A Proposal for a Three Detector Short-Baseline Neutrino Oscillation Program in the Fermilab Booster Neutrino Beam (1503.01520v1)

Abstract: A Short-Baseline Neutrino (SBN) physics program of three LAr-TPC detectors located along the Booster Neutrino Beam (BNB) at Fermilab is presented. This new SBN Program will deliver a rich and compelling physics opportunity, including the ability to resolve a class of experimental anomalies in neutrino physics and to perform the most sensitive search to date for sterile neutrinos at the eV mass-scale through both appearance and disappearance oscillation channels. Using data sets of 6.6e20 protons on target (P.O.T.) in the LAr1-ND and ICARUS T600 detectors plus 13.2e20 P.O.T. in the MicroBooNE detector, we estimate that a search for muon neutrino to electron neutrino appearance can be performed with ~5 sigma sensitivity for the LSND allowed (99% C.L.) parameter region. In this proposal for the SBN Program, we describe the physics analysis, the conceptual design of the LAr1-ND detector, the design and refurbishment of the T600 detector, the necessary infrastructure required to execute the program, and a possible reconfiguration of the BNB target and horn system to improve its performance for oscillation searches.

• The paper introduces a three-detector setup with LAr-TPC technology to simultaneously measure neutrino oscillations through appearance and disappearance channels.
• It details the use of LAr1-ND, MicroBooNE, and the relocated ICARUS-T600 to reduce systematic uncertainties and enhance sensitivity to sterile neutrinos.
• Results are expected to probe LSND and MiniBooNE anomalies with near 5σ sensitivity, potentially challenging existing neutrino oscillation models.

Short-Baseline Neutrino Physics Program at Fermilab

The academic discourse on neutrino physics has been periodically reinvigorated by reports of experimental anomalies suggesting new physics beyond the well-substantiated three-neutrino paradigm. The document outlines a Short-Baseline Neutrino (SBN) experimental program utilizing three liquid argon time projection chamber detectors (LAr-TPCs) to investigate these anomalies, particularly hints of sterile neutrinos—a hypothesized class of neutrinos not interacting via the standard weak nuclear force—at an eV mass-scale. The program is hosted along the Booster Neutrino Beam (BNB) at Fermilab, which provides a critical environment to perform sensitive searches both for new neutrino states and to elucidate neutrino-argon interaction cross-sections.

Scientific Rationale and Infrastructure

This program aims to address experimental hints from LSND and MiniBooNE of neutrino oscillations involving a fourth neutrino state, often termed a sterile neutrino. The outlined apparatus comprises three distinct detectors: LAr1-ND, MicroBooNE, and ICARUS-T600, strategically spaced at various baselines downstream from the BNB source. A key feature in the program's sensitivity is its capability to detect neutrino oscillations through both appearance and disappearance channels simultaneously, offering robust cross-validation across different datasets and reducing systematic uncertainties typically associated with single-detector oscillation experiments.

Detection Objectives

The ICARUS-T600, a well-established large-scale detector originally deployed at the Gran Sasso Laboratory, is relocated to Fermilab to serve as the far detector. It leverages its extensive operational experience and technological prowess to contribute significant mass and baseline, thus enhancing the program's detection sensitivity for muon and electron neutrino disappearance, and critically, electron neutrino appearance.

In parallel, LAr1-ND functions at a proximal baseline offering high event rates for precise measurement of intrinsic BNB neutrino flux and reducing correlated systematics in conjunction with the far detector. Meanwhile, MicroBooNE acts as a mid-baseline detector nearing completion, allowing it to spearhead early phases of data acquisition and understand the neutrino cross-sections with argon crucial for interpreting potential oscillations.

Methodological Approach

The methodological framework employs advanced imaging capabilities inherent to LAr-TPC technology, known for its millimetric resolution and excellent particle identification due to extensive ionization tracking. The experimental setup achieves superior sensitivity to neutrino properties by optimizing parameters such as the configuration of the Booster beam, detector spacing, and mass hierarchy. Notably, the program emphasizes near-future improvements to the beam infrastructure—introducing a two-horn system designed to double the flux rate and capitalize on the statistical power requisite for confirming or refuting sterile neutrino existence.

Expected Results and Implications

With projected exposures, the resultant data from SBN are anticipated to fully probe the parameter space around the LSND-allowed neutrino oscillation regions with high confidence levels, potentially reaching a $\sim 5\sigma$ sensitivity. Moreover, the diversity of oscillation channels inspected enhances the measurement robustness against confounding variables endemic to oscillatory experiments.

The program, if successful, stands to reaffirm or challenge known neutrino oscillation models and explore uncharted domains of particle physics with significant implications for theoretical frameworks, cosmological models, and experimental designs in future neutrino research.

Conclusion

The SBN project at Fermilab presents a comprehensive approach to untangle the complexities of neutrino oscillation physics probing beyond the Standard Model hypothesis of sterile neutrinos. By capitalizing on LAr-TPC technology and collaborative international expertise, the initiative is poised not only to shed light on speculated anomalies but also to provide pivotal input for the broader agenda of neutrino physics and future large-scale neutrino observatories.