PROSPECT: A Precision Reactor Oscillation and Spectrum

ExperimentXianyi Zhang

Illinois Institute of TechnologyPROSPECT Collaboration

1

The Reactor Antineutrino

❖ Fission reactors generate antineutrinos through β-decay.

❖ Mainly 4 fission source isotopes of reactor antineutrino.

❖ Reactor antineutrino experiments:➢ Antineutrino spectrum of

fission reactor.➢ Oscillation of reactor

antineutrino.

2

Neutrino Oscillation and Spectrum, arXiv:1503.01059

The Reactor Antineutrino Anomaly

❖ The latest neutrino flux measurement of Daya Bay experiment showed deficit from prediction.

❖ The spectral prediction models of reactor antineutrino are different.

❖ Latest multi-baseline reactor experiments found deviation of neutrino spectrum.

3

Spectrum Predictions, arXiv:1470.1281 DYB Spectrum and Flux, arXiv:150804233

PROSPECT Experiment

❖ Reactor: a Highly Enriched Uranium (HEU) reactor - High Flux Isotope Reactor, at ORNL.

❖ Baseline: 7 - 12 m (movable).❖ Detector: optically segmented Li-6

loaded liquid scintillator (LiLS) antineutrino detector.

4

Physics Goal - Probe a Sterile Neutrino

Flux deficit: a possible hint of oscillation from antineutrino to a sterile neutrino.

❖ A right-handed singlet of neutrino.❖ One sterile neutrino is suggested with a

Δm2 ~ 1 eV2.

5

Oscillated spectra on baselines

Null-oscillated spectra on baselines

Sensitivity of oscillation of PROSPECT

PROSPECT Cross-section

Phase I + II

Phase I

DayaBay

Physics Goal - Spectrum Measurement

❖ Direct spectral measurement to the Highly Enriched Uranium (HEU) reactor, σ=4.5%/√E.

❖ Compare the absolute spectrum of reactor antineutrino with recent models of spectrum.

❖ Set new reference of reactor spectrum for future reactor antineutrino experiments.

6

The Antineutrino Detection

❖ Detect Inverse Beta Decay (IBD) of antineutrino.❖ The e+ event (prompt event) and n-capture event

(~40μs delayed event) of LiLS generated scintillation light.

❖ Photomultiplier Tubes (PMT) detect scintillation light.

❖ The Pulse Shape Discrimination (PSD) of scintillator to distinguish the signal from backgrounds.

7

Inverse Beta Decay

Cf-252(n, Li)

n

γ

IBD-like Fast neutron

Accidental γ

Detector Design

❖ Optically segmented by reflectors.❖ The segmentation makes 12x10 elongated elemental ADs (cells).❖ Each elongated cell has PMTs attached on both sides, enabling position

reconstruction of the IBD events.

8

Progress

9

● Background survey and prototype studies have been ongoing since 2014. (Will be presented in P. Surukuchi’s talk.)

● A 2-cell prototype is in plan to test the segmentation of detector.

● Preparing the hardware for construction are in progress, including reflector fabrication, reflector evaluation, mechanical and compatibility tests.

● Simulations for experiment is underway.

Prototype StudiesResearch and Development

Timeline

10

PROSPECT 60

Summary

❖ Reactor antineutrino anomaly gives hint of possible new physics and incomplete reactor model.

❖ The PROSPECT experiment aims to measure the spectrum and flux of antineutrino from HFIR in short baseline to explain the anomaly.

❖ The R&D of PROSPECT detector is ongoing. Prototypes of PROSPECT have been deployed.

❖ During the experiment, we will test best fit at 3σ in 1 year, the favor region of oscillation at 3σ in 3 years. Phase II will test the region at 5σ.

11

Thank you!

12

Backup - Phase II

13

Motivation:

❖ Measurement covers more oscillation cycles.❖ Increase the statistical uncertainty.

Parameters:

❖ Baseline: 16 - 20 m.❖ Target mass: ~10 t.❖ Segmented IBD detector.

PROSPECT Phase II, 16 - 20 m

PROSPECT Phase I, 7 -12 m

Backup

14

A 3x3 mockup will be built to demonstrate the mechanics of the detector by 2016

● Commission the detector. 2016 - 2017● A possible Phase II.

● PROSPECT starts data taking. 2017 - 2020● Measure the spectrum and flux of antineutrino

generated from HFIR.● Look for the signature of sterile neutrino.