Vices and virtues of Higgs effective field theories at large energy

Abstract

We study constraints on new physics from Higgs production at the LHC in the context of an effective field theory (EFT), focusing on Higgs searches in H V (V = W, Z) associated production which are particularly sensitive to the high-energy behavior of certain dimension-six operators. We show that analyses of these searches are generally dominated by a kinematic region where the generic EFT expansion breaks down, and we establish under which conditions they can nevertheless be meaningful. For example, constraints from these searches on the Wilson coefficients of operators whose effects grow with energy can be established in scenarios where a particular combination of fermions and the Higgs are composite and strongly coupled: then, bounds from Higgs physics at high energy are complementary to LEP1 and competitive with LEP2.

Complete Higgs sector constraints on dimension-6 operators

“…We thank A. Knochel and the authors of ref. [137] for pointing out to us that the previous version of this paper underestimated the ATLAS p T V constraints due to a misinterpretation of the expected number of SM events in table 5 of ref. [110], which actually corresponds to a best fit signal strength of 0.…”

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].…”

The effective Standard Model after LHC Run I

“…As an example, we note that the signal-strength dependence of the overflow bin onc HW for the ATLAS 8-TeV same-flavour distribution is found to be µ ATLAS8 last-bin = 1 + 3.45c HW + 234c 2 HW , 9 The applicability of the effective field theory approach to this TGC analysis is discussed in the appendix. 10 The validity of the effective field theory at such high pT may be restricted only to certain models [127,128], but the range of validity will increase as the current precision of LHC TGC measurements is improved. and we keep only the linear term in our global fits.…”