The weak production of Λ particles in antineutrino–proton scattering and the contributions of the form factors

Abstract

In support of proposed experiments which might be carried out by the MINER νA Collaboration and eventually elsewhere, we study the strangeness changing charged current reactions ν ¯ L + p → Λ + L + where L stands for an electron, muon, or tau lepton. We calculate the total and differential cross sections for these reactions from near threshold to several GeV. We also obtain the contributions of the various form factors and interference terms to the total and differential cross sections. The calculation is phenomenologically based and makes use of SU(3) relations to obtain the standard vector current form factors and data from Λ beta decay to obtain the axial current form factor. We also make estimates for the contributions of the pseudoscalar form factor and for the F E and F S form factors to the total and differential cross sections. The latter two are second class current form factors for the corresponding p ↔ n transition and forbidden by G-parity but are not forbidden here. We discuss our results and consider under what circumstances we might extract the various form factors. In particular we wish to test the SU(3) obtained form factors and to test the assumptions made in determining the others over a range of q 2 values.