Forward neutrino production and event rates at the Future Circular Collider for hadron collisions

TL;DR

The paper investigates forward neutrino production and detection prospects at a proposed FCC-hh with $\sqrt{s}=100$ TeV and an integrated luminosity of $1~\text{ab}^{-1}$, focusing on a FASERν-like detector placed 0.5 or 2 km downstream. The authors combine forward-physics tuned Pythia8 simulations with LHAPDF PDFs to estimate neutrino fluxes up to $E_\nu \sim 50$ TeV and compute charged-current interaction rates using a $128~\text{kg}$ tungsten target, including detector efficiencies. A key novelty is the evaluation of direct $W^{\pm}$ production from neutrino–nucleus interactions, using virtual-photon mediated cross sections, with projections suggesting observability in the full FCC-hh program. They validate the approach by cross-checks against EPOS-LHC-R and existing FASER data, showing qualitative agreement and demonstrating the method's robustness while highlighting generator-dependent rate differences. The results indicate FCC-hh forward neutrinos could enable precision SM tests and potential BSM probes, and the framework scales to larger detectors and alternate placements.

Abstract

A proposed future ultra high energy collider such as the Future Circular Collider is expected to produce intense and collimated neutrino beams from weak hadron decays. In this study, we estimate the production yields of such neutrinos from proton-proton collisions at a center-of-mass energy of 100~TeV and an integrated luminosity of 1~ab$^{-1}$. Based on a hypothetical detector positioned either 0.5~km or 2~km downstream from the interaction point along the beamline, we derive the expected rates of charged current neutrino scattering events and their extension to neutrino energies of up to 50~TeV. We, for the first time, also evaluate the feasibility of observing the experimentally unverified direct production of $W^{\pm}$ bosons from neutrino-nucleus interactions.

Figures (8)

• Figure 1: Panels (a) and (b) illustrate $\sigma_{c\bar{c}X}$ and $\sigma_{b\bar{b}X}$ as functions of the $pp$ collision energy $\sqrt{s}$. The green solid line in panel (a) represents $\sigma_{\rm inel}$ from SoftQCD:inelastic. The dashed lines correspond to cross sections derived from hadron counting, while the dotted lines in panels (a) and (b) represent the values obtained from HardQCD:hardccbar and HardQCD:hardbbbar, respectively. The red, blue, and black curves denote the results for Tune:pp=14, 19, and 20, respectively.
• Figure 2: Longitudinal production positions $|z_{\rm production}|$ for $\nu_e$, $\nu_\mu$, and $\nu_\tau$, respectively, from top to bottom. Left and right panels show those when the target is positioned 0.5 km and 2 km from the $pp$ collision point, respectively, where the target surface area is $23.4\times9$ cm$^2$. The blue shaded, hollow, and red hatched are contributed from $B$, charmed, and light particles, respectively. Note that the events with $|z_{\rm production}|$ less than 1 m are not shown in the plots and the total event numbers are actually more than those shown in figure \ref{['FIG:Energy']} later with the neutrino energy threshold of 0.5 TeV.
• Figure 3: Neutrino energy distributions above 0.5 TeV for $\nu_e$, $\nu_\mu$, and $\nu_\tau$, respectively, from top to bottom. Left and right panels show those when the target is positioned 0.5 km and 2 km from the $pp$ interaction point, respectively, where the target surface area is $23.4\times9$ cm$^2$. The blue shaded, hollow, and red hatched are contributed from $B$, charmed, and light particles, respectively.
• Figure 4: Expected numbers of the charged current interactions of scattered neutrino energy for $\nu_e$, $\nu_\mu$, and $\nu_\tau$, respectively, from top to bottom, where the black solid lines and red dashed lines are them from Pythia8 and EPOS.LHC-REPOS.LHC-R, respectively. The left and right panels are the cases with the detector locations of 0.5 km and 2 km, respectively. A subset of the entire FASER$\nu$ detector target corresponding to a mass of approximately 128 kg only was used for them.
• Figure 5: Expected $W^{\pm}$ production of scattered neutrino energy for $\nu_e$, $\nu_\mu$, and $\nu_\tau$, respectively, from top to bottom, where the black solid lines and red dashed lines are them from Pythia8 and EPOS.LHC-R, respectively. The left and right panels are the cases with the detector locations of 0.5 km and 2 km, respectively. A subset of the entire FASER$\nu$ detector target corresponding to a mass of approximately 128 kg only was used for them.