Comparing EFT and exact one-loop analyses of non-degenerate stops

Abstract

We develop a universal approach to the one-loop effective field theory (EFT) using the Covariant Derivative Expansion (CDE) method. We generalise previous results to include broader classes of UV models, showing how expressions previously obtained assuming degenerate heavy-particle masses can be extended to non-degenerate cases. We apply our method to the general MSSM with non-degenerate stop squarks, illustrating our approach with calculations of the coefficients of dimension-6 operators contributing to the hgg and hγγ couplings, and comparing with exact calculations of one-loop Feynman diagrams. We then use present and projected future sensitivities to these operator coefficients to obtain present and possible future indirect constraints on stop masses. The current sensitivity is already comparable to that of direct LHC searches, and future FCC-ee measurements could be sensitive to stop masses above a TeV. The universality of our one-loop EFT approach facilitates extending these constraints to a broader class of UV models.

The gauge-Higgs legacy of the LHC Run I

“…One caveat applies to these results the same way it applies to the Higgs analyses alone [6,7,[79][80][81][82][83][84][85]. 1 If we consider the dimension-six Lagrangian of eq.…”

“…Com- puting the effects of dimension-eight operators appears to be one way of estimating the theoretical uncertainties which enter the translation of our dimension-six results into actual models. However, detailed studies in the Higgs sector [79][80][81][82][83][84][85] indicate that individual dimension-eight contributions are not necessarily a good measure for these uncertainties. Therefore, the effective theory interpretation of the results on the truncated dimension-six Lagrangian shown in figure 4 should be done with care.…”

“…The dashed lines illustrate the effects from individual dimension-six operators, suggesting that we should be able to derive powerful constraints from the ATLAS measurements. The fact that the last bin extends to large transverse momenta also suggests that we have to be careful interpreting our dimension-six analysis in terms of an effective field theory expansion [6,7,[79][80][81][82][83][84][85].…”

Effective field theory of integrating out sfermions in the MSSM: Complete one-loop analysis

“…The degenerated mass case result is obtained in [2,3]. The nondegenerate mass results for c GG , c WW , c BB and c WB are obtained in [4], however the latter three are in a different basis. Here it is straightforward to check that for the Higgs diphoton coupling the combination of terms proportional to y 2 t X 2 t from the latter three operators conspires to cancel the ðM 2 q − M 2 t Þ −1 and the logarithmic term, going back to a form consistent with the Higgs low energy theorem.…”

“…One can match any desirable UV models to the SM EFT [2][3][4][5][6], but before that some generalizations of the CDE technique need to be made. In addition to the generalization to fermionic degree of freedom (DOF) which has extra gamma matrices related contributions [3,6], for realistic model parameters the original treatment of only degenerated large scales in [2,3] is based on an oversimplified assumption to be dropped.…”