Work

Prospect for measurement of CP-violating parameters of $${B}_{s}^{0}\to \phi \gamma $$ at the Tera Z factory

Year: 2026

Type: article

Abstract: A bstract The b → sγ transition is a critical flavor-changing neutral current (FCNC) process that could be used to probe CP parity violation (CPV) and new physics (NP). Future electron-positron colliders operating as Tera-Z factories, such as the Circular Electron-Positron Collider (CEPC) and the Future Circular Collider (FCC-ee), offer unique advantages for studying flavor physics, as they provide large data samples, clean collision environments, and superior detector performance. Based on fast simulation studies, we quantify the anticipated precision for measuring $${B}_{s}^{0}\to \phi \gamma $$ at the CEPC Z pole operation, showing that the relative statistical uncertainty could be (0 . 107 ± 0 . 004)%, improved by approximately two orders of magnitude compared to existing measurements. Additionally, we perform a time-dependent analysis of the $${B}_{s}^{0}\to \phi \gamma $$ decay, accounting for $${B}_{s}^{0}\text-{\overline{B} }_{s}^{0}$$ mixing to extract the mixing-induced and CP-violating parameters $${\mathcal{A}}_{\phi \gamma }^{\Delta }$$ , 𝒞 ϕγ , and 𝒮 ϕγ . Using the central values of the LHCb measurements as inputs, the anticipated precisions of these parameters are evaluated as: $$\begin{array}{c}{A}_{\phi \gamma }^{\Delta }=-0.670\pm 0.021\left(stat.\right)\pm 0.040\left(syst.\right),\\ {\mathcal{C}}_{\phi \gamma }=0.110\pm 0.010\left(stat.\right)\pm 0.008\left(syst.\right),\\ {\mathcal{S}}_{\phi \gamma }=0.430\pm 0.010\left(stat.\right)\pm 0.010\left(syst.\right).\end{array}$$ These promising results not only highlight the physics potential of the CEPC but also provide a critical reference for similar future e + e − facilities, notably the FCC-ee.

Source: Journal of High Energy Physics

DOI: 10.1007/jhep10(2026)147