Optimal Fermi-averaging t-matrix for ($π^+$,$K^+$) reactions in $Λ$ quasi-free region

Abstract

We propose an optimal Fermi-averaging for an elementary $π^+$+$n$$\to$$K^+$+$Λ$ t-matrix under the on-energy-shell condition, in order to describe ($π^+$,$K^+$) reactions on a nuclear target in the framework of a distorted-wave impulse approximation. We apply it to calculate $Λ$ quasi-free spectra from $^{12}$C($π^+$,$K^+$) reactions at $p_π$= 1.20 GeV/c and 1.05 GeV/c, and compare them with experimental data. The results show that the calculated spectra are in excellent agreement with the data, because the energy-dependence originates from the nature of the optimal Fermi-averaging t-matrix.

10 pages, 3 figures