[Theory-seminars] Theory Seminar Monday

[Joseph Karpie]

Hey everyone,

We will be having a remote Theory seminar next week Monday at 1pm. Even though it's remote please join us in L102 or on Zoom. Below is the info

Speaker: Joshua Miller (Temple U)

Zoom: https://jlab-org.zoomgov.com/j/1609930756?pwd=ueEK8URNt4sE0KVSkKnxYmfgoARBMJ.1

Title: Proton GPDs from Lattice QCD

Abstract: Understanding the internal structure of the proton remains one of the central challenges in nuclear physics. Lattice QCD provides a first-principles framework for accessing partonic distribution functions that characterize parton dynamics within the proton. Among these, generalized parton distributions (GPDs) play a key role, as they provide a unified description of both the longitudinal momentum and spatial structure of quarks and gluons, thereby, along with the transverse momentum–dependent distributions (TMDs), enable a three-dimensional picture of the proton. Extracting the x-dependence of GPDs rely on off-forward matrix elements of non-local operators, which, traditionally, were performed in the symmetric frame. In such a setup, the momentum transfer is evenly shared between the initial and final hadron states. A novel approach introduced in 2022 instead employs any frame, allowing these matrix elements to be expressed in terms of Lorentz-invariant amplitudes, which can then be systematically mapped onto GPDs. This methodology has now been implemented for the unpolarized, helicity, and transversity GPDs. The proof-of-concept calculations we will present employ a proton boost of P_3 = 1.25 GeV, with the x-dependence extracted via Large Momentum Effective Theory (LaMET). Results are presented at zero skewness using an N_f =2+1+1 ensemble of maximally twisted mass fermions with clover improvement, corresponding to a pion mass of about 260 MeV.


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Joe Karpie
Pronouns: He/His/Him
Postdoctoral Fellow
Theoretical and Computational Physics Center
Jefferson Lab

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