Neutrino nonstandard interactions: Confronting COHERENT and LHC data

TL;DR

This work presents a consistent NSI framework that connects low-energy CEvNS data from COHERENT with high-energy LHC constraints through a $Z'$-mediated simplified model. It shows that NSI bounds depend strongly on the mediator mass $m_{Z'}$ and that collider searches can decisively break degeneracies present in CEvNS analyses, especially for $m_{Z'}\gtrsim 80$ GeV. By examining scenarios with NSIs in the neutrino sector alone and with NSIs extended to charged leptons, the paper demonstrates robust complementarity: COHERENT constrains flavor structure at low energies, while LHC data determine the energy scale and probe axial currents that CEvNS cannot. The results underscore the value of combining low- and high-energy data to comprehensively test NSIs in a UV-complete, yet simplified, vector-mediated framework, with future experiments like Cryo-CsI+NaI and FASERν further tightening the remaining degeneracies.

Abstract

We study the complementarity between COHERENT and LHC searches in testing neutrino nonstandard interactions (NSIs) through the completion of the effective field theory approach within a $Z'$ simplified model. Our results show that LHC bounds are strongly dependent on the $Z'$ mass, with relatively large masses excluding regions in the parameter space that are allowed by COHERENT data and its future expectations. We demonstrate that the combination of low- and high-energy experiments results in a viable approach to break NSI degeneracies within the context of simplified models.

Figures (3)

• Figure 1: Constraints on NSI coupling, $\varepsilon$, as a function of $m_{Z'}$ from LHC and COHERENT data, for the cases where the $Z'$ couples equally to up and down quarks (top) and where it couples exclusively to either up or down quarks (bottom). In both scenarios, the $Z'$ interacts only with neutrino leptons . Mono- and dijet results are shown as black and red areas, respectively, while bounds from COHERENT data are depicted as horizontal lines. The gray region in the top-right corner corresponds to the parameter space where the validity of the EFT approach, given by Eq. \ref{['eq:pert']}, is not fulfilled.
• Figure 2: Allowed parameter space at 95% C.L. from COHERENT and LHC data in the $(\varepsilon^{dV}_{ee},\varepsilon_{ee}^{uV})$ (top row), $(\varepsilon^{dV}_{\mu\mu},\varepsilon_{\mu\mu}^{uV})$ (central row), and $(\varepsilon_{ee}^{uV},\varepsilon^{uV}_{\mu\mu})$ (bottom row) planes. The allowed parameter space from COHERENT CsI+LAr data is shown as a light orange region, while LHC results appear as blue regions, with shades from light to dark corresponding to $m_{Z'}$ values of 70 (light blue), 80 (blue), 100 (dark blue), and 300 (black) GeV. Future projections from COHERENT Cryo-CsI+NaI are represented by a dashed line boundary, while FASER ones are depicted as a light green region. The yellow band in the bottom left panel shows the oscillation data bounds taken from Coloma:2017ncl. The right panel in each row shows an enlarged area of the corresponding left panel.
• Figure 3: Constraints on the NSI parameter $\varepsilon$ as a function of $m_{Z'}$ from LHC and COHERENT data for the cases where the $Z'$ couples equally to up and down and couples equally to all lepton flavors. We display monojet (black), dielectron (violet), dimuon (yellow), and ditau (green) results and COHERENT bounds are depicted as horizontal lines.