Ryohei Sugiura ; Yutaka Ushiroda

2023
The University of Tokyo Tokyo

Abstract: Abstract B0 -> φ KS0 decay process is dominated by b -> s sbar s penguin transition, which is sensitive to the contribution from new physics. B0 -> φ KS0 decay is particularly suited for the search of new physics due to the small theoretical uncertainty and suppressed tree diagram contribution within Standard Model. However, the measurement of CP asymmetry for B0 -> φ KS0 is affected by other resonant and non-resonant decays due to the same final state B0 -> K+ K− KS0. In order to solve interference between decay processes and measure CP violating parameters of B0 -> φ KS0 decay precisely, a study of time-dependent CP asymmetries including multiple decay processes is carried out with Dalitz plot technique. B0 -> f0 KS0, B0 -> fX KS0, B0 → χc0 KS0 and non-resonant B0 -> K+ K− KS0 are taken into consideration to solve possible interference. This thesis describes a study of time-dependent CP asymmetry using e+e− energy-asymmetric collision data including 387 × 10^6 B0Bbar0 pairs collected at Belle II experiment. The result is φ_1(φ KS0) = 28.9 ± 10.1(stat) ± 1.7(syst)◦ A_CP(φ KS0) = 0.07 ± 0.18(stat) ± 0.04(syst). The existence of CP violation is confirmed at 2.4σ significance, and the result is consistent with SM within 0.6σ.

Note: Presented on 21 07 2023
Note: PhD