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

We measured a set of pi(+/-)Sigma(-/+), pi(0)Sigma(0), and pi(-)Sigma(0) invariant mass spectra below and above the (K) over bar N mass threshold in K -induced reactions on deuteron. The measured pi Sigma mass spectral shape is well reproduced via the two-step mechanism, i.e., a neutron knocked out at a forward angle from a deuteron by an incident K-, with the (K) over bar recoiled backward reacting with the residual nucleon to produce pi and Sigma. We deduced the S-wave (K) over bar N -> pi Sigma and (K) over bar N -> (K) over bar N scattering amplitudes in the isospin 0 channel in the framework of a (K) over bar N and pi Sigma coupled channel. We find that a resonance pole corresponding to Lambda(1405) is located at 1417.7(-7.4)(+6.0) (fitting errors)(-1.0)(+1.1) (systematic errors) + [-26.1(-7.9)(+6.0) (fitting errors)(-2.0)(+1.7) (systematic errors)] i MeV/c(2), closer to the (K) over bar N mass threshold than the value determined by the Particle Data Group. (c) 2022 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).