd/CP = (1.2 ±5.0 (stat) ±0.7 (syst))×10^−2,and no evidence for CP violation is found.