Physics at the front-end of a neutrino factory: a quantitative appraisal

TL;DR

The paper delivers a comprehensive, quantitative assessment of physics potential at the front end of a neutrino factory, focusing on deep inelastic neutrino scattering, polarized and unpolarized parton densities, strong coupling determination, electroweak measurements, charm and strange quark dynamics, and beyond-Standard-Model sensitivity. It combines LO and NLO QCD frameworks with simulated ν-Factory data to project statistical and systematic uncertainties, emphasizing flavor decomposition, strange sea asymmetries, and the role of gluon polarization. Key findings include substantial improvements in gluon and valence quark PDFs, the potential to resolve s and sbar through tagged charm, and competitive determinations of αs and sin^2 theta_W, along with unique access to nuclear effects and heavy-quark phenomenology. The work also outlines robust strategies for probing new physics via precision electroweak tests and polarization observables, and it highlights the synergistic value of heavy-quark and Λ polarization studies in this experimental program.

Abstract

We present a quantitative appraisal of the physics potential for neutrino experiments at the front-end of a muon storage ring. We estimate the forseeable accuracy in the determination of several interesting observables, and explore the consequences of these measurements. We discuss the extraction of individual quark and antiquark densities from polarized and unpolarized deep-inelastic scattering. In particular we study the implications for the undertanding of the nucleon spin structure. We assess the determination of alpha_s from scaling violation of structure functions, and from sum rules, and the determination of sin^2(theta_W) from elastic nu-e and deep-inelastic nu-p scattering. We then consider the production of charmed hadrons, and the measurement of their absolute branching ratios. We study the polarization of Lambda baryons produced in the current and target fragmentation regions. Finally, we discuss the sensitivity to physics beyond the Standard Model.

Figures (31)

• Figure 1: Bottom: for 50 GeV muons decaying along a straight section of length $L=100,200$ and 1000m, we plot the fraction of the muon-neutrino flux contained within a circle of radius $R$, at a distance of 30m from the end of the straight section. Top: average $\nu_{\mu}$ energy for the three beam configurations, as a function of $R$.
• Figure 2: CC event rates, in units of $10^6$, as function of Lab-frame neutrino spectra, for several detector and beam configurations. The dashed lines on the left include cuts on the final-state muon ($E_{\mu} {$E_μ$}>3$ GeV) and on the final-state hadronic energy ($E_{had}>1$ GeV). The solid lines have no energy-threshold cuts applied. The three set of curves correpsond to different detector radiuses (50, 10 and 5 cm, from top to bottom).
• Figure 3: Same as Fig. \ref{['fig:50gev']}, but for 100 GeV muon beams.
• Figure 4: Event rates, in different bins of $(x,Q^2)$, for the default beam and detector configuration ($E_{\mu} {$E_μ$}=50$ GeV, $L=100$ m, $R=50$ cm).
• Figure 5: $x$ and $Q^2$ binning for the generation of CC events. The crosses correspond to the weighted bin centers.