Vector boson fusion at multi-TeV muon colliders

Abstract

High-energy lepton colliders with a centre-of-mass energy in the multi-TeV range are currently considered among the most challenging and far-reaching future accelerator projects. Studies performed so far have mostly focused on the reach for new phenomena in lepton-antilepton annihilation channels. In this work we observe that starting from collider energies of a few TeV, electroweak (EW) vector boson fusion/scattering (VBF) at lepton colliders becomes the dominant production mode for all Standard Model processes relevant to studying the EW sector. In many cases we find that this also holds for new physics. We quantify the size and the growth of VBF cross sections with collider energy for a number of SM and new physics processes. By considering luminosity scenarios achievable at a muon collider, we conclude that such a machine would effectively be a “high-luminosity weak boson collider,” and subsequently offer a wide range of opportunities to precisely measure EW and Higgs couplings as well as discover new particles.

Higgs and BSM Physics at the Future Muon Collider

“…The flux of possible polarization states of W partons in the muon beam structure can be seen in Figure 4 from Ref. [82] and it roughly falls a fifth power of the WW center-of-mass energy tracker variable √ τ = m WW / √ s. Clearly the boson fusion processes can give significant enhancements of the total rates for new physics states, but are largely subdominant to 2 → 2 Drell-Yan close to the kinematic reach of the machine. Therefore, the reach over the energy frontier of a highenergy muon collider can be estimated simply looking at the Drell-Yan rates.…”

“…An educated guess for a model-independent comparison of pp and + − direct reach for new physics can be found in Ref. [82]. The outcome is that a 14 TeV center-of-mass energy + − collider can be as powerful to probe directly heavy new physics as a 100 TeV pp collider.…”

Probing electroweak phase transition with multi-TeV muon colliders and gravitational waves

“…On the other hand, due to the small QCD backgrounds, the muon collider is rather clean, allowing very precise measurements. The physics potential of a high energy muon collider has been discussed since the 1990s [65,66], while it receives a renewed interest recently [67][68][69][70][71][72][73][74][75][76][77][78][79][80][81][82][83][84].…”

Detector Performance Studies at a Muon Collider

“…Moreover, while in the case of hadronic composite-particles collisions the interactions occur between their constituents that carry only a fraction of the total energy, in leptonic collisions all the center-of-mass energy is available for the relevant short-distance processes, opening the way to an unprecedented Physics potential. A vast Physics reach is accessible to a muon collider that ranges from high precision measurements of known standard model processes in an unexplored energy regime to the possible direct detection of new heavier states up to half the collision energy [1]. In particular, a muon collider represents a gateway to the Higgs sector, allowing precise measurements of the Higgs boson couplings to fermions and bosons and the Higgs boson self-couplings and, hence, a full determination of the Higgs potential [2].…”