Abstract
SND@LHC is an approved experiment equipped to detect scatterings of neutrinos produced in the far-forward direction at the LHC, and aimed to measure their properties. In addition, the detector has a potential to search for new feebly interacting particles (FIPs) that may be produced in proton-proton collisions. In this paper, we discuss signatures of new physics at SND@LHC for two classes of particles: stable FIPs that may be detected via their scattering, and unstable FIPs that decay inside the detector. We estimate the sensitivity of SND@LHC to probe scatterings of leptophobic dark matter and decays of neutrino, scalar, and vector portal particles. Finally, we also compare and qualitatively analyze the potential of SND@LHC and FASER/FASERν experiments for these searches.
Highlights
One of the recent proposals is the Scattering and Neutrino Detector (SND@LHC) facility [15–17], which aims to study scatterings of high-energy SM neutrinos produced in the far-forward direction at the LHC in the ATLAS interaction point
This detector can be used to search for new particles that scatter to neutrinos, such as light dark matter (LDM) particles that interact with the SM particles via portal mediators, playing the role of feebly interacting particles (FIPs)
Examples are: LDM scattering off electrons or protons; rare neutrino scattering events induced by new physics, as the trident reaction ν + n → p + χ + l with missing transverse momentum [30, 31], or the process ν + Z → ν + Z + l + ̄l [32]; an excess of charged current (CC) ντ events, such as in models with neutrinophilic mediators coupled exclusively to τ lepton flavor [33]
Summary
We will focus on the NC/CC, given the uncertain status of the background for the elastic signature. Where Nν bg is the number of neutrino background events, and we assume that the detection efficiency is equal to one. For small masses mV 0.5, the mediator is mainly produced from π, η decays, as shown in figure 5. A similar increase occurs for Nν bg, since neutrinos are abundantly produced in decays of pions, and we can use the same scaling for the total neutrino events, Nν bg ∝ geomldet. The estimate reads: αB,SND@LHC 1.5, NC/CC signature αB,FASERν (4.9)
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