Rate and CP-asymmetry sum rules in B→KπB \to K \pi

The observed violation of $A_{CP}(B^0 \to K^+ \pi^-) = A_{CP}(B^+ \to K^+ \pi^0)$ has been recently mentioned as a puzzle for the standard model. We point out that while this violation may be accounted for by a large color-suppressed tree amplitude, a sum rule involving three or four $B\to K\pi$ CP asymmetries should hold. The current experimental status of these sum rules and of a sum rule for $B\to K\pi$ decay rates is presented.Comment: 4 pages, no figures, to be submitted to Phys. Rev. D (Brief Reports). Remark and references adde

Background check for anomalous like-sign dimuon charge asymmetry

The D0 Collaboration has reported an excess of roughly one percent of $\mu^- \mu^-$ pairs over $\mu^+ \mu^+$ pairs in $\bar p p$ collisions at a center-of-mass energy $\sqrt{s} = 1.96$ GeV at the Fermilab Tevatron, when known backgrounds are subtracted. This excess, if ascribed to CP violation in meson-antimeson mixing of non-strange or strange neutral $B$ mesons, is about 40 times that expected in the Standard Model (SM). We propose a null test, based on a tight restriction on the muon impact parameter $b$, to confirm that this excess is indeed due to $B$ mesons. If the asymmetry is due to anomalous CP violation in $B_s$-$\bar B_s$ mixing then a tight restriction on $b$ would increase by a factor two the net asymmetry from neutral $B$ mixing, while the sample of dimuons from neutral $B$ decays will be reduced significantly relative to background events.Comment: 7 pages, 2 figures, to be published in Phys. Rev. D. Abstract expanded; text and acknowledgment adde

Rates and Asymmetries in B→KπB \to K \pi Decays

We discuss a potential discrepancy in an approximate relation among $B \to K \pi$ rates which, with increased statistical significance, would imply new physics in $\Delta I=1$ transitions. An approximate relation between CP-violating rate differences in $B^0/\bar{B}^0 \to K^{\pm}\pi^{\mp}$ and $B^{\pm} \to K^{\pm}\pi^0$ is used to combine these rate differences to reduce upper limits on the two CP asymmetries. These rates and asymmetries are used to update bounds on the CKM phase $\gamma$.Comment: 11 pages, LaTeX, 3 figures, a reference added, to be published in Phys. Lett.