Long-baseline neutrino oscillation physics potential of the DUNE experiment

Abstract

The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is determined, based on a full simulation, reconstruction, and event selection of the far detector and a full simulation and parameterized analysis of the near detector. Detailed uncertainties due to the flux prediction, neutrino interaction model, and detector effects are included. DUNE will resolve the neutrino mass ordering to a precision of 5$\sigma$, for all $\delta _{\mathrm{CP}}$ values, after 2 years of running with the nominal detector design and beam configuration. It has the potential to observe charge-parity violation in the neutrino sector to a precision of 3$\sigma$ (5$\sigma$) after an exposure of 5 (10) years, for 50% of all $\delta _{\mathrm{CP}}$ values. It will also make precise measurements of other parameters governing long-baseline neutrino oscillation, and after an exposure of 15 years will achieve a similar sensitivity to $\sin ^{2} 2\theta _{13}$ to current reactor experiments.

1 Introduction

The Deep Underground Neutrino Experiment (DUNE) is a next-generation, long-baseline neutrino oscillation experiment which will carry out a detailed study of neutrino mixing utilizing high-intensity $\nu _\mu$ and ${\bar{\nu }}_\mu$ beams measured over a long baseline. $\hbox {DUNE}$ is designed to make significant contributions to the completion of the standard three-flavor picture by measuring all the parameters governing $\nu _1$–$\nu _3$ and $\nu _2$–$\nu _3$ mixing in a single experiment. Its main scientific goals are the definitive determination of the neutrino mass ordering, the definitive observation of $\hbox {charge-parity symmetry violation (CPV)}$ for more than 50% of possible true values of the charge-parity violating phase, $\delta _{\mathrm{CP}}$, and precise measurement of oscillation parameters, particularly $\delta _{\mathrm{CP}}$, $\sin ^22\theta _{13}$, and the octant of $\theta _{23}$. These measurements will help guide theory in understanding if there are new symmetries in the neutrino sector and whether there is a relationship between the generational structure of quarks and leptons [1]. Observation of $\hbox {CPV}$ in neutrinos would be an important step in understanding the origin of the baryon asymmetry of the universe [2, 3].

The $\hbox {DUNE}$ experiment will observe neutrinos from a high-power neutrino beam peaked at $\sim$2.5 GeV but with a broad range of neutrino energies, a $\hbox {near detector (ND)}$ located at Fermi National Accelerator Laboratory, in Batavia, Illinois, USA, and a large $\hbox {liquid argon time-projection}$ $\hbox {chamber (LArTPC) far detector (FD)}$ located at the 4850 ft level of Sanford Underground Research Facility (SURF), in Lead, South Dakota, USA, 1285 km from the neutrino production point. The neutrino beam provided by $\hbox {Long-Baseline Neutrino Facility (LBNF)}$ [4] is produced using protons from Fermilab’s Main Injector, which are guided onto a graphite target, and a traditional horn-focusing system to select and focus particles produced in the target [5]. The polarity of the focusing magnets can be reversed to produce a beam dominated by either muon neutrinos or muon antineutrinos. A highly capable $\hbox {ND}$ will constrain many systematic uncertainties for the oscillation analysis. The 40-kt (fiducial) $\hbox {FD}$ is composed of four 10 kt (fiducial) LArTPC modules [6,7,8]. The deep underground location of the $\hbox {FD}$ reduces cosmogenic and atmospheric sources of background, which also provides sensitivity to nucleon decay and low-energy neutrino detection, for example, the possible observation of neutrinos from a core-collapse supernova [5].

The entire complement of neutrino oscillation experiments to date has measured five of the neutrino mixing parameters [9,10,11]: the three mixing angles $\theta _{12}$, $\theta _{23}$, and $\theta _{13}$, and the two squared-mass differences $\varDelta m^{2}_{21}$ and $|\varDelta m^{2}_{31}|$, where $\varDelta m^2_{ij} = m^2_{i} - m^{2}_{j}$ is the difference between the squares of the neutrino mass states in eV$^{2}$. The neutrino mass ordering (i.e., the sign of $\varDelta m^{2}_{31}$) is unknown, though recent results show a weak preference for the normal ordering [12,13,