Searching for sterile neutrinos with reactor experiments Jonathan

Searching for sterile neutrinos with reactor experiments Jonathan Gaffiot, Ph. D. CEA Saclay: IRFU – Service de Physique Nucléaire Nucifer project - STEREO project 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 1

REACTOR ANTINEUTRINO ANOMALY 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 2

Neutrino spectra • Uranium 235 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 3

Reactor Antineutrino Anomaly • 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 4

4 th neutrino hypothesis • Disparition of neutrinos: new oscillation ? New oscillation to sterile n? Atmospheric oscillation Solar oscillation G. Mention et al. , Phys. Rev. D 83, 073006 (2011) 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 5

Anomaly contours Reactor norm + reactor shape + gallium Reactor norm + shape (Bugey 3 15 m/40 m) Reactor norm only 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 6

Detector specifications and challenges • 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 7

Nucifer DANSS ON GOING PROJECTS 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 8

Nucifer experiment Contact: T. Lasserre, D. Lhuillier, M. Fallot • 70 MW 7 m 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 9

Commissioning and data taking • Data taking since april 2012 60 Co – Agreement from French National Security Agency (ASN) • Remote control & automatic data transfert • Accurate monitoring (Rates, gains, P, T…) • Detector works well ! 09/15/2012 CEA Irfu – Service de Physique Nucléaire Reactor shutdown Am. Be - Jonathan Gaffiot - Reactor experiments to test sterile nu's 10

Accidental background pool primary loop concrete • Primary loop water activation – High energy g leakage from 16 N • New south lead wall – Lead already acquired – Installation at end of 2012 09/15/2012 CEA Irfu – Service de Physique Nucléaire 2 m East 1. 2 m South water deactivation circuit core 3 m • Reactor OFF background on expectation 4 m 3. 35 m Barycenters of the PMT’s charges - Jonathan Gaffiot - Reactor experiments to test sterile nu's 11

Liquid scintillator upgrade • 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 12

Contour after upgrades • Upgrades planned to be finished early 2013 • With upgrades: 300 days @ Osiris MC detector response Ref spectra uncertainty Expected spectrum distortion - Error stat only 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 13

DANSS experiment Contact: V. Egorov • 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 14

SCRAAM STEREO NEUTRINO-4 POSEIDON NEW DEDICATED PROJECTS 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 15

SCRAAM project Contact: N. Bowden • Spectral distortion @SONGS (24 m), DE/E=10% @ 1 Me. V sin 2(2 q) =0. 165, Dm 2 =2. 4 e. V 2 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 16

STEREO project Contact: D. Lhuillier • French and German project • ILL research reactor (Grenoble): 40 cm 36 cm – 57 MW, highly enriched U – Compact: h = 80 cm, Φ = 40 cm • Dedicated detector: – 5 segments: L and E oscillation – Active outer layer: high efficiency + veto – Muon flux attenuation = 4, thick CH 2 and Pb walls (70 t) Site being discussed with ILL Target: Gd-doped liquid scintillator 09/15/2012 5 m CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 17

STEREO contour and phase shift • A phase shift of the oscillation is expected, no input from reactor. • Unambiguous signature of neutrino oscillation MC detector response Ref spectra uncertainty Best fit, shape + norm, 300 days 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 18

NEUTRINO-4 experiment Contact: A. Serebrov • SM-3 reactor in Dimitrovgrad (Russia): – 100 MW compact core (35 x 42 cm 3) • 2 detector geometries currently studied: – 24 sections 1. 4 x 1. 0 m 3 – 5 sections moveable at 6 -12 m • Preparation at WWR-M reactor in Gatchina • Future realization at SM-3 5 m detector at SM-3, 95% C. L. core 24 sections 5 sections WWR-M reactor, 18 MW Shielding studies 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's SM-3 reactor 19

POSEIDON – POsition SEns. Itive Detector Of Neutrino Contact: A. Derbin • • Gd loaded liquid scintillator detector: 2. 1 x 1. 3 m 3 • Region of sensitivity: δm 2 = (0. 3 - 6) e. V 2 sin 2(2 q)≥ 0. 01 64 6” PMTs 15 cm Veto+anti 511 LAB+PPO+Gd • Energy and spatial resolution should allow to observe the oscillation curves for different Eν 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 20

Conclusions • 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 21

Back-up 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 22

Shape only data • Bugey 3 comparison 40 m/15 m: Bugey (1995) • ILL pattern (not statistically significant) ILL (1981 – reanalysis 1995) 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 23

Nucifer Intallation Lead fro nt wall Shielding support Lead g shieldin CH 2 shielding Filling 09/15/2012 Muon veto CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 24

Photoelectron calibration • LED + fiber + diffuser single photoelectron signal • Automatic fit of spe (16 ch) pedestal + gain • Others LED for stability, linearity • Pedestal +- 0. 5% • Gain +- 2. 5 % • Measured each run or 10 runs (need statistic) 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 25

Sources simulation 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 26

Pulse Shape Discrimination in Nucifer PXE 50% - Dodecane 50% 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 27

Reactor Spectrum Calculation a 23 5 U u a 239 P Sensitivity to plutonium content 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 28

Neutrinos & non proliferation 1 m 3 detector 25 m away from a 3 GW reactor 2000 interactions/d Reactor operating at constant power At fixed power the n rate decreases as Pu accumulates in the core P (GW) Arrêt réacteur rechargement d’ 1/3 du combustible A neutrino working group was created last year by the AIEA 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 29

Passive Shielding Concrete Study of cosmic rays attenuation at surface performed for the MAJORANA collaboration* Favor thick light materials. Iron Lead *Cosmic 09/15/2012 Ray Interactions in Shielding Materials, E. Aguayo et al, PNNL-20693 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 30

STEREO shape only contours Background shape uncertainty 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 31

DANSS contour from Saclay team Shape only analysis • Core size prevents effective oscillation detection 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 32

Mean cross-section per fission ν -flux: 235 U +3. 7%, 239 Pu +4. 2%, 241 Pu +4. 7%, 238 U +9. 8% (σfpred ) Neutron lifetime decrease by a few % (σfpred ) Off-equilibrium corrections (σfpred ) Updated cross-sections per fission: new/old +4. 7% +5. 0% +9. 7% +5. 2% 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 33

n spectrum emitted by a reactor = S all fission products 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 34

Accurate prediction of reactor n spectra Reactor data Reactor evolution codes Thermal power δPth ~ 0. 5% at commercial reactors Fraction of fissions from isotope k, δak=few % Nuclear databases E released per fissions of isotope k, δEk≈0. 3% 09/15/2012 CEA Irfu – Service de Physique Nucléaire ν spectrum per fission Dominant source of uncertainty - Jonathan Gaffiot - Reactor experiments to test sterile nu's 35

Reactor Spectrum Calculation Cross section / fission: Detected spectrum / fission 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 36

The guts of Sk(E) Sum of all fission products’ activities Sum of all β-branches of each fission product Theory of βdecay 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 37

Theory of b-decay Fermi theory: Phase space Fermi Shape factor function of forbidden • • W = total energy W 0 = end-point p = momentum Z = Nuclear charge Corrections: Finite size of nuclear electric charge Screening of Atomic e - Finite size distrib. QED of decaying radiative neutron correction Weak magnetism n branch obtained by replacing: W W 0 -W, Gb Gn 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 38

Corrections to Fermi theory n spectrum corrections Example of a single branch with Z=46 A=117 E 0=10 Me. V b spectrum corrections P. Huber • Total fission spectra is a sum over a quasi continuous end-point distribution +/- cancellation at low E, adds up at high E. • Can’t neglect this when looking for oscillation patterns or accurate total rate. 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 39

Neutron Life time Continuous decrease of tn in the history of measurements Latest average including MAMBO II result: tn = 881. 5 s 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 40

ILL data: reference b- Spectra Accurate e- measurements @ ILL in Grenoble (1978 -89) Magnetic BILL spectrometer Emitted b spectra per fission e. Target foil (235 U, 239 Pu, 241 Pu) in thermal n flux ILL research reactor (Grenoble, France) 09/15/2012 W. Mampe et al. , Nucl. Instrum. Meth. 154 (1978). A. A. Hahn, K. Schreckenbach et al. , Phys. Let. B 218, 365 (1989)+ refs therein CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 41

Normalization of ILL data • Dominant systematic error : 1. 8 % (1 s) • Absolute calibration via internal conversion electron lines of known partial cross section per neutron capture • Correlated across all energy bins of all isotopes + directly propagates into the converted antineutrino spectra. 115 In(n, g)116 m. In & 207 Pb(n, g)208 Pb: absolute normalization 113 Cd(n, g)114 Cd : relative normalization 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 42

e- n conversion • Exact conversion requires complete knowledge from fission yield down to b- transition between parent ground (or isomeric)-state and daughter states b-branch level Fission product level • Lot of relevant quantities: Z, A, End-points, Jp, nuclear matrix elements, branching ratios, fission yields, life time… but scarce data as E 0 increases 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 43

Conversion of reference e- spectra 1 - Fit total e- spectrum with a sum of 30 effective b branches determined by iterative method (instead of ~10, 000+ real branches) 2 - Convert each effective e- branches to ν branches 3 - Sum all converted ν branches to get total ν spectrum K. Schreckenbach et al. , Phys. Lett. 99 B, 251 (1981). A. A. Hahn et al. , Phys. Lett. 218 B, 365 (1989). 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 44

ILL n spectra Emitted spectrum / fission • Converted energy spectrum S(E) for 235 U, 239 Pu and 241 Pu. • Reference spectra over the last 25 years • Ab initio calculation for 238 U spectrum + new data from FRM 2 • (Nils Haag et al. ) 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 45

New Predictions of n Spectra Th. Mueller et al, Phys. Rev. C 83, 054615 (2011) Residuals to reference ILL data +3% normalization shift with respect to ILL ν spectrum Similar result for 235 U and Pu isotopes, +9. 8% for 238 U because of more complete ab initio approach. Origin of the bias well identified: - Effective implementation of corrections to Fermi theory - Nuclear charge distribution of virtual branches 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 46

Confirmed by Independent Work P. Huber, Phys. Rev. C 84, 024617(2011) New conv. with simple b-shape Mixed-approach ILL inversion Confirms global increase of predicted spectrum Fixes remaining oscillations of mixed-approach prediction Extra deviation at high energy from more complete correction to Fermi theory. ν -flux: 235 U +3. 7%, 239 Pu +4. 2%, 241 Pu +4. 7% 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 47

Reanalysis of All Short Baseline experiments 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 48

19 measurements @ L<100 m Krasnoyarsk Rovno Bugey Savannah River Goesgen ILL Different detector technics, different core compositions, different backgrounds, … 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 49

19 measurements @ L<100 m Variety of detection techniques, baselines, core compositio meas/pred 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 50

Correlation Matrix (correlation matrix on Ratios) (in %) Bugey-4 15 m Rovno 91 18 m Bugey-3 15 m Bugey-3 40 m Bugey-3 92 m Goesgen 38 m Goesgen 45 m Goesgen 65 m ILL 9 m Krasno 33 m Krasno 92 m Krasno 57 m SRP I 18 m SRP II 25 m Rovno 88 1 I 18 m Rovno 88 2 I 18 m Rovno 88 1 S 18 m Rovno 88 2 S 25 m Rovno 88 3 S 18 m 3. 0 3. 9 3. 0 5. 1 5. 0 14. 1 5. 0 6. 5 6. 0 7. 6 6. 0 9. 5 6. 0 5. 1 4. 1 20. 3 4. 1 3. 7 3. 8 3. 7 6. 9 7. 8 7. 2 Global 2% correlated norm error of ILL β-spectra Block correlations come from identical detector, technology or n source 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 51

238 U b spectrum soon to be published New 238 U data @ FRMII reactor, Munich n flux Natural U foil • Anchor point of 235 U measurement: - Background well understood. - Comparison to ILL spectrum cancels most uncertainties. b MWC Plastic Scintillator N. Haag, K. Schrekenbach et al. Ø N. Haag Ph. D. thesis to be published by end of this year. Ø Analysis of electron data is final, conversion to neutrino on progress. 09/15/2012 CEA Irfu – Service de Physique Nucléaire - Jonathan Gaffiot - Reactor experiments to test sterile nu's 52