LHCb

Abstract:

Measurements of CP observables in B ± →D (⁎) K ± and B ± →D (⁎) π ± decays are presented, where D (⁎) indicates a neutral D or D ⁎ meson that is an admixture of D (⁎)0 and D¯ (⁎)0 states. Decays of the D ⁎ meson to the Dπ 0 and Dγ final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the B candidate invariant mass distribution. Decays of the D meson are fully reconstructed in the K ± π ∓ , K + K − and π + π − final states. The analysis uses a sample of charged B mesons produced in pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0 fb −1 taken at centre-of-mass energies of s=7, 8 and 13 TeV, respectively. The study of B ± →D ⁎ K ± and B ± →D ⁎ π ± decays using a partial reconstruction method is the first of its kind, while the measurement of B ± →DK ± and B ± →Dπ ± decays is an update of previous LHCb measurements. The B ± →DK ± results are the most precise to date.

Abstract:

Bose-Einstein correlations of same-sign charged pions, produced in proton-proton collisions at a 7 TeV centre-of-mass energy, are studied using a data sample collected by the LHCb experiment. The signature for Bose-Einstein correlations is observed in the form of an enhancement of pairs of like-sign charged pions with small four-momentum difference squared. The charged-particle multiplicity dependence of the Bose-Einstein correlation parameters describing the correlation strength and the size of the emitting source is investigated, determining both the correlation radius and the chaoticity parameter. The measured correlation radius is found to increase as a function of increasing charged-particle multiplicity, while the chaoticity parameter is seen to decrease.

Abstract:

The first observation of the decay of a B0 meson to a purely baryonic final state, B0→pp¯ , is reported. The proton-proton collision data sample used was collected with the LHCb experiment at center-of-mass energies of 7 and 8 TeV and corresponds to an integrated luminosity of 3.0 fb^−1. The branching fraction is determined to be B(B0→pp¯)=(1.25±0.27±0.18)×10^−8, where the first uncertainty is statistical and the second systematic. The decay mode B0→pp¯ is the rarest decay of the B0 meson observed to date. The decay B0s→pp¯ is also investigated. No signal is seen and the upper limit B(B0s→pp¯)<1.5×10^−8 at 90% confidence level is set on the branching fraction.

Abstract:

A measurement of the shape of the differential decay rate and the associated Isgur-Wise function for the decay Λ0b→Λ+cμ−¯νμ is reported, using data corresponding to 3  fb^−1 collected with the LHCb detector in proton-proton collisions. The Λ+cμ−¯νμ(+anything) final states are reconstructed through the detection of a muon and a Λ+c baryon decaying into pK−π+, and the decays Λ0b→Λ+cπ+π−μ−νμ¯ are used to determine contributions from Λ0b→Λ*+cμ−ν¯ μ decays. The measured dependence of the differential decay rate upon the squared four-momentum transfer between the heavy baryons, q2, is compared with expectations from heavy-quark effective theory and from unquenched lattice QCD predictions.