Radiative energy loss and p perpendicular to-broadening of high energy partons in nuclei

The medium-induced p(perpendicular to)-broadening and induced gluon radiation spectrum of a high energy quark or gluon traversing a large nucleus is studied, Multiple scattering of the high energy parton in the nucleus is treated in the Glauber approximation. We show that -dE/dz, the radiative energy loss of the parton per unit length, grows as L, the length of the nuclear matter, as does the characteristic transverse momentum squared of the parton p(perpendicular to W)(2). We find -dE/dz = 1/8 alpha(s)N(c)p(perpendicular to W)(2) holds independent of the details of the parton-nucleon scatterings so long as L is large and so long as perturbative QCD applies at short distances. Numerical estimates suggest that p(perpendicular to)-broadening and energy loss may be significantly enhanced in hot matter as compared to cold matter, thus making the study of such quantities a possible signal for quark-gluon plasma formation.