Search for strange tribaryons in the 4He (Kstop-, n π±) reaction

H. Yim, H. Bhang, J. Chiba, Seonho Choi, Y. Fukuda, T. Hanaki, R. S. Hayano, M. Iio, T. Ishikawa, S. Ishimoto, T. Ishiwatari, K. Itahashi, M. Iwai, M. Iwasaki, P. Kienle, J. H. Kim, Y. Matsuda, H. Ohnishi, S. Okada, H. OutaM. Sato, S. Suzuki, T. Suzuki, D. Tomono, E. Widmann, T. Yamazaki

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)


We have recently reported on an indication of the strange tribaryon state, S+, with a mass M ∼ 3140 MeV / c2 and width Γ < 23 MeV / c2, in the neutron time-of-flight (TOF) spectrum of the 4He (Kstop-, n π±) reaction of the KEK-PS E471 experiment in a search for the deeply bound narrow K- p p n (total isospin T = 0) state. In an attempt to confirm the state and search for other possible T = 0, 1 tribaryonic states, we have re-measured the neutron energy spectrum of the same reaction in the KEK-PS E549 experiment with an upgraded setup for which the TOF resolution was improved 1.5 times and the statistics was increased 6 times. However, in the neutron spectra, we find such a smooth distribution that we conclude the state is either not so strong to stick out of the inclusive background or too broad to be identified as a distinct peak. We estimated the upper limits of the formation probability of the possible tribaryonic state for three widths, 0, 20, and 40 MeV / c2. The obtained upper limit (95% CL) for a state as narrow as 20 MeV / c2 is at most 1% per stopped kaon over the wide mass range of 3000-3200 MeV/c2, while it reaches to 4 ∼ 5 % at around 3140 MeV/c2 for Γ ≥ 40 MeV / c2, implying the possible existence of unknown processes including tribaryonic formation.

Original languageEnglish
Pages (from-to)43-49
Number of pages7
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Issue number1
Publication statusPublished - 2010 Apr 26
Externally publishedYes


  • Deeply bound kaonic nuclear state
  • Kaon absorption
  • Strange tribaryon

ASJC Scopus subject areas

  • Nuclear and High Energy Physics


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