Eur. Phys. J. A (2008) 38: 209-217
https://doi.org/10.1140/epja/i2008-10662-x

Regular Article - Experimental Physics

np → ηd near threshold and the s -wave ηN amplitude

¹ Instituto Politécnico Nacional, Escuela Superior de Fısica y Matemáticas, Edificio 9, 07738, México D.F., Mexico
² Instituto Superior Técnico, Centro de Fısica Teórica de Partıculas, and Department of Physics, Av. Rovisco Pais, 1049-001, Lisboa, Portugal

^* e-mail: humberto@esfm.ipn.mx

Received: 26 June 2008
Revised: 22 September 2008
Accepted: 10 October 2008
Published online: 30 October 2008

Abstract

We calculate the process np → ηd near threshold using a separable potential model of the coupled ηN - πN - ππN subystems, and a relativistic three-body calculation for the ηd scattering amplitude. The ππN channels are represented by an effective σN channel, and we compare the case where the σ and π masses are related by m _σ = 2m _π and no width is considered, to another where the mass and width of the σ -meson are taken from ππ scattering data. The np → ηd cross-section can be well described up to about 60MeV by models where the real part of the ηN scattering length lies between 0.4≤Re(a _ηN)≤0.6 fm which allows us to determine the s -wave ηN scattering amplitude for -60≤E≤60 MeV.