$\pi$-$K$ scattering lengths at finite temperature in the Nambu--Jona-Lasinio model

Abstract

The transition amplitude for $\pi K$ scattering is evaluated within the SU(3) Nambu--Jona-Lasinio model. Ordering terms according to the expansion in $1/N_c$ leads to a box-like diagram, $t$ channel diagrams that admit scalar isoscalar $(\sigma ,{\sigma }^{\prime })$ exchanges, and a $u$ channel exchange of a scalar isodoublet ${\sigma }_K$ that has quantum numbers corresponding to the $K_0^{\ast }(1430)$. Both the Pauli-Villars and O(3) regularization procedures are used to evaluate the T=0 values of the $l=0$ scattering lengths $a_0^{3/2}$ and $a_0^{1/2}$. The finite temperature dependence is studied. We find that the variation in the $t$ channel in the calculation of $a_0^{3/2}$ leads to a change in $a_0^{3/2}$ of a factor of about two over the temperature range of T=150 MeV.