A search for new physics: The Belle II experiment

At the beginning of the universe there were equal quantities of matter and anti-matter and yet 13.7 billion years later, the universe is completely dominated by matter. How did this happen? Asymmetries in the interactions of fundamental matter particles and their anti-matter counterparts are likely to be responsible for the matter dominance of the universe and our own existence. However, the known asymmetries do not seem to be sufficient and seem to require new particles or new interactions beyond the Standard Model of Particle Physics. A team of University of Hawaiʻi at Mānoa Department of Physics and Astronomy researchers and those from 23 nations seek to answer these questions and other mysteries of the Universe with the Belle II experiment.

A milestone was reached on April 11 as the Belle II detector was “rolled-in” to the collision point of the SuperKEKB particle accelerator. The UH Belle II team plays a leading role in the beam background commissioning detector (BEAST II) and the readout systems of the iTOP (imaging Time Of Propagation) detector and the KLM (KLong Muon) detector. Following the roll-in, the UH team is preparing for the 2017 summer cosmic ray run in which all of the components of the Belle II outer detector are integrated. The first run with collisions of the electron and positron particle beams will start in February 2018.

The term “roll-in” refers to the operation of moving the entire 1,400 ton Belle II detector system, following the completion of the assembly and integration of the various components, from its assembly area to the beam collision point. The Belle II detector and the SuperKEKB accelerator are now an integrated unit.

large group of worker standing near huge machine

Workers at KEK celebrate the completion of Belle II roll-in (image copyright: Belle II/KEK)

International team explores the beginning of the universe

The Belle II experiment is an international collaboration hosted by KEK in Tsukuba, Japan. Using a state-of-the-art experimental apparatus, Belle II explores the mysteries of the beginning of the universe. The Belle II detector precisely measures elementary particle interactions artificially created with the upgraded SuperKEKB accelerator.

In the Belle II experiment, researchers will observe various elementary particles generated from high energy electron-positron collisions using the 8-meter tall Belle II detector consisting of seven types of subdetectors and investigate the various kinds of elementary particles that emerge from these collisions. The detector will provide measurements of the directions, momenta and energies of the newly produced particles. Compared to the earlier Belle experiment, Belle II has much improved measurement precision and can handle an order of magnitude higher rate from accelerator induced background.

More than 700 researchers from around the world participate in the Belle II experiment. Their goal is to find a significant “deviation” from the Standard Model of particle physics and perhaps determine which of the many proposed new theories describes the world of elementary particles.

UH Mānoa Professors Tom BrowderSven Vahsen and Gary Varner along with other UH Mānoa postdoctoral researchers and graduate students participated in the first Belle experiment at Tsukuba, Japan’s KEK B factory. It is celebrated for its critical role in experimentally verifying the theoretical scheme of Kobayashi and Maskawa, winners of the 2008 Nobel Prize in Physics.

Browder is now the Belle II spokesperson, Vahsen is leading the BEAST II beam background group and Varner is leading the U.S. readout electronics efforts. UH Mānoa is responsible for major components of the Belle II particle identification readout systems using Varner’s renowned “oscilloscope on a chip” application specific integrated circuits (ASICs) as well as the BEAST II background commissioning system, which detects neutrons with Vahsen’s innovative micro-time projection chambers

In addition to the three UH Mānoa faculty members, current members of the Belle II project are postdoctoral scholars Oscar HartbrichDmitri KotchetkovPeter LewisTobias Weber and engineers Matt Andrew, Isar Mostafanezhad and Luca Macchiarulo and graduate students Shawn DubeyMichael HedgesChris Ketter and Ilsoo Seong.

Belle II collaborators

The other U.S. institutions collaborating on Belle II are Carnegie-Mellon UniversityUniversity of CincinnatiLuther CollegeKennesaw StateIndiana UniversityUniversity of PittsburghUniversity of South AlabamaUniversity of South CarolinaVirginia Polytechnic InstituteWayne State University and Pacific Northwest National Lab.