Higher twist jet broadening and classical propagation

Abstract

The transverse broadening of jets produced in deep-inelastic scattering (DIS) off a large nucleus is studied in the collinear limit. A class of medium enhanced higher twist corrections are re-summed to calculate the transverse momentum distribution of the produced collinear jet. In contrast to previous approaches, resummation of the leading length enhanced higher twist corrections is shown to lead to a two dimensional diffusion equation for the transverse momentum of the propagating jet. Results for the average transverse momentum obtained from this approach are then compared to the broadening expected from a classical Langevin analysis for the propagation of the jet under the action of the fluctuating color Lorentz force inside the nucleons. The set of approximations that lead to identical results from the two approaches are outlined. The relationship between the momentum diffusion constant $D$ and the transport coefficient $\hat{q}$ is explicitly derived.Comment: 17 pages, 6 figures, revtex4, references added, typos corrected, discussion update

Parton transport via transverse and longitudinal scattering in dense media

“…The phase factor is found to have a structure similar to the case without longitudinal drag [35]. Thus, the remaining integrals over the longitudinal momentum fractions x i 's can be done in a similar way.…”

“…Here we only consider the case of n = m, i.e., the same number of scatterings in both the amplitude and the complex conjugate. The case where n = m, either constitute higher twist nucleon matrix elements or unitarity corrections to terms where the produced quark experiences scatterings min(n, m) times [35]. For the case of 2n (n = m) gluon insertions, we may first simplify the matrix elements of the gluon vector potentials in the nuclear state.…”

“…This approach is closely linked with the multiple scattering versions of the Higher Twist (msHT) scheme [19,35] and our presentation will lie in-between these two approaches: we will not use the GiSCET Lagrangian; however, the power counting rules of the different momentum components will be similar to those used in the Ref. [33].…”

“…In this work, as in Refs. [19,35], the struck parton is assumed to possess a momentum q = (q + , q − , q ⊥ ) ∼ (λ 2 Q, Q, λQ), where Q is a hard scale and λ is a small dimensionless number. In the previous papers, the gluons off which the jet scatters were assumed to have a momentum k ∼ (λ 2 , λ 2 , λ)Q.…”

Theory of jet quenching in ultra-relativistic nuclear collisions

“…This parameter not only quantifies the transverse momentum broadening of the jet [31,32], but also controls the size of medium-induced radiative energy loss. As has been pointed out in Ref.…”