LHCb

Abstract:

A measurement of the cross-section for W → eν production in pp collisions is presented using data corresponding to an integrated luminosity of 2 fb−1 collected by the LHCb experiment at a centre-of-mass energy of √s=8 TeV. The electrons are required to have more than 20 GeV of transverse momentum and to lie between 2.00 and 4.25 in pseudorapidity. The inclusive W production cross-sections, where the W decays to eν, are measured to be (Formula presented.) where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. Differential cross-sections as a function of the electron pseudorapidity are measured. The W+/W− cross-section ratio and production charge asymmetry are also reported. Results are compared with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. Finally, in a precise test of lepton universality, the ratio of W boson branching fractions is determined to be B(W → eν)=B(W → µν) = 1:020 ± 0:002 ± 0:019 where the first uncertainty is statistical and the second is systematic.[Figure not available: see fulltext.]

Abstract:

The B0sπ± invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to 3fb^-1 of pp collision data at √s=7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X(5568) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B0sπ± final state. The same limits also apply to a possible exotic meson decaying through the chain B*0sπ±, B*0s → B0sγ where the photon is excluded from the reconstructed decays.

Abstract:

The ratio of branching fractions RK/π ≡ ℬ(Bc+ → J/ψK+)/ℬ(Bc+ → J/ψπ+) is measured with pp collision data collected by the LHCb experiment at centre-of-mass energies of 7 TeV and 8 TeV, corresponding to an integrated luminosity of 3 fb−1. It is found to be RK/π = 0.079 ± 0.007 ± 0.003, where the first uncertainty is statistical and the second is systematic. This measurement is consistent with the previous LHCb result, while the uncertainties are significantly reduced.

Abstract:

© 2016 The Author(s) Measurements of CP observables in B ± →DK ± and B ± →Dπ ± decays are presented where the D meson is reconstructed in the final states K ± π ∓ , π ± K ∓ , K + K − , π + π − , K ± π ∓ π + π − , π ± K ∓ π + π − and π + π − π + π − . This analysis uses a sample of charged B mesons from pp collisions collected by the LHCb experiment in 2011 and 2012, corresponding to an integrated luminosity of 3.0 fb −1 . Various CP-violating effects are reported and together these measurements provide important input for the determination of the unitarity triangle angle γ. The analysis of the four-pion D decay mode is the first of its kind.