Li M. Quasiclassical Gluon Fields and Low's Soft Theorem at Small Momentum-Fraction x.
PHYSICAL REVIEW LETTERS 2024;
133:021902. [PMID:
39073955 DOI:
10.1103/physrevlett.133.021902]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/29/2024] [Revised: 06/06/2024] [Accepted: 06/10/2024] [Indexed: 07/31/2024]
Abstract
In the high-energy limit, soft gluons can be approximately described by quasiclassical gluon fields. It is well known that the gluon field is a pure gauge field on the transverse plane at eikonal order. We derived the complete next-to-eikonal order solutions of the classical Yang-Mills equations for soft gluons in the dense nuclear regime. Utilizing these solutions, it is shown that Low's soft theorem at small x can be obtained by considering off-diagonal matrix elements of quasiclassical chromoelectric field between single-gluon states in the dilute regime. We further propose on extending Low's soft theorem at small x to incorporate the effects of gluon saturation in the dense regime.
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