[Paper Review] The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe

C. Adams, D. L. Adams+480 more|arXiv (Cornell University)|Jul 28, 2013

Neutrino Physics ResearchPhysics and Astronomy277 references179 citations

TL;DR

The Long-Baseline Neutrino Experiment (LBNE) proposes a world-class neutrino facility using a megawatt-class proton accelerator at Fermilab, a near detector, and a large liquid argon time-projection chamber at the Sanford Underground Research Facility, 1,300 km away. This setup enables high-sensitivity studies of neutrino oscillations to probe CP violation, neutrino mass ordering, and proton decay—key to understanding matter-antimatter asymmetry and the origin of heavy elements.

ABSTRACT

The preponderance of matter over antimatter in the early Universe, the dynamics of the supernova bursts that produced the heavy elements necessary for life and whether protons eventually decay --- these mysteries at the forefront of particle physics and astrophysics are key to understanding the early evolution of our Universe, its current state and its eventual fate. The Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed plan for a world-class experiment dedicated to addressing these questions. LBNE is conceived around three central components: (1) a new, high-intensity neutrino source generated from a megawatt-class proton accelerator at Fermi National Accelerator Laboratory, (2) a near neutrino detector just downstream of the source, and (3) a massive liquid argon time-projection chamber deployed as a far detector deep underground at the Sanford Underground Research Facility. This facility, located at the site of the former Homestake Mine in Lead, South Dakota, is approximately 1,300 km from the neutrino source at Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino charge-parity symmetry violation and mass ordering effects. This ambitious yet cost-effective design incorporates scalability and flexibility and can accommodate a variety of upgrades and contributions. With its exceptional combination of experimental configuration, technical capabilities, and potential for transformative discoveries, LBNE promises to be a vital facility for the field of particle physics worldwide, providing physicists from around the globe with opportunities to collaborate in a twenty to thirty year program of exciting science. In this document we provide a comprehensive overview of LBNE's scientific objectives, its place in the landscape of neutrino physics worldwide, the technologies it will incorporate and the capabilities it will possess.

Motivation & Objective

• To investigate the fundamental asymmetry between matter and antimatter in the early Universe by measuring CP violation in neutrino oscillations.
• To determine the neutrino mass ordering—whether the lightest neutrino state is heavier or lighter than the other two—through long-baseline neutrino oscillation measurements.
• To search for proton decay, a key prediction of grand unified theories, using a massive underground detector.
• To study neutrino behavior in core-collapse supernovae to understand the origin of heavy elements necessary for life.
• To establish a scalable, flexible, and cost-effective experimental platform for long-term, international collaboration in neutrino physics.

Proposed method

• Utilizes a megawatt-class proton accelerator at Fermilab to produce a high-intensity neutrino beam.
• Deploys a near detector located just downstream of the neutrino source to measure initial neutrino flux and composition.
• Employs a large liquid argon time-projection chamber as a far detector, situated 1,300 km away at the Sanford Underground Research Facility.
• Leverages the 1,300 km baseline to maximize sensitivity to CP violation and neutrino mass ordering in oscillation patterns.
• Uses liquid argon time-projection chamber technology for high-precision tracking and energy measurement of neutrino interactions.
• Incorporates scalability and modularity to allow for future upgrades and additional physics programs.

Experimental results

Research questions

• RQ1 What is the degree of CP violation in the neutrino sector, and does it explain the matter-antimatter asymmetry in the early Universe?
• RQ2 What is the neutrino mass ordering—normal or inverted—based on long-baseline oscillation measurements?
• RQ3 Does the proton decay via any of the predicted channels, and if so, at what rate?
• RQ4 How do neutrinos behave during core-collapse supernovae, and what role do they play in nucleosynthesis?
• RQ5 Can the LBNE facility be adapted to study other rare processes or new physics beyond the Standard Model?

Key findings

• The 1,300 km baseline provides optimal sensitivity to both CP violation and neutrino mass ordering in long-baseline neutrino oscillation experiments.
• The use of a liquid argon time-projection chamber enables high-resolution tracking and energy reconstruction of neutrino interactions, enhancing measurement precision.
• The experiment is designed to be scalable and flexible, allowing for future upgrades and integration of additional physics goals.
• The facility is positioned to provide transformative discoveries in neutrino physics over a 20–30 year program of operation.
• LBNE offers a unique opportunity for global collaboration in addressing fundamental questions about the universe’s matter dominance and ultimate fate.
• The experimental configuration is cost-effective and well-suited to detect rare processes such as proton decay and supernova neutrinos.