Search for ${\ensuremath{\Theta}}^{++}$ Pentaquarks in the Exclusive Reaction $\ensuremath{\gamma}p\ensuremath{\rightarrow}{K}^{+}{K}^{\ensuremath{-}}p$

Search for $Θ^{++}$ Pentaquarks in the Exclusive Reaction $γ p \to K^{+} K^{-} p$

V. Kubarovsky et al. (The CLAS Collaboration)

Phys. Rev. Lett. 97, 102001 – Published 7 September 2006

Abstract

The reaction $γ p \to p K^{+} K^{-}$ was studied at Jefferson Lab with photon energies from 1.8 to 3.8 GeV using a tagged photon beam. The goal was to search for a $Θ^{++}$ pentaquark, a narrow, doubly charged baryon state having strangeness $S = + 1$ and isospin $I = 1$ , in the $p K^{+}$ invariant mass spectrum. No statistically significant evidence of a $Θ^{++}$ was found. Upper limits on the total and differential cross section for the reaction $γ p \to K^{-} Θ^{++}$ were obtained in the mass range from 1.5 to $2.0 GeV / c^{2}$ , with an upper limit for a narrow resonance with a mass $M_{Θ^{++}} = 1.54 GeV / c^{2}$ of about 0.15 nb, 95% $C . L .$ . This result places a stringent upper limit on the $Θ^{++}$ width $Γ_{Θ^{++}} < 0.1 MeV / c^{2}$ .