  We study unpolarized cross sections for the endothermic nonresonant
reactions: pion pion to rho rho for I=2, KK to K*K* for I=1, KK* to K*K* for
I=1, pion K to rho K* for I=3/2, pion K* to rho K* for I=3/2, rho K to rho K*
for I=3/2, and pion K* to rho K for I=3/2, which take place in hadronic matter.
We provide a potential that is given by perturbative QCD with loop corrections
at short distances, becomes a distance-independent and temperature-dependent
value at long distances, and has a spin-spin interaction with relativistic
modifications. The Schrodinger equation with the potential yields
temperature-dependent meson masses and mesonic quark-antiquark relative-motion
wave functions. In the first Born approximation with the quark-interchange
mechanism, the temperature dependence of the potential, meson masses and wave
functions brings about temperature dependence of unpolarized cross sections for
the seven nonresonant reactions. Noticeably, rapid changes of pion and K radii
cause an increase in peak cross sections while the temperature approaches the
critical temperature. Parametrizations of the numerical cross sections are
given for their future applications in heavy ion collisions.
