Long-range two-body final-state interactions and direct CP asymmetry in {B}^{+}\to{\pi}^{+} {K}^{0} decay

TL;DR

This paper calculates the direct CP asymmetry in B+ to pi+ K0 decay, incorporating long-range inelastic final-state interactions, and finds a moderate enhancement of asymmetry contrary to some recent claims.

Contribution

It introduces a detailed calculation of FSI effects on CP asymmetry in B+ decays, including multiple channels and Regge exchange models, challenging previous large asymmetry claims.

Findings

CP asymmetry is enhanced by a factor of ~3 due to FSI

The asymmetry remains below 10-20% as claimed in some literature

Long-range inelastic FSI significantly influence CP asymmetry calculations

Abstract

We present a calculation of the direct CP asymmetry, $A_{CP}^{dir}$, for the process $B^+ \to \pi^+ K^0$ including the effects of long-range inelastic final-state interactions (FSI). We admit three channels in our calculation: $B^+ \to (\pi^+ K^0), (\eta K^+)$, and $(D_s^+ \bar{D}^0)$. The strong scattering is described in terms of Pomeron and Regge exchanges. We find that the direct CP asymmetry is enhanced by a factor of $\sim 3$ as a result of FSI, but remains well short of the claims of (10 - 20)% in recent literature. A critical assessment of papers claiming large CP asymmetries is also presented.