Two-to-Two Processes at an Electron-Muon Collider

Abstract

Based on a recent proposal to build an electron-muon collider, we study two-to-two production processes e − μ + ⟶ f f ¯ , γ γ that originate from dimension 6 and 8 operators. We compare the sensitivity to those effective couplings obtained at the collider with that of low energy measurements of μ ⟶ e γ , μ ⟶ e e ¯ e , and μ ⟶ e conversion that have recently been reported in the literature. Whereas for the production of first family fermions, the sensitivity of the collider processes is much weaker; for the second and third family fermions, it is similar or stronger than that of low-energy processes. In the case of e − μ + ⟶ γ γ , the sensitivity to a dimension 8 contact operator turns out to be the strongest in comparison.

An electron-muon collider: what can be probed with it?

“…The limits for the first family fermions are not shown in Table I but can be seen in Ref. [11]. They turn out to be two or three orders of magnitude weaker than those reported in Ref.…”

“…With the idea of taking advantage of the (almost) absence of SM backgrounds for two-to-two processes we turn our attention to four-fermion couplings that involve the eµ pair and two other leptons or quarks [11]. These couplings can be probed with low energy measurements like µ → eγ, µ − → e − e + e − and µA → eA conversion reactions in nuclei [12].…”

“…In this talk, we refer to a study on two-to-two processes at a µ + e − collider for center-of-mass (CM) energies of order a few TeV [11]. In Ref.…”

“…In Ref. [11] we consider four-fermion µef f effective interactions and obtain limits from a nonobservation of f f final states in two-to-two interactions. In addition, we consider the dimension 6 flavor changing magnetic dipole eµγ coupling as well as the dimension 8 contact term eµγγ for the e − µ + → γγ annihilation process.…”

Systematically Testing Singlet Models for $(g-2)_μ$

“…Muon colliders have recently attracted considerable interest as successor machines to the LHC [55][56][57][58][59][60][61][62][63][64]. Representative muon colliders concepts at the energy frontier may feature multi-TeV scale center-of-mass energies and luminosities of order ∼ ab −1 .…”