Abstract
We consider modifications of the Higgs potential due to new physics at high energy scales. These upset delicate cancellations predicted by the Standard Model for processes involving Higgs bosons and longitudinal gauge bosons, and lead to a breakdown of the theory at high energies. We focus on modifications of the Higgs trilinear coupling and use the violation of tree-level unitarity as an estimate of the scale where the theory breaks down. We obtain a completely model-independent bound of underset{sim }{<} 13 TeV for an order-1 modification of the trilinear. We argue that this bound can be saturated only in fine-tuned models, and the scale of new physics is likely to be much lower. The most stringent bounds are obtained from amplitudes involving multiparticle states that are not conventional scattering states. Our results show that a future determination of the Higgs cubic coupling can point to a well-defined scale of new physics that can be targeted and explored at future colliders.
Highlights
The deviation in one coupling will not give very much information about what kind of new physics is responsible
If the new physics that gives rise to the deviation occurs at a mass scale M that is much larger than mh, physics below the scale M can be described by an effective theory with the same degrees of freedom as the Standard Model
We have considered the scales of unitarity violation in a theory where the low-energy Higgs potential is modified from the Standard Model prediction
Summary
Whose coefficients in units of v do not fall off for higher powers, and it is not surprising that this predicts high multiplicity processes with low scales of unitarity violation These examples show that the existence of contact interaction terms with many Higgs bosons, which were the origin of the strong unitarity bounds derived above, is not a model-independent consequence of a deviation in the h3 coupling. This unitarity violation arises in processes involving many Higgs and gauge particles and W and Z bosons, and these can be canceled if the parameters of the low-energy Higgs potential obey special relations Allowing for these cancellations, there is still a model-independent bound that depends only on the deviation in the Higgs cubic, but the scale of unitarity violation is much higher (∼ 13 TeV). This scale is potentially accessible to a future 100 TeV pp collider, it will be more challenging
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