Pentaquark Theta+(1540) production in gamma N ---> K anti-K N

Dec, 2004
42 pages
Published in:
  • Phys.Rept. 423 (2006) 49-89
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Abstract:
The recent developments in the search of exotic pentaquark hadrons are briefly reviewed. We then focus on investigating how the exotic pentaquark Θ(1540)\Theta(1540) baryon production can be identified in the γNKKˉN\gamma N \to K \bar{K} N reactions, focusing on the influence of the background (non-Θ\Theta production) mechanisms. By imposing the SU(3) symmetry and using various quark model predictions, we are able to fix the coupling constants for evaluating the kaon backgrounds, the KKˉK\bar{K} production through the intermediate vector meson and tensor meson photoproduction, and the mechanisms involving intermediate Λ(1116)\Lambda(1116), Λ(1405)\Lambda(1405), Λ(1520)\Lambda(1520), Σ(1193)\Sigma (1193), Σ(1385)\Sigma(1385), and Δ(1232)\Delta (1232) states. The total cross section data of γpK+Kp\gamma p \to K^+K^- p is then used to fix the form factors which regularize the background amplitudes so that the signal of Θ(1540)\Theta(1540) in γnK+Kn\gamma n \to K^+K^-n and γpK0Kˉ0p\gamma p \to K^0\bar{K}^0p cross sections can be predicted. We find that the predicted K+KK^+K^- and K+nK^+ n invariant mass distributions of the γnK+Kn\gamma n \to K^+ K^- n reaction can qualitatively reproduce the shapes of the JLab data. However, the predicted Θ(1540)\Theta(1540) peak can not be identified unambiguously with the data. High statistics experiments are needed to resolve the problem. We also find that an even-parity Θ\Theta is more likely to be detected, while it will be difficult to identify an odd-parity Θ\Theta, even if it exists, from the background continuum, if its coupling constants are small as in the present quark model predictions.
Note:
  • 49 pages, 18 figures, REVTeX, to appear in Phys. Rep
  • 13.60.Le
  • 14.80.-j
  • 13.60.Rj
  • photon nucleon: inelastic scattering
  • K: pair production
  • Theta(1540): photoproduction
  • symmetry: SU(3)
  • quark
  • background
  • vector meson: photoproduction