The mass spectra of neutral mesons K0​,π0​,η,η′ on
temperature-quark chemical potential (T−μ) plane in the presence of a
constant magnetic field is investigated in the SU(3) NJL model. As a
Goldstone boson of chiral symmetry breaking, the mass of K0​ meson increases
with temperature and/or quark chemical potential, and we observe two kinds of
mass jumps of K0​ meson in media, which is induced by the mass jump of
constituent quarks and the magnetic field, respectively. Due to the breaking of
isospin symmetry between u and d quarks in magnetic fields, the mixing of
π0​−η−η′ mesons occurs and this leads to rich structures of their
mass spectra. For instance, π0​ mass is influenced by the strange quark.
There appear the change of increase ratio of π0​ mass at high μ and
vanishing T and the π0​ mass jump crossing over the threshold of two
times of strange quark mass at finite T and μ. The mass ordering of
π0​, η, η′ mesons varies in media, due to their mass jumps, which
are induced by the mass jump of constituent quarks or the magnetic field.Comment: 8 pages, 4 figure