Observation of charmonium pairs produced exclusively in pp collisions

Abstract

The CP-violating asymmetry a s sl is studied using semileptonic decays of B0 s and B0 s mesons produced in pp collisions at a centre-of-mass energy of 7 TeV at the LHC, exploiting a data sample corresponding to an integrated luminosity of 1.0 fb−1 . The reconstructed final states are D± s µ ∓, with the D± s particle decaying in the φπ± mode. The D± s µ ∓ yields are summed over B0 s and B0 s initial states, and integrated with respect to decay time. Data-driven methods are used to measure efficiency ratios. We obtain a s sl = (−0.06 ± 0.50 ± 0.36)%, where the first uncertainty is statistical and the second systematic.