Theory Seminar - Yong Zhao

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Speaker: Yong Zhao (Argonne National Lab)

Title: Factorization connecting continuum and lattice TMDs

Abstract: The transverse-momentum-dependent parton distributions (TMDs) describe the intrinsic 3D motion of quarks and gluons inside the hadron, and they are of great interest to Jefferson Lab and the future Electron-Ion Collider. Recent years have seen exciting development in the lattice QCD calculation of TMDs, which include the quasi-TMDs in large-momentum effective theory (LaMET), a general framework that has also led to significant progress in calculating collinear parton distributions, and the Lorentz-invariant approach. In particular, LaMET has enabled the lattice calculation of the collinear and soft sectors of the TMD, making it possible to obtain its dependence on all the kinematic variables. In this talk, I will discuss the relation between lattice TMDs and the continuum physical TMD in the modern Collins scheme, the latter of which is defined with off-the-light-cone Wilson lines. I will show that the quasi-TMD in a large-momentum hadron state is equivalent to a new scheme, the Large Rapidity (LR) scheme, which differs from the Collins scheme only by the order of the light-cone limit and ultraviolet regularization. This leads to a factorization (or matching) relation between these quantities, which is a crucial step in obtaining the TMDs. The results imply that there is no mixing between various quark flavors or gluons when matching Collins and quasi TMDs, making the calculation of individual flavors and gluon TMDs easier than anticipated. I will also discuss implications for other physical-to-lattice scheme factorizations.