dmscatter: A Fast Fortran Program for WIMP-Nucleus Scattering

Oliver Gorton, Changfeng Jiao, and Calvin Johnson

Computes the differential event rate per recoil energy for WIMP-nucleon scattering events. This code is based on the Mathematica package, DMFormFactor described in this arXiv link.

Can be used as a standard Fortran program via the command line, or via our convenient Python interfaces, which offer a minimal interface, optionally extensible to the full capabilities of the underlying program.

Read the paper:

• Link to CPC Publication (2022)
• Link to arXiv:2209.09187

Read the documentation:

• Link to PDF

Dev Contacts

• Oliver Gorton, PhD student (email: [email protected])
• Calvin Johnson, PI (email: [email protected])

Compile

To compile the program, you must have the gfortran compiler and make installed. to compile an OpenMP-parallel version of the code, navigate to the make directory and run:

make openmp

To compile a serial version of the code, instead run:

make dmscatter

Both options create the executable dmscatter in the bin directory. (Many of the example Python scripts expect to find it there.) Note that if you want to switch between and serial or parallel version, you must run make clean in-between compiles.

Run with Python

The main Python interface to the code can be imported and called:

import sys
sys.path.append("../python")
import dmscatter as dm

If necessary, replace "../python" with the path to the dmscatter/python diretory on your system.

To run one of the example Python scripts, try moving to examples and running:

python3 exampleXe.py

More extensive documentation can be found in the manual document.

EventrateSpectra

The main function in this module, used to compute the differential event-rate spectra. The interface looks like this:

EventrateSpectra(Z, N, dres=None, target=None, epmin=1, epmax=1000, epstep=1,
        controlwords={}, cp=None, cn=None, cs=None, cv=None,
        exec_path='dmscatter', name=None)

Here is an example call to this function:

import sys
sys.path.append("../python")
import dmscatter as dm
Recoilenergykev, Eventrate = dm.EventrateSpectra(
            Z = 54,
            N = 77,
            target = "../targets/Xe/xe131gcn",
            cn = [0.00048, 0,0,0,0,0,0,0,0,0,0,0,0,0,0],
            exec_path='../bin/dmscatter' )

A more detailed example is given in examples/exampleXe.py.

NucFormFactor

The other availale function is for computing nuclear form factors. The interface is

NucFormFactor(Z, N, dres=None, target=None, epmin=1, epmax=1000, epstep=1,
    controlwords={}, exec_path='dmscatter', name=".nucFFspectra")

Here is an example call to this function:

Wfunc = dm.NucFormFactor(
        Z = 54,
        N = 77,
        dres = "../targets/Xe/xe131gcn",
        controlwords = cwords,
        epmin = 0.001,
        epmax = 10.0,
        epstep = 0.001,
        exec_path='../bin/dmscatter')
print(Wfunc(q=0.001))

A more detailed example is given in examples/exampleXeFF.py.

Validation plots

We include a script for generating validation tests against data generated with DMFormFactor (the Mathematica package). After compiling the code, navigate to test and run

make test

After a few minutes, and if you have pandoc installed, a file called validation.pdf should be generated with a number of plots comparing the output of dmscatter against DMFormFactor. If you don't have pandoc, you can still view the plots individually in the test directory.

Directory

Directory	Description
bin	This directory is created once you compile the code from the build directory.
make	Compile the code with the included Makefile here.
docs	Manual and other documentation
data	Nuclear structure information: the density matrix files (.dres)
examples	Example Python scripts using our Python wrapper
python	Python modules containing the wrapper for dmscatter
src	Fortran source code and Makefile. Compile the code here.
test	Test script and validation data.