Present status on experimental search for pentaquarks

Abstract

It has been ten years since the first report for a positive strangeness pentaquark-like baryon state. However the existence of the pentaquark state is still controversial. Some contradictions between the experiments are unsolved. In this paper we review the experimental search for the pentaquark candidates $\Theta^+$, $\Theta^{++}$, $\Xi^{--}$, $\Theta_c^0$ and $N^*$ in details. We review the experiments with positive results and compare the experiments with similar conditions but opposite results.Comment: 20 latex pages, 2 figures, to appear in IJMPA as a revie

First observation ofγγ→pp¯K+K−and search for exotic baryons in

“…It was a candidate for a uudds pentaquark state. However, it was not confirmed in larger-statistics data samples in the same experiment and was most probably not a genuine state [12].…”

Partial wave analysis

“…The evidence for the existence of Θ + (1540) faded away in a number of precision experiments (even though further evidence is reported in several more recent experiments, see [147] for a recent review. In contrast to Θ + (1540), the peak at about 1685 MeV became increasingly significant with better experiments at ELSA and MAMI [148][149][150], its existence is beyond doubt.…”

Θ+Search at HERMES with Deuterium and Hydrogen Targets

“…However, increased experimental precision failed to confirm most of these initial reports. This together with many experiments reporting negative results lead to the generally accepted notion that there is no substantial evidence for the existence of the Θ + state [10,11].…”