Abstract
We illustrate the potential of a very high energy lepton collider (from 10 to 30 TeV center of mass energy) to explore new physics indirectly in the vector boson fusion double Higgs production process and in direct diboson production at high energy. Double Higgs production is found to be sensitive to the anomalous Higgs trilinear coupling at the percent level, and to the Higgs compositeness ξ parameter at the per mille or sub-per mille level thanks to the measurement of the cross-section in the di-Higgs high invariant mass tail. High energy diboson (and tri-boson) production is sensitive to Higgs-lepton contact interaction operators at a scale of several tens or hundred TeV, corresponding to a reach on the Higgs compositeness scale well above the one of any other future collider project currently under discussion. This result follows from the unique capability of the very high energy lepton collider to measure Electroweak cross-sections at 10 TeV energy or more, where the effect of new physics at even higher energy is amplified. The general lesson is that the standard path towards precision physics, based on measurements of high-statistics processes such as single and double Higgs production, is accompanied at the very high energy lepton collider by a second strategy based on measurements at the highest available energy.
Highlights
Our results will be independent of the nature of the colliding leptons, because they are based on simple leading-order predictions without Initial State QED Radiation (ISR) and with monochromatic beams
The general lesson is that the standard path towards precision physics, based on measurements of highstatistics processes such as single and double Higgs production, is accompanied at the very high energy lepton collider by a second strategy based on measurements at the highest available energy
We have studied the potential of a Very High Energy Lepton collider (VHEL) to probe indirectly non-SM phenomena through precision measurements, outlining the coexistence of two distinct approaches
Summary
We consider the direct 2 → 2 production of a pair of SM (vector or Higgs) bosons, and we restrict our attention to BSM effects that grow quadratically with the energy in the zero-. In Universal theories, the two parameters combinations CW + CHW and CB + CHB control other interactions, generated by equations of motion, analog to eq (2.1) but involving quarks rather than leptons. The latter interactions induce growing-with-energy effects in diboson production at hadron colliders, that can be probed at the HL-LHC and at the FCC-hh [22]. This enables a comprehensive comparison of the VHEL sensitivity with the reach (see [26]) of all the other (hadronic or leptonic) future collider projects. High energy probes performed at the VHEL will pass this threshold
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