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

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