RUI: Studies of Heavy Quarkonium Spectroscopy with Belle and Belle II

Luther College, Decorah IA

Investigators

Abstract

One of the major intellectual achievements of the 20th century was the development of the Standard Model (SM) of particle physics. This model succeeded in classifying all of the elementary particles known at the time into a hierarchy of groups having similar quantum properties. The validity of this model to date was recently confirmed by the discovery of the Higgs boson at the Large Hadron Collider (LHC) at the CERN laboratory near Geneva Switzerland. However, the Standard Model as it currently exists leaves open many questions about the universe, including such fundamental questions as to why the mass of the Higgs boson has the value it has. To answer these questions it is necessary to go beyond the present picture of the Universe described by the Standard Model to the next phase of development, Beyond the Standard Model (BSM). Investigations in BSM physics probe such questions as why matter dominates over anti-matter in the Universe, the values of the masses of the fundamental constituents of matter, the quarks and the leptons, the size of the mixings among the quarks, and separately among the leptons, and the properties of dark matter. This project will focus on the study of the properties of special types of particles, mesons, whose nature can reveal information about fundamental physics beyond the Standard Model. The work in this award will use data collected at the Belle experiment at the High Energy Accelerator Research Organization (KEK) laboratory in Japan. Belle is built around the interaction region of an asymmetric electron-positron collider. The main goal of Belle is to detect particles made of a quark-anti-quark pair, so called mesons. In particular those mesons made of charm quarks (charmonium) and bottom quarks (bottomonium). These mesons are described in the SM by the theory of Quantum Chromodynamics (QCD). By studying these mesons, one can probe for BSM fundamental physics processes such as Charge Parity (CP) violation, rare meson decays and possible exotic particles which could indicate the presence of Dark Matter. The Belle Experiment at KEK in Japan has the world's largest data samples recorded at the bottomonium resonances in the mass range of 10 GeV, the so-called Upsilon resonances. At these resonant energies the electron positron beam particles have a much higher probability of producing B mesons, allowing experimenters to acquire large statistics and observe rare phenomena . The central aim of this RUI program of research by the Luther College group is to study the spectroscopy of bottomonium and related states, with a focus on resonant states that probe the limits of our understanding of Quantum Chromodynamics (QCD) and improving the theoretical understanding in lattice QCD (the techniques used to make computer predictions of QCD calculations). The Luther College program provides an unusual opportunity for undergraduate students to become meaningfully involved in a world-leading experiment, taking part in every aspect of Belle data analysis, and in the development of software tools for the upgraded experiment, Belle II.