1304.1655 (D0 Collaboration)

An improved measurement of direct CP violation parameters in B^+- ->
J/psi K^+- and B^+- -> J/psi pi^+- decays    [PDF]

D0 Collaboration

We present a measurement of the direct CP-violating charge asymmetry in B^+- mesons decaying to J/psi K^+- and J/psi pi^+- where J/psi decays to mu^+ mu^-, using 10.4 fb^-1 of proton-antiproton collisions collected by the D0 detector during Run II at the Fermilab Tevatron Collider. A difference in the yield of B^- and B^+ mesons in these decays is found by fitting to the difference between their reconstructed invariant mass distributions resulting in asymmetries of ajpk = [ 0.59 +/- 0.36 ]%, which is the most precise measurement to date, and ajppi = [ -4.2 +/- 4.8 ]%. Both measurements are consistent with standard model predictions.

View original: http://arxiv.org/abs/1304.1655