micrOMEGAs: Version 1.3

TL;DR

micrOMEGAs1.3 provides a robust, numerically precise framework for computing the relic density of the LSP in the MSSM by solving a Boltzmann equation with a relativistic thermal average and including all tree-level annihilation and coannihilation channels. It achieves high accuracy by employing loop-corrected sparticle masses and mixings from SLHA-compliant spectrum calculators, Higgs masses and widths with QCD and Delta m_b corrections, and a comprehensive set of constraints (g-2, b to s gamma, B_s to mu mu). The package integrates CalcHEP-generated cross-sections for MSSM processes, supports both weak-scale and GUT-scale inputs, and offers flexible interfaces to major spectrum codes (Suspect, SoftSUSY, SPHENO, Isajet) for realistic modeling and collider-relevant simulations. Together, these features enable precise relic-density predictions in Higgs-resonance and coannihilation regions and facilitate collider studies through cross-sections and widths across the MSSM parameter space, with practical applicability via CalcHEP sessions and example workflows.

Abstract

We present the latest version of micromegas, a code that calculates the relic density of the lightest supersymmetric particle in the MSSM. All tree-level processes for the annihilation of the LSP are included as well as all possible coannihilation processes with neutralinos, charginos, sleptons, squarks and gluinos. The cross-sections extracted from CalcHEP are calculated exactly using loop-corrected masses and mixings as specified in the SUSY Les Houches Accord. Relativistic formulae for the thermal average are used and care is taken to handle poles and thresholds by adopting specific integration routines. The input parameters can be either the soft SUSY parameters in a general MSSM or the parameters of a SUGRA model specified at some high scale (GUT). In the latter case, a link with Suspect, Softsusy, Spheno and Isajet allows to calculate the supersymmetric spectrum, Higgs masses, as well as mixing matrices. Higher-order corrections to Higgs couplings to quark pairs including QCD as well as some SUSY corrections (deltaMb) are implemented. Routines calculating (g-2), bsgamma and bsmumu are also included. In particular the bsgamma routine includes an improved NLO for the SM and the charged Higgs while the SUSY large tan(beta) effects beyond leading-order are included. This new version also provides cross-sections for any 2->2 process as well as partial decay widths for two-body final states in the MSSM allowing for easy simulation at colliders.