Synchrotron radiation by fast fermions in heavy-ion collisions

We study the synchrotron radiation of gluons by fast quarks in strongmagnetic field produced by colliding relativistic heavy-ions. We argue that dueto high electric conductivity of plasma, time variation of the magnetic fieldis slow and estimate its relaxation time. We calculate the energy loss due tosynchrotron radiation of gluons by fast quarks. We find that the typical energyloss per unit length for a light quark at LHC is a few GeV per fm. This effectalone predicts quenching of jets with $p_\bot$ up to about 20 GeV. We also showthat the spin-flip transition effect accompanying the synchrotron radiationleads to a strong polarization of quarks and leptons with respect to thedirection of the magnetic field. Observation of the lepton polarization mayprovide a direct evidence of existence of strong magnetic field in heavy-ioncollisions.Comment: 10 pages, 6 figures; v3: estimate of the relaxation time of magnetic field is revised, acknowledgment adde