Decay widths of the neutral CP-even MSSM Higgs bosons in the Feynman-diagrammatic approach

TL;DR

This work delivers a precise calculation of the lightest MSSM CP-even Higgs decays to fermions by embedding complete one-loop propagator corrections, including external-momentum dependence, and dominant two-loop O(ααs) effects within a Feynman-diagrammatic framework. It adds QED and QCD (gluon and gluino) vertex corrections, and offers both the full propagator-corrected results and an α_eff approximation that absorbs propagator effects into an effective mixing angle. The study finds that two-loop propagator corrections substantially suppress h→bb and h→ττ widths (with noticeable kinematic shifts from lower M_h), while h→cc can modestly increase; gluino vertex corrections can be large at high tanβ, influencing branching ratios, especially BR(h→ττ). Comparisons with RG-improved approaches show general agreement across most of parameter space, validating the method while highlighting regions where differences up to ~50% arise due to α_eff and endpoint effects, underscoring the need for complete calculations in precision Higgs phenomenology.

Abstract

In the Minimal Supersymmetric Standard Model (MSSM) we incorporate the Higgs-boson propagator corrections, evaluated up to two-loop order, into the prediction of $Γ$(h -> ff) and BR(h -> ff) for f = b, c, $τ$. The propagator corrections consist of the full one-loop contribution, including the effects of non-vanishing external momentum, and corrections of O(alpha alpha_s) at the two-loop level. The results are supplemented with the dominant one-loop QED corrections and final state QCD corrections from both gluons and gluinos. The effects of the two-loop propagator corrections and of the one-loop gluino contributions are investigated in detail. Our results are compared with the result obtained within the renormalization group approach. Agreement within 10% is found for most parts of the MSSM parameter space.

Figures (12)

• Figure 1: $\Gamma(h \to b\bar{b})$ is shown as a function of $M_h$. The Higgs-propagator corrections have been evaluated at the one- and at the two-loop level. The QED, gluon and gluino contributions are included. The other parameters are $\mu = -100 \,\, \mathrm{GeV}$, $M_2 = m_{\tilde{q}}$, $m_{\tilde{g}} = 500 \,\, \mathrm{GeV}$, $A_b = A_t$, $\tan \beta\space = 3, 40$. The result is given in the no-mixing and maximal-mixing scenario.
• Figure 2: $\Gamma(h \to b\bar{b})$, $\Gamma(h \to \tau^+\tau^-)$ and $\Gamma(h \to c\bar{c})$ are shown as a function of $M_h$. The Higgs-propagator corrections have been evaluated at the one- and at the two-loop level. The QED, gluon and gluino contributions are included. The other parameters are $\mu = -100 \,\, \mathrm{GeV}$, $M_2 = m_{\tilde{q}}$, $m_{\tilde{g}} = 500 \,\, \mathrm{GeV}$, $A_b = A_t$, $\tan \beta\space = 3, 40$. The result is given in the no-mixing scenario.
• Figure 3: $BR(h \to b\bar{b})$ is shown as a function of $M_A$ and $M_h$ for the same settings as in Fig. \ref{['fig:Ghbb']}. The QED, gluon and gluino contributions are included.
• Figure 4: $BR(h \to b\bar{b})$ is shown as a function of $M_A$. The Higgs boson self-energies are evaluated at the one-loop and at the two-loop level with and without momentum dependence (see eq. (\ref{['zeroexternalmomentum']})). The other parameters are $\tan \beta = 25$, $m_{\tilde{q}} = 500 \,\, \mathrm{GeV}$, $m_{\tilde{g}} = 400 \,\, \mathrm{GeV}$, $M_2 = 400 \,\, \mathrm{GeV}$, $X_t = 400 \,\, \mathrm{GeV}$, $A_b = A_t$, $\mu = -1000 \,\, \mathrm{GeV}$.
• Figure 5: $\Gamma(h \to b\bar{b})$ is shown as a function of $M_h$ for three values of $\tan \beta$. The Higgs-propagator corrections have been evaluated at the two-loop level in the no-mixing scenario. The dotted curves shows the results containing only the pure self-energy corrections. The results given in the dashed curves in addition contain the QED correction and the gluon-exchange contribution. The solid curves show the full result, including also the gluino correction. The other parameters are $\mu = -100 \,\, \mathrm{GeV}$, $M_2 = m_{\tilde{q}}$, $A_b = A_t$.