Abstract
A search for C!P violation in charmless four-body decays of {varLambda } ^0_{b} and {varXi } ^0_{b} baryons with a proton and three charged mesons in the final state is performed. To cancel out production and detection charge-asymmetry effects, the search is carried out by measuring the difference between the C!P asymmetries in a charmless decay and in a decay with an intermediate charmed baryon with the same particles in the final state. The data sample used was recorded in 2011 and 2012 with the LHCb detector and corresponds to an integrated luminosity of 3 text { fb} ^{-1} . A total of 18 C!P asymmetries are considered, either accounting for the full phase space of the decays or exploring specific regions of the decay kinematics. No significant C!P-violation effect is observed in any of the measurements.
Highlights
All measurements of CP violation performed so far are consistent with the predictions of the Standard Model (SM) [1]
Nonvanishing CP-violating asymmetries have been observed in the decays of both K and B mesons [2]
CP violation has not been observed in baryon decays, some indications for nonvanishing CP asymmetries in bflavoured baryon decays have been reported by the LHCb collaboration [3–6]
Summary
All measurements of CP violation performed so far are consistent with the predictions of the Standard Model (SM) [1]. The charmless B-meson decays are identified by reconstructing the invariant-mass distributions of candidates using the pion or kaon mass instead of the proton mass hypothesis, in the high-mass sidebands defined as msideband < m( phh h ) < 6400 MeV/c2, where msideband = 5680 MeV/c2 for pπ −π +π − and p K − K +π − final states, and msideband = 5840 MeV/c2 for pK −π +π −, pK −π + K − and pK − K + K − final states This background contribution is reduced by the optimisation of the proton PID requirement. A number of background contributions consisting of fully reconstructed b-baryon decays into the two-body Λ+c h, Ξc+h, three-body Dph or (cc) ph combinations, where (cc) represents a charmonium resonance, may produce the same final state as the signal They have similar invariant-mass distribution of the b-baryon candidate as the signal along with a similar selection efficiency. I j j where N j is the number of events related to the component j and Pj,i is the probability distribution function for component j evaluated at the mass of the candidate i
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