Light-cone path integral approach to the induced radiation in QED and QCD: basic concepts and recent applications

I discuss the basic ideas of the light-cone path integral approach to the induced radiation in QED and QCD and recent applications to the induced parton energy loss.Comment: 5 pages, 4 figures. Talk given at the International Workshop Diffraction-2004, Cala Gonone, Sardinia, Italy, 18-23 Sept 2004; to appear in the Proceedings. Minor correction

Jet color chemistry and anomalous baryon production in AAAA-collisions

We study anomalous high-$p_T$ baryon production in $AA$-collisions due to formation of the two parton collinear $gq$ system in the anti-sextet color state for quark jets and $gg$ system in the decuplet/anti-decuplet color states for gluon jets. Fragmentation of these states, which are absent for $NN$-collisions, after escaping from the quark-gluon plasma leads to baryon production. Our qualitative estimates show that this mechanism can be potentially important at RHIC and LHC energies.Comment: 20 pages, 4 figures, Eur.Phys.J. versio

Transition radiation in the quantum regime as a diffractive phenomenon

We demonstrate that the transition photon radiation and pair creation can be interpreted as a diffractive phenomenon in terms of the light-cone wave functions in a way similar to the Good-Walker approach [6] to the diffraction dissociation. Our formulas for spectra agree with those obtained by Baier and Katkov [5] within the quasiclassical operator method. However, there is some disagreement with earlier results by Garibyan [4].Comment: 7 pages. The journal version published in Phys. Lett.

Effect of electric field of the electrosphere on photon emission from quark stars

We investigate the photon emission from the electrosphere of a quark star. It is shown that at temperatures $T\sim 0.1-1$ MeV the dominating mechanism is the bremsstrahlung due to bending of electron trajectories in the mean Coulomb field of the electrosphere. The radiated energy flux from this mechanism exceeds considerably both the contribution from the bremsstrahlung due to electron-electron interaction and the tunnel $e^{+}e^{-}$ pair creation.Comment: 9 pages, 2 figure

Parton energy loss in glasma

We study the synchrotron-like gluon emission in $AA$-collisions from fast partons due to interaction with the coherent glasma color fields. Our results show that for RHIC and LHC conditions the contribution of this mechanism to parton energy loss is much smaller than the radiative energy loss in the plasma phase.Comment: 14 pages, 3 figure

Angular Dependence of the Radiative Gluon Spectrum and the Energy Loss of Hard Jets in QCD Media

The induced momentum spectrum of soft gluons radiated from a high energy quark propagating through a QCD medium is derived in the BDMPS formalism. A calorimetric measurement for the medium dependent energy lost by a jet with opening angle $\theta_{{\rm cone}}$ is proposed.The fraction of this energy loss with respect to the integrated one appears to be the relevant observable.It exhibits a universal behaviour in terms of the variable $\theta^2_{{\rm cone}} L^3 \hat q$ where $L$ is the size of the medium and $\hat q$ the transport coefficient. Phenomenological implications for the differences between cold and hot QCD matter are discussed.Comment: 13 pages and 7 figures, RevTe

Energy loss in high energy heavy ion collisions from the Hydro+Jet model

We investigate the effect of energy loss of jets in high energy heavy ion collisions by using a full three-dimensional space-time evolution of a fluid combined with (mini-)jets that are explicitly evolved in space-time. In order to fit the pi^0 data for the Au+Au collisions at sqrt(s_{NN}) = 130 GeV, the space-time averaged energy loss dE/dx(tau <= 3 fm/c) = 0.36 GeV/fm is extracted within the model. It is found that most energy loss occurs at the very early time less than 2 fm/c in the QGP phase and that energy loss in the mixed phase is negligible within our parameterization for jet energy loss. This is a consequence of strong expansion of the system.Comment: 4 pages, 5 figures; one figure adde

Diffraction in Charged Current DIS

We present the QCD calculation of the diffractive structure function for charged current DIS. In particular we analyse the perturbatively tractable excitation of heavy quarks. We emphasize the peculiarities of the Regge factorization breaking in excitation of open charm.Comment: 16 pages LateX, 5 eps figures include

Tomography of cold and hot QCD matter : tools and diagnosis

The probability distribution D(epsilon) in the energy loss incurred by incoming and outgoing hard quarks in a QCD medium is computed numerically from the BDMPS gluon spectrum. It is shown to follow an empirical log-normal behavior which allows us to give the quenching weight a simple analytic parameterization. The dependence of our results under the infrared and ultraviolet sensitivity of the gluon spectrum is investigated as well. Finally, as an illustration, we discuss and compare estimates for the quenching of hadron spectra in nuclear matter and in a quark-gluon plasma to HERA and RHIC preliminary data.Comment: 29 pages, 11 figures. Typo corrected in Eq.(4.17

Decisive test of color transparency in exclusive electroproduction of vector mesons

The exclusive production of vector mesons in deep inelastic scattering is a hard scattering process with the well controlled size of quark configurations which dominate the production amplitude. This allows an unambiguous prediction of color transparency effects in the coherent and incoherent production of vector mesons on nuclei. We demonstrate how the very mechanism of color transparency leads to a belated onset of color transparency effects as a function of $Q^{2}$. We conclude that the $Q^{2}$ dependence of the exclusive $\rho^{0}$-meson production on nuclei and nucleons observed in the Fermilab E665 experiment gives a solid evidence for the onset of color transparency. We propose the scaling relation between the $\rho^{0}$ and the $J/\Psi$ production, which further tests the mechanism of color transparency in exclusive (virtual) photoproduction.Comment: 11 pages, 4 figures on the request from [email protected], Juelich preprint KFA-IKP(Th)-1993-27. \phantom{.}\hspace{9cm}{\sl 8 November 1993