[Theory-seminars] Cake Seminar

[Joseph Karpie]

Hey yall,

Please join us in L102 today at 1pm for a Cake Seminar by Kiminad Mamo.
Zoom: https://jlab-org.zoomgov.com/j/1615168742?pwd=UL5q5N2WwMQS7NymAK4k0ffwbA8tue.1

Title:
 From Light-Meson and Heavy-Quarkonia Production to Proton Structure:
Holographic Amplitudes, Gluonic GFFs, and All-Skewness GPDs

Abstract:
I will present a unified, string-based holographic framework for
exclusive electro- and photoproduction at Jefferson Lab and future EIC,
applied consistently to light mesons and heavy quarkonia. The scattering
amplitude is built from Witten diagrams with Reggeized t‑channel
exchange and admits a conformal partial‑wave (Gegenbauer/Mellin)
representation—an infinite sum over conformal moments of the underlying
GPDs. This construction makes the t‑channel dynamics (Reggeon/Pomeron)
explicit while enforcing support, crossing, and polynomiality by design.

For J/psi (and Upsilon) electro/photoproduction the same amplitude
connects near‑threshold and high‑energy regimes and enables an
experimental determination of the proton’s gluonic gravitational form
factors A(t) and D(t). Using this holographic amplitude, the J/psi‑007
Collaboration at JLab extracted A(t) and D(t) from exclusive data, tying
cross sections to the proton’s mass radius, pressure, and shear; the
resulting gluonic GFFs are in very good agreement with lattice‑QCD
determinations over the probed spacelike range. Electromagnetic
form‑factor results in the same soft‑wall framework are used to
calibrate the relevant Regge scales and normalizations.

I will also outline our forthcoming neutral‑pion analysis above the
resonance region. The anomaly‑fixed Chern‑Simons VAV coupling controls
the forward t‑channel residue F_t(Q^2, s, t), while nucleon s/u Born
terms account for central/backward angles. A single holographic form
factor governs the observed Q^2 and t dependences and yields transverse
dominance at forward angles—providing a clean bridge to the
deep‑exclusive regime and a direct link to transversity‑GPD conformal
moments.

Motivated by the amplitude–GPD duality above, I will introduce a
conformal‑moment parametrization of quark and gluon GPDs valid at any
skewness. With minimal Regge input anchored by electromagnetic and
gravitational form factors, the resulting GPDs agree with lattice
benchmarks in both moment space and reconstructed x‑space and deliver
testable predictions for JLab and future EIC.


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

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