[Paper Review] Simulations of neutrino oscillations for a wide band beam from CERN to LENA

J. Peltoniemi|ArXiv.org|Nov 25, 2009

Neutrino Physics Research4 citations

TL;DR

This paper proposes using LENA, a 50-kton liquid scintillator detector at Pyhäsalmi Mine, Finland, as the far detector for a wide band neutrino beam from CERN over a 2288 km baseline. Simulations show the setup enables high-precision measurements of neutrino oscillation parameters, including mass hierarchy, CP violation, and $θ_{23}$ octant, with performance approaching the theoretical optimum for a 1–6 GeV beam.

ABSTRACT

Neutrino oscillations from a wide band beam of 1-6 GeV at CERN to LENA, a 50 kton liquid scintillator, at Pyhasalmi mine 2288 km apart are simulated. The performance is very promising and this can be considered as a realistic alternative for the next long baseline experiment. Different performance factors and baselines are compared and the studied setup is found to be sufficiently close to a realistic optimum.

Motivation & Objective

• To evaluate the feasibility and performance of a wide band neutrino beam from CERN to LENA at 2288 km baseline for measuring neutrino oscillation parameters.
• To assess whether LENA’s detector characteristics—mass, energy resolution, tracking, and background rejection—support high-precision oscillation measurements.
• To compare the performance of this setup against other baselines and detector configurations, identifying optimal conditions for discovering mass hierarchy and CP violation.
• To determine the impact of beam spectrum uncertainty and detector design assumptions on sensitivity to $\theta_{13}$, $\delta$, and $\theta_{23}$.
• To evaluate whether LENA’s vertical orientation and fiducial volume constraints significantly degrade performance, and if so, whether cost-effective workarounds exist.

Proposed method

• Simulations use the GLoBES toolchain to model neutrino oscillations over a 2288 km baseline with a 1–6 GeV wide band beam from CERN.
• The neutrino spectrum is modeled based on Fermilab and BNL simulations, with a total flux of $8 \times 10^{-4}$ neutrinos per m² per POT at 1 km.
• Oscillation parameters are set to current best-fit values: $\Delta m_{21}^2 = (7.59 \pm 0.21) \times 10^{-5}$ eV², $\Delta m_{31}^2 = (2.43 \pm 0.13) \times 10^{-3}$ eV², $\sin^2 2\theta_{13} < 0.074$, $\sin^2 2\theta_{12} = 0.87$, $\sin^2 2\theta_{23} = 0.99$.
• Sensitivity is evaluated via $\theta$-reach, mass hierarchy discrimination, and CP-violation sensitivity, with marginalization over all other parameters and $\delta$ variation.
• Detector performance is modeled under conservative assumptions: 1% density profile accuracy, 10% energy resolution, and fiducial volume reduction due to vertical orientation.
• Backgrounds are modeled as beam-induced electron neutrinos and misidentified leptons; neutral current backgrounds are considered if above 1%.

Experimental results

Research questions

• RQ1 Can a 50-kton liquid scintillator detector like LENA achieve high-precision measurements of neutrino oscillation parameters with a wide band beam from CERN over 2288 km?
• RQ2 How does the 2288 km baseline compare to other baselines in terms of sensitivity to mass hierarchy and CP violation?
• RQ3 To what extent does LENA’s vertical orientation and fiducial volume constraints degrade performance, and can this be compensated for?
• RQ4 How sensitive are the results to uncertainties in the beam spectrum and detector energy resolution?
• RQ5 What is the required beam power and detector mass to achieve discovery sensitivity for $\theta_{13}$ and $\delta$?

Key findings

• The 2288 km baseline provides optimal sensitivity for mass hierarchy determination and is highly effective for CP violation and $\theta_{23}$ octant measurements.
• For $\sin^2 2\theta_{13} \sim 0.03$, the mass splitting $\Delta m_{31}^2$ is measurable at $\pm 0.04 \times 10^{-3}$ eV² (3σ precision).
• The angle $\theta_{13}$ is determined with an accuracy of $\pm 0.2$ in $\sin^2 2\theta_{13}$, and $\theta_{23}$ with $\pm 0.05$ (3σ) when $\sin^2 2\theta_{13} \sim 0.03$.
• Even with 10% energy resolution, performance remains strong; poorer resolution beyond 10% degrades sensitivity, especially for CP violation.
• Background from beam-induced electron neutrinos is the dominant concern, but detector-based identification and fiducial volume optimization can mitigate it.
• The detector’s vertical orientation reduces fiducial mass by ~5–10 ktons, but this is not a significant performance burden due to the dominant electron neutrino signal being well-reconstructed.