Precision Reactor Upgrade significantly expands oscillation Oscillation and physics reach in unique parameter space

] prospect.yale.edu ] ] 2 2 90% CL 90% CL 2 90% CL SPECTrum Experiment: PROSPECT, 1 yr Sensitivity PROSPECT, 2 yr Optimized Sensitivity PROSPECT, 2 yr Optimized Sensitivity PROSPECT, 2 yr Sensitivity DANSS Exclusion PROSPECT, 2 yr Optimized Sensitivity, σspectrum = 5% [eV [eV PROSPECT, 2 yr Optimized Sensitivity NEOS Exclusion [eV DYB Exclusion KATRIN Exclusion 2 41 PROSPECT, Current Sensitivity 2 41 STEREO, Current Exclusion 2 41 PROSPECT-I demonstrated PROSPECT, Current Exclusion STEREO, Expected Sensitivity LBN CPV Ambiguity Limit m m 10 m SBL + Gallium Anomaly (RAA + Evolution), 95% CL

Δ 10 Δ 10 Upgrade & Science Goals Δ excellent performance

H. Pieter Mumm for the PROSPECT collaboration 6 Primary Physics Goals Li capture Search for sterile neutrino oscillation 1 1 1 • Nuclear recoil within unique parameter space important for the reactor anomaly and Long Baseline Electronic recoil experiments. 235 • High-resolution U spectrum and flux 10−1 10−1 10−1 measurement addresses observed shape 10−2 10−1 1 10−2 10−1 1 10−2 10−1 1 sin22θ sin22θ sin22 discrepancies 14 14 θ14 Pulse shape discrimination (PSD) PROSPECT measurement strategy capable scintillator with high light yield • Unique 6Li-doped liquid scintillator as inverse Left: Comparison of sterile oscillation sensitivities for current and projected PROSPECT-II datasets. allows for excellent background beta decay target; distinct IBD topology Center: Projected PROSPECT-II sensitivity compared to selected short-baseline reactor experiments. rejection and > 5%/ E resolution. • Highly segmented array for background Right: Overlap of three year PROSPECT-II sensitivity with relevant regions of parameter space rejection and event localization • ~ 7m baseline to very compact highly- PROSPECT-II uniquely addresses a high Δ m2 region between enriched reactor core provides unique 1 eV2 - 15 eV2, and will reach the 5o sin2(2�14) sensitivity over sensitivity at high Δm2. • Robust oscillation signature; simultaneous much of this range (impacting interpretation of LBN CP violation) spectrum measurement at multiple baselines PROSPECT-II Concept Upgrade reduces uncertainties below 5% Reusable, risk-reducing design, highly Detailed Monte Carlo of systematics validated leveraged on PROSPECT-I lessons learned, through key parts of spectrum with extensive calibration campaign

3 same footprint at HFIR ×10− 0.5 Antineutrino Early PROSPECT-I IBD spectrum Detector 0.4 Reactor off

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0 Thin UVT acrylic 0 2 4 6 8 10 12 Viton gasketwindow Teflon-lined Al Clamp PMT array PMT support containment vessel prompt ionization [MeV]

HFIR Core Early PROSPECT-I data demonstrated 3:1 Robust Design: signal to background, best for a surface • PMTs separated from liquid scintillator, repairable/ deployed antineutrino detector replaceable Please see other PROSPECT posters and talk Scintillator system drain-and-replace capable • Left: PROSPECT 235U spectrum measurement uncertainties after two years of PROSPECT-II data. Updated Event Selection for the PROSPECT Experiment, #158 Performance upgrade options: Measurement of the Uranium-235 Antineutrino Spectrum by PROSPECT, #516 Right: Expected PROSPECT-II precision in measuring the amplitude (n) of a bump-like feature in the PROSPECT: Latest results for Sterile Neutrino Oscillation search, #408 • +40% in fiducial volume - improved statistics 4-6 MeV prompt energy regime as observed by Daya Bay, RENO and Double Chooz. PROSPECT upgrade and science goals, #540 • x 2 increase in 6Li concentration - increased A Joint Measurement of the 235U Reactor Antineutrino Spectrum, #556 efficiency & reduced background Supported by: • Potential multi-site or multi-reactor operation; PROSPECT-II will address hypotheses for the origin of the increased oscillation sensitivity spectral excess between 4 -6 MeV at high confidence level

Supported by: prospect.yale.edu