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.
Highlights
With the main objective of measuring Higgs boson properties, there has been renewed interest in muon colliders [1–3]
Based on a recent proposal to build an electron-muon collider, we study two-to-two production processes e−μ+ ⟶ f f, γγ 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 ⟶ eγ, μ ⟶ eee, and μ ⟶ e conversion that have recently been reported in the literature
Summary
With the main objective of measuring Higgs boson properties, there has been renewed interest in muon colliders [1–3]. LFV operators are already being strongly constrained from low energy measurements like muon decays and μ − e transitions [28–30]. For the two-photon production e−μ+ ⟶ γγ, we address the contribution from the LFV dipole operator, that is very strongly constrained by μ ⟶ eγ, and we consider as well a dimension 8 contact operator that is bound more strictly by our results than by low-energy measurements. We estimate limits on the coefficients in the same way we did, but we carry out a detailed Monte Carlo analysis of signal and background processes.
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