Journal Article

Prospect for measurement of CP-violating observables in $$ {B}_s^0\\to {D}_s^{\\mp }{K}^{\\pm } $$ decays at a future Z factory

Peng, Ji, Wang, Xiaolin, Zhao, Mingrui, Chen, Shanzhen, Ruan, Manqi, Li, Hengne

2025

Overview

A precise determination of the CKM angle γ from $$ {B}_s^0 $$ B s 0 oscillations in $$ {B}_s^0\\to {D}_s^{\\mp }{K}^{\\pm } $$ B s 0 → D s ∓ K ± decays offers a critical test of the Standard Model and probes for new physics. We present a comprehensive study on the prospects of measuring γ at a future Tera- Z factory, utilizing the baseline detector concept of the Circular Electron Positron Collider (CEPC). A two-dimensional simultaneous fit framework, incorporating flavor tagging, decay time resolution modeling, and acceptance corrections, is developed using full Monte Carlo simulations of $$ {B}_s^0\\to {D}_s^{\\mp}\\left(\\to {K}^{\\mp }{K}^{\\pm }{\\pi}^{\\mp}\\right){K}^{\\pm } $$ B s 0 → D s ∓ → K ∓ K ± π ∓ K ± decays and inclusive background processes. The effective flavor tagging power reaches 23.6%, while the decay time resolution is determined to be 26 fs. Projecting to full statistics of signal events across three dominant $$ {D}_s^{-} $$ D s − decay channels, we estimate a statistical precision of σ ( γ ) = 0 . 69 ° , which corresponds to 4.1 Tera- Z boson equivalent data. This study has established the feasibility of sub-degree level γ measurements at a Z factory, highlighting its unique advantages in time-dependent CP violation studies through ultra-precise vertexing and background suppression capabilities.