First Model-Independent Measurement of the Spin Triplet $p\hat{I}›$ Scattering Length from Final State Interaction in the $\vec{p}p\to p{K}^{+}\hat{I}›$ Reaction

Abstract

The $\vec{p}p\to p{K}^{+}\hat{I}›$ reaction has been measured with the COSY-TOF detector at a beam momentum of $2.7\mathrm{GeV}/c$. The polarized proton beam enables the measurement of the beam analyzing power by the asymmetry of the produced kaon ($A_N^K$). This observable allows the $p\hat{I}›$ spin triplet scattering length to be extracted for the first time model independently from the final-state interaction in the reaction. The obtained value is $a_t=(-2.55_{-1.39}^{+0.72}{}_{\text{stat.}}\pm 0.6_{\text{syst.}}\pm 0.3_{\text{theo.}})\mathrm{fm}$. This value is compatible with theoretical predictions and results from model-dependent analyses.

Revised version as accepted for publication in PRC