The physics case for an electron-muon collider

Abstract

An electron muon collider is proposed here targeting at multi-ab −1 integrated luminosities at various stages, involving asymmetrical collision profile of, e.g., 20-200 GeV, 50-1000 GeV and 100-3000 GeV for the electron and muon beam energy, respectively. This novel collider can serve as a powerful machine to probe lepton flavor violation and measure Higgs boson properties precisely. The collision of an electron and a muon beam leads to less physics backgrounds compared with either an electron-electron or a muon-muon beam, as physics processes appear mostly through vector boson fusion or scattering. The asymmetrical beam energy tends to have collision products boosted towards the electron beam side, which can be exploited to reduce beam-induced background from muon beam upstream to a large extent.

Physics potential of a muon-proton collider

“…As Ref. [29] pointed out, the BIB can be reduced by a large extent if the signal final-state particles are largely boosted towards the other beam side 2 . As we will see, because of the proton parton distribution, this is indeed the case for µp collisions even if the proton beam energy is one order of magnitude larger than the muon one.…”

“…More recently electron-muon head-on collisons have also been studied for the first time in Refs [29,30]…”

Two-to-two processes at an electron-muon collider

“…The idea of electron-muon collisions has been analyzed in past decades [19]- [24], and recently it has been brought up again in a study of an extra Z boson with generic couplings that could be searched for through a Lepton Flavor Violating (LFV) process like e − µ + → e + µ − [25]. In a subsequent article, the construction of a high energy e − µ + collider has been proposed [26]. Besides the clear capability of probing muon LFV effects like the Heµ coupling, this machine could even test the Higgs-bottom quark coupling [26].…”

“…In a subsequent article, the construction of a high energy e − µ + collider has been proposed [26]. Besides the clear capability of probing muon LFV effects like the Heµ coupling, this machine could even test the Higgs-bottom quark coupling [26]. One important advantage of such a machine is the very low level of SM background processes as they come mostly from vector boson fusion.…”

“…Third, we will assume an integrated luminosity of order 1 ab −1 (as in Ref. [26]) and require a minimum cross section of 0.04fb from the operator contribution. Such a cross section yields a significant amount of 40 events.…”