In Pursuit of New Physics with B^0_s -> K^+K^-

TL;DR

This paper explores the B^0_s -> K^+K^- decay to determine the CKM angle gamma and investigates its potential to reveal new physics through CP violation and mixing measurements at collider experiments.

Contribution

It provides an updated analysis of gamma using B^0_s -> K^+K^- data and proposes new observables for detecting new physics in B^0_s mixing at LHCb.

Findings

Gamma consistent with unitarity triangle fits

Correlations between lifetime, CP asymmetry, and mixing phase identified

Guidelines for future measurements at LHCb and Tevatron

Abstract

The B^0_s -> K^+K^- decay is the U-spin partner of B^0_d -> pi^+\pi^- and allows a determination of the angle gamma of the unitarity triangle of the Cabibbo-Kobayashi-Maskawa matrix. Using updated information on the branching ratio and the relevant hadronic form factors, we discuss the picture that emerges for gamma from the currently available data, which is in good agreement with the fits of the unitarity triangle. We point out that the B^0_s -> K^+K^- decay also offers interesting probes to search for new physics in B^0_s-\bar B^0_s mixing, thereby complementing the well-known B^0_s -> J/psi phi analyses. The relevant observables are the effective lifetime of this channel and its mixing-induced CP asymmetry. We calculate correlations between these quantities and the CP-violating B^0_s-\bar B^0_s mixing phase, which serve as target regions for improved measurements at the Tevatron and the early data taking at the LHCb experiment. Finally, we discuss the expected situation for the optimal determination of gamma at LHCb, exploiting precise measurements of the CP violation in B^0_s -> K^+K^-.