Seminar in Hadronic Physics

Particle production in a field theory coupled to a strong external source

François Gelis

SPhT
Saclay

We consider a field theory coupled to a time-dependent external source, as in the Color Glass Condensate framework, and we study some general properties of the distribution of produced particles. We derive a formula for the probability of producing a given number of particles, in terms of cuts through vacuum-vacuum diagrams, and we show that the distribution of multiplicities is non Poissonian, even in the classical approximation. We then show how to calculate moments of the distribution of multiplicities. In particular, at leading order, the average multiplicity is easily obtained from the retarded solution of the classical field equation of motion. Then we explain how the simplifications that occur in the calculation of moments are due to an extension of the Abramovsky-Gribov-Kancheli cancellations.