  We discuss the magnetic responses of vector meson masses based on the hidden
local symmetry (HLS) model in constant magnetic field, described by the
lightest two-flavor system including the pion, rho and omega mesons in the
spectrum. The effective masses influenced under the magnetic field are
evaluated in a way of the derivative/chiral expansion established in the HLS
model. At the leading order O(p^2) the g-factor of the charged rho meson is
fixed to be 2, implying that the rho meson at this order is treated just like a
point-like spin-1 particle. Beyond the leading order, one finds anomalous
magnetic interactions of the charged rho meson, involving the anomalous
magnetic moment, which give corrections to the effective mass. It is then
suggested that up to O(p^4) the charged rho meson tends to become massless. Of
interest is that nontrivial magnetic-dependence of neutral mesons emerges to
give rise to the significant mixing among neutral mesons. Consequently, it
leads to the dramatic enhancement of the omega meson mass, which is testable in
future lattice simulations. Corrections from terms beyond O(p^4) are also
addressed.
