Observation ofBc+→J/ψDs+andBc

Abstract

The decays B are observed for the first time using a dataset, corresponding to an integrated luminosity of 3 fb À1 , collected by the LHCb experiment in proton-proton collisions at center-of-mass energies of ffiffi ffi s p ¼ 7 and 8 TeV. The statistical significance for both signals is in excess of 9 standard deviations. The following ratios of branching fractions are measured to be

First Observation of a BaryonicBc+Decay

“…In conclusion, the decay B In combination with previous results by LHCb [7,11], the B þ c mass is determined to be 6274.7 AE 0.9ðstatÞAE 0.8ðsystÞ MeV=c 2 .…”

“…A combination of this result with previous LHCb measurements [7,11] gives 6274.7 AE 0.9ðstatÞ AE 0.8ðsystÞ MeV=c 2 . In the combination of the mass measurements, the total uncorrelated uncertainties, including the statistical uncertainty and the systematic uncertainties due to the mass fit model and FSR, are used as the weights.…”

“…The impact of the uncertainty of the B þ c lifetime is evaluated from the variation of the relative efficiency when the B þ c lifetime is changed by 1 standard deviation of the LHCb measurement [12]. The systematic uncertainty associated with the reconstruction efficiency of the two additional hadron tracks, p andp, in the B þ c → J=ψppπ þ mode compared to the B þ c → J=ψπ þ mode, is also studied, considering the uncertainty due to the hadronic interaction probability, the track finding efficiency, and the efficiency of the track quality requirements [7]. Different assumptions for the pion PID efficiency in the kinematic regions where no calibration efficiency is available introduce a systematic uncertainty.…”

“…The effect of geometrical acceptance is evaluated by comparing the efficiencies obtained from samples simulated with different data taking conditions. The systematic uncertainty due to the trigger requirement is studied by comparing the trigger efficiency in data and simulated samples, using a large J=ψ sample [7,44]. The impact of the uncertainty of the B þ c lifetime is evaluated from the variation of the relative efficiency when the B þ c lifetime is changed by 1 standard deviation of the LHCb measurement [12].…”

S-wave ground state charmonium decays ofBcmesons in the perturbative QCD approach

“…At the current level accuracy, around 5 × 10 10 B c events are expected to be produced each year [6]. Up to now, the LHCb collaboration has measured the B c mass with 6273 AE 1.3ðstatÞ AE 1.6ðsystÞ MeV=c 2 [7] and some new channels, such as B þ c → J=ψπ þ π − π þ [8], B þ c → J=ψK þ [9], B þ c → ψð2SÞπ þ [10], B þ c → J=ψD ðÃÞþ s [11], B þ c → J=ψK þ K − π þ [12], B þ c → B 0 s π þ [13], and B þ c → J=ψ3π þ 2π − [14] for the first time. We can see all of the observed processes involving the J=ψ final state, due to the narrow peak of J=ψ and the high purity of J=ψ → l þ l − , the decay modes containing the signal of J=ψ meson are among the most easily reconstructible B c decay modes.…”