Date on Senior Honors Thesis

5-2021

Document Type

Senior Honors Thesis

Degree Name

B.S.

Department

Physics and Astronomy

Degree Program

College of Arts and Sciences

Author's Keywords

geant4; belle 2; KLM; validation; DQM; KEK

Abstract

The Belle II Experiment at the SuperKEKB collider in Tsukuba, Japan is the latest of a new generation of B-factory experiments, designed to produce B meson particles in abundance. The aim of the Belle II experiment is to "discover new physics in the decay of the bottom quark (b), charm quark (c) and tau lepton (τ) and explore the dark sector." The SuperKEKB collider aims to produce instantaneous luminosities of upwards of 8 × 1035 cm−2 s−1, nearly an order of magnitude higher than previous B- factory experiments Belle and BABAR. Software packages, such as physics modules for the popular Geant4 simulation toolkit, must be validated before they are incorporated into the Belle II framework. An example of one such validation campaign is outlined in this thesis. A thorough study is carried out on the novel Belle2 PhysicsList, and its suitability for use is surveyed. Before the detector can be used for physics analysis it must be vetted in a data-taking period. The procedure for data assurance, known as data quality monitoring (DQM), is discussed for the K-Long (KL0 ) and Muon (KLM) Detector. A selection of DQM plots are shown for reference, as these plots are used to diagnose the health and performance of the detector. The conclusions presented show the Belle2 PhysicsList is comparable with the default FTFP_BERT list, and is acceptable for use. Results from DQM work show that the Belle II detector is well-equipped to handle the high-luminosity environment at SuperKEKB with the help of upgraded detector elements and revised software packages.

Lay Summary

This work describes studies done with a modern-day particle detector, the Belle II Detector, installed at the asymmetric high energy collider SuperKEKB hosted at the Japanese National Laboratory (KEK) in Tsukuba, Japan. SuperKEKB collides elec- trons and positrons at the center of the Belle II detector at an intensity never-before explored with a goal of observing new physics phenomenon in the decays of bottom (b) and charm (c) quarks, tau leptons (τ), or from the dark sector. The data from the experiment is collected by several sub-detectors, the largest and outermost of which is the K-Long (KL0) and Muon (KLM) Detector. Analysis of Belle II data requires a simulation toolkit, Geant4, to model the response of the detector to the passage of high energetic particles produced as a result of an electron-positron collision. This work highlights a validation study of a Geant4 software module, the Belle2 Physic- sList as well as a quality assurance study of the KLM subdetector. The findings presented show the Belle2 PhysicsList adequately mirrors the performance of the de- fault PhysicsList while reducing CPU requirements by up to 25%. The data quality monitoring (DQM) process has furthermore shown the KLM detector is operating efficiently and is prepared for physics analysis data-taking.

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