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Leading-Order Gluon-Pair Production from a Space-Time Dependent Chromofield  [PDF]
Dennis D. Dietrich,Gouranga C. Nayak,Walter Greiner
Physics , 2000,
Abstract: We describe gluon-pair production from a space-time dependent chromofield via vacuum polarization within the framework of the background field method of QCD. The processes we consider are first order in the action. We derive the corresponding source terms for gluon pair production for situations that can be described by a 1+1 dimensional approach. Especially, we observe that within the range of applicability of our approach the principal contribution to gluon production is included. Gluon production from a space-time dependent chromofield will play an important role in the production and evolution of the quark-gluon plasma in ultra relativistic heavy-ion collisions at RHIC and LHC.
Gluon Pair Production from a Space-Time Dependent Classical Chromofield via Vacuum Polarization  [PDF]
Gouranga C. Nayak,Dennis D. Dietrich,Walter Greiner
Physics , 2001,
Abstract: We investigate the production of gluon pairs from a space-time dependent classical chromofield via vacuum polarization within the framework of the background field method of QCD. The investigation of the production of gluon pairs is important in the study of the evolution of the quark-gluon plasma in ultra-relativistic heavy-ion collisions at RHIC and LHC.
Phase Space Description of the Leading Order Quark and Gluon Production from a Space-Time Dependent Chromofield  [PDF]
Dennis D. Dietrich,Gouranga. C. Nayak,Walter Greiner
Physics , 2000, DOI: 10.1103/PhysRevD.64.074006
Abstract: We derive source terms for the production of quarks and gluons from the QCD vacuum in the presence of a space-time dependent external chromofield A_{cl} to the order of S^{(1)}. We found that the source terms for the parton production processes A_{cl} -> q\bar{q} and A_{cl},A_{cl}A_{cl} -> gg also include the annihilation processes q\bar{q} -> A_{cl} and gg -> A_{cl},A_{cl}A_{cl}. The source terms we derive are applicable for the description of the production of partons with momentum p larger rhan gA which itself must be larger than \Lambda_{QCD}. We observe that these source terms for the production of partons from a space-time dependent chromofield can be used to study the production and equilibration of the quark-gluon plasma during the very early stages of an ultrarelativistic heavy-ion collision.
Schwinger Mechanism for Gluon Pair Production in the Presence of Arbitrary Time Dependent Chromo-Electric Field
Nayak, Gouranga C.
High Energy Physics - Phenomenology , 2007, DOI: 10.1140/epjc/s10052-008-0819-8
Abstract: We study Schwinger mechanism for gluon pair production in the presence of arbitrary time-dependent chromo-electric background field $E^a(t)$ with arbitrary color index $a$=1,2,...8 in SU(3) by directly evaluating the path integral. We obtain an exact expression for the probability of non-perturbative gluon pair production per unit time per unit volume and per unit transverse momentum $\frac{dW}{d^4x d^2p_T}$ from arbitrary $E^a(t)$. We show that the tadpole (or single gluon) effective action does not contribute to the non-perturbative gluon pair production rate $\frac{dW}{d^4x d^2p_T}$. We find that the exact result for non-perturbative gluon pair production is independent of all the time derivatives $\frac{d^nE^a(t)}{dt^n}$ where $n=1,2,....\infty$ and has the same functional dependence on two casimir invariants $[E^a(t)E^a(t)]$ and $[d_{abc}E^a(t)E^b(t)E^c(t)]^2$ as the constant chromo-electric field $E^a$ result with the replacement: $E^a \to E^a(t)$. This result may be relevant to study the production of a non-perturbative quark-gluon plasma at RHIC and LHC.
Schwinger Mechanism for Gluon Pair Production in the Presence of Arbitrary Time Dependent Chromo-Electric Field in Arbitrary Gauge
Nayak, Gouranga C
High Energy Physics - Phenomenology , 2008, DOI: 10.1142/S0217751X10047865
Abstract: We study non-perturbative gluon pair production from arbitrary time dependent chromo-electric field E^a(t) with arbitrary color index a =1,2,...8 via Schwinger mechanism in arbitrary covariant background gauge \alpha. We show that the probability of non-perturbative gluon pair production per unit time per unit volume per unit transverse momentum \frac{dW}{d^4xd^2p_T} is independent of gauge fixing parameter \alpha. Hence the result obtained in the Fynman-'t Hooft gauge, \alpha=1, is the correct gauge invariant and gauge parameter \alpha independent result.
Schwinger Mechanism for Gluon Pair Production in the Presence of Arbitrary Time Dependent Chromo-Electric Field in Arbitrary Gauge  [PDF]
Gouranga C Nayak
Physics , 2008, DOI: 10.1142/S0217751X10047865
Abstract: We study non-perturbative gluon pair production from arbitrary time dependent chromo-electric field E^a(t) with arbitrary color index a =1,2,...8 via Schwinger mechanism in arbitrary covariant background gauge \alpha. We show that the probability of non-perturbative gluon pair production per unit time per unit volume per unit transverse momentum \frac{dW}{d^4xd^2p_T} is independent of gauge fixing parameter \alpha. Hence the result obtained in the Fynman-'t Hooft gauge, \alpha=1, is the correct gauge invariant and gauge parameter \alpha independent result.
Constraints on the Proton's Gluon Density from Lepton-Pair Production  [PDF]
E. L. Berger,M. Klasen
Physics , 2000,
Abstract: Massive lepton-pair production, the Drell-Yan process, should be a good source of independent constraints on the gluon density, free from the experimental and theoretical complications of photon isolation that beset studies of prompt photon production. We provide predictions for the spin-averaged and spin-dependent differential cross sections as a function of transverse momentum $Q_T$.
Quark-antiquark pair production in space-time dependent fields  [PDF]
Dennis. D. Dietrich
Physics , 2004, DOI: 10.1103/PhysRevD.70.105009
Abstract: Fermion-antifermion pair-production in the presence of classical fields is described based on the retarded and advanced fermion propagators. They are obtained by solving the equation of motion for the Dirac Green's functions with the respective boundary conditions to all orders in the field. Subsequently, various approximation schemes fit for different field configurations are explained. This includes longitudinally boost-invariant forms. Those occur frequently in the description of ultrarelativistic heavy-ion collisions in the semiclassical limit. As a next step, the gauge invariance of the expression for the expectation value of the number of produced fermion-antifermion pairs as a functional of said propagators is investigated in detail. Finally, the calculations are carried out for a longitudinally boost-invariant model-field, taking care of the last issue, especially.
Pair Production of Neutral Higgs Particles in Gluon--Gluon Collisions  [PDF]
T. Plehn,M. Spira,P. M. Zerwas
Physics , 1996, DOI: 10.1016/0550-3213(96)00418-X
Abstract: Pair production processes of neutral Higgs particles will allow us to study the trilinear Higgs couplings at future high--energy colliders. Several mechanisms give rise to multi--Higgs final states in hadron interactions. In the present paper we investigate Higgs pair production in gluon--gluon collisions. After recapitulating pair production in the Standard Model, the analysis of the cross sections is carried out in detail for the neutral Higgs particles in the minimal supersymmetric extension.
Electron-Positron Pair Production in Space- or Time-Dependent Electric Fields
Kleinert, Hagen;Ruffini, Remo;Xue, She-Sheng
High Energy Physics - Phenomenology , 2008, DOI: 10.1103/PhysRevD.78.025011
Abstract: Treating the production of electron and positron pairs by a strong electric field from the vacuum as a quantum tunneling process we derive, in semiclassical approximation, a general expression for the pair production rate in a $z$-dependent electric field $E(z)$ pointing in the $z$-direction. We also allow for a smoothly varying magnetic field parallel to $E(z)$. The result is applied to a confined field $E(z)\not=0$ for $|z|\lesssim \ell $, a semi-confined field $E(z)\not=0$ for $ z\gtrsim 0 $, and a linearly increasing field $E(z)\sim z$. The boundary effects of the confined fields on pair-production rates are exhibited. A simple variable change in all formulas leads to results for electric fields depending on time rather than space. In addition, we discuss tunneling processes in which empty atomic bound states are spontaneously filled by negative-energy electrons from the vacuum under positron emission. In particular, we calculate the rate at which the atomic levels of a bare nucleus of finite size $r_{\rm n}$ and large $Z\gg 1$ are filled by spontaneous pair creation.
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