Transverse Spectra of Radiation Processes in Medium

We develop a formalism for evaluation of the transverse momentum dependence of cross sections of the radiation processes in medium. The analysis is based on the light-cone path integral approach to the induced radiation. The results are applicable in both QED and QCD

Anomalous mass dependence of radiative quark energy loss in a finite-size quark-gluon plasma

We demonstrate that for a finite-size quark-gluon plasma the induced gluon radiation from heavy quarks is stronger than that for light quarks when the gluon formation length becomes comparable with (or exceeds) the size of the plasma. The effect is due to oscillations of the light-cone wave function for the in-medium $q\to gq$ transition. The dead cone model by Dokshitzer and Kharzeev neglecting quantum finite-size effects is not valid in this regime. The finite-size effects also enhance the photon emission from heavy quarks.Comment: 8 pages, 3 figure

On the use of running αs\alpha_s in calculations of radiative energy loss of fast partons in a quark-gluon plasma

The incorporation of running $\alpha_s$ for the gluon emission vertex in calculations of radiative parton energy loss in a quark-gluon plasma is discussed. It is argued that the virtuality scale for running $\alpha_s$ for induced gluon emission is determined by the square of the transverse momentum of the emitted gluon rather than by the square of the invariant mass of the final two-parton state often used in the literature.Comment: 5 pages, 2 figures, published in JETP Letter

Coherent final state interaction in jet production in nucleus-nucleus collisions

We study the coherent final state interaction of an energetic parton produced in AA collisions caused by the change in the cutoff scale and running coupling constant from the vacuum to QGP. We demonstrate that the contribution of this new mechanism to the energy loss may be of the order of magnitude of the induced gluon radiation. However, an accurate evaluation of this medium effect is a difficult task because there is a strong cancellation between the cutoff and running coupling constant effects. The uncertainties in the contribution of the coherent final state interaction restrict strongly the accuracy of jet tomographic analyses of the matter density produced in AA reactions.Comment: 9 pages, Late

On the Energy Loss of High Energy Quarks in a Finite-Size Quark-Gluon Plasma

We study within the light-cone path integral approach the induced gluon emission from a fast quark passing through a finite-size QCD plasma. We show that the leading log approximation used in previous studies fails when the gluon formation length becomes of the order of the length of the medium traversed by the quark. Calculation of the energy loss beyond the leading log approximation gives the energy loss which grows logarithmically with quark energy contrary to the energy independent prediction of the leading log approximation.Comment: 7 pages, 0 figure

Induced photon emission from quark jets in ultrarelativistic heavy-ion collisions

We study the induced photon bremsstrahlung from a fast quark produced in AA-collisions due to multiple scattering in quark-gluon plasma. For RHIC and LHC conditions the induced photon spectrum is sharply peaked at photon energy close to the initial quark energy. In this region the contribution of the induced radiation to the photon fragmentation function exceeds the ordinary vacuum radiation. Contrary to previous analyses our results show that at RHIC and LHC energies the final-state interaction effects in quark-gluon plasma do not suppress the direct photon production, and even may enhance it at p_{T} about 5-15 GeV.Comment: 11 pages, 4 figure

The role of finite kinematic bounds in the induced gluon emission from fast quarks in a finite size quark-gluon plasma

We study the influence of finite kinematic boundaries on the induced gluon radiation from a fast quark in a finite size quark-gluon plasma. The calculations are carried out for fixed and running coupling constant. We find that for running coupling constant the kinematic correction to the radiative energy loss is small for quark energy larger than about 5 GeV. Our results differ both analytically and numerically from that obtained by the GLV group [6]. The effect of the kinematic cut-offs is considerably smaller than reported in [6].Comment: 11 pages, 4 figure

Radiative parton energy loss and jet quenching in high-energy heavy-ion collisions

We study within the light-cone path integral approach [3] the effect of the induced gluon radiation on high-p_{T} hadrons in high-energy heavy-ion collisions. The induced gluon spectrum is represented in a new form which is convenient for numerical simulations. For the first time, computations are performed with a realistic parametrization of the dipole cross section. The results are in reasonable agreement with suppression of high-p_{T} hadrons in Au+Au collisions at \sqrt{s}=200 GeV observed at RHIC.Comment: 12 pages, 3 epsi figures. Typos correcte