Partial Wave Analysis of the Reaction $p(3.5 GeV)+p \to pK^+\Lambda$ to Search for the "$ppK^-$" Bound State

TL;DR

This study used partial wave analysis to investigate the $pK^+\Lambda$ reaction at 3.5 GeV, finding no evidence for the hypothesized $ppK^-$ bound state and setting upper limits on its production cross-section.

Contribution

It applies a comprehensive partial wave analysis to search for the $ppK^-$ bound state in proton-proton collisions, providing the first quantitative upper limits on its contribution.

Findings

No significant $ppK^-$ signal detected.

Upper limit for $ppK^-$ contribution is 2-12% of total cross section.

Production cross-section of $ppK^-$ is constrained between 0.7 and 4.2 microbarns.

Abstract

Employing the Bonn-Gatchina partial wave analysis framework (PWA), we have analyzed HADES data of the reaction $p(3.5GeV)+p\to pK^{+}\Lambda$. This reaction might contain information about the kaonic cluster "$ppK^-$" via its decay into $p\Lambda$. Due to interference effects in our coherent description of the data, a hypothetical $\overline{K}NN$ (or, specifically "$ppK^-$") cluster signal must not necessarily show up as a pronounced feature (e.g. a peak) in an invariant mass spectra like $p\Lambda$. Our PWA analysis includes a variety of resonant and non-resonant intermediate states and delivers a good description of our data (various angular distributions and two-hadron invariant mass spectra) without a contribution of a $\overline{K}NN$ cluster. At a confidence level of CL$_{s}$=95\% such a cluster can not contribute more than 2-12\% to the total cross section with a $pK^{+}\Lambda$ final state, which translates into a production cross-section between 0.7 $\mu b$ and 4.2 $\mu b$, respectively. The range of the upper limit depends on the assumed cluster mass, width and production process.