Neutralino Decays in the Complex MSSM at One-Loop: a Comparison of On-Shell Renormalization Schemes

TL;DR

This paper presents a detailed one-loop calculation of neutralino decay widths in the complex MSSM, comparing two renormalization schemes, and highlights the significance of higher-order corrections for collider phenomenology.

Contribution

It provides the first comprehensive one-loop decay width calculations for neutralinos in the cMSSM with a comparison of on-shell renormalization schemes, including implementation into FeynHiggs.

Findings

Higher-order corrections reach 10-15% for decay widths involving the LSP.

Corrections to Higgs boson decay channels are up to 20-30%.

Scheme differences are below 0.1%, indicating small theoretical uncertainties.

Abstract

We evaluate two-body decay modes of neutralinos in the Minimal Supersymmetric Standard Model with complex parameters (cMSSM). Assuming heavy scalar quarks we take into account all two-body decay channels involving charginos, neutralinos, (scalar) leptons, Higgs bosons and Standard Model gauge bosons. The evaluation of the decay widths is based on a full one-loop calculation including hard and soft QED radiation. Of particular phenomenological interest are decays involving the Lightest Supersymmetric Particle (LSP), i.e. the lightest neutralino, or a neutral or charged Higgs boson. For the chargino/neutralino sector we employ two different renormalization schemes, which differ in the treatment of the complex phases. In the numerical analysis we concentrate on the decay of the heaviest neutralino and show the results in the two different schemes. The higher-order corrections of the heaviest neutralino decay widths involving the LSP can easily reach a level of about 10-15%, while the corrections to the decays to Higgs bosons are up to 20-30%, translating into corrections of similar size in the respective branching ratios. The difference between the two schemes, indicating the size of unknown two-loop corrections, is less than order(0.1%). These corrections are important for the correct interpretation of LSP and Higgs production at the LHC and at a future linear e+e- collider. The results will be implemented into the Fortran code FeynHiggs.