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Pion and Quark Annihilation Mechanisms of Dilepton Production in Relativistic Heavy-Ion Collisions

D. Anchishkin·R. Naryshkin
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Abstract

We revise the pion-pion and quark-quark annihilation mechanisms of dilepton production during relativistic heavy-ion collisions. We focus on the modifications caused by the specific features of intramedium pion states rather than by medium modification of the rho-meson spectral density. The main ingredient emerging in our approach is a form-factor of the multi-pion (multi-quark) system. Replacing the usual delta-function the form-factor plays the role of distribution which, in some sense, "connects" the 4-momenta of the annihilating and outgoing particles. The difference between the c.m.s. velocities attributed to annihilating and outgoing particles is a particular consequence of this replacement and results in the appearance of a new factor in the formula for the dilepton production rate. We obtained that the form-factor of the multi-pion (multi-quark) system causes broadening of the rate which is most pronounced for small invariant masses, in particular, we obtain a growth of the rate for the invariant masses below two masses of the annihilating particles.

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D. Anchishkin, R. Naryshkin. 2005-07-27. Pion and Quark Annihilation Mechanisms of Dilepton Production in Relativistic Heavy-Ion Collisions. https://doi.org/10.1142/s0217732305018311

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