Solve the hypertriton lifetime puzzle

2020 Fiscal Year Final Research Report

• Project/Area Number: 17H04842
• Research Category: Grant-in-Aid for Young Scientists (A)
• Allocation Type: Single-year Grants
• Research Field: Particle/Nuclear/Cosmic ray/Astro physics
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: MA Yue 国立研究開発法人理化学研究所, 開拓研究本部, 専任研究員 (80639576)
• Project Period (FY): 2017-04-01 – 2021-03-31
• Keywords: hypertriton lifetime / Cherenkov calorimeter

Outline of Final Research Achievements

We have proposed a new experiment (J-PARC E73) to solve the hypertriton lifetime puzzle with a novel production method (K-, pi0). We demonstrated the feasibility with 4He target as J-PARC T77 experiment in 2020. We collected a world record of ~1k ^4_{\Lambda}H events with ~10 times better signal to noise ratio than previous KEK results. Our new approach may also find application for other experiments need pi0 identification such as neutron-rich hypernuclear gamma-ray spectroscopy.
As a pilot run of the E73 experiment, we have successfully measured the hypertriton production cross section in May 2021. We have clearly observed pi- from both 2-body and 3-body decay of hypertriton ground state. This observation provides the first direct determination for the hypertriton ground state spin. We are looking forward to accumulating enough statistics and solve the hypertriton lifetime puzzle in the near future with our original approach.

Free Research Field

Experimental Nuclear Physics

Academic Significance and Societal Importance of the Research Achievements

As the lightest hypernucleus, hypertriton provides the foundation for our understanding for YN interaction. With the support of this Kakenhi, our J-PARC E73 experiment essentially improved our understanding for hypertriton with our original production method (K-, pi0).