Reactor An3neutrinos: il buono, il bru;o, il ca<vo Dan Dwyer (LBNL) Neutrino Oscilla/on Workshop Otranto, Italy Sep. 5, 2016 Reactor An/neutrinos Fission of ac3nides (235U, 238U, 239Pu, 241Pu) produce neutron-­‐rich daughter fragments. β-­‐decays of daughters emit electrons and an3neutrinos. O(10k) unique decays Cumula3ve fission yields for a commercial reactor Ex: 97Y β-­‐decay, 9 known branches >1000 known fragments from ENDF/B.vii Total Reactor νe Spectrum: Daughter decay rate Sep. 5, 2016 Branching fracEon Branch spectrum Reactor An/neutrinos -­‐ D. Dwyer 2 The ‘Cast’ of Measurements Reactor νe Measurements Fission e-­‐ Measurements Fission and Nuclear Decay Measurements Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 3 Fission An/neutrino Emission Daya Bay: arXiv:1607.05378 Recent experiments: High sta/s/cs: 106 an/neutrinos Low background: ~1%-­‐level RENO: Neutrino2016 1.2M an/neutrinos Double Chooz: Neutrino2016 Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 4 Fission Electron Emission Measurements at ILL: Expose fission parents to thermal neutrons Measure total outgoing β-­‐ energy spectra Uncertain/es at the ~2%-­‐level Phys. LeV. B160, 325 (1985), Phys. LeV. B118, 162 (1982) Phys. LeV. B218, 365 (1989), Phys. Rev. LeV. 112, 122501 (2014) Phys. Rev. C83, 054615 (2011) Phys. Rev. C84, 024617 (2011) Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 5 -­‐
β Conversion Fission e-­‐ Measurements Vogel, Huber Phys. Rev. C76, 025504 (2007) Phys. Rev. C84, 024617 (2011) Nuclear correc3ons: Differ for e-­‐ and νe. -­‐ Coulomb -­‐ Finite nuclear size -­‐ Weak magne/sm -­‐ Screening -­‐ Radia/ve Sep. 5, 2016 AnEneutrinos Example: 117 X with E =10 MeV 46
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Electrons Reactor An/neutrinos -­‐ D. Dwyer 6 -­‐
β Conversion Fission e-­‐ Measurements Vogel, Huber Mueller et al. Phys. Rev. C83, 054615 (2011) Models predict νe rate and spectrum with ~3% precision. Fission and Nuclear Decay Measurements Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 7 Rate Discrepancy Measurement of total an/neutrino flux disagrees with models arXiv:1607.05378 a.k.a. The Reactor Anomaly: Phys. Rev. D83, 073006 (2011) Considered possible evidence of non-­‐interac3ng (sterile) neutrino states. Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 8 Spectrum Discrepancy RENO: Neutrino2016 Recent νe spectra also disagree with β-­‐ conversion models. Daya Bay: arXiv:1607.05378 Double CHOOZ: Neutrino2014 Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 9 Possible origins? What might cause the difference between the e-­‐ and νe spectra? Hayes et. al., Phys. Rev. D92, 033015 (2015) ✖ ✖ ✖ ✔ ✔ 1) Non-­‐fission sources of an/neutrinos 2) The forbidden nature of some beta decay transi/ons 3) 238U fission as a source of the shoulder 4) The rela/vely harder PWR neutron spectrum 5) A possible error in the in the ILL beta-­‐decay measurements Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 10 Summa/on Calcula/on Fission e-­‐ Measurements Vogel, Fallot, Sonzogni, Hayes, Dwyer+Langford Fission and Nuclear Decay Measurements Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 11 Here Be Dragons… Exis/ng nuclear databases have significant uncertain/es Missing Details: Are tabulated fission and decay data comprehensive? -­‐ Fission: What about possible very short-­‐lived unstable daughters? -­‐ Decay: 6% of yield has no corresponding ENDF decay informa/on eg. Phys. Rev. C24, 1543 (1981) Biased Data: Are there systema/c biases in the yield or beta decay data? -­‐ Uncertainty from assump/on of reactor equilibrium, parent fission rates. -­‐ Pandemonium Effect: Tabulated branches biased toward high-­‐endpoints. Beta Decay Shape Correc3ons: eg. Phys. Rev. LeV. 109, 202504 (2012) How do forbidden decay correc/ons impact spectrum? -­‐ Mismatch of decay ini/al-­‐final spin and parity can distort spectrum eg. Phys. Rev. LeV. 112, 202501 (2014) Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 12 Dominant Branches Eight dominant branches give 5-­‐7 MeV shoulder in the calcula/on. Calcula/on predicts ~42% of rate in 5-­‐7 MeV caused by these 8 beta decay branches. Dwyer and Langford, Phys. Rev. LeV. 114, 012502 (2015) Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 13 Dominant Branches Eight prominent branches cause 5-­‐7 MeV excess in the calcula/on. Energy Spectra: Allowed shape + IBD cross-­‐sec/on Uncertain3es: Fission Yield Branch frac/on 92Rb most significant If nuclear data accurate, calculated 5-­‐7 MeV shoulder seems robust. Are the fission yields and branching frac/ons accurate for these prominent branches? Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 14 Nuclear Data Woes Recent error found in ENDF/B.vii thermal fission yield tables. Sonzogni et. al., Phys. Rev. LeV. 116, 132502 (2016) Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 15 Missing Decays Fission daughter nuclei with unknown decays must be modeled. ~70% of daughters lack decay data, but only amount to ~5% of reactor yield. Hayes et. al., Phys. Rev. D92, 033015 (2015) Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 16 Inconsistent Databases Calculated spectrum depends on which nuclear database is used. Key difference: 96Y fission yield. Sep. 5, 2016 Hayes et. al., Phys. Rev. D92, 033015 (2015) Reactor An/neutrinos -­‐ D. Dwyer 17 Poten/al Measurements Fission Yields @ ILL (Lohengrin) Fission Yields @ LANSCE (NIFFTE) Total Absorp. Spec. @ IGISOL (DTAS) Precision νe Spectra at Research Reactors: Different fuel composi/on, neutron energy Total Absorp. Spec. @ ORNL (MTAS) STEREO, PROSPECT, etc. arXiv:1512.06656 Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 18 Total Absorp/on Spectroscopy Recent measurements of prominent daughters: 96gsY, 92Rb, 142Cs Rasco et. al., Phys. Rev. LeV. 117, 092501 (2016) MTAS Result 142Cs ENDF Predic/on Results in significant changes in β-­‐decay spectra of 142Cs and 92Rb See also IGISOL DTAS: Guadilla et. al., NIM B376, 334 (2016) Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 19 Summary Fission e-­‐ Measurements Rate Spectrum Origin? Different fission neutron energy? Problem with e-­‐ measurements? Rate? (Difficult) Spectrum? (Poten3al) Fission and Nuclear Decay Measurements Sep. 5, 2016 Reactor An/neutrinos -­‐ D. Dwyer 20