The role of Δ++∗(1620) resonances in pp→nK+Σ+ reaction and its important implications

The pp→nK+Σ+ reaction is a very good isospin 3/2 filter for studying Δ++∗ decaying to K+Σ+. With an effective Lagrangian approach, contributions from a previous ignored sub-K+Σ+-threshold resonance Δ++∗(1620)1/2− are fully included in addition to those already considered in previous calculations. It is found that the Δ++∗(1620)1/2− resonance gives an overwhelmingly dominant contribution for energies very close to threshold, with a very important contribution from the t-channel ρ exchange. This solves the problem that all previous calculations seriously underestimate the near-threshold cross section by order(s) of magnitude. Many important implications of the results are discussed.