Precision Study of the $\ensuremath{\eta}^{3}\mathrm{He}$ System Using the $dp\ensuremath{\rightarrow}^{3}\mathrm{He}\ensuremath{\eta}$ Reaction

Precision Study of the $η {}^{3}{He}$ System Using the $d p \to {}^{3}{He} η$ Reaction

T. Mersmann et al.

Phys. Rev. Lett. 98, 242301 – Published 13 June 2007

Abstract

The differential and total cross sections for the $d p \to {}^{3}{He} η$ reaction have been measured in a high precision high statistics COSY-ANKE experiment near threshold using a continuous beam energy ramp up to an excess energy $Q$ of 11.3 MeV with essentially 100% acceptance. The kinematics allowed the mean value of $Q$ to be determined to about 9 keV. Evidence is found for the effects of higher partial waves for $Q ≳ 4 MeV$ . The very rapid rise of the total cross section to its maximum value within 0.5 MeV of threshold implies a very large $η {}^{3}{He}$ scattering length and hence the presence of a quasibound state extremely close to threshold.