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

TL;DR

This study searched for the hypothesized $ heta^{++}$ pentaquark in photon-proton collisions but found no evidence, setting strict upper limits on its production cross section and width.

Contribution

First experimental search for $ heta^{++}$ pentaquark in photon-proton reactions, establishing upper limits on its production and properties.

Findings

No significant evidence of $ heta^{++}$ was observed.

Upper limit on production cross section is approximately 0.15 nb.

The results constrain the possible width of the $ heta^{++}$.

Abstract

The reaction $\gamma p \to pK^+K^-$ 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 $\Theta^{++}$ pentaquark, a narrow doubly charged baryon state having strangeness S=+1 and isospin I=1, in the $pK^+$ invariant mass spectrum. No statistically significant evidence of a $\Theta^{++}$ was found. Upper limits on the total and differential production cross section for the reaction $\gamma p \to K^-\Theta^{++}$ 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 $M_{\Theta^{++}}=1.54$ GeV/c$^2$. This result places a very stringent upper limit on the $\Theta^{++}$ width.