Impact of tag-side interference on time-dependent CP asymmetry measurements using coherent B0 B0bar pairs

TL;DR

This paper investigates how tag-side interference affects time-dependent CP asymmetry measurements in B meson decays, quantifying uncertainties and proposing methods to minimize their impact in experiments at B factories.

Contribution

It provides a detailed evaluation of tag-side interference effects on CP asymmetry measurements and offers strategies to reduce associated uncertainties.

Findings

Uncertainty in CP asymmetry measurement is about 2% or less.

Tag-side interference can produce asymmetries comparable to the signal in certain analyses.

Recommendations are given to incorporate interference effects in time-dependent CP violation studies.

Abstract

Interference between CKM-favored b --> c ubar d and doubly-CKM-suppressed bbar --> ubar c dbar amplitudes in final states used for B flavor tagging gives deviations from the standard time evolution assumed in CP-violation measurements at B factories producing coherent B0 B0bar pairs. We evaluate these deviations for the standard time-dependent CP-violation measurements, the uncertainties they introduce in the measured quantities, and give suggestions for minimizing them. The uncertainty in the measured CP asymmetry for CP eigenstates is ~2% or less. The time-dependent analysis of D*pi, proposed for measuring sin(2 beta + gamma), must incorporate possible tag- side interference, which could produce asymmetries as large signal asymmetry.