jpacPhoto
Framework for amplitude analysis involving single meson production via quasi-elastic scattering of a real photon on a nucleon target. Focus on expandability and easy interfacing with Monte-Carlo tools and event generators.
Such processes are of interest at many experiments at JLab and the future EIC.
Requires ROOT (tested with version 6.17) with MathMore libraries installed.
INSTALLATION
To install clone normally and use:
mkdir build && cd build
cmake ..
cmake --build . --target installThis will create a jpacPhoto/lib with the linkable library.
If you wish to also build the full suite of executables (e.g. to reproduce plots in 1(https://arxiv.org/abs/1907.09393) and 2(https://arxiv.org/abs/2008.01001)) you need to install the jpacStyle library and set environment variable as such:
# for bash
export JPACSTYLE=/path/to/jpacStyle
# for csh
setenv JPACSTYLE /path/to/jpacStyleAMPLITUDES
The main object of interest is the abstract amplitude class. This allows you to build observables from helicity amplitudes:
- Probability distribution ( Σ_λ | A |^2 )
- Differential cross section ( dσ / dt )
- Integrated total cross section ( σ )
- Polarization asymmetries ( A_LL and K_LL )
- Spin density matrix elements ( ρ^α_λ,λ' )
- Integrated beam asymmetry ( Σ_4pi )
- Beam asymmetry in the y-direction ( Σ_y )
- Parity asymmetry ( P_σ )
Available amplitudes, so far, include:
- Baryon resonance (s-channel)
- Pomeron exchange (t-channel)
- (fixed-spin and reggeized) Charged pseudo-scalar meson exchange (t-channel)
- (fixed-spin and reggeized) Vector meson exchange (t-channel)
- Primakoff effect off nuclear target (t-channel)
- (fixed-spin) Dirac fermion exchange (u-channel)
- (fixed-spin) Rarita-Schwinger fermion exchange (u-channel)
Incoherent (interfering) sums of amplitudes may be constructed through the amplitude_sum class.
REFERENCES
- [1] Double Polarization Observables in Pentaquark Photoproduction
- [2] XYZ spectroscopy at electron-hadron facilities: Exclusive processes
- [3] JPAC Website
