Nonperturbative effects on radiative energy loss of heavy quarks

Abstract

The radiative energy loss of fast partons traveling through the quark-gluon plasma (QGP) is commonly studied within perturbative QCD (pQCD). Nonperturbative (NP) effects, which are expected to become important near the critical temperature, have been much less investigated. Here, we utilize a recently developed T-matrix approach to incorporate NP effects for gluon emission off heavy quarks propagating through the QGP. We set up four cases that contain, starting from a Born diagram calculation with color-Coulomb interaction, an increasing level of NP components, by subsequently including (remnants of) confining interactions, resummation in the heavy-light scattering amplitude, and off-shell spectral functions for both heavy and light partons. For each case we compute the power spectra of the emitted gluons, heavy-quark transport coefficients (drag and transverse-momentum broadening,q), and the path-length dependent energy loss within a "QGP brick" at fixed temperature. Investigating the differences in these quantities between the four cases illustrates how NP mechanisms affect gluon radiation processes. While the baseline perturbative processes experience a strong suppression of soft radiation due to thermal masses of the emitted gluons, confining interactions, ladder resummations and broad spectral functions (re-)generate a large enhancement toward low momenta and low temperatures. For example, for a 10 GeV charm quark at 200 MeV temperature, they enhance the transport coefficients by up to a factor of 10, while the results smoothly converge to perturbative results at sufficiently hard scales.

Heavy quark energy loss through polarization and radiation in the hot QCD medium

“…is the four-momentum of the emitted gluon from the HQ, and E 5 is the energy of the emitted gluon. The transport coefficient, X r for the radiative processes in the QP medium is given as [36,48,49,57,58 where X c is the transport coefficient for the collisional processes defined in equation (22). This analysis assumes soft gluon emission, where the momentum of the emitted gluon, k 5 , approaches zero.…”

“…Many authors have studied this aspect through different approaches [21][22][23][24][25][26][27][28][29][30]. In this article, we particularly chose to compare the energy loss of the HQs through medium polarization [31][32][33] and gluon emission or radiation [34][35][36]. The former corresponds to the HQ's soft interaction with the plasma modes, while the latter is the inelastic process where HQs emit gluons (2 → 3 process) or radiate while propagating through the QGP medium.…”

Heavy-Light Susceptibilities in a Strongly Coupled Quark-Gluon Plasma

“…Taking advantage of the progress in lQCD [5,6,[19][20][21][22], we have developed a thermodynamic T -matrix approach [23,24] which was rooted in three sets of lQCD data: the HQ free energy, Euclidean quarkonium correlator ratios, and the EoS for N f =2+1 light-quark flavors. The lQCD results were instrumental in constraining the input parameters for the T -matrix approach, in particular its in-medium driving kernel and the effective thermal-parton masses, and subsequently enabled controlled studies of spectral and transport properties of the QGP [23,25,26].…”

Heavy quark transport in an anisotropic hot QCD medium: Collisional and Radiative processes

“…[19][20][21][22][23] for the recent studies. The two dominant processes that contribute to the energy loss of heavy quark in the medium are namely, the collisional (elastic interaction) and the inelastic interactions like gluon bremsstrahlung [24][25][26][27][28][29][30]. The heavy quark transport, its energy loss, and the associated physical observables such as nuclear suppression factor R AA , flow coefficients, etc have been investigated in several works in the literatures [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45].…”