Nonlinear dynamics of soft boson collective excitations in hot QCD plasma II: plasmon -- hard-particle scattering and energy losses
In a general line with our first work (Ann.Phys.302(2002),172; hep-ph/0207316), within hard thermal loop approximation a general theory of the scattering for an arbitrary number of colorless plasmons off hard thermal particles of hot QCD-medium is considered. Using generalized Tsytovich correspondence principle, a connection between matrix elements of the scattering processes and a certain effective current, generating these processes is established. The iterative procedure of calculation of these matrix elements is defined, and a problem of their gauge-invariance is discussed. An application of developed theory to a problem of calculating energy losses of energetic color particle propagating through QCD-medium is considered. It is shown that for limiting value of the plasmon occupation number ($\sim 1/g^2$, where $g$ is a strong coupling) energy losses caused by spontaneous scattering process of energetic particle off soft-gluon waves is of the same order in the coupling as other known losses type: collision and radiation ones. The Fokker-Planck equation, describing decceleration (acceleration) and diffusion in momentum space of beam of energetic color particles scattering off soft excitations of quark-gluon plasma, is derived.