Collision broadening of rho meson in a dropping mass scenario
  Vector mesons containing light quarks are thought to have their masses reduced in dense nuclear matter, sacrificing some of their energy to the scalar field which becomes appreciable at finite baryon density. Model calculations find masses which fall by a couple tens of percents in normal nuclear matter, and by several hundred MeV in dense matter. We estimate the collision rate for rho mesons in such a scenario and at finite temperature. Compared to its free-mass value, the collision rate changes by nearly a factor of two both above and below, depending on the density. This collision broadening effect could be important for estimates of low-mass dilepton production in heavy-ion collisions. 
K. L. Haglin