The K +π - elastic scattering cross section as observed in K +p→K +π-Δ++ from 3 to 13 GeV/ c

Abstract

The four-body reaction K +p→K + π - Δ ++ is analysed in a sample of 77 300 bubble chamber events of K +p→K + π - π +p for beam momenta from 2.5 to 12.6 GeV/ c to study the K +π - elastic scattering cross section. The relative merits of several analytic continuations to the pion pole are discussed. Maximum likelihood method is used and, for each experiment fits are performed simultaneously over the whole range of the M(p π +), m(K + π -) and t variables. The K +π - cross section is parametrized in terms of the down solution for the s-wave, a p-wave resonating at the K ∗(890) and a d-wave resonating at the K ∗(1420). Fitted values are obtained for the four-body cross section, the s-wave contribution to the K +π - cross section, and the masses and widths of the K ∗(890) and K ∗(1420).