DarkPACK: A modular software to compute BSM squared amplitudes for particle physics and dark matter observables

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We present here a new package to automatically generate a complete library of 2 to 2 squared amplitudes at leading order in any New Physics model. The package is written in C++ and is based on the MARTY software. The numerical library generated allows for the computation of relic density by embedding the algorithms of SuperIso Relic. Program summaryProgram Title:DarkPACKCPC Library link to program files:https://doi.org/10.17632/dwm6g5ff2c.1Developer's repository link:https://gitlab.in2p3.fr/darkpack/darkpack-publicLicensing provisions: GPLv3Programming language: C++Nature of problem: Creating an all-in-one package that allows for the generation of 2→2 squared amplitudes and related quantities starting from the Lagrangian density. The package has also to provide tools to compute 〈σv〉 and the relic density. The aim is to have a modular tool as user-friendly as possible that provides dark matter observables starting from a BSM Lagrangian density.Solution method: We created a package that computes 2→2 squared amplitudes and related quantities, starting from the Lagrangian density. The package is based on MARTY 1.6[1], since MARTY provides a comprehensive environment that allows for the generation of a ready to use numerical library, starting from the Lagrangian density of the model. This would be very difficult to realize with other softwares, since the user would need to generate the Feynman rules from the Lagrangian density with some software (e.g. Sarah [2]), then use them to generate the squared amplitudes with some other software (e.g. CalcHEP [3] or MadGraph [4]), with a passage of inputs and need of coordination among more codes. Therefore, DarkPACK relies on the creation of a super-set of MARTY's capabilities, intended to generate a structure of the numerical library and to add essential features such as running of the Standard Model parameters. The user needs to implement the model in a C++ file that makes use of MARTY. Moreover, the user needs to use the functions we provide to implement fundamental features for the computation of the relic density. A configuration by hand of the inputs is needed as well, since each model has different input parameters. The package provides also tools to compute the relic density.