A measurement of the CP asymmetry difference between Λc+ → pK − K + and pπ−π+ decays (English)

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The difference between the CP asymmetries in the decays Λc+ → pK−K+ and Λc+ → pπ−π+ is presented. Proton-proton collision data taken at centre-of-mass energies of 7 and 8 TeV collected by the LHCb detector in 2011 and 2012 are used, corresponding to an integrated luminosity of 3 fb−1. The Λc+ candidates are reconstructed as part of the Λb0 → Λc+μ−X decay chain. In order to maximize the cancellation of production and detection asymmetries in the difference, the final-state kinematic distributions of the two samples are aligned by applying phase-space-dependent weights to the Λc+ → pπ−π+ sample. This alters the definition of the integrated CP asymmetry to ACPwgt(pπ−π+). Both samples are corrected for reconstruction and selection efficiencies across the five-dimensional Λc+ decay phase space. The difference in CP asymmetries is found to be ΔACPwgt=ACP(pK−K+)−ACPwgt(pπ−π+)=(0.30±0.91±0.61)%, where the first uncertainty is statistical and the second is systematic.[Figure not available: see fulltext.].