© 2016

Search for the Pentaquark Θ+ via the π−p → K−X Reaction at J-PARC


Part of the Springer Theses book series (Springer Theses)

Table of contents

  1. Front Matter
    Pages i-xiii
  2. Manabu Moritsu
    Pages 1-26
  3. Manabu Moritsu
    Pages 27-48
  4. Manabu Moritsu
    Pages 49-84
  5. Manabu Moritsu
    Pages 85-93
  6. Manabu Moritsu
    Pages 95-103
  7. Manabu Moritsu
    Pages 105-106
  8. Back Matter
    Pages 107-123

About this book


This theses reports on an experimental search for an exotic hadron, Θ+(1540) pentaquark, which is a genuine exotic hadron with a five-quark system of uuddsbar. The results of this book support that the existence of Θ+ was strongly constrained. 

The Θ+ pentaquark was searched for via the π- p → K- X reaction using a beam momentum of 2.01 GeV/c at the J-PARC hadron experimental facility, taking advantage of high-statistics and high-resolution compared with previous experiments, some of which claimed the evidence of Θ+. In order to realize a good missing-mass resolution of 2 MeV, the beam spectrometer and superconducting kaon spectrometer were constructed.

No clear peak was observed in the missing mass spectrum of the π- p → K- X reaction, and the upper limit of the production cross section was found to be less than 0.28 μb/sr at the 90% confidence level in a mass region of 1500–1560 MeV/c2. This upper limit is an order of magnitude smaller than that of the previous KEK experiment. Compared with a theoretical calculation using the effective Lagrangian approach, the decay width of Θ+ was evaluated. The upper limits on the decay width were estimated to be 0.36 and 1.9 MeV for the Θ+ spin-parity of 1/2+ and 1/2-, respectively. These are quite small for a width of ordinary hadron resonances, and the existence of Θ+ was strongly constrained and is doubtful.


DIANA and Belle Collaborations Exotic hadron search J-PARC K1.8 beam line J-PARC hadron experimental facility Pentaquark search Pion-induced reaction for strangeness production Superconducting kaon spectrometer

Authors and affiliations

  1. 1.Department of PhysicsOsaka UniversityKyotoJapan

About the authors

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