Possible quantum numbers of the pentaquark \Theta^+(1540) in QCD sum rules

TL;DR

This paper uses QCD sum rules to explore possible quantum numbers of the pentaquark 540, identifying the most probable state and discussing potential scattering state contamination.

Contribution

It introduces a method to establish a valid Borel window using difference of correlators and high-dimension operator expansion for pentaquark analysis.

Findings

0,3/2^+ state is the most probable candidate for 540

States with 0,1/2^- and 1,1/2^- are found at higher masses

Discusses potential contamination by KN scattering states

Abstract

The QCD sum rule technique is employed to investigate pentaquark states with strangeness S = +1 and IJ^P = 0,1/2^\pm, 1,1/2^\pm, 0,3/2^\pm, 1,3/2^\pm. Throughout the calculation, emphasis is laid on the establishment of a valid Borel window, which corresponds to a region of the Borel mass, where the operator product expansion converges and the presumed ground state pole dominates the sum rules. Such a Borel window is achieved by constructing the sum rules from the difference of two independent correlators and by calculating the operator product expansion up to dimension 14. Furthermore, we discuss the possibility of the contamination of the sum rules by possible KN scattering states. As a result, we conclude that the 0,3/2^+ state seems to be the most probable candidate for the experimentally observed \Theta^+(1540), while we also obtain states with 0,1/2^-, 1,1/2^-, 1,3/2^+ at somewhat higher mass regions.