Sneha Malde

Abstract:

The decays B+→J/ψ3π+2π− and B+→ψ(2S)π+π+π− are observed for the first time using a data sample corresponding to an integrated luminosity of 3.0 fb^-1, collected by the LHCb experiment in proton-proton collisions at the centre-of-mass energies of 7 and 8TeV. The branching fractions relative to that of B+→ψ(2S)K+ are measured to be B(B+ → J/ ψ3π+2π−)/B(B+ → ψ (2S)K+) = (1.88±0.17±0.09)×10^−2, B(B+ → ψ (2S)π+π+π−)/B(B+ → ψ (2S)K+) = (3.04±0.50±0.26)×10^−2,where the first uncertainties are statistical and the second are systematic.

Abstract:

A search for the decays Bc+→J/ψD(∗)0K+ and Bc+→J/ψD(∗)+K∗0 is performed with data collected at the LHCb experiment corresponding to an integrated luminosity of 3 fb-1. The decays Bc+→J/ψD0K+ and Bc+→J/ψD∗0K+ are observed for the first time, while first evidence is reported for the Bc+→J/ψD∗+K∗0 and Bc+→J/ψD+K∗0 decays. The branching fractions of these decays are determined relative to the Bc+→J/ψπ+ decay. The Bc+ mass is measured, using the J/ψD0K+ final state, to be 6274.28±1.40(stat)±0.32(syst) MeV/c2. This is the most precise single measurement of the Bc+ mass to date.

Abstract:

A search for the B0→K+K− decay is performed using pp-collision data collected by LHCb. The data set corresponds to integrated luminosities of 1.0 and 2.0  fb^−1 at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than 5 standard deviations. The analysis also results in an improved measurement of the branching fraction for the B0s→π+π− decay. The measured branching fractions are B(B0→K+K-)=(7.80±1.27±0.81±0.21)×108 and B(B0sπ+π−)=(6.91±0.54±0.63±0.19±0.40)×10^−7. The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the B0→K+π− branching fraction used as a normalization. For the B0s mode, the fourth accounts for the uncertainty on the ratio of the probabilities for b quarks to hadronize into B0s and B0 mesons.

Abstract:

Decays of the Ξ−b and Ω−b baryons to the charmless final states ph−h'−, where h(') denotes a kaon or pion, are searched for with the LHCb detector. The analysis is based on a sample of proton-proton collision data collected at center-of-mass energies √s=7 and 8 TeV, corresponding to an integrated luminosity of 3 fb^−1. The decay Ξ−b→pK−K− is observed with a significance of 8.7 standard deviations, and evidence at the level of 3.4 standard deviations is found for the Ξ−b→pK−π− decay. Results are reported, relative to the B−→K+K−K− normalization channel, for the products of branching fractions and b-hadron production fractions. The branching fractions of Ξ−b→pK−π− and Ξ−b→pπ−π− relative to Ξ−b→pK−K− decays are also measured.

Abstract:

The first full amplitude analysis of $B^+\to J/\psi \phi K^+$ with $J/\psi\to\mu^+\mu^-$, $\phi\to K^+K^-$ decays is performed with a data sample of 3 fb$^{-1}$ of $pp$ collision data collected at $\sqrt{s}=7$ and $8$ TeV with the LHCb detector. The data cannot be described by a model that contains only excited kaon states decaying into $\phi K^+$, and four $J/\psi\phi$ structures are observed, each with significance over $5$ standard deviations. The quantum numbers of these structures are determined with significance of at least $4$ standard deviations. The lightest is best described as a $D_s^{\pm}D_s^{*\mp}$ cusp, but a resonant interpretation is also possible with mass consistent with, but width much larger than, previous measurements of the claimed $X(4140)$ state. The model includes significant contributions from a number of expected kaon excitations, including the first observation of the $K^{*}(1680)^+\to\phi K^+$ transition.