Comparison repository for GlueX amplitude models

This repository was created during PWA working group meetings for GlueX at Jefferson Lab, July 31st to August 4th, 2023. Live notes for these discussions can be found here on HackMD. Each meeting was organised like a 'hackathon' and the results of these programming sessions can be found on compwa.github.io/gluex-amplitude.

The main target for the week was to implement a simple intensity function for two-pseudoscalar system with photo-production:

where $Z{l}^{m}(\Omega,\Phi)=Y{l}^{m}(\Omega)e^{-i\Phi}$ is a phase-rotated spherical harmonic, $\Omega$ is the solid angle, $\Phi$ is the angle between the production and polarization planes, $P_{\gamma}$ is the polarization magnitude, $[l]$ are the partial wave amplitudes, $m$ is the associated m-projection, $k$ refers to a spin flip ($k=1$) or non-flip ($k=0$) at the nucleon vertex, and $\kappa$ is an overall phase space factor.

The details for this model have been worked out in 10.1103/PhysRevD.100.054017 (2019).

The amplitude model is implemented in AmpTools and symbolically in Python using SymPy with additional tools from amptools (ComPWA Project). Dynamics are not yet included (model-indepedent by binning over energy). So we are just comparing linar combinations of spherical harmonics, but the comparison can be extended by investigating final states with a vector meson and/or parametrizing dynamic lineshapes.

Installation

This repository comes with AmpTools as a submodule, under extern/AmpTools. If you clone this repository as:

shell git clone https://github.com/compwa/gluex-amplitude --recurse-submodules

you should get AmpTools as well. Alternatively, if you have already cloned the repository, you can initialize the submodule with:

shell git submodule update --init

All required dependencies can be installed within an isolated virtual environment through the Pixi package manager. Installation instructions can be found here.

To build all source code, simply run:

shell pixi run build

Other Pixi tasks can be listed with

shell pixi task list

In particular, you can build the website with the Python notebook with the doc task:

shell pixi run doc

Open docs/_build/html/index.html to view the resulting HTML pages. In VSCode, you can view the output HTML files by searching for "Live Preview: Start Server" through the command pallette (Ctrl+Shift+P).

Finally, to automatically run style checks over files you are committing, it is recommended to install pre-commit:

shell pixi global install --expose pre-commit pre-commit-uv pre-commit install --install-hooks