– Modern ARtificial Theoretical phYsicist A C++ framework automating theoretical calculations Beyond the Standard Model

Abstract

Studies Beyond the Standard Model (BSM) will become more and more important in the near future with the rapidly increasing amount of data from different experiments around the world. The full study of BSM models is in general an extremely time-consuming task involving long and difficult calculations. It is in practice not possible to do exhaustive predictions in these models by hand. Here we present MARTY, a new C++ framework that fully automates calculations from the Lagrangian to physical quantities such as amplitudes or cross-sections. It can fully simplify, automatically and symbolically, physical quantities in a very large variety of models and compute Wilson coefficients in effective theories. This will considerably facilitate BSM studies in flavour physics. Contrary to the existing public codes in this field MARTY aims at providing a unique, free, open-source, powerful and user-friendly tool for high-energy physicists studying predictive BSM models, in effective or full theories up to the one-loop level, which does not rely on any external package. With a few lines of code one can gather final expressions that may be evaluated numerically for statistical analysis. Program summaryProgram Title: MARTYCPC Library link to program files:https://doi.org/10.17632/y7n82jcj8d.1Developer’s repository link: https://marty.in2p3.frLicensing provisions: GPLv3Programming language: C++Supplementary material: GNU-GSL [1], LoopTools [2]Nature of problem: Beyond the Standard Model phenomenology often requires one-loop theoretical calculations. These calculations must be done analytically because a numerical evaluation of such quantities is not possible, the number of terms being too large for any computer to handle. The required simplifications are very long and error prone, which justifies the effort to automate them. A dedicated computer algebra system is therefore needed. Some packages written with Mathematica [3] – a private and closed software for symbolic manipulations – can perform such calculations. There are usually multiple packages to interface, the user needs to pay for Mathematica and the calculation of Wilson coefficients for BSM and at the one-loop level is complicated to automate.Solution method: MARTY is a code written for BSM phenomenology that comes with its own computer algebra system, CSL, and automates the calculation of theoretical quantities at the one-loop level, in a very large variety of BSM models. This provides a unique C++ code, free and open-source, that can be used to do model building and calculate any kind of amplitudes, squared amplitudes or Wilson coefficients in BSM scenarios starting from a given Lagrangian. From the developers point of view, having such a code, independent of any other framework using only the C++ standard library (C++17 standard), is a great opportunity to develop it even further implementing new simplification procedures, different types of calculation and more.