Learning from Radiation at a Very High Energy Lepton Collider

Abstract

We study the potential of lepton collisions with about 10 TeV center of mass energy to probe Electroweak, Higgs and Top short-distance physics at the 100 TeV scale, pointing out the interplay with the long-distance (100 GeV) phenomenon of Electroweak radiation. On one hand, we find that sufficiently accurate theoretical predictions require the resummed inclusion of radiation effects, which we perform at the double logarithmic order. On the other hand, we notice that short-distance physics does influence the emission of Electroweak radiation. Therefore the investigation of the radiation pattern can enhance the sensitivity to new short-distance physical laws. We illustrate these aspects by studying Effective Field Theory contact interactions in di-fermion and di-boson production, and comparing cross-section measurements that require or that exclude the emission of massive Electroweak bosons. The combination of the two types of measurements is found to enhance the sensitivity to the new interactions. Based on these results, we perform sensitivity projections to Higgs and Top Compositeness and to minimal Z new physics scenarios at future muon colliders.

Muon Collider Physics Summary

“…An incomplete list of the many possible measurements is provided in Ref. [24], including the resummed effects of EW radiation on the cross section predictions. It is worth emphasizing that also charged final states such as W H or ν are copiously produced at a muon collider.…”

“…Fig. 6: Left panel: 95% reach on the Composite Higgs scenario from high-energy measurements in diboson and di-fermion final states [24]. The green contour display the sensitivity from "Universal" effects related with the composite nature of the Higgs boson and not of the top quark.…”

The physics case of a 3 TeV muon collider stage

“…-The expected precision for single-Higgs observables at the 3 and 10 TeV muon colliders from the preliminary results of [51]. -As in the HL-LHC case, we also include the projections from high-energy measurements in twoto-two fermion processes, expressed in terms of W and Y from [52], and in diboson processes µ + µ − → ZH, W + W − , µν → W H, W Z from Ref. [5,52].…”

“…-As in the HL-LHC case, we also include the projections from high-energy measurements in twoto-two fermion processes, expressed in terms of W and Y from [52], and in diboson processes µ + µ − → ZH, W + W − , µν → W H, W Z from Ref. [5,52]. -The expected precision for the Higgs self-coupling from the measurement of the di-Higgs invariant mass in µ + µ − → ννHH from Ref.…”

Complementary Signals of Lepton Flavor Violation at a High-Energy Muon Collider

“…Because the colliding objects are second-generation fermions themselves, muon colliders have a particular aptitude for testing physics with generation-specific couplings [37][38][39][40][41][42][43][44][45][46][47][48][49]. Finally, high-energy muons have a large probability to radiate collinear gauge bosons in their collisions [3,[50][51][52][53], and can thus act efficiently as "vector boson colliders", with large rates for VBF processes that can be used both to search for new physics [54][55][56][57][58][59][60][61][62] and to make precision measurements of the electroweak sector [63][64][65][66][67][68][69][70][71][72]. That the muons are color-neutral, and produce far fewer hadronic backgrounds, makes them particularly well-suited for this purpose.…”