Search for $\hat{I}{˜}^{++}$ Pentaquarks in the Exclusive Reaction ${\hat{I}}^{3}p\to K^{+}{K}^{-}p$

Abstract

The reaction ${\hat{I}}^{3}p\to p{K}^{+}{K}^{-}$ 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 $\hat{I}{˜}^{++}$ 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 $\hat{I}{˜}^{++}$ was found. Upper limits on the total and differential production cross section for the reaction ${\hat{I}}^{3}p\to K^{-}\hat{I}{˜}^{++}$ were obtained in the mass range from 1.5 to 2.0 GeV/c${}^2$, with an upper limit of about 0.15 nb, 95% C.L. for a narrow resonance with a mass $M_{\hat{I}{˜}^{++}}=1.54$ GeV/c${}^2$. This result places a very stringent upper limit on the $\hat{I}{˜}^{++}$ width.

6 pages, 4 figures