Search for Theta+ via K+p -> pi+X reaction with a 1.2 GeV/c K+ beam

TL;DR

This study searched for the exotic Theta+ particle via the K+p -> pi+X reaction with a 1.2 GeV/c K+ beam but found no evidence, setting a stringent upper limit on its production cross section and implications for theoretical models.

Contribution

The paper provides the first experimental upper limit on the Theta+ production cross section in this reaction at KEK-PS, challenging certain theoretical models.

Findings

No clear peak observed in the missing mass spectrum.

Upper limit of 3.5 ub/sr on differential cross section.

Results suggest the t-channel process or coupling constant is very small.

Abstract

The Theta+ was searched for via the K+p -> pi+X reaction using the 1.2 GeV/c K+ beam at the K6 beam line of the KEK-PS 12 GeV Proton Synchrotron. In the missing mass spectrum of the K+p -> pi+X reaction, no clear peak structure was observed. Therefore a 90 % C.L. upper limit of 3.5 ub/sr was derived for the differential cross section averaged over 2degree to 22degree in the laboratory frame of the K+p -> pi+Theta+ reaction. This upper limit is much smaller than the theoretical calculation for the t-channel process where a K0* is exchanged. From the present result, either the t-channel process is excluded or the coupling constant of g_{K*N\Theta} is quite small.