Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

TL;DR

The paper articulates the physics program for DUNE at LBNF, detailing how a high-intensity, tunable neutrino beam, a near detector, and a large liquid-argon time-projection chamber at a deep underground site enable transformative measurements of neutrino oscillations, the mass hierarchy, and leptonic CP violation. It also maps the broader physics landscape, including nucleon decay, atmospheric neutrinos, and core-collapse supernova neutrinos, to a cohesive, international experimental effort, while addressing systematic uncertainties and beam- and detector-design optimizations. The work presents sensitivity projections under multiple beam designs, outlines the role of the Near Detector in constraining muon/electron fluxes and cross sections, and discusses potential beyond-Standard-Model signals such as NSI, sterile neutrinos, and Lorentz/CPT violation. Collectively, this program promises high-significance discoveries in CP violation, precise tests of the three-flavor paradigm, and complementary searches for new physics with broad astrophysical and cosmological implications. The practical impact lies in enabling a comprehensive, long-baseline, multi-facility neutrino program capable of probing fundamental questions about the origin of matter, unification of forces, and the properties of neutrinos across terrestrial and cosmic contexts.

Abstract

The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described.

Figures (46)

• Figure 1: The appearance probability at a baseline of 1300 km, as a function of neutrino energy, for $\delta_{\rm CP}$ = $-\pi/2$ (blue), 0 (red), and $\pi/2$ (green), for neutrinos (left) and antineutrinos (right), for normal hierarchy. The black line indicates the oscillation probability if $\theta_{13}$ were equal to zero.
• Figure 2: True-to-reconstructed energy smearing matrices for $\nu_e$ (top), $\nu_\mu$ (center) and $\nu_\tau$ (bottom) CC interactions extracted from the Fast MC and used as inputs to GLoBES. Left: Used in the $\nu_e$ appearance sample. Right: Used in the $\nu_\mu$ disappearance samples
• Figure 3: True-to-reconstructed energy smearing matrices for NC interactions extracted from the Fast MC and used as inputs to GLoBES. Left: Used in the $\nu_e$ appearance sample. Right: Used in the $\nu_\mu$ disappearance sample.
• Figure 4: Analysis sample detection $\times$ selection efficiencies for the various signal and background modes extracted from the Fast MC and used as inputs to GLoBES. Top: Used in the $\nu_e$ appearance sample. Bottom: Used in the $\nu_\mu$ disappearance sample. Left: Neutrino beam mode. Right: Antineutrino beam mode. The NC backgrounds (and $\nu_\mu$ CC backgrounds for the appearance mode) have been increased by a factor of 10 for visibility.
• Figure 5: $\nu_e$ and $\bar{\nu}_e$ appearance spectra: Reconstructed energy distribution of selected $\nu_e$ CC-like events assuming a 150 [inter-unit-product=${}\cdot{}$] exposure in the neutrino-beam mode (left) and antineutrino-beam mode (right), for a total 300 [inter-unit-product=${}\cdot{}$] exposure. The plots assume normal mass hierarchy and $\delta_{\rm CP} = 0$. The spectra are shown for both the CDR reference beam design and the optimized beam design as described in Section \ref{['sec:physics-lbnosc-beam-req']}.