[Theory-seminars] Theory Seminar TODAY

[Pia Jones Petrak]

On 21-09-2025 13:57, Joseph Karpie via Theory-seminars wrote:
> Hey everyone,
>
> We will be having a remote Theory seminar 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.
>
>
>
> --
> Joe Karpie
> Pronouns: He/His/Him
> Postdoctoral Fellow
> Theoretical and Computational Physics Center
> Jefferson Lab
>
>
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-- 
Pia Leonie Jones Petrak
Postdoctoral Fellow
Theoretical and Computational Physics Center
Jefferson Lab
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