May 22, 2020.
The research at High Energy Accelerator Research Organization (KEK) focuses on flavor physics and CP violation measurements which will provide an importance test of the standard model and new physics. The accelerator at KEK is SuperKEKB, an upgraded of KEKB. SuperKEKB is an asymmetric electron–positron collider. The beam energies were set for B and anti-B meson production (B-factory). The intended luminosity is 8x1035 cm–2 s–1. This project will run for a decade and the goal is to collect an integrated luminosity of 50 ab–1.
Fig. 1 Schematic diagram of the SUPERKEKB (from https://www.belle2.org/).
The detector uses in the project is called the Belle II detector. The detector consists of [1,2]
- Pixel Detector (PXD) and Silicon Vertex Detector (SVD) for measuring vertex position.
- Central Drift Chamber (CDC): tracking detector.
- Aerogel Ring Imaging Cherenkov Counter (ARICH): particle identification.
- Barrel Particle Identification Detector (TOP): particle identification.
- Electromagnetic Calorimeter (ECL): measuring photon and measuring kaon together with KLM.
- K0L and Muon Detector (KLM): measuring kaon (K0L) and identifying muons.
Fig. 2 Schematic diagram of the Belle II Detector (from http://neurotrigger.org/).
Our Chiang Mai University team has joined the project in the CDC group. CDC is a wire chamber which provides trajectory of the passing charged particle. Most of the calibration work in CDC is finished. Although the momentum resolution might not be optimal yet, the current momentum resolution is sufficient for data analysis and already is an improvement over the Belle detector momentum resolution . After operating for a year with full set Belle II detector, the SuperKEKB has produced 1 paper on the search for Z’ boson , and a little more than hundred proceedings on the Belle II detectors, and the preliminary physics results .
1. S. Hashimoto et al., editors, Letter of Intent for KEK Super B Factory (Part-II, Detector), KEK Report 04-4 (2004).
2. T. Abe et al., The Belle II Technical Design Report, KEK Report 2010-1 (2010).
3. Dong Van Thanh, Study of lepton flavor violation with a high-resolution tracking device for Belle II experiment, Ph.D. dissertation, Department of Particle and Nuclear Physics, School of High Energy Accelerator Science, The Graduate University for Advanced Studies, Japan (2018).
4. I. Adachi et al. (Belle II Collaboration), Search for an Invisibly Decaying Z′ boson at Belle II in e+e− → µ+µ−(e±µ ±) Plus Missing Energy Final States, Phys. Rev. Lett. 124, 141801 (2020).
Asst. Prof. Dr. Khem Chirapatpimol
Dept. of Physics and Materials Science, Fac. of Science, Chiang Mai University, Chiang Mai-50200, Thailand