Particle production in field theories coupled to strong external sources, I: Formalism and main results

Abstract

We develop a formalism for particle production in a field theory coupled to a strong time-dependent external source. An example of such a theory is the Color Glass Condensate. We derive a formula, in terms of cut vacuum-vacuum Feynman graphs, for the probability of producing a given number of particles. This formula is valid to all orders in the coupling constant. The distribution of multiplicities is non-Poissonian, even in the classical approximation. We investigate an alternative method of calculating the mean multiplicity. At leading order, the average multiplicity can be expressed in terms of retarded solutions of classical equations of motion. We demonstrate that the average multiplicity at next-to-leading order can be formulated as an initial value problem by solving equations of motion for small fluctuation fields with retarded boundary conditions. The variance of the distribution can be calculated in a similar fashion. Our formalism therefore provides a framework to compute from first principles particle production in proton-nucleus and nucleus-nucleus collisions beyond leading order in the coupling constant and to all orders in the source density. We also provide a transparent interpretation (in conventional field theory language) of the well known Abramovsky-Gribov-Kancheli (AGK) cancellations. Explicit connections are made between the framework for multi-particle production developed here and the framework of Reggeon field theory.

Initial energy density and gluon distribution from the glasma in heavy-ion collisions

“…That is, we assume a harmonic oscillator and count the number of quanta. The concrete procedure is that we divide the field energy with momentum k ⊥ by the (free) gluon energy quanta k ⊥ to infer the gluon distribution contained in the fields, which is consistent with the multiplicity computation by the reduction formula [34]. We define in this way the gluon distribution as…”

High Energy Scattering in Quantum Chromodynamics

“…Eq. (29) gives the structure functions T 1,2 as a series of terms, each of which has factorized x and Q 2 dependences. (The functions D r;s,i (r = 1, 2) are related to the Fourier transform of C s,i (y 2 ), and thus can only depend on the invariant Q 2 ).…”

Wilson-line and color charge density correlators and the production ofη'in the color glass condensate forppand<

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