First observation of $\gamma \gamma \to p \bar{p} K^+ K^-$ and search for exotic baryons in $pK$ systems

The process γγ→pp¯K+K- and its intermediate processes are measured for the first time using a 980 fb-1 data sample collected with the Belle detector at the KEKB asymmetric-energy e+e- collider. The production of pp¯K+K- and a Λ(1520)0 (Λ¯(1520)0) signal in the pK- (p¯K+) invariant mass spectrum are clearly observed. However, no evidence for an exotic baryon near 1540 MeV/c2, denoted as Θ(1540)0 (Θ¯(1540)0) or Θ(1540)++ (Θ(1540)--), is seen in the pK- (p¯K+) or pK+ (p¯K-) invariant mass spectra. Cross sections for γγ→pp¯K+K-, Λ(1520)0p¯K++c.c. and the products σ(γγ→Θ(1540)0p¯K++c.c.)B(Θ(1540)0→pK-) and σ(γγ→Θ(1540)++p¯K-+c.c.)B(Θ(1540)++→pK+) are measured. We also determine upper limits on the products of the χc0 and χc2 two-photon decay widths and their branching fractions to pp¯K+K- at the 90% credibility level.

Note:

9 pages, 9 figures

electron positron: annihilation
electron positron: colliding beams
K: pair production
baryon: exotic
Theta(1540)
mass spectrum: (K pi)
Lambda(1520)
exchange: two-photon
cross section: branching ratio: upper limit
BELLE

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Figures(0)

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