Indication for Light Sneutrinos and Gauginos from Precision Electroweak Data
G. Altarelli, F. Caravaglios, G. F. Giudice, P. Gambino, G. Ridolfi
TL;DR
This paper investigates whether minimal supersymmetric extensions of the Standard Model can alleviate tensions in electroweak precision data and harmonize with the Higgs mass bound. It adopts the epsilon formalism ($\epsilon_1,\epsilon_2,\epsilon_3,\epsilon_b$) to map precision observables onto new-physics corrections and scans MSSM parameter space with light sleptons and sneutrinos, potentially accompanied by light gauginos and moderate $\tan\beta$. A key finding is that when the leptonic $\sin^2\theta_{\rm eff}$ path is favored, light sneutrinos in the $55$--$80$ GeV range and sleptons just above current limits can improve the global fit relative to the SM, though the outcome is sensitive to $\Delta\alpha_h$ and $m_t$. This yields a phenomenologically accessible MSSM region with concrete predictions for the Tevatron and LHC, illustrating how precision data can hint at low-mass superpartners.
Abstract
The present Standard Model fit of precision data has a low confidence level, and is characterized by a few inconsistencies. We look for supersymmetric effects that could improve the agreement among the electroweak precision measurements and with the direct lower bound on the Higgs mass. We find that this is the case particularly if the 3.6 sigma discrepancy between sin^2 theta_eff from leptonic and hadronic asymmetries is finally settled more on the side of the leptonic ones. After the inclusion of all experimental constraints, our analysis selects light sneutrinos, with masses in the range 55-80 GeV, and charged sleptons with masses just above their experimental limit, possibly with additional effects from light gauginos. The phenomenological implications of this scenario are discussed.