Zhang Tingyu ; Hiroaki Aihara

2020
University of Tokyo Tokyo

Abstract: n the Standard Model, the single irreducible complex phase in the Cabibbo-Kobayashi- Maskawa (CKM) quark-mixing matrix causes the effects of Charge-Parity (CP) violation. The Belle and BaBar Collaborations have experimentally confirmed the existence of CP violation in the B meson system. Starting from 2009, as the next-generation B-factory experiment located at the SuperKEKB accelerator complex in Tsukuba, Japan, Belle II aims to reach 40 times larger luminosity and to collect 50 times more data than its predecessor for measurements of the Standard Model parameters with better precision and searching for new physics phenomena over the 8 years operation period. In the B factory, most electrons and positrons collide at center-of-mass energy of Υ (4s) resonance to produce clean B-B ̄ pairs with no fragmentation particles. The design of asym- metric beam energies provides a boost to the center-of-mass in lab frame, thus allowing time dependent decay rate and CP violation measurements to be performed. In the time dependent measurements, the proper-time resolution function is a necessary piece that refers to the resolution between measured and true evolution of time. At the very early stage of physics run in Belle II starting from 2019, several prompt attempts to the parameterization of proper-time resolution function has been made. I took part in the research project to develop an artificial proper-time resolution function that is comparable with Belle. In this thesis, we present the development of such optimized event- by-event model being constructed and validated by lifetime fits on Monte Carlo simulations and 8.7 fb−1 experimental data collected in Belle II. The goal of such study is to provide the necessary tools for improved measurements of time evolution of B mesons.

Note: Presented on 22 07 2020
Note: MSc