Why is LaMET an effective field theory for partonic structure?
Abstract
Partons are effective degrees of freedom describing the structure of hadrons involved in highenergy collisions. Familiar theories of partons are QCD lightfront quantization and softcollinear effective theory, both of which are intrinsically Minkowskian and appear unsuitable for classical Monte Carlo simulations. A ``new'' form of the parton theory has been formulated in term of the oldfashioned, Feynman's infinite momentum frame, in which the parton degrees of freedom are filtered through infinitemomentum external states. The partonic structure of hadrons is then related to the matrix elements of static (equaltime) correlators in the state $P^z=\infty\rangle$. This representation lays the foundation of largemomentum effective theory (LaMET) which approximates parton physics through a systematic $M/P^z$ expansion of the lattice QCD matrix elements at a finite but large momentum $P^z$, and removes the residual logarithmic$P^z$ dependence by the standard effectivefieldtheory matching and running.
 Publication:

arXiv eprints
 Pub Date:
 July 2020
 DOI:
 10.48550/arXiv.2007.06613
 arXiv:
 arXiv:2007.06613
 Bibcode:
 2020arXiv200706613J
 Keywords:

 High Energy Physics  Phenomenology;
 High Energy Physics  Lattice;
 High Energy Physics  Theory;
 Nuclear Theory
 EPrint:
 8 pages, 3 figures