Interdependence of the new “MUON G-2” result and the W-boson mass

Abstract

AbstractThe electroweak (EW) sector of the Minimal Supersymmetric extension of the Standard Model (MSSM), assuming the lightest neutralino as Dark Matter (DM) candidate, can account for a variety of experimental results. This includes the DM direct detection limits, the searches for EW superpartners at the LHC, and in particular the discrepancy between the experimental result for the anomalous magnetic moment of the muon, $$(g-2)_\mu $$ ( g - 2 ) μ , and its Standard Model (SM) prediction. The new “MUON G-2” result, combined with the older BNL result on $$(g-2)_\mu $$ ( g - 2 ) μ , yields a deviation from the SM prediction of $$\Delta a_\mu = ({25.1}\pm {5.9}) \times 10^{-10}$$ Δ a μ = ( 25.1 ± 5.9 ) × 10 - 10 , corresponding to $${4.2}\,\sigma $$ 4.2 σ . Using this updated bound, together with the other constraints, we calculate the MSSM prediction for the mass of the W boson, $$M_W$$ M W . We assume contributions only from the EW sector, i.e. the colored sector of the MSSM, in agreement with the search limits, is taken to be heavy. We investigate five scenarios, distinguished by the mechanisms which yield a relic DM density in agreement with the latest Planck bounds. We find that with the new $$(g-2)_\mu $$ ( g - 2 ) μ result taken into account and depending on the scenario, values up to "Equation missing" are reached. The largest values are obtained for wino DM and in the case of slepton co-annihilation, where points well within the $$1\,\sigma $$ 1 σ range of the experimental world average of $$M_W^{\mathrm {exp}}= 80.379 \pm 0.012 \,\, \mathrm {GeV}$$ M W exp = 80.379 ± 0.012 GeV are reached, whereas the SM predicts a too small value of $$M_W^{\mathrm {SM}}= 80.353 \,\, \mathrm {GeV}$$ M W SM = 80.353 GeV . We analyze the dependence of $$M_W^{\mathrm {MSSM}}$$ M W MSSM on the relevant masses of the EW superpartners and demonstrate that future $$M_W$$ M W measurements, e.g. at the ILC, could distinguish between various MSSM realizations. Sizable contributions to $$M_W^{\mathrm {MSSM}}$$ M W MSSM are associated with a relatively light $$\tilde{\chi }_{1}^0$$ χ ~ 1 0 , accompanied by either a light chargino or a light smuon, setting interesting targets for future collider searches.