Neutralino decays in the complex MSSM at one loop: A comparison of on-shell renormalization schemes

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 O(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. * email: Aoife.Bharucha@desy.de † Former address The chargino/neutralino sector of the cMSSMWhile many details about the renormalization of the cMSSM can already be found in Refs. [37,38,45,46], we repeat here the most relevant aspects in order to give a complete picture and to facilitate the comparison between the two employed renormalization schemes. The chargino/neutralino sector contains two soft SUSY-breaking gaugino mass parameters M 1 and M 2 corresponding to the bino and the wino fields, respectively, as well as the Higgs superfield mixing parameter µ, which, in general, can be complex. Since not all the possible phases of the cMSSM Lagrangian are physical, it is possible (without loss of generality) to choose some parameters real. This applies in particular to one out of the three parameters M 1 , M 2 , and M 3 , the gluino mass parameter. For the numerical analysis in Sec. 4 we choose M 2 to be real, however for the renormalization scheme I introduced below [45,46], we do not make such an assumption, and the analytical derivation of the renormalization constants is performed for a complex M 2 , discussed further in Sec. 4.The starting point for the renormalization procedure of the chargino/neutralino sector is the part of the Fourier transformed MSSM Lagrangian which is bilinear in the chargino and neutralino fields,

Higgs decays into charginos and neutralinos in the complex MSSM: a full one-loop analysis

“…[58] and will be included into the code FeynHiggs. These results were obtained in a renormalization scheme [39,[59][60][61][62][63][64][65] which has been shown to yield stable results over nearly the full cMSSM parameters space. In this work we take another step in the direction of completion of the calculation of all two-body decays at the one-loop level in the cMSSM in this stable and reliable renormalization scheme: we calculate all two-body decay modes of the Higgs bosons to charginos and neutralinos in the cMSSM.…”

“…[62] and references therein; see in particular Refs. [63][64][65]. In this paper we use the so-called "CCN" scheme, i.e.…”

“…2.2; Ref. [64]), where we use consistently the scheme detailed in Ref. [62] for all two-body decays simultaneously.…”

Two-loop corrections to the muon magnetic moment from fermion/sfermion loops in the MSSM: detailed results

“…We choose the renormalization of the chargino/neutralino sector as detailed in refs. [63,64,77,78]. The lightest neutralino and both charginos are defined on-shell, which fixes the definitions of δM 1 , δM 2 and δµ in the following way (other schemes can be found in ref.…”

One-loop effects on MSSM parameter determination via chargino production at the LC

“…In the following we will therefore only discuss the parameter renormalization of the chargino and neutralino sector briefly, and for further details about the chargino field renormalization and the renormalization of other sectors we refer the reader to refs. [14,15,19,44].…”