Neutrinos and Collider Physics

Abstract

We review the collider phenomenology of neutrino physics and the synergetic aspects at energy, intensity and cosmic frontiers to test the new physics behind the neutrino mass mechanism. In particular, we focus on seesaw models within the minimal setup as well as with extended gauge and/or Higgs sectors, and on supersymmetric neutrino mass models with seesaw mechanism and with Rparity violation. In the simplest type-I seesaw scenario with sterile neutrinos, we summarize and update the current experimental constraints on the sterile neutrino mass and its mixing with the active neutrinos. We also discuss the future experimental prospects of testing the seesaw mechanism at colliders and in related low-energy searches for rare processes, such as lepton flavor violation and neutrinoless double beta decay. The implications of the discovery of lepton number violation at the Large Hadron Collider for leptogenesis are also studied.

Impact of sterile neutrinos on nuclear-assisted cLFV processes

“…Shaded surfaces reflect the violation of at least one phenomenological or cosmological bound (see section 2.3, as well as [112,113]). The different solid lines correspond to the reach of future facilities: the projected exclusion limit from the LHC (14 TeV centre of mass energy, with 300 fb −1 data [113]); the expected sensitivity of FCC-ee regarding the production of heavy (RH) sterile neutrinos from Z → ν ν s (estimated 10 12 Z decays, for a 10-100 cm decay length [114]); DUNE (former LBNE, a beam dump experiment, searching for the decay products of sterile neutrinos produced in charmed meson decays) [115]; SHiP (a fixed-target experiment using high-intensity proton beams at the CERN SPS [116,117]). As can be seen, there is little overlap between points associated with BR(µ − e − → e − e − , N) within COMET sensitivity and the reach of the above mentioned facilities.…”

“…In addition to the expected sensitivity reach of the experiments already mentioned in section 4. future linear collider (ILC) expected sensitivity (solid blue) in (|U ei | 2 , m i ) panels, which has been obtained assuming a √ s = 500 GeV and luminosity of 500 fb −1 [113,118]; the conservative and optimistic (solid red and dashed red respectively) projected limits at 90% C.L. in (|U τ i | 2 , m i ) panels, from semileptonic tau decays at a future B-factory [119].…”

Electron electric dipole moment in Inverse Seesaw models

“…Extensions of the SM with sterile fermions, which accommodate oscillation data, may also have an impact on other observables, such as charged lepton flavour violation (cLFV) in Higgs [34][35][36], neutral Z boson [37][38][39] and meson decays [40][41][42][43][44]. Sterile fermions may also contribute to lepton flavour conserving observables such as the dipole moments of charged leptons [45][46][47].…”

“…The relevant process is e + e − → ν i ν * j → ν i e ± W ∓ where i ≤ 3 and j ≥ 4, which violates lepton number conservation. This has allowed to exclude certain regimes of the mixing angles |U αi | [35]. Searches at the LHC for a same sign di-lepton channel pp → W ± * → ℓ ± ν i → ℓ ± ℓ ± jj (where i ≥ 4 and j denotes a jet), have led to further bounds for m i O(100 GeV): for values of the integrated luminosity of 20 fb −1 at √ s = 8 TeV, LHC data already allows to constrain the mixing angle |U αi | for sterile neutrino masses up to 500 GeV [71,72].…”

A clockwork WIMP

“…In this case, the most sensitive additional channel is provided by same-sign dilepton plus jets with no missing energy. The 300 fb −1 dataset will allow to probe couplings allowed by EWPT up to m ψ ≈ 300 GeV [20]. Finally, future electroweak precision tests at lepton colliders would provide a strong indirect probe of the mechanism.…”