arXiv subjects

D. Schiff

Publications and source records attributed to D. Schiff.

25 records · Page 2Linked to original sources

arXiv1996

Radiative energy loss and $p_{\perp}$-broadening of high energy partons in nuclei

The medium-induced $p_{\perp}$-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 $p_{\perp W}^2$. We find dE/dz = (1/8)α_s N_c $p_{\perp W}^2$ holds independent of the details of the parton-nucleon scatterings so long as L is large. Numerical estimates suggest that $p_{\perp}$-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.

hep-ph↗

arXiv1996

Radiative energy loss of high energy quarks and gluons in a finite volume quark-gluon plasma

The medium induced energy loss spectrum of a high energy quark or gluon traversing a hot QCD medium of finite volume is studied. We model the interaction by a simple picture of static scattering centres. The total induced energy loss is found to grow as $L^2$, where $L$ is the extent of the medium. The solution of the energy loss problem is reduced to the solution of a Schrödinger-like equation whose ``potential'' is given by the single-scattering cross section of the high energy parton in the medium. These resuls should be directly applicable to a quark-gluon plasma.

hep-ph↗

arXiv1996

The Landau-Pomeranchuk-Migdal effect in QED

The calculation of the radiative energy loss encountered by a fast charged particle which undergoes multiple scattering is being investigated. A detailed derivation of the Landau-Pomeranchuk-Migdal coherent effect in QED is given, focusing on the specific feature of the Coulomb interaction. As a result the radiation intensity per unit length in the coherent regime is shown to be proportional to $\sqrt ω$ for a photon energy $ω$ times a logarithmic enhancement which is determined exactly.

hep-ph↗

arXiv1994

Induced Gluon Radiation in a QCD Medium

Soft gluon radiation induced by multiple scattering of a fast quark or gluon propagating through QCD matter is discussed. After revisiting the Landau-Pomeranchuk-Migdal effect in QED we show that large formation times of bremsstrahlung quanta determine the QCD radiation intensity (in analogy to QED) and derive the gluon energy spectrum. Coherent suppression takes place as compared to the Bethe-Heitler situation of independent emissions. As a result the energy loss of fast partons in a QCD medium depends on the incident energy $E$ similarly to QED, $-dE/dz \propto \sqrt{E}$.

hep-ph↗

arXiv1993

Soft Photon Production Rate in Resummed Perturbation Theory of High Temperature QCD

We calculate the production rate of soft real photons from a hot quark -- gluon plasma using Braaten -- Pisarski's perturbative resummation method. To leading order in the QCD coupling constant $g$ we find a logarithmically divergent result for photon energies of order $gT$, where $T$ is the plasma temperature. This divergent behaviour is due to unscreened mass singularities in the effective hard thermal loop vertices in the case of a massless external photon.

hep-ph↗

arXiv1993

The heavy fermion damping rate puzzle

: We examine again the problem of the damping rate of a moving heavy fermion in a hot plasma within the resummed perturbative theory of Pisarski and Braaten. The ansatz for its evaluation which relates it to the imaginary part of the fermion propagator pole in the framework of a self-consistent approach is critically analyzed. As already pointed out by various authors, the only way to define the rate is through additional implementation of magnetic screening. We show in detail how the ansatz works in this case and where we disagree with other authors. We conclude that the self-consistent approach is not satisfactory.

hep-ph↗

arXiv1992

Gauge Dependence of the Resummed Thermal Gluon Self Energy

The gauge dependence of the hot gluon self energy is examined in the context of Pisarski's method for resumming hard thermal loops. Braaten and Pisarski have used the Ward identities satisfied by the hard corrections to the n-point functions to argue the gauge fixing independence of the leading order resummed QCD plasma damping rate in covariant and strict Coulomb gauges. We extend their analysis to include all linear gauges that preserve rotational invariance and display explicitly the conditions required for gauge fixing independence. It is shown that in covariant gauges the resummed damping constant is gauge fixing independent only if an infrared regulator is explicitly maintained throughout the calculation.

hep-ph↗