A measurement of the CP asymmetry difference between Λ c +  → pK−K+ and pπ−π+ decays

Robert Appleby, William Barter, Silvia Borghi, Christopher Burr, Stefano De Capua, Deepanwita Dutta, Evelina Gersabeck, Marco Gersabeck, Lucia Grillo, George Lafferty, Igor Babuschkin, Andrew Mcnab, Christopher Parkes, Gediminas Sarpis, Mark Williams, Roger Barlow, Lorenzo Capriotti, The LHCb Collaboration

Research output: Contribution to journalArticlepeer-review


The difference between the CP asymmetries in the decays Λ c + → pK K + and Λ c + → 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 Λ c + candidates are reconstructed as part of the Λ b 0 → Λ c +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 Λ c + → pπ π + sample. This alters the definition of the integrated CP asymmetry to A CP wgt(pπ π +). Both samples are corrected for reconstruction and selection efficiencies across the five-dimensional Λ c + 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.].

Original languageEnglish
Article number182
Number of pages21
JournalThe Journal of High Energy Physics
Issue number3
Early online date29 Mar 2018
Publication statusPublished - 2018


  • CP violation
  • Charm physics
  • Flavor physics
  • Hadron-Hadron scattering (experiments)


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