@article{76f83772c76045dc8c00b87a73235438,

title = "Instantons in the saturation environment",

abstract = "We show that instanton calculations in QCD become theoretically well defined in the gluon saturation environment which suppresses large-size instantons. The effective cutoff scale is determined by the inverse of the saturation scale. We concentrate on two most important cases: the small-x tail of a gluon distribution of a high-energy hadron or a large nucleus and the central rapidity region in a high-energy hadronic or heavy-ion collision. In the saturation regime the gluon density in a single large ultrarelativistic nucleus is high and gluonic fields are given by the classical solutions of the equations of motion. We show that these strong classical fields do not affect the density of instantons in the nuclear wave function compared to the instanton density in the vacuum. A classical solution with nontrivial topological charge is found for the gluon field of a single nucleus at the lowest order in the instanton perturbation theory. In the case of ultrarelativistic heavy-ion collisions a strong classical gluonic field is produced in the central rapidity region. We demonstrate that this field introduces a suppression factor of exp{-cρr nuclei, τ is the proper time and c ≈ 1 is the gluon liberation coefficient. This factor suggests that gluonic saturation effects at the early stages of nuclear collisions regulate the instanton-size distribution in the infrared region and make the instanton density finite by suppressing large-size instantons.",

keywords = "Heavy-ion collisions, Infrared safety, Parton saturation, QCD instantons",

author = "Dmitri Kharzeev and Kovchegov, {Yuri V.} and Eugene Levin",

note = "Funding Information: We would like to thank Ian Balitsky, Dmitri Diakonov, Asher Gotsman, Uri Maor, Larry McLerran, John Negele, Victor Petrov, Rob Pisarski, Maxim Polyakov, Edward Shuryak and Larry Yaffe for many informative and stimulating discussions. The research of D.K. is supported by the U.S. Department of Energy under contract No. DE-AC02-98CH10886. The work of Yu.K. was supported in part by the U.S. Department of Energy under Grant No. DE-FG03-97ER41014. The research of Yu. K. and E. L. was sponsored in part by the BSF grant # 9800276 and by Israeli Science Foundation, founded by the Israeli Academy of Science and Humanities.",

year = "2002",

month = mar,

day = "11",

doi = "10.1016/S0375-9474(01)01276-3",

language = "אנגלית",

volume = "699",

pages = "745--769",

journal = "Nuclear Physics A",

issn = "0375-9474",

publisher = "Elsevier",

number = "3-4",

}