[PPT] - PROSPECT Precision Oscillation and Spectrum Experiment Karsten M. PowerPoint Presentation

SLIDE 1

Karsten M. Heeger Yale University

n behalf of the PROSPECT collaboration

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PROSPECT

Precision Oscillation and Spectrum Experiment

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Karsten Heeger, Yale University Moriond 2019

mean energy of νe: 3.6 MeV

nly disappearance

experiments possible

Reactor Antineutrinos

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νe from β-decays, pure νe source

f n-rich fission products
n average ~6 beta decays until stable

> 99.9% of νe are produced by fissions in

235U, 238U, 239Pu, 241Pu

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Karsten Heeger, Yale University Moriond 2019

Reactor Antineutrino “Anomalies” (RAA)

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Flux Deficit

Deficit due to extra (sterile) neutrino

scillations or artifact of flux predictions?

Spectral Deviation

Measured spectrum does not agree with predictions.

Daya Bay, CPC 41, No. 1 (2017)

Understanding reactor flux and spectrum anomalies requires additional data

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Karsten Heeger, Yale University Moriond 2019

Reactor Antineutrino “Anomalies” (RAA)

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Flux Deficit

Deficit due to extra (sterile) neutrino

scillations or artifact of flux predictions?

Spectral Deviation

Measured spectrum does not agree with predictions.

Daya Bay, CPC 41, No. 1 (2017)

Understanding reactor flux and spectrum anomalies requires additional data

Phys. Rev. D 83, 073006 (2011)

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Karsten Heeger, Yale University Moriond 2019

Shielding Active Inner Detector

Precision Oscillation and Spectrum Experiment

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Antineutrino Detector HFIR Core

Objectives Search for short-baseline oscillation at <10m Precision measurement of 235U reactor νe spectrum

Relative Spectrum Measurement relative measurement of L/E and spectral shape distortions Segmented, 6Li-loaded Detector unoscillated spectrum

scillated spectrum

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Karsten Heeger, Yale University Moriond 2019

Experimental Site

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Power: 85 MW Core shape: cylindrical Size: h=0.5m r=0.2m Duty-cycle: 46%, 7 cycles/yr, 24 days Fuel: HEU (235U)

Reactor Core highly-enriched (HEU): >99% of νe flux from 235U fission High Flux Isotope Reactor, ORNL compact reactor core, detector near surface, little overburden

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Karsten Heeger, Yale University Moriond 2019

PROSPECT Detector Design

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ation access along full segment length has successfully detected antineutr ent close to a reactor

119cm Floor Concrete Monolith

BORATED POLYETHELYNE INNER DETECTOR ARRAY WATER BRICK NEUTRON SHIELD

tilted array for calibration access

Optimized shielding to reduce cosmogenic backgrounds

Single 4,000 L 6Li-loaded liquid scintillator (3,000 L fiducial volume) 11 x 14 (154) array of optically separated segments Very low mass separators (1.5 mm thick) Corner support rods allow for full in situ calibration access Double ended PMT readout, with light concentrators good light collection and energy response ~5%√E energy resolution full X,Y,Z event reconstruction

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Karsten Heeger, Yale University Moriond 2019

Background Rejection

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Pieter Mumm National Institute of Standards and Technology For the PROSPECT Collaboration

Combine:

PSD
Shower veto
Event topology
Fiducialization

A sequence of cuts leveraging spatial and timing characteristics of an IBD yields > 104 background suppression and signal to background of > 1:1.

IBD-like rate per segment n+H

12C inelastic

Rate and shape of residual IBD-like background can be measured during multiple interlaced reactor-off periods.

showers topology fiducialization PSD

rate [mHz/segment] 0.0 0.5 1.0 1.5 2.0

1.27 0.69 0.42 0.39 0.35 0.30 0.32 0.32 0.31 0.30 0.36 0.44 0.72 1.34 0.92 0.21 0.10 0.08 0.08 0.06 0.08 0.05 0.05 0.09 0.05 0.10 0.20 0.92 0.70 0.13 0.04 0.03 0.02 0.02 0.01 0.03 0.01 0.02 0.03 0.04 0.13 0.68 0.64 0.11 0.03 0.02 0.03 0.02 0.02 0.02 0.02 0.02 0.02 0.03 0.15 0.64 0.64 0.13 0.02 0.03 0.03 0.02 0.02 0.01 0.03 0.03 0.03 0.04 0.11 0.69 0.75 0.12 0.05 0.03 0.02 0.01 0.02 0.01 0.03 0.03 0.03 0.02 0.11 0.70 0.78 0.12 0.04 0.02 0.02 0.02 0.02 0.03 0.02 0.02 0.03 0.03 0.17 0.78 0.83 0.17 0.03 0.03 0.02 0.04 0.02 0.04 0.04 0.04 0.05 0.04 0.15 0.83 1.00 0.17 0.07 0.03 0.04 0.05 0.05 0.04 0.05 0.04 0.05 0.05 0.17 1.03 1.36 0.34 0.18 0.14 0.15 0.14 0.15 0.15 0.12 0.14 0.14 0.19 0.35 1.31 2.15 1.20 0.94 0.86 0.83 0.78 0.79 0.72 0.76 0.82 0.89 1.00 1.18 2.15

segment x 5 10 segment z 2 4 6 8 10

Simulation Cosmogenic background Simulation

PROSPECT - arXiv:1808:00097

neutrinos

Detector design further optimized for background rejection

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x

Assembly in 30s (video)

Assembly of First Row November 1, 2017

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Final Row Installation November 17, 2017

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Dry Commissioning Dec 2017 - Jan 2018

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February 2018 Arrival at ORNL In Position at HFIR Filling from Mixing Tank First Muon Track

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February 2018 Arrival at ORNL In Position at HFIR Filling from Mixing Tank Hadronic Shower

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February 2018 Arrival at ORNL In Position at HFIR Filling from Mixing Tank IBD Candidate

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Karsten Heeger, Yale University Moriond 2019

0.0 0.5 1.0 1.5 2.0 2.5 3.0 0.02 0.04 0.06 0.08 0.10 rec

/E

E

σ (a)

Cs 137 Na 22 Na 22 nH Co 60 rec E E Resolution Model 0.0 0.5 1.0 1.5 2.0 2.5 3.0

[MeV]

rec

E

20 40 60

Rate [Hz] (b)

Na data 22 Best fit MC 0.0 0.5 1.0 1.5 2.0 2.5 3.0

Energy [MeV] γ Average

0.96 0.98 1.00 1.02 1.04 MC

/E

rec

E (c)

Cs 137 Na 22 Na 22 nH Co 60

Energy Reconstruction

Gamma sources (137Cs, 60Co, 22Na) deployed throughout detector, measure single segment response Fast-neutron tagged 12B: High-energy beta spectrum calibration

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4.5% at 1MeV

Resolution and Reconstruction

0.5 1 1.5 2 2.5 3 [MeV]

rec

E 0.02 0.04 0.06

Arb. Unit

(a) Gamma Sources Cs

137

Co

60 Cs 137 Co 60 Best fit MC

2 4 6 8 10 12 14 [MeV]

rec

E 0.2 0.4 0.6 0.8 Rate [mHz/MeV] B Spectrum

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(b)

MC/data for calibration peaks agrees to better than 1σ Full-detector Erec within ±1% of Etrue High light collection: 795±15 PE/MeV

E[MeV] Phys.Rev.Lett. 121 (2018) no.25, 251802 PROSPECT Collaboration

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Karsten Heeger, Yale University Moriond 2019

03/05 03/22 04/08 04/25 05/12 05/30 Date (MM/DD) 500 1000 1500 Events per day

Correlated Accidentals

First Oscillation Analysis Data Set

33 days of Reactor On 28 days of Reactor Off Correlated S/B = 1.36 Accidental S/B = 2.25 24,608 IBDs detected Average of ~750 IBDs/day IBD event selection defined and frozen on 3 days of data

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reactor on reactor off reactor on

maintenance calibration

Preliminary

Phys.Rev.Lett. 121 (2018) no.25, 251802 PROSPECT Collaboration

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Karsten Heeger, Yale University Moriond 2019

Neutrino Rate vs Baseline

Observation of 1/r2 behavior throughout detector volume Bin events from 108 fiducial segments into 14 baseline bins 40% flux decrease from front of detector to back

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PRELIMINARY Baseline (m) 7 7.5 8 8.5 9 Normalized IBD counts 0.6 0.8 1

Data

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1/r

Data

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1/r Data A/r2 fit

Phys.Rev.Lett. 121 (2018) no.25, 251802 PROSPECT Collaboration

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Karsten Heeger, Yale University Moriond 2019

Neutrino Spectrum vs Baseline

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Spectrum at baseline Full detector spectrum

1 2 3 4 5 6 7 Prompt Energy (MeV) 0.01 0.02 0.03 0.04 0.05 0.06 Rate Null oscillation Baseline 1 Baseline 2 Baseline 3 Baseline 4 Baseline 5 Baseline 6 Null oscillation Baseline 1 Baseline 2 Baseline 3 Baseline 4 Baseline 5 Baseline 6 Null oscillation Baseline 1 Baseline 2 Baseline 3 Baseline 4 Baseline 5 Baseline 6 Null oscillation Baseline 1 Baseline 2 Baseline 3 Baseline 4 Baseline 5 Baseline 6

Prompt Energy Rate

Null Oscillation 6.7-7.1m 7.1-7.5m 7.5-8.0m 8.0-8.4m 8.4-8.8m 8.8-9.2m

Spectral Distortion vs Baseline Compare spectra from 6 baselines to measured full-detector spectrum Null-oscillation would yield a flat ratio for all baselines Direct ratio search for oscillations, reactor model independent

7 1 2 3 4 5 6 7 Prompt Spectrum(MeV)

1 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

1 2 3 4 5 6 7 Prompt Spectrum(MeV)

1.8 Ratio

1 2 3 4 5 6 7 Prompt Spectrum(MeV) 1 2 3 4 5 6 7 Prompt Energy (MeV) 1 2 3 4 5 6 7 Prompt Energy (MeV) 1 2 3 4 5 6 7 Prompt Energy (MeV)

1.8 Ratio

1 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

3 4 5 (MeV)

rec

Prompt E

1 2 3 4 5 6 7 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

6.7-7.1 m Data RAA

1 2 3 4 5 6 7 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2

8.0-8.4 m

1 2 3 4 5 6 7 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 7.1-7.5 m 1 2 3 4 5 6 7 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 8.4-8.8 m 1 2 3 4 5 6 7 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 7.5-8.0 m 1 2 3 4 5 6 7 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 8.8-9.2 m

Phys.Rev.Lett. 121 (2018) no.25, 251802 PROSPECT Collaboration

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Karsten Heeger, Yale University Moriond 2019

Oscillation Search Results

Disfavors RAA best-fit point at >95% CL (2.2𝝉)

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Feldman-Cousins based

confidence intervals for

scillation search
Covariance matrices captures

all uncertainties and energy/ baseline correlations

Critical 𝜓2 map generated

from toy MC using full covariance matrix

95% exclusion curve based
n 33 days Reactor On
peration
Direct test of the Reactor

Antineutrino Anomaly RAA best fit

Phys.Rev.Lett. 121 (2018) no.25, 251802 PROSPECT Collaboration

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Karsten Heeger, Yale University Moriond 2019

New Measurement of 235U Spectrum

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Prompt Energy Spectrum measured spectrum with good S/B at surface 1.7/1 (0.8-7.2 MeV) ~ 6x greater statistics than ILL (1981) 40.2 days of reactor-on exposure, 37.8days of reactor-off exposure

~ 31,000 IBD candidate events (reactor-off candidate events scaled to match exposure)

Preliminary

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Karsten Heeger, Yale University Moriond 2019

Prompt Energy Spectrum

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Preliminary

Is PROSPECT consistent with Huber

235U model for HFIR HEU reactor?

χ2/ndf = 52.1/31 p-value = 0.01 Huber model broadly agrees with spectrum but exhibits large χ2/ndf with respect to measured spectrum, not a good fit. Deviations mostly in two energy regions. Statistics limited measurement.

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Karsten Heeger, Yale University Moriond 2019

Prompt Energy Spectrum

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Prompt Positron Energy (MeV) 2 4 6 8 Entries / 250 keV 5000 10000 15000 20000 Data Full uncertainty Reactor uncertainty ILL+Vogel Integrated Prompt Energy (MeV) 2 4 6 8 Ratio to Prediction 0.8 0.9 1 1.1 1.2 (Huber + Mueller) 4 1 Prompt Energy (MeV) 2 4 6 8 4 − 10

Shape of measured 235U spectrum not inconsistent with the deviation relative to prediction observed at LEU reactors.

Daya Bay

Preliminary

How does PROSPECT compare to “bump” in θ13 experiments?

best-fit excess

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Karsten Heeger, Yale University Moriond 2019

Summary

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PROSPECT started taking data on March 6, 2018 Background rejection and energy resolution meet expectation and match Monte Carlo. World-leading signal-to-background for a surface-based detector (<1 mwe overburden). Observed antineutrinos from HFIR with good signal/background. First oscillation analysis on 33 days of reactor-on data disfavors the RAA best-fit at 2.2𝝉. With a surface-based detector, highest-statistics measurement of

235U antineutrino spectrum from HEU reactor to date.

Based on results of PROSPECT and other experiments sterile neutrinos are increasingly disfavored

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prospect.yale.edu

Funding provided by: 14 Institutions, 70 collaborators