Acta Physica Polonica B

Vol. 37, No. 12, December 2006, page 3253


Three Lectures on Multi-Particle Production in the Glasma

F. Gelis, R. Venugopalan

In the Color Glass Condensate (CGC) effective field theory, when two large sheets of Colored Glass collide, as in a central nucleus--nucleus collision, they form a strongly interacting, non-equilibrium state of matter called the Glasma. How Colored Glass shatters to form the Glasma, the properties of the Glasma, and the complex dynamics transforming the Glasma to a thermalized Quark Gluon Plasma (QGP) are questions of central interest in understanding the properties of the strongly interacting matter produced in heavy ion collisions. In the first of these lectures, we shall discuss how these questions may be addressed in the framework of particle production in a field theory with strong time dependent external sources. Albeit such field theories are non-perturbative even for arbitrarily weak coupling, moments of the multiplicity distribution can in principle be computed systematically in powers of the coupling constant. We will demonstrate that the average multiplicity can be (straightforwardly) computed to leading order in the coupling and (remarkably) to next-to-leading order as well. The latter are obtained from solutions of small fluctuation equations of motion with {retarded boundary conditions}. In the second lecture, we relate our formalism to results from previous 2+1 and 3+1 dimensional numerical simulations of the Glasma fields. The latter show clearly that the expanding Glasma is unstable; small fluctuations in the initial conditions grow exponentially with the square root of the proper time. Whether this explosive growth of small fluctuations leads to early thermalization in heavy ion collisions requires at present a better understanding of these fluctuations on the light cone. In the third and final lecture, motivated by recent work A. Bialas, M. Jeżabek, Phys. Lett. {B590}, 233 (2004), we will discuss how the widely observed phenomenon of limiting fragmentation is realized in the CGC framework.

PACS numbers: 12.38.--t, 12.38.Mh, 25.75.Nq



 
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