Study of direct CP violation in $B^{\pm} \to J/\psi K^{\pm}(\pi^{\pm})$ decays

TL;DR

This paper reports a search for direct CP violation in B± decays to J/ψ K± and J/ψ π± using data from the D0 experiment, finding asymmetries consistent with the Standard Model predictions.

Contribution

First measurement of charge asymmetries in B± → J/ψ K± and J/ψ π± decays with precision comparable to new physics predictions.

Findings

Charge asymmetry in B± → J/ψ K± is +0.0075 ± 0.0061 (stat.) ± 0.0027 (syst.)

Charge asymmetry in B± → J/ψ π± is -0.09 ± 0.08 (stat.) ± 0.03 (syst.)

Results are consistent with Standard Model expectations.

Abstract

We present a search for direct CP violation in $B^{\pm} \to J/\psi K^{\pm}(\pi^{\pm})$ decays. The event sample is selected from 2.8 fb$^{-1}$ of $p\bar{p}$ collisions recorded by D0 experiment in Run II of the Fermilab Tevatron Collider. The charge asymmetry $A_{CP}(B^+ \to J/\psi K^+) = +0.0075 \pm 0.0061$(stat.)$\pm 0.0027$(syst.) is obtained using a sample of approximately 40 thousand $B^{\pm} \to J/\psi K^{\pm}$ decays. The achieved precision is of the same level as the expected deviation predicted by some extensions of the standard model. We also measured the charge asymmetry $A_{CP}(B^+ \to J/\psi \pi^+) = -0.09 \pm 0.08$(stat.)$\pm 0.03$(syst.).