Large Nc, chiral approach to Mη′ at finite temperature

We study the temperature dependence of the η and η′ meson masses within the framework of U(3)L XU(3)R chiral perturbation theory, up to next-to-leading order in a simultaneous expansion in momenta, quark masses and number of colors. We find that both masses decrease at low temperatures, but only very slightly. We analyze higher order corrections and argue that large Nc suggests a discontinuous drop of Mη′ at the critical temperature of deconfinement Tc, consistent with a first order transition to a phase with approximate U(1)A symmetry. ©2000 The American Physical Society.