Prospect for measurement of the CP-violating phase  in the channel at a future Z factory

Xiaomei Li; Manqi Ruan; Mingrui Zhao

doi:10.1140/epjc/s10052-024-13217-3

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2024) 84: 859
https://doi.org/10.1140/epjc/s10052-024-13217-3

Regular Article – Theoretical Physics

Prospect for measurement of the CP-violating phase $ϕ_{s}$ $\phi _s$ in the $B_{s} \to J / ψ ϕ$ $B_{s}\rightarrow J/\psi \phi$ channel at a future Z factory

Xiaomei Li¹, Manqi Ruan² and Mingrui Zhao¹^,3^c

¹ Science and Technology on Nuclear Data Laboratory, China Institute of Atomic Energy, Beijing, China
² Institute of High Energy Physics, Chinese Academy of Sciences, Beijing, China
³ Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark

^c mingrui.zhao@mail.labz0.org

Received: 14 August 2023
Accepted: 11 August 2024
Published online: 27 August 2024

Abstract

The CP-violating phase $ϕ_{s}$ $\phi _s$ , the $B_{s}$ $B_{s}$ decay width ( $Γ_{s}$ $\varGamma _s$ ), and the $B_{s}$ $B_{s}$ decay width difference ( $Δ Γ_{s}$ $\varDelta \varGamma _s$ ) are sensitive probes to new physics and can constrain the heavy quark expansion theory. The potential for the measurement at future Z factories is studied in this manuscript. It is found that operating at Tera-Z mode, the expected precision can reach: $σ (ϕ_{s}) = 4.6 mrad$ $\sigma (\phi _s) = 4.6~\textrm{mrad}$ , $σ (Δ Γ_{s}) = 2.4 {ns}^{- 1}$ $\sigma (\varDelta \varGamma _s) = 2.4~\mathrm {ns^{-1}}$ and $σ (Γ_{s}) = 0.72 {ns}^{- 1}$ $\sigma (\varGamma _s) = 0.72~\mathrm {ns^{-1}}$ . The precision of $ϕ_{s}$ $\phi _s$ is 40% larger than the expected precision with the LHCb experiment at HL-LHC. If operating at 10-Tera-Z mode, the precision of $ϕ_{s}$ $\phi _s$ can be measured at 45% of the precision obtained from the LHCb experiment at HL-LHC. However, the measurement of $Γ_{s}$ $\varGamma _s$ and $Δ Γ_{s}$ $\varDelta \varGamma _s$ cannot benefit from the excellent time resolution and tagging power of the future Z-factories. Only operating at 10-Tera-Z mode can the $Γ_{s}$ $\varGamma _s$ and $Δ Γ_{s}$ $\varDelta \varGamma _s$ reach an 18% larger precision than the precision expected to be obtained from LHCb at HL-LHC. The control of penguin contamination at the future Z-factories is also discussed.

© The Author(s) 2024

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