EPIPROD revision history

James J. Kelly
Department of Physics
University of Maryland
College Park, MD 20742 USA

EPIPROD is a program originally written by T. E. Payerle, as my student, to calculate observables and response functions for pion electroproduction experiments. The work began in 1993 while I was on sabbatical in NIKHEF and started with an earlier program by R. W. Lourie, with corrections and considerably expanded capabilities. Version 2.3.6 was released in 1995 and is the last version with which Payerle was involved. Since then I have extensively rewritten EPIPROD and expanded its capabilities.  Eta production became available in Version 3.0, Monte Carlo event generation became available in Version 4.0, and data analysis routines became available in Version 5.0

We strongly recommend that new users begin with the most recent version available.  Brief descriptions of some intermediate versions are retained here to document development of features, but dates are only approximate.

Version 2.3.6 (March, 1995)

Final version of the pion electroproduction code by T. E. Payerle.  Among its features are:

• all 4 charge states
• recoil polarization
• Born diagrams with pseudoscalar coupling
• resonances with Breit-Wigner parametrization or external amplitudes
• several useful models implemented with minimal input required
• interactive input
• figures using GPLOT or TOPDRAWER
• extensive set of procedures for transforming between common representations of the amplitudes, response functions, and observables
• automated production of standardized figures
• user manual with detailed formalism

Version 3.0 (September, 1997)

Electroproduction of pseudoscalar mesons on nucleon targets.  

New features:

• extensive rewriting with streamlined and generalized formalism
• eta production
• photoproduction
• inclusive cross sections versus Q² or W
• nonresonant diagrams with pseudoscalar and/or pseudovector coupling
• BMZ model of eta production
• larger variety of transformation procedures

• input is now from files only
• standardized figures are no longer available because they utilized graphics packages that are not readily available. An output file is provided which can be used by most modern graphics programs.
• several specialized models have been omitted in the present release and may be restored in later versions
• the documentation has not yet been updated

Version 3.1

• corrects some errors
• more flexible input of resonance amplitudes
• calculates angular asymmetries for cross sections and polarization observables

Version 3.2 (March, 1998)

• projects multipole amplitudes via angular integration
• Legendre expansion of angular distributions for partial cross sections
• bidirectional transformations between CGLN and helicity amplitudes

Version 4.0 (March, 2000)

• reorganized for more efficient implementation within Monte Carlo event generators
• more streamlined coding and I/O
• mixed pseudoscalar/pseudovector coupling
• interpolation within tables of multipole amplitudes from external source

Version 4.3.2 (December, 2002)

• Makefiles redesigned for use with gmake, permitting versions for several platforms to be supported on the same file system
• compatibility with linux g77 compiler
• SAID model

Version 5.1 (June, 2003)

• fit Legendre expansions to data for response functions or for cross section and polarization
• fit multipole amplitudes to data for response functions or for cross section and polarization
• fit response functions to data for phi distributions
• project Legendre amplitudes from model calculations
• reduced response functions with sin(theta) factors removed

Version 5.2 (July, 2004)

• streamlined and more uniform input/output structure
• file names based upon environment variables
• additional options
• relatively complete documentation
• L/T analysis using parallel kinematics
• baseline multipoles projected for models that do not use multipole input files
• pseudodata based upon data set -- data replaced by model calculations with fluctuations according to experimental uncertainties

Version 5.3 (October, 2004)

• option for replacing cross section data with model calculations for testing purposes
• more flexible target polarization options
• improved output formatting
• input/output for Monte Carlo routines more consistent with other modes

Version 5.4 (July, 2005)

• option for reading response functions from a single internally labeled file with format similar to plot output
• input of initial parameters from file or output of final parameters to file
• kinematical bin centering corrections in multipole or Legendre fits
• two sets of vary codes possible for multipole fits
• quadrupole ratios computed using projected Legendre coefficients
• unitary isobar model
• tabular multipole output for charge or isospin amplitudes

Please report errors or problems to: James J. Kelly
Last revised: July 22, 2005