Higgs boson production in high energy proton-nucleus collisions

TL;DR

The paper develops a hybrid theoretical framework that treats the dense nucleus with color glass condensate dynamics while employing the Lipatov approximation for the proton, to study Higgs boson production in high-energy proton-nucleus collisions. It shows that Higgs production cross sections can be expressed using Weizsäcker-Williams gluon TMDs and that the results reproduce TMD factorization in the dilute regime, while highlighting the breakdown of naive $k_t$ factorization in dense media. The approach provides a consistent link between CGC, TMD, and $k_t$ formalisms, and offers a practical path to access linearly polarized gluon distributions through central Higgs production and related processes. These findings have implications for understanding saturation effects and for extracting $h_1^{\perp g}$ in high-energy hadronic collisions.

Abstract

We study Higgs boson production from gluon-gluon fusion at mid-rapidity in high energy proton-nucleus collisions. For this process the presently still little known gluon distribution function $h_1^{\perp g}$ gives a numerically relevant contribution. We show by explicite calculation that using CGC (color glass condensate) model input the result obtained in the naive k_t factorization approach matches the result obtained in the TMD factorization framework for a dilute medium. We also verify the earlier finding that the k_t factorization formalism for Higgs production breaks down in a dense medium. In doing so we formulate a hybrid model which allows one to treat such reactions theoretically.

Figures (3)

• Figure 1: Feynman rules for the eikonal line, which is represented by a double line. $a,b,c$ denote color indices.
• Figure 2: The diagrams contributing to gluon production. The dash lines represent the re-summed interactions of the incoming gluon or color source inside the proton with the classical color field of the nucleus.
• Figure 3: The generic diagrams contributing to Higgs boson production. The multiple scattering of the incoming gluon or color source inside the proton by the classical gauge field have to be re-summed to all orders. $p_H$ denotes the Higgs boson momentum.