Experimental Search for Pentaquarks

The experimental evidence for pentaquarks, both old an new, is discussed. Constraints due to $K^+N$ scattering data from previous decades is first reviewed, followed by experiments with positive evidence and those with null results. Finally, the problem of the narrow width of the Theta+ pentaquark is discussed, along with theoretical implications.Comment: Review article for Progress in Particle and Nuclear Physics (34 pages

Evidence for the Strangeness S=+1 Pentaquark from LEPS and CLAS Experiments

There are now several experimental collaborations that have seen evidence for a narrow state in the mass spectrum of the ($nK^+$) system. Two of these experiments, from the LEPS collaboration in Japan and the CLAS collaboration in the USA, are described briefly. Both use similar photoproduction reactions with a $K^+K^-$ pair in the final state. In addition, data from the CLAS collaboration for the $\gamma p \to K_s K^+ n$ reaction are presented for the first time, which has no prominant peak in the ($nK^+$) mass spectrum when the $K_s$ angle is limited to forward angles.Comment: Hadron 2003 Conference Proceedings (5 pages

A Method to Unambiguously Determine the Parity of the Theta+ Pentaquark

With the recent discovery of the $\Theta(1540)$ pentaquark, the question of its parity is paramount since this will constrain the correct description of its internal structure. We show that the measurement of the spin singlet and triplet cross sections for the reaction $\vec{p}\vec{p} \to \Sigma^+ \Theta^+$ will unambiguously determine the parity of the $\Theta^+$.Comment: 3 page

Search for Pentaquarks at BABAR

The results of searches for the strange pentaquark states, Theta(1540)+, Xi(1860)-- and Xi(1860)0 in data recorded by the BABAR experiment are presented. We search for these three states inclusively in 123.4 fb^-1 of e+ e- annihilation data produced at the PEP-II asymmetric storage rings; we find no evidence for their production in any physics process, and set limits on their production rates that are well below the measured rates for conventional baryons. We also search for Theta(1540)+ produced in interactions of electrons or hadrons in the material of the inner part of the detector. No evidence for this state is found in a sample with much higher statistics than similar electroproduction experiments that claim a signal.Comment: 4 pages, 4 postscript figues, contributed to the Proceedings of QCD 05, Montpellie