Physics Opportunities with PROSPECT-II

TL;DR

PROSPECT-II aims to enhance sterile neutrino searches by deploying an upgraded detector capable of high-precision spectral measurements within a year, addressing unresolved anomalies in short-baseline neutrino experiments.

Contribution

It introduces an improved detector design for PROSPECT-II to explore high $oldsymbol{ ext{Δ}m^2}$ sterile neutrinos with rapid deployment and impactful physics results.

Findings

Addresses unexamined high $oldsymbol{ ext{Δ}m^2}$ sterile neutrino parameter space.

Proposes a detector upgrade enabling faster, more precise measurements.

Aims to clarify the sterile neutrino anomalies and complement existing experiments.

Abstract

The PROSPECT experiment has substantially addressed the original 'Reactor Antineutrino Anomaly' by performing a high-resolution spectrum measurement from an enriched compact reactor core and a reactor model-independent sterile neutrino oscillation search based on the unique spectral distortions the existence of eV$^2$-scale sterile neutrinos would impart. But as the field has evolved, the current short-baseline (SBL) landscape supports many complex phenomenological interpretations, establishing a need for complementary experimental approaches to resolve the situation. While the global suite of SBL reactor experiments, including PROSPECT, have probed much of the sterile neutrino parameter space, there remains a large region above 1 eV$^2$ that remains unaddressed. Recent results from BEST confirm the Gallium Anomaly, increasing its significance to $\sim 5\sigma$, with sterile neutrinos providing a possible explanation of this anomaly. Separately, the MicroBooNE exclusion of electron-like signatures causing the MiniBooNE low-energy excess does not eliminate the possibility of sterile neutrinos as an explanation. Focusing specifically on the future use of reactors as a neutrino source for beyond-the-standard-model physics and applications, higher-precision spectral measurements still have a role to play. These recent results have created a confusing landscape which requires new data to disentangle the seemingly contradictory measurements. To directly probe $\overline{\nu}_{e}$ disappearance from high $\Delta m^2$ sterile neutrinos, the PROSPECT collaboration proposes to build an upgraded and improved detector, PROSPECT-II. It features an evolutionary detector design which can be constructed and deployed within one year and have impactful physics with as little as one calendar year of data.