The Rate for $e^+e^-\to B B^\pm π^\mp$ and its Implications for the Study of CP Violation, $B_s$ Identification, and the Study of $B$ Meson Chiral Perturbation Theory

Abstract

H.~Yamamoto has proposed employing $B$ mesons produced in conjunction with a single charged pion at an $Υ$ resonance for studies of CP violation in the neutral $B$ meson system at a symmetric $e^+$-$e^-$ collider. The sign of the charged pion would tag the neutral $B$ meson. We estimate this branching ratio, employing the heavy meson chiral effective field theory. We find a negligible branching ratio to $B B^{\pm} π^{\mp}$ at the $Υ$(5S) and a branching ratio of only a few percent at the $Υ$(6S). However, if nonresonant studies of neutral $B$ mesons should prove feasible, Yamamoto's proposal could be a good method for tagging neutral $B$'s for the study of CP violation at a symmetric collider. We also explore the possibility of studying $B_s$ at the $Υ$(5S). The rate is low but depends sensitively on the precise value of the mass of the $B_s$. The background we compute is comparable to the rate at the largest allowed value of the $B_s$ mass. Finally, we discuss the extraction of the axial pion coupling to $B$ mesons from measurement of the $B\bbarπ$ branching fraction in a restricted region of phase space, where chiral perturbation theory should work well.