Chemical potential response of pseudoscalar meson masses in the Nambu--Jona-Lasinio model

Using the Nambu--Jona-Lasinio (NJL) model we study chemical potential response of the pion and kaon masses as a function of temperature and chemical potential, i.e., dm/d\mu (T, \mu). First, we obtain the responses assuming the vector-axial vector coupling is zero (g_V=0). Then, we include a non-zero g_V and study the effects of g_V on the responses. We find that the behavior of dm/d\mu for the pion is quite different from that for the kaon. It means that dm/d\mu is much dependent on the mass difference between the two quarks, i.e., the u and s quarks (or even between the u and d quarks). Our results may give a clue to future studies of dm/d\mu on the lattice.