EFT at FASERν

Abstract

We investigate the sensitivity of the FASERν detector to new physics in the form of non-standard neutrino interactions. FASERν, which will be installed 480 m downstream of the ATLAS interaction point, will for the first time study interactions of multi-TeV neutrinos from a controlled source. Our formalism — which is applicable to any current and future neutrino experiment — is based on the Standard Model Effective Theory (SMEFT) and its counterpart, Weak Effective Field Theory (WEFT), below the electroweak scale. Starting from the WEFT Lagrangian, we compute the coefficients that modify neutrino production in meson decays and detection via deep-inelastic scattering, and we express the new physics effects in terms of modified flavor transition probabilities. For some coupling structures, we find that FASERν will be able to constrain interactions that are two to three orders of magnitude weaker than Standard Model weak interactions, implying that the experiment will be indirectly probing new physics at the multi-TeV scale. In some cases, FASERν constraints will become comparable to existing limits — some of them derived for the first time in this paper — already with 150 fb−1 of data.

Snowmass White Paper: Beyond the Standard Model effects on Neutrino Flavor

“…From the reactor neutrino experiments Daya Bay and RENO and taking into account the EFT effect on nuclear beta and inverse beta decay interactions we can get constraints on the right handed, scalar and tensor interactions using the νe → νe transition: [ ud R ] eµ,eτ ∼ (0.05−0.1), where X = R, S, T [96]. Using the same approach the SMEFT coefficients were studied at the FASERν detector at LHC, where new physics effects on the neutrino production through meson decays and neutrino detection through Deep Inelastic Scattering (DIS) were studied [98]. It was shown that FASERν detector has the capability to constraint new physics at the multi-TeV scale, for some 4-fermion interactions giving constraints that are much better than the existing constraints in the literature (see e.g.…”

Neutrino Scattering Measurements on Hydrogen and Deuterium: A Snowmass White Paper

“…Using CCQE as a signal channel, one could probe flavor-dependent structures. This idea is discussed within the context of non-standard interactions and SM effective field theory (SMEFT) in [201,202]. Projections in [201] rely on charged-current to neutral-current cross section ratios σ CC /σ NC , and explicitly neglect uncontrolled theoretical uncertainties related to argon's complex nuclear structure and non-zero isospin.…”

Non-standard neutrino and Z′ interactions at the FASERν and the LHC

“…FASERν is primarily designed for the purpose of identifying the flavors of neutrinos [38,39], the discovery potential of FASERν for new physics discussed in [40][41][42][43]. The expected sensitivity for each flavor at FASERν is shown in figure 6.…”