Malcolm John

Abstract:

A measurement of the phase difference between the short- and long-distance contributions to the B+→K+μ+μ− decay is performed by analysing the dimuon mass distribution. The analysis is based on pp collision data corresponding to an integrated luminosity of 3fb^-1 collected by the LHCb experiment in 2011 and 2012. The long-distance contribution to the B+→K+μ+μ− decay is modelled as a sum of relativistic Breit-Wigner amplitudes representing different vector meson resonances decaying to muon pairs, each with their own magnitude and phase. The measured phases of the J/ψ and ψ(2S) resonances are such that the interference with the short-distance component in dimuon mass regions far from their pole masses is small. In addition, constraints are placed on the Wilson coefficients, C9 and C10, and the branching fraction of the short-distance component is measured.

Abstract:

The ratio of branching fractions and the difference in CP asymmetries of the decays B+ → J/ψπ+ and B+ → J/ψK+ are measured using a data sample of pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 3 fb^−1 at centre-of-mass energies of 7 and 8 TeV. The results are B(B+→J/ψπ+)/B(B+→J/ψK+)=(3.83±0.03±0.03)×10^−2, ACP(B+→J/ψπ+)−ACP(B+→J/ψK+)=(1.82±0.86±0.14)×10^−2, where the first uncertainties are statistical and the second are systematic. Combining this result with a recent LHCb measurement of A^CP (B+ → J/ψK+) provides the most precise estimate to date of CP violation in the decay B+→J/ψπ+, A^CP(B+→J/ψπ+)=(1.91±0.89±0.16)×10^−2..

Abstract:

Using proton-proton collision data corresponding to an integrated luminosity of 3.0 fb^-1, recorded by the LHCb detector at centre-of-mass energies of 7 and 8TeV, the B+c → D0K+ decay is observed with a statistical significance of 5.1 standard deviations. By normalising to B+ → D0π+ decays, a measurement of the branching fraction multiplied by the production rates for B+c relative to B+ mesons in the LHCb acceptance is obtained, RD0K = fc/fu X B(B+c → D0K+) = (9.3 +2.8/-2:5 ± 0.6) X 10^-7, where the first uncertainty is statistical and the second is systematic. This decay is expected to proceed predominantly through weak annihilation and penguin amplitudes, and is the first B+c decay of this nature to be observed.

Abstract:

The first observation of the decay ηc(2S) → pp is reported using proton–proton collision data corresponding to an integrated luminosity of 3.0fb^−1 recorded by the LHCb experiment at centre-of-mass energies of 7 and 8 TeV. The ηc(2S)resonance is produced in the decay B+→[cc¯]K+. The product of branching fractions normalised to that for the J/ψ intermediate state, Rηc(2S), is measured to be Rηc (2S) ≡ B(B+→ηc(2S)K+)×B(ηc(2S)→ p¯p )/B(B+→ J/ψ K+)×B( J/ψ → p¯p ) = (1.58±0.33±0.09)×10^−2, where the first uncertainty is statistical and the second systematic. No signals for the decays B+→X(3872)(→pp¯)K+and B+→ψ(3770)(→pp¯p)K+are seen, and the 95% confidence level upper limits on their relative branching ratios are found to be RX(3872)<0.25 ×10−2and Rψ(3770)<0.10. In addition, the mass differences between the ηc(1S)and the J/ψstates, between the ηc(2S)and the ψ(2S)states, and the natural width of the ηc(1S)are measured as M J/ψ − Mηc (1S) = 110.2±0.5 ±0.9MeV, Mψ(2S) − Mηc (2S) = 52.5±1.7±0.6MeV, Γηc (1S) = 34.0±1.9±1.3MeV.