The effective field theory of low scale see-saw at colliders

Abstract

We study the Standard Model effective field theory ($$\nu $$νSMEFT) extended with operators involving right-handed neutrinos, focussing on the regime where the right-handed neutrinos decay promptly on collider scales to a photon and a Standard Model neutrino. This scenario arises naturally for right-handed neutrinos with masses of the order $$m_N \sim 0.1 \dots 10\, \,\text {GeV}$$mN∼0.1⋯10GeV. We limit the relevant dimension-six operator coefficients using LEP and LHC searches with photons and missing energy in the final state as well as pion and tau decays. While bounds on new physics contributions are generally in the TeV scale for order one operator coefficients, some coefficients, however, remain very poorly constrained or even entirely evade bounds from current data. Consequently, we identify such weakly constrained scenarios and propose new searches for rare top and tau decays involving photons to probe potential new physics in the $$\nu $$νSMEFT parameter space. Our analysis highlights the importance of performing dedicated searches for new rare tau and top decays.

Heavy neutral leptons in effective field theory and the high-luminosity LHC

“…[72] for operators involving the Higgs boson, and in ref. [73] for the four-fermion operators. Further collider studies of N R SMEFT include refs.…”

Anomalous dimensions from gauge couplings in SMEFT with right-handed neutrinos

“…We briefly comment on some phenomenological consequences of our results; for earlier work see refs. [20][21][22][23][24][25]. Semileptonic decays of the b quark are topical given that both charged current and neutral current decay measurements are hinting at new physics.…”

Global constraints on neutral-current generalized neutrino interactions

“…However, this is out of the scope of this work. Several analyses have set constraints on some of this additional coefficients using different measurements from LHC, LEP, and the projected sensitivities from future collider facilities [35][36][37][38]. In defining the Lagrangian in eq.…”