CP violation and determination of the $bs$ "flat" unitarity triangle at FCCee

TL;DR

This paper assesses FCCee's potential to precisely measure two angles of the 'flat' unitarity triangle related to CP violation, enhancing tests of the Standard Model's CP sector with unprecedented accuracy.

Contribution

It provides a detailed analysis of FCCee's expected precision in measuring the angles of the 'flat' unitarity triangle, a novel focus for testing CP violation.

Findings

Expected errors on angles α_s and β_s are better than 0.4° and 0.035°.

Measurements will significantly improve the testing of the Standard Model's CP sector.

Complementary to other measurements, these angles will help verify the unitarity of the CKM matrix.

Abstract

We investigate the sensitivity with which two angles of the "flat" unitarity triangle, defined by $V_{ub}^* V_{us} + V_{cb}^* V_{cs} + V_{tb}^* V_{ts} =0$, can possibly be measured directly at FCCee. We show that the measured errors on the angle $\alpha_s = \arg(- V_{ub}^* V_{us} /V_{tb}^* V_{ts})$ and $\beta_s = \arg(-V_{tb}^* V_{ts} / V_{cb}^* V_{cs})$ should be better than $0.4^\circ$ and $0.035^\circ$, respectively. These measurements, combined with the measurement of the 3rd angle $\gamma_s = \arg(- V_{cb}^* V_{cs}/ V_{ub}^* V_{us})$, discussed in a different paper, will contribute to probe further the consistency of the CP sector of the Standard Model with unprecedented level of accuracy.