Francis M. Burk | Searcharxiv

arXiv2026

Neutrino Fluxes at a Muon Collider

While muon colliders are primarily considered precision machines for new physics searches at the energy frontier, they are also intense sources of high-energy neutrinos. Large fluxes of electron and muon neutrinos are produced in the decay of beam muons, especially along the straight sections around the experiments. In this work, we re-evaluate these neutrino fluxes using the latest design of a \SI{10}{TeV} muon collider and find that fluxes around the interaction region are almost two orders of magnitude higher than earlier estimates. We also compute the fluxes of neutrinos produced in $μ^+μ^-$ collisions, electromagnetic showers induced by electrons from muon decay, and interactions of neutrinos close to the collider ring. We find that these additional neutrino sources are non-negligible and would lead to a sizable number of neutrino interactions of all flavors, including several tau neutrino events, in a ton-scale detector placed in the forward direction. We discuss the physics opportunities offered by muon collider neutrinos in the context of QCD and nuclear physics, electroweak precision measurements, and searches for new physics.

hep-ph↗

arXiv2026

Drell-Yan Production of New Particles at Fixed-Target Experiments: Heavy Neutral Lepton as a Case Study

We demonstrate the sensitivity of Drell-Yan production processes from deep inelastic scattering in searches for beyond-the-Standard Model (BSM) physics at fixed-target or beam-bump experiments. We take heavy neutral leptons (HNLs) as a case study, produced from the decay of a light vector boson mediator with mass in the range of $2-20$ GeV, which itself is generated via the Drell-Yan process. The produced HNLs subsequently decay into Standard Model final states. We consider several current and future experiments, including SBND, DarkQuest, DUNE Near Detector (ND), and SHiP. Utilizing $νπ^0$ and $νe^+e^-$ final states from HNL decays, we find that the Drell-Yan mechanism provides important contributions and significantly enhances the HNL search sensitivity, owing to the production of energetic final-state particles that are more readily detectable over the expected backgrounds. We find that at $90\%$ C.L. sensitivity, for gauge couplings $g_{X} \sim 10^{-2}\ (10^{-3})$ and kinematically accessible mass range, SBND and DarkQuest can probe the HNL flavor mixing $|U_{\ell}| \sim 3\times 10^{-4}\ (10^{-3})$, whereas DUNE ND and SHiP may extend the sensitivity down to the Type-I Seesaw prediction of $|U_{\ell}| \sim 10^{-5}$. Finally, for our chosen benchmark $|U_{\ell}| = 10^{-3}$ outside of the current experimental constraints, with a fixed mass ratio $m_{Z'}/m_N = 2.1$, and working within the $U(1)_{B-L}$, $U(1)_{B-3L_τ}$, and $U(1)_{B}$ parameter spaces, we find that both SBND and DarkQuest can probe $g_{X} \sim 10^{-3}$, DUNE ND can reach $g_{X} \sim 10^{-4}$, and SHiP can probe down to $g_{X}\sim 5\times 10^{-6}$. Our approach provides a powerful new technique to study HNL production at future fixed-target experiments and can readily be extended to other light BSM particle production within a broader class of dark sector models.

hep-ph↗