CP Asymmetries in bar B -> bar K* (-> bar K pi) l+ l- and Untagged bar B_s,B_s -> phi (-> K+ K-) l+ l- Decays at NLO

TL;DR

This paper analyzes CP asymmetries in rare B meson decays at NLO, highlighting potential signals of new physics and proposing measurement methods for CP phases in untagged decay modes.

Contribution

It provides a detailed study of CP asymmetries in B decays at NLO, identifying T-odd asymmetries as sensitive probes of non-standard CP violation.

Findings

CP asymmetries in SM are <1%, but can be O(1) with new physics.

T-odd asymmetries can reach O(1), T-even up to 0.1.

Proposes measurement strategies for CP phases in untagged decays.

Abstract

The decay bar B -> bar K* (-> bar K pi) l+ l- offers great opportunities to explore the physics at and above the electroweak scale by means of an angular analysis. We investigate the physics potential of the seven CP asymmetries plus the asymmetry in the rate, working at low dilepton mass using QCD factorization at next-to leading order (NLO). The b ->s CP asymmetries are doubly Cabibbo-suppressed \lesssim 1 % in the Standard Model and its extensions where the CKM matrix is the only source of CP violation. Three CP asymmetries are T-odd, and can be O(1) in the presence of non-standard CP violation. The T-even asymmetries can reach O(0.1), limited by the small strong phases in the large recoil region. We furthermore point out an easy way to measure CP phases from time-integrated, untagged bar B_d, B_d -> K* (-> K0 pi0) l+ l- and bar B_s,B_s -> phi (-> K+ K-) l+ l- decays. Analyses of these CP asymmetries can rule out, or further support the minimal description of CP violation through the CKM mechanism. Experimental studies are promising for (super) flavor factories and at hadron colliders.