QCD Evolution Workshop 2023

Session

GPDs

May 25, 2023, 10:15 AM

Auditorium Joliot Curie (IJCLab, Orsay (FRANCE))

Conveners

GPDs

• Emilie Li (IJCLAB)

GPDs

• Emilie Li (IJCLAB)

GPDs

• Cédric Lorcé (Ecole polytechnique)

47. GPD studies with hard exclusive processes

Marija Čuić

5/25/23, 10:15 AM

We report on recent results on extraction of generalized parton distributions and relevant form factors from deeply virtual Compton scattering (DVCS) and deeply virtual meson production (DVMP) data. Using the more recent proton DVCS data, we extract the set of leading Compton form factors (CFFs) with uncertainties and, by adding neutron DVCS data, we separate the contributions of up and down...

42. Generalized Parton Distribution from Lattice QCD: New Developments

Swagato Mukherjee

5/25/23, 11:00 AM

Traditionally, lattice QCD computations of generalized parton distributions (GPDs) have been carried out in a symmetric frame, where the transferred momentum is symmetrically distributed between the incoming and outgoing hadrons. Such frames require a separate calculation for each value of the momentum transfer, increasing significantly the computational cost. I will present a newly developed...

12. Three-loop mixing matrix for flavor-singlet operators

Vladimir Braun (University of Regensburg)

5/25/23, 11:25 AM

Conformal symmetry of QCD is restored at the Wilson-Fisher critical point in noninteger space-time dimensions. Correlation functions of multiplicatively renormalizable operators with different anomalous dimensions at the critical point vanish identically.
We show that this property allows one to calculate off-diagonal parts of the anomalous dimension matrices for leading-twist operators from...

14. Resummation of threshold logarithms in deeply-virtual Compton scattering

Jakob Schönleber (University of Regensburg)

5/25/23, 11:50 AM

I derive an all-order resummation formula for the logarithmically enhanced contributions proportional to αsnx±ξ \frac{\alpha_s^n}{x\pm \xi } x±ξαsn​​ log (ξ±x2ξ)k {\left(\frac{\xi \pm x}{2\xi}\right)}^k (2ξξ±x​)k in the quark coefficient function of deeply-virtual-Compton scattering and the pion-photon transition form factor in momentum space. The resummation is performed at the...

82. The gluon GPD from moderate to small x using partial twist expansion

Dr Yacine Mehtar-Tani (Brookhaven National Laboratory)

5/25/23, 12:15 PM

We will discuss the gluon GPD from moderate to small x using partial twist expansion.

76. Generalized TMD distributions

Renaud BOUSSARIE (CPHT, CNRS, Ecole polytechnique, IP Paris)

5/25/23, 2:20 PM

Generalized Transverse Momentum Dependent (GTMD) distributions provide the most complete information on the structure of hadrons one can hope to constrain via experiments described in perturbative QCD. Using their Fourier transforms, Wigner distributions, it is possible to write very intuitive definitions for some physical properties inside hadrons such as the decomposition of its spin between...

66. Higher-twist contributions to deeply-virtual and photoproduction of mesons

Kornelija Passek-Kumerički (Ruđer Bošković Institute, Zagreb, Croatia)

5/25/23, 2:45 PM

Both deeply-virtual and photoproduction of mesons offer promising access
to generalized parton distributions and complementary description of different kinematical regions. Higher-twist effects have been identified as especially important in the case of the production of pseudo-scalar mesons. This was confirmed by recent evaluation of the complete twist-3 contribution to π production and its...

11. Prospects for extracting GPDs through photon-meson pair photoproduction

Saad Nabeebaccus (IJCLab)

5/25/23, 3:10 PM

We discuss the photoproduction of a photon-meson pair in the collinear factorisation framework as a channel for the extraction of GPDs. What makes this channel interesting, from among the family of $2 \to 3$ processes, is that depending on the chosen meson (and its polarisation) in the final state, one is able to probe chiral-even and chiral-odd GPDs, as well as gluonic GPDs, all at the...

81. Exclusive J/psi photoproduction: connecting PDFs and GPDs

Chris Flett (IJCLab)

5/25/23, 3:35 PM

21. Deeply Virtual Compton Scattering at Next-to-Next-to-Leading Order: Singlet Case

Yao Ji

Deeply-virtual Compton scattering gives access to the generalized parton distributions that encode the information on the transverse position of quarks and gluons in the proton with dependence on their longitudinal momentum. In anticipation of the high-precision experimental data and prominent gluon contribution in a broad kinematic range from the Electron-Ion Collider, we have calculated the...

46. Nucleon spin decomposition with one dynamical gluon

Chandan Mondal

There is a well-known puzzle: one of the fundamental properties of the proton, its spin, is not the same as the sum of its constituent quark spins. The gluon's contribution to the proton spin is nonvanishing and likely sizable. Yet, there remain large uncertainties about the gluon’s contribution and resolving this issue is one of the major goals of the upcoming Electron-Ion-Colliders. We...

54. Quantum entanglement and parton distribution functions

varun vaidya

Calculating Parton Distribution functions(PDFs) analytically has been a long standing problem in Nuclear physics. In this talk, I ll propose a new approach towards solving this problem by borrowing ideas from Quantum information science. In particular, I ll put forward a possible emergent minimum free energy principle based on the quantum entanglement properties of partons making up bound...

55. Shedding light on shadow generalized parton distributions

Eric Moffat (Argonne National Lab)

The feasibility of extracting generalized parton distributions (GPDs) from deeply-virtual Compton scattering (DVCS) data has recently been questioned because of the existence of an infinite set of so-called ``shadow GPDs'' (SGPDs). These SGPDs are process-dependent and manifest as multiple solutions (at a fixed $Q^2$) to the inverse problem that needs to be solved to infer GPDs from DVCS data....

10. Transverse Imaging

Matthias Burkardt (NMSU)

Generalized Parton Distributions have been linked to many other observables. For example, GPDs can be used to determine the contribution to orbital angular momentum. Furthermore, they can be used to determine the distribution of quarks in the transverse plane. For both these applications the x $\xi$ dependence needs to be disentangled. I plan to discuss the role of QCD evolution in this process.