The neutrino magnetic moment portal: cosmology, astrophysics, and direct detection

Abstract

We revisit the physics of neutrino magnetic moments, focusing in particular on the case where the right-handed, or sterile, neutrinos are heavier (up to several MeV) than the left-handed Standard Model neutrinos. The discussion is centered around the idea of detecting an upscattering event mediated by a transition magnetic moment in a neutrino or dark matter experiment. Considering neutrinos from all known sources, as well as including all available data from XENON1T and Borexino, we derive the strongest up-to-date exclusion limits on the active-to-sterile neutrino transition magnetic moment. We then study complementary constraints from astrophysics and cosmology, performing, in particular, a thorough analysis of BBN. We find that these data sets scrutinize most of the relevant parameter space. Explaining the XENON1T excess with transition magnetic moments is marginally possible if very conservative assumptions are adopted regarding the supernova 1987 A and CMB constraints. Finally, we discuss model-building challenges that arise in scenarios that feature large magnetic moments while keeping neutrino masses well below 1 eV. We present a successful ultraviolet-complete model of this type based on TeV-scale leptoquarks, establishing links with muon magnetic moment, B physics anomalies, and collider searches at the LHC.

Lepton-quark fusion at Hadron colliders, precisely

“…Leptoquark collider searches so far were mainly focused on the pair production mechanism driven by QCD interactions, while the role of the defining leptoquark interaction to a quark and a lepton was invoked in decays. However, interesting flavor effects occur when the leptoquark coupling is large(ish) [77][78][79][80][81][82][83][84][85][86][87][88][89][90][91], consequently predicting richer collider phenomenology on the production side. Building on refs.…”

Neutrino beam-dump experiment with FASER at the LHC

“…In this study, instead, we will focus on BSM scenarios predicting neutrino upscatterings into BSM heavy neutral leptons (HNLs) that are mediated by light vector particles or photons in the dipole portal model (see, e.g., refs. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40] for further discussion about the models and their phenomenology). As we show, in such scenarios the BSM neutrino scatterings can lead to new types of signatures in the FASER and FASERν detectors.…”

Constraints on general neutrino interactions with exotic fermion from neutrino-electron scattering experiments

“…or the solar neutrinos with magnetic moment can also provide a plausible source for the peak-like excess. However, both of the two scenarios have tension with stellar cooling constraints [14,[17][18][19][20][21]. Some studies instead proposed to explain the XENON1T excess through the electron recoil by solar neutrinos with the sterile neutrino DM in the final states of inelastic scattering [10,11].…”

“…The two kinds of signals are governed by the same interactions between SM neutrino and the exotic fermion. The relevant interactions are inevitably constrained by the precision measurements in neutrino experiments [14,15]. In this work we study the constraints on general neutrino interactions with sub-GeV exotic fermion from neutrino-electron scattering experiments.…”

“…[2][3][4][5][6][7][8][9]. There are also plenty of novel models and signatures proposed to search for sub-GeV DM through the scattering off electrons [10][11][12][13][14][15].…”