Charge identification of low-energy particles for double-strangeness nuclei in nuclear emulsion

Kimbara, Shinji*; Ekawa, Hiroyuki; Hayakawa, Shuhei; Yoshida, Junya; 12 of others*

A development has been achieved in the identification method of the charges 1 to 5 of nuclides from the decay of double hypernuclei to be uniquely recognized by their nuclear species. The method is basically the measurement of track volume by the widths, depths, and angles of tracks of exposed nuclei of H, He, Li, Be, and B in nuclear emulsion at Riken Projectile-fragment Separator of RIKEN Radioactive Isotope Beam Factory. After their calibration by particles, we obtained a quadric function to present a unified recognition of tracks with volume ratios of five nuclei to the particles. The function in the emulsion has been applied to a candidate event of a hypernucleus for identification of the production and decay processes. We succeeded in recognizing a daughter nuclear fragment of a single- hypernucleus as He with a likelihood ratio of 0.9; the process was then uniquely identified as + N Be + He + .