LHCb

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.

Abstract:

The TORCH detector will provide charged particle pi/K/p identification up to 10 GeV/c, combining Time-of-Flight and Cherenkov techniques to achieve a timing resolution of 70 ps for single photons. Based on a scalable design, a Time-of-Flight electronics readout system has been developed to instrument a novel customized 512-channel Micro Channel Plate (MCP) device. A Gigabit Ethernet-based readout scheme that operates the TORCH demonstration unit consisting of ten such MCPs will be reported. The trigger and clock distribution will also be discussed.

Abstract:

A search for the non-resonant decays Bs0 → μ+μ−μ+μ− and B0 → μ+μ−μ+μ− is presented. The measurement is performed using the full Run 1 data set collected in proton-proton collisions by the LHCb experiment at the LHC. The data correspond to integrated luminosities of 1 and 2 fb −1 collected at centre-of-mass energies of 7 and 8 TeV, respectively. No signal is observed and upper limits on the branching fractions of the non-resonant decays at 95% confidence level are determined to be ℬ(Bs0→μ+μ−μ+μ−) < 2.5×10^−9, ℬ(Bs0→μ+μ−μ+μ−) < 6.9×10^−10