Strangeness plus-one ($S=+1$) resonance-state $P^{+*}_0$ via $K^+n\to K^{*0}p$

Abstract

In our current study, we delve into the peak-like structure observed during the reaction process of $K^+n\to K^{0}p$ at approximately $\sqrt{s}\sim2.5$ GeV. Our focus centers on exploring the potential $S=+1$ resonance $P^{+*}_0\equiv P^*_0$ as an excited state within the extended vector-meson and baryon ($VB$) antidecuplet. To achieve this aim, we employ the effective Lagrangian method in conjunction with the $(u,t)$-channel Regge approach, operating within the tree-level Born approximation. We thoroughly examine various spin-parity quantum numbers for the resonance, resulting in a compelling description of the data, where $M_{P^*_0}\approx2.5$ GeV and $Γ_{P^*_0}\approx100$ MeV. Furthermore, we propose an experimental technique to amplify the signal-to-noise ratio ($S/N$) for accurately measuring the resonance. Notably, our findings reveal that background interference diminishes significantly within the $K^*$ forward-scattering region in the center-of-mass frame when the $K^*$ is perpendicularly polarized to the reaction plane. Additionally, we explore the recoil-proton spin asymmetry to definitively determine the spin and parity of the resonance. This study stands to serve as a valuable reference for designing experimental setups aimed at investigating and comprehending exotic phenomena in QCD. Specifically, our insights will inform future J-PARC experiments, particularly those employing higher kaon beam energies.