# More On Large-Momentum Effective Theory Approach to Parton Physics

## TL;DR

This paper discusses the Large-Momentum Effective Theory (LaMET) approach for simulating parton physics in lattice QCD, clarifying its advantages and relation to Ioffe-time distribution methods, emphasizing the importance of large momentum limits.

## Contribution

It provides a detailed exposition of LaMET, explaining its lack of power divergence issues and comparing it with Ioffe-time distribution methods for extracting parton distributions.

## Key findings

- LaMET avoids the usual power divergence problem in lattice QCD.
- Both LaMET and Ioffe-time methods require large momentum limits for precision.
- Proper error quantification is essential for comparing extraction methods.

## Abstract

Large-Momentum Effective Theory (or LaMET) advocated by the present authors provides a direct approach to simulate parton physics in Eulidean lattice QCD theory. Recently, there has been much interest in this theory in the literature, with some questioning its validity and effectiveness. Here we provide some discussions aiming at a further exposition of this approach. In particular, we explain why it does not have the usual power divergence problem in lattice QCD calculations for the moments of parton distributions. We show that although the Ioffe-time distribution provides an alternative way to extract the parton distribution from the same lattice observable, it also requires the same large momentum limit as in LaMET to obtain a precision calculation. With a proper quantification of errors, both extraction methods should be compared with the same lattice data.