Global analyses of Higgs portal singlet dark matter models using GAMBIT

Abstract

We present global analyses of effective Higgs portal dark matter models in the frequentist and Bayesian statistical frameworks. Complementing earlier studies of the scalar Higgs portal, we use GAMBIT to determine the preferred mass and coupling ranges for models with vector, Majorana and Dirac fermion dark matter. We also assess the relative plausibility of all four models using Bayesian model comparison. Our analysis includes up-to-date likelihood functions for the dark matter relic density, invisible Higgs decays, and direct and indirect searches for weakly-interacting dark matter including the latest XENON1T data. We also account for important uncertainties arising from the local density and velocity distribution of dark matter, nuclear matrix elements relevant to direct detection, and Standard Model masses and couplings. In all Higgs portal models, we find parameter regions that can explain all of dark matter and give a good fit to all data. The case of vector dark matter requires the most tuning and is therefore slightly disfavoured from a Bayesian point of view. In the case of fermionic dark matter, we find a strong preference for including a CP-violating phase that allows suppression of constraints from direct detection experiments, with odds in favour of CP violation of the order of 100:1. Finally, we present DDCalc 2.0.0, a tool for calculating direct detection observables and likelihoods for arbitrary non-relativistic effective operators.

GAMBIT and its application in the search for physics Beyond the Standard Model

“…The core GAMBIT software is written in C ++ 11, but interfaces seamlessly with extensions and existing physics codes written in Python, Mathematica, Fortran and C. Since the release of GAMBIT 1.0.0 in 2017 [110], the most notable updates have been versions 1.1 (adding support for Mathematica) [111], 1.2 (adding support for Python and higher-spin Higgs portal models) [112], 1.3 (adding support for axion and axion-like particles) [113] and 1.4 (adding support for right-handed neutrinos) [114]. The current public release is v1.4.2.…”

“…The GAMBIT build system allows users to select and automatically download, configure and build whatever combination of backends they prefer to use, and the dependency resolver automatically adapts to the presence or absence of different backends when selecting which functions to connect to others. Backends presently supported in version 1.4.2 of GAMBIT are Capt'n General [112], DarkSUSY [118,119], DDCalc [112,120], FeynHiggs [121][122][123][124][125], gamLike [120], GM2Calc [126], HiggsBounds [127][128][129], HiggsSignals [130], micrOMEGAs [131][132][133][134][135][136][137], nulike [18,41], Pythia [138,139], SPheno [140,141], SuperIso [115][116][117], SUSYHD [142] and SUSY-HIT [143]. Many more are also already supported in the current development version, which will be released in 2020.…”

“…Refs. [112,113] for recent examples), and frequentist model testing by providing information that can be used to perform statistical simulations (see Ref. [145] for a detailed example).…”

“…Although SpecBit can be extended to include any model, its development has tended to proceed through updates that add functionality for the specific models targeted in GAMBIT physics papers. To date, this includes functions for GUT- [150] and weak-scale [145,151] parameterisations of the MSSM, singlet DM models with either a scalar, fermion or vector DM candidate [112,152,153], minimal electroweak triplet and quintuplet DM [154,155], and a low-energy object that holds SM-like particle information. A range of backends is used to supply the SpecBit calculations, including SPheno [140,141] and FlexibleSUSY [156] for BSM mass spectrum calculations.…”

“…Perturbative unitarity is violated at energies above this mass. In the GAMBIT analysis [112], this issue was avoided by excluding the region of parameter space…”