Search for the pentaquark via the P^0_{{c bar}s} --> phi,pi,p decay

TL;DR

This paper reports the first experimental search for the pentaquark P^0_{c̄s} in Fermilab data, setting upper limits on its production relative to known decays, and constraining its possible existence.

Contribution

It provides the first search results and upper limits for the P^0_{c̄s} pentaquark, a predicted exotic state, using high-energy collision data.

Findings

Upper limits set at 90% confidence level for P^0_{c̄s} production

No definitive evidence for P^0_{c̄s} observed in the data

Constraints on the cross section times branching ratio for the decay

Abstract

We report results of the first search for the pentaquark P_{{c bar}s} which is predicted to be a doublet of states: P^0_{{c bar}s}=({c bar} s u u d) and P^-_{{c bar}s}=({c bar} s d d u). A search was made for the decay P^0_{{c bar}s} --> phi,pi,p in data from Fermilab experiment E791, in which 500 GeV/c pi^- beam interacted with nuclear targets. We present upper limits at 90% confidence level for the ratio of cross section times branching fraction of this decay to that for the decay D_s --> phi,pi. The upper limits are 0.031 and 0.063 for M(P^0_{{c bar}s}) = 2.75 and 2.86 GeV/c^2, respectively, assuming a P^0_{{c bar}s} lifetime of 0.4 ps.