  It is argued that the experimentally observed phenomenon of asymmetric vector
mesons produced in nuclear media during high energy nucleus-nucleus collisions
can be explained as Cherenkov and Fano effects. The mass distributions of
lepton pairs created at meson decays decline from the traditional Breit-Wigner
shape in the low-mass wing of the resonance. That is explained by the positive
real part of the amplitude in this wing for classic Cherenkov treatment and
further detalized in quantum mechanics as the interference of direct and
continuum states in Fano effect. The corresponding parameters are found from
the comparison with rho-meson data and admit reasonable explanation.
