Large-momentum effective theory

Xiangdong Ji, Yizhuang Liu, Yu-Sheng Liu, Jian-Hui Zhang, and Yong Zhao
Rev. Mod. Phys. 93, 035005 – Published 30 August 2021

Abstract

Since the parton model was introduced by Feynman more than 50 years ago, much has been learned about the partonic structure of the proton through a large body of high-energy experimental data and dedicated global fits. However, limited progress has been made in calculating partonic observables such as the parton distribution function (PDFs) from the fundamental theory of strong interactions, quantum chromodynamics (QCD). Recently some advocated for a formalism, large-momentum effective theory (LaMET), through which one can extract parton physics from the properties of the proton traveling at a moderate boost factor such as γ25. The key observation behind this approach is that Lorentz symmetry allows the standard formalism of partons in terms of light-front operators to be replaced by an equivalent one with large-momentum states and time-independent operators of a universality class. With LaMET, the PDFs, generalized PDFs or generalized parton distributions, transverse-momentum-dependent PDFs, and light-front wave functions can all be extracted in principle from lattice simulations of QCD (or other nonperturbative methods) through standard effective field theory matching and running. Future lattice QCD calculations with exascale computational facilities could help one to understand the experimental data related to the hadronic structure, including those from the upcoming electron-ion colliders dedicated to exploring the partonic landscape of the proton. Here the progress made in the past few years in the development of the LaMET formalism and its applications is reviewed, with an emphasis on a demonstration of its effectiveness from initial lattice QCD simulations.

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  • Received 14 April 2020

DOI:https://doi.org/10.1103/RevModPhys.93.035005

© 2021 American Physical Society

Physics Subject Headings (PhySH)

Particles & Fields

Authors & Affiliations

Xiangdong Ji*

  • Maryland Center for Fundamental Physics, Department of Physics, University of Maryland, College Park, Maryland 20742, USA and Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China

Yizhuang Liu

  • Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China and Institute of Theoretical Physics, Jagiellonian University, 30-348 Kraków, Poland

Yu-Sheng Liu

  • Tsung-Dao Lee Institute, Shanghai Jiao Tong University, Shanghai 200240, China

Jian-Hui Zhang§

  • Center of Advanced Quantum Studies, Department of Physics, Beijing Normal University, Beijing 100875, China

Yong Zhao

  • Physics Department, Brookhaven National Laboratory Building 510A, Upton, New York 11973, USA and Physics Division, Argonne National Laboratory, Lemont, Illinois 60439, USA

  • *xji@umd.edu
  • yizhuang.liu@uj.edu.pl
  • mestelqure@gmail.com
  • §zhangjianhui@bnu.edu.cn
  • yong.zhao@anl.gov

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Issue

Vol. 93, Iss. 3 — July - September 2021

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