Dmscatter: A fast program for WIMP-nucleus scattering

Abstract

Recent work [1,2], using an effective field theory framework, have shown the number of possible couplings between nucleons and the dark-matter-candidate Weakly Interacting Massive Particles (WIMPs) is larger than previously thought. Inspired by an existing Mathematica script that computes the target response [2], we have developed a fast, modern Fortran code, including optional OpenMP parallelization, along with a user-friendly Python wrapper, to swiftly and efficiently explore many scenarios, with output aligned with practices of current dark matter searches. A library of most of the important target nuclides is included; users may also import their own nuclear structure data, in the form of reduced one-body density matrices. The main output is the differential event rate as a function of recoil energy, needed for modeling detector response rates, but intermediate results such as nuclear form factors can be readily accessed. Program summaryProgram Title: dmscatterCPC Library link to program files:https://doi.org/10.17632/6fm7d4m2py.1Developer's repository link:https://github.com/ogorton/dmscatterLicensing provisions: MITProgramming languages: Fortran, PythonNature of problem: Simulating the event rate of nuclear recoils from collisions with dark matter for a variety of different nuclear targets and different nucleon-dark matter couplings.Solution method: The event rate is an integral over the product of the nuclear and dark matter response functions, weighted by the expected dark matter flux. To compute the nuclear response, reduced one-body nuclear density matrices are coupled to multipole expansion of operators computed analytically in a harmonic oscillator basis. The nuclear structure input, in the form of one-body densities matrices, are supplied by outside code; we provide a library of the most prominent targets.