Measurement of direct CP violation parameters in B^+/- -> J/psi K^+/- and B^+/- ->J/psi pi^+/- decays with 10.4 fb^-1 of Tevatron data

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 the full Run II data set of 10.4 fb^-1 of proton-antiproton collisions collected using the D0 detector 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 +/- 0.37]%, which is the most precise measurement to date, and ajppi= [-4.2 +/- 4.5]%. Both measurements are consistent with standard model predictions.