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Future gamma-ray spectroscopic experiment (J-PARC E63) on $^4_{\Lambda}$H

Not scheduled
15m
2nd Floor

2nd Floor

Renaissance Portsmouth-Norfolk Waterfront Hotel 425 Water Street Portsmouth, VA 23704
Abstract Submission

Speaker

Dr Takeshi Yamamoto (KEK IPNS)

Description

The charge symmetry breaking (CSB) effect reported in the A=4 mirror hypernuclei is one of the hot topics in strangeness nuclear physics. Precise gamma-ray spectroscopy with an energy resolution of a few keV is a powerful tool to investigate such an effect. Recently, a gamma-ray spectroscopy study of $^4_{\Lambda}$He was performed at the J-PARC K1.8 beam line (J-PARC E13) for this purpose. $^4_{\Lambda}$He hypernuclei were produced by the $(K^-,\pi^-)$ reaction with a 1.5 GeV/$c$ kaon beam. The excitation energy of first excited state of $^4_{\Lambda}$He(1$^+$) was successfully determined to be 1.406$\pm $0.004 MeV. On the other hand, that of the mirror hypernucleus ($^4_{\Lambda}$H) was reported as 1.09$\pm $0.02 MeV in average from old studies. By comparing these results, we conformed the existence of CSB effect in the excitation energy. Reported values of the excitation energy ($E_x [^4_{\Lambda}$H(1$^+$)]) in old studies show rather large deviation. In these measurements, the energy accuracy was limited by statistics and the gamma-ray response function including the resolution as well as the Doppler broadening effect. Therefore, our next step is a more precise measurement of the excitation energy of $^{4}_{\Lambda}$H($1^{+}$) to experimentally establish the A=4 mirror hypernuclei system. We are planing a gamma-ray spectroscopy of $^4_{\Lambda}$H at the J-PARC K1.1 beam line (J-PARC E63) via the $^7$Li$(K^-,\pi^-)$ reaction. We selected the SKS spectrometer system for tagging the reaction, which is common with the previous J-PARC E13. The gamma-ray energy will be measured with a Ge detector array, Hyperball-J, of which performance was already established. An outline of the J-PARC E63 experiment will be given in this contribution.

Primary author

Dr Takeshi Yamamoto (KEK IPNS)

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