Pole position of \(\Lambda(1405)\) measured in \(d(K^-,n)\pi\Sigma\) reactions

Abstract

We measured a set of \(\pi^\pm\Sigma^\mp\), \(\pi^0\Sigma^0\), and \(\pi^-\Sigma^0\) invariant mass spectra below and above the \(\bar{K}N\) mass threshold in \(K^-\)-induced reactions on deuteron. We deduced the \(S\)-wave \(\bar{K}N\rightarrow\pi\Sigma\) and \(\bar{K}N\rightarrow\bar{K}N\) scattering amplitudes in the isospin 0 channel in the framework of a \(\bar{K}N\) and \(\pi\Sigma\) coupled channel. We find that a resonance pole corresponding to \(\Lambda(1405)\) is located at 1417.7\(^{+6.0}_{-7.4}\)(fitting errors)\(^{+1.1}_{-1.0}\)(systematic errors) + \([-26.1^{+6.0}_{-7.9}\)(fitting errors)\(^{+1.7}_{-2.0}\)(systematic errors)]\(i\) MeV/\(c^2\), closer to the \(\bar{K}N\) mass threshold than the value determined by the Particle Data Group.