An international collaboration led by Prof. S.N. Nakamura (Graduate School of Science, Tohoku University), Prof. J. Pochodzalla, Dr. P. Achenbach (Mainz University) and Prof. L. Tang (Hampton University) has been developing a new experimental technique -- the decay-pion spectroscopy of electro-produced hypernuclei since 2011. This technique observes pions from two-body weak-decay of hypernuclei to measure precise masses of hypernuclei.
In a world first, the international collaboration used this new technique to successfully measure the mass of [4ΛH], which consists of one proton, two neutrons and one Λ particle.
The best resolution, 540 keV(FWHM), of the mass measurement of hypernuclei was achieved at the Jefferson Lab (USA) for [12ΛB] using the (e,e'K+) reaction by the international collaboration led by Profs. Nakamura and Tang.
However the achieved resolution by this new method is 150 keV(FWHM) which is more than three times better than the previous world record.
This new measurement will contribute greatly to solving the puzzle of the Charge Symmetry Breaking of the Λ-N interaction.
Young researchers supported by the Japan Society for the Promotion of Science (JSPS) -- the Strategic Young Researchers Overseas Visit Program for Accelerating Brain Circulation (R2201) and Core-to-Core program (21002) -- played essential roles in the success of this project.
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