Future of Reactor Experiments

Transcription

1 Future of Reactor Experiments Nobel Prize to Fred Reines Precision measurement of Δm12 2. Evidence for oscillation First observation of reactor antineutrino disappearance 2011/ The year of θ 13 Daya Bay Double Chooz Reno? 1980s & 1990s - Reactor neutrino flux measurements in U.S. and Europe First observation of (anti)neutrinos KamLAND Savannah River Chooz Karsten M. Heeger University of Wisconsin 1

2 Physics with Reactor νe Discoveries and Precision Measurements of Neutrino Properties Antineutrino Discovery Reactor νe Spectra νe Oscillations Searches for New Physics neutrino magnetic moment and coherent scattering searches Reactor Monitoring and Application fuel burnup and isotopic composition Suekane s talk 2

3 Reactor Antineutrinos Source ν e from β-decays of n-rich fission products 238 U Detection inverse β-decay ν e + p e + + n observable rate and energy spectrum Arbitrary calculated reactor spectrum Flux From Bemporad, Gratta and Vogel observed Observable spectrum! Spectrum mean energy ~ 3.6 MeV crosssection Cross Section 239 Pu 241 Pu 235 U only disappearance experiments possible neutrino energy (MeV) 235 U: 238 U: 239 Pu: 241 Pu = 0.570: 0.078: : ~ 200 MeV per fission ~ 6 ν e per fission ~ 2 x ν e /GW th -sec ν e scattering Events (/kg/day/kev) ν e e(sm) ν e N(SM) 1 1 c/kg/kev/d ν e e(mm) recoil energy (kev 3

4 3-Neutrino Mixing Parameters from Reactors Δm 2 P ee 1 sin 2 2θ 13 sin 2 31 L Δm cos 4 θ 13 sin 2 2θ 12 sin E ν 4E ν 2 L Results

5 3-Neutrino Mixing Parameters from Reactors Δm 2 P ee 1 sin 2 2θ 13 sin 2 31 L Δm cos 4 θ 13 sin 2 2θ 12 sin E ν 4E ν 2 L Results KamLAND Δm 2 12 from KamLAND precision θ12 from solar

6 3-Neutrino Mixing Parameters from Reactors Δm 2 P ee 1 sin 2 2θ 13 sin 2 31 L Δm cos 4 θ 13 sin 2 2θ 12 sin E ν 4E ν 2 L Results KamLAND Δm 2 12 from KamLAND precision θ12 from solar EH1 EH2 Daya Bay, RENO, DC 13 sin 2 2θ EH Weighted Baseline [km]

7 3-Neutrino Mixing Parameters from Reactors Δm 2 P ee 1 sin 2 2θ 13 sin 2 31 L Δm cos 4 θ 13 sin 2 2θ 12 sin E ν 4E ν 2 L Near Future sin 2 2θ13 improvements Daya Bay collects statistics RENO may improve systematic error DC builds near detector Results KamLAND Δm 2 12 from KamLAND precision θ12 from solar sin 2 2θ13 expected to be known to ~0.005 by end of 2012 (with certain assumptions of experiments) EH1 EH2 Daya Bay, RENO, DC EH Weighted Baseline [km] 13 sin 2 2θ13 Ref: Machado et al, arxiv:

8 3-Neutrino Mixing Parameters from Reactors Δm 2 P ee 1 sin 2 2θ 13 sin 2 31 L Δm cos 4 θ 13 sin 2 2θ 12 sin E ν 4E ν 2 L Future - running experiments sin 2 2θ13 to 4-5% from Daya Bay, 3 years some improvements in analysis, Daya Bay currently statistics limited Δm 2 13 from reactors large θ13 allows spectral analysis Results EH1 EH2 Daya Bay, RENO, DC EH Weighted Baseline [km] 13 KamLAND Δm 2 12 from KamLAND precision θ12 from solar sin 2 2θ13 precision reactor νe spectra e.g. Daya Bay several 100k events in near-site spectra Future - proposed sin 2 θ12 to ~2% from dedicated reactor experiment at optimized L~60km 60 GW kt y exposure, ~4% systematic error from near detector 5 Bandyopadhyay et al., Phys. Rev. D67 (2003) Luk, private communication 2003 Minakata et al., hep-ph/ Bandyopadhyay et al., hep-ph/

9 Mass Hierarchy and Reactor νe Oscillation Measure spectrum at 1st oscillation maximum of θ12 oscillation scintillator oil buffer water tank in principle, determine mass hierarchy from precision measurements of Δm 2 31 and Δm 2 32 Δm 2 21 is only 3% of Δm 2 32 S.T. Petcov et al., PLB533(2002)94 S.Choubey et al., PRD68(2003) J. Learned et al., hep-ex/ L. Zhan, Y. Wang, J. Cao, L. Wen, PRD78:111103, 2008 PRD79:073007, 2009

10 Mass Hierarchy and Reactor νe Oscillation Measure spectrum at 1st oscillation maximum of θ12 oscillation scintillator oil buffer water tank optimize baseline for detector, L=58km extremely good E resolution of 3%/ E e.g. 20kton, 15, PMTs S.T. Petcov et al., PLB533(2002)94 S.Choubey et al., PRD68(2003) J. Learned et al., hep-ex/ L. Zhan, Y. Wang, J. Cao, L. Wen, PRD78:111103, 2008 PRD79:073007, 2009

11 Mass Hierarchy and Reactor νe Oscillation Daya Bay II scintillator oil buffer water tank Site Investigation Mass Hierarchy Sensitivity candidate site (~60km) NH IH 50k events = 20 kton, 3 years 96% 100k events 3σ Haifeng Ref: Y. Wang, J. Cao, et al nuturn 2012 Daya Bay Sub-1% precision 3-v oscillation physics in Δm 2 12, Δm 2 23, and sin 2 θ12 possible

12 Beyond 3-v Mixing with Reactors ν flux predictions & very short baselines 10 m new prediction 100 m 1 km Average = ± (χ 2 =19.6/19) reactor θ13 near detector km reactor θ13 far detector 1-2km adapted from Laserre, HEP2011 updates in new reactor antineutrino spectra - re-analysis of 19 short-baseline reactor results - neutron lifetime correction, off-equilibrium effects net 3% upward shift in energy averaged fluxes Ref: Lhuillier et al deficit from flux normalization problem or from additional oscillation at L~O(1-10m)? nuclear physics vs new physics? 9

13 Neutrino Anomalies & Sterile ν Hypothesis LSND MiniBoone Ga Anomaly Cosmology (WMAP) R=0.86±0.05 Anomalies in 3-v interpretation of global neutrino oscillation data LSND (νe appearance) MiniBoone (νe appearance) Ga anomaly Neff in cosmology Short-baseline reactor anomaly (νe disappearance) if new oscillation signal, requires Δm 2 ~ O(1eV 2 ) and sin 2 2θ > 10-3 very short baseline oscillation for reactor v, Losc ~ 2-10m systematics or experimental effects? need to test each experimental effect source experiments (Lasserre) acc experiments (Shaevitz) 10

14 Reactor Monitoring Experiments for Sterile v Searches NUCIFER at Osiris core: σ~0.3m baseline: 7m Pre-industrial, unattended reactor neutrino monitor May be used to test reactor anomaly with compact core. PSD R&D for background rejection. Ref: Lhuillier, APP

15 Reactor Monitoring Experiments for Sterile v Searches SCRAAM: Southern California Reactor Antineutrino Anomaly Monitor Spectral (24m), 1MeV sin 2 (2θ) =0.165, Δm 2 =2.4 ev 2 core : ~3m, fixed baseline: 24m Adapt existing compact detector design/technology, limited by backgrounds Limitations: Existing designs require overburden for background reduction limits range of deployment sites, especially very close (<10m) to compact cores ATR 5σ (300 days) SONGS 5σ (150 days) Ref: Bowden, poster

16 Reactor Monitoring Experiments for Sterile v Searches SCRAAM: Southern California Reactor Antineutrino Anomaly Monitor Spectral (24m), 1MeV sin 2 (2θ) =0.165, Δm 2 =2.4 ev 2 rate core : ~3m, fixed baseline: 24m Adapt existing compact detector design/technology, limited by backgrounds Limitations: Existing designs require overburden for background reduction limits range of deployment sites, especially very close (<10m) to compact cores ATR 5σ (300 days) SONGS 5σ (150 days) shape Ref: Bowden, poster

17 Short Baseline ν Oscillation Searches Some Experimental Issues Reactor Core Size small core preferred Baseline Spread at detector from core assume point detector at 10m Detector Technology Choice localize events, PSD(?) for background rejection, good E resolution for spectrum single volume, position reconstruction events ILL HFIR ATR SONGS NSBR ATR ILL HFIR Baseline spread washes out oscillation signal LLN NSBR SONGS distance (m) segmented detector Mumm, KMH 14

18 Worldwide Effort Towards Optimized Sterile v Search Stereo at ILL, France POSEIDON at Reactor PIK, Russia Observed / Expected L = 9.2 m L = 10.0 m L = 10.8 m 64 6 PMTs 15 cm Veto+anti511 LAB+PPO+Gd 1x1x2m target vessel filled with Gd-LS 5 baseline bins by foils ) 2 (ev m 2 new shape-only analysis E vis (MeV) shift detector to verify oscillation signal Gd-LS Detector: 2.1x1.3x1.3 m 3 Energy resolution: σ = 7% at 1 MeV Spatial resolution: σx = 15 cm at 1 MeV Energy and spatial resolution to measure oscillation curves for different Eν Exp 95 % CL Exp 99 % CL Exp 5 CL RAA 95 % CL RAA 99 % CL Best Fit sin (2 new ) aim to detect oscillatory signature 15

19 Worldwide Effort Towards Optimized Sterile v Search Neutrino4, Russia passive shielding Pb, CH2(B) muon veto Hanaro-SBL, Korea multisection detector for segmentation in radial direction active shielding multi-zone active background rejection LS- 6 Li or Gd-LS scintillator? n Gd 156 Gd +8MeV n+ Li He+ H MeV - γ-α coincidence can effectively reject backgrounds - PSF with 6 Li-loaded scintillator may enable on-surface detector with minimal overburden 16

20 Worldwide Effort Towards Optimized Sterile v Search DANSS, Russia Ricochet, USA movable distance also used for neutrino magnetic moment searches with Ge detectors signal detection through coherent scattering 17

21 Opportunities with Reactor Neutrinos in the US Reactor Power Fuel Baselines Detector Status NRL, MIT 5.5 MW 235U >3-4m proposal (Ricochet, MIT) NBSR, NIST 20 MW 235U 4-11 m proposal (Mumm, KMH) ATR, Idaho 250 MW 235U 12 m proposal (SCRAAM, LLNL) 6m site studies (Mumm, KMH) 3 m (in water) site studies (Mumm, KMH) HFIR, Oak Ridge 85 MW 235U >7m SONGS, San Onofre 2700 MW 235, 238U, 239, 241Pu 24 m ongoing (LLNL) key reactor features: power, baseline, core size, on-off cycle fuel, overburden fuel element 74 cm fuel 18 cm 52.8 cm NBSR ATR HFIR SONGS established access to variety of research and commercial reactors in user mode neutron and near-surface backgrounds are key issues Karsten Heeger, Univ. of Wisconsin Neutrino2012, Kyoto, June 4,

22 Scattering Studies Searches for New Physics with νe Scattering Gemma-II, Kalinin NPP, Russia Events (/kg/day/kev) ν e e(sm) ν e N(SM) ν e e(mm) 1 c/kg/kevpd 1 recoil energy (kev Requirement: low-background, rare event studies Goal: Aiming for sub-kev Ge detector for coherent scattering, neutrino magnetic moment, goal sensitivity of 1x μb TEXONO Challenges: excess of sub-kev events, - not fully explained with background model - moved to Jinping underground lab, China, to reduce backgrounds 19

23 Scientific Opportunities with Reactor νe at Short Baselines Reactor cores, fuel, and antineutrino spectra - precision studies of reactor antineutrino spectra, data sets with several 100k events - studies of fuel composition and burnup cycle - studying HEU to LEU core conversion at US research reactors - background studies during on-off cycles at research reactor Background studies and detector development - understand high n and γ environment near reactors - segmented vs monolithic detectors with position reconstruction - scintillators for neutron detection (Gd and Li-doped, LAB vs water) - test of on-surface antineutrino detectors with minimum overburden Searches for new physics - Understanding reactor anomaly & test sterile v hypothesis - requires unique signatures: oscillation in E and distance - neutrino magnetic moment and coherent scattering searches? 20

24 Summary For > 50 years reactor experiments have played an important role in neutrino physics, in both discoveries and precision measurements. Current reactor experiments (L~1-2km) will provide precision data on θ13, and reactor antineutrino spectra. Data taking for next ~3-5 years. Intermediate-baseline (L~60km) reactor antineutrino experiments may be used for a precision measurement of θ12, and determination of the mass hierarchy. Very short baseline (L~10m) measurements offer opportunities for precision studies of the reactor spectra, fuel evolution and searches for new physics. On-surface neutrino monitors may be developed. Reactor νe enable a rich program in probing neutrino properties, detector development, and nuclear monitoring with neutrinos. Thanks to many colleagues for slides and material: A. Bernstein, N. Bowden, J. Cao, A. Derbin, Y. Kim, T. Lasserre, D. Lhuillier, A. Serebrov, A. Starostin, M. Yeh, Y. Wang, H. Wong, et al. 21

25 Karsten Heeger, Univ. of Wisconsin NUSS, July 13, 2009