# GPDs

Next-generation studies of partonic spatial imaging at an Electron-Ion Collider

The main purpose of the working group:

• perform impact dtudies via global fits of different GPDs models and probes;
• create a powerful and flexibale software tool for the EIC users community that would ensure propagation of knowledge;
• use the GPD-based tables of Compton form factors (CFFs) calculated within this common framework to seed a novel Monte Carlo generator for DVCS and meson production, featuring second order initial- and finalstate radiative effects;
• employ this novel generator to test reconstruction of kinematics and carefully define detector requirements for exclusive processes, a particularly timely study at this stage;
• assess the feasibility of extracting the D-term from precise measurement of differential cross sections.

The group is typically meeting remotely every other Monday at 10:30am EDT (New York time zone), using bluejeans.

## Meetings AGENDA

INDICO PAGE https://indico.bnl.gov/category/267/

## How to connect to meetings

Meeting URL
Meeting ID
383 476 545

Want to dial in from a phone? Dial one of the following numbers:
+1.408.740.7256 (US (San Jose))
+1.408.317.9253 (US (Primary, San Jose))
Enter the meeting ID and passcode followed by #

Connecting from a room system?
Dial: bjn.vc or 199.48.152.152 and enter your meeting ID & passcode

## MILOU with 3d tables

The MILOU code has been copied to CEA GitLab: https://drf-gitlab.cea.fr/milou/milou (authentication required). This git project contains several branches:

• the development branch is 'master' (it is also the default branch)
• the original/initial code is stored in 'original' branch (this branch is protected - no one can modify it)
• '3d_tables' branch contains the version being under development where (xB, Q2, t) DVCS Compton form factors are used (note: this version is under development and not fully tested).

To clone a given branch use either:

    git clone git@drf-gitlab.cea.fr:milou/milou.git -b _branch_name_


or

    git clone https://drf-gitlab.cea.fr/milou/milou.git -b _branch_name_


for either ssh or https authentication. Here, '_branch_name_' is the name of branch to be cloned.

New features and options of MILOU with 3d tables:

• uneccecery files are removed.
• makefiles are updated.
• 2d interpolation method is replaced by 3d version being a part of CERNLIB.
• 'ITFORM 8' enables t-dependence as encoded in 3d tables. Other values of 'ITFORM' enforce MILOU to probe the tables at t=0 and to apply t-dependence as indicated by the set value - this allows to keep the backward compatibility.
• the size of 3d tables is indicated to MILOU by 'NXGRID', 'NQGRID' and 'NTGRID' options (the last one is new).
• 3d tables are populated with CFFs generated using PARTONS with GK GPD model (at this moment only LO is available)