Review of Neutrino Coherent Scattering Belkis Cabrera-Palmer March 20, 2009

1. Review of Neutrino Coherent Scattering Belkis Cabrera-Palmer March 20, 2009 Sandia National Laboratories Lawrence Livermore National Laboratory

2. Outline • physics of neutrino coherent scattering • cross section and rates • NPP monitoring • solar neutrino background

3. Neutrino Coherent Scattering ,k’  ,k Z R N, q It has never been observed!

4. q <<   • Same for all neutrino flavors R, M, Z,N • Cross section enhanced by N2 (N is # of neutrons) T, • Estimation of events for reactor neutrinos: Cross section • Coherence applies when momentum transfer 1/R(Germanium) ~ 38 MeV 1/R(Argon) ~ 47 MeV 

5. I ~ hundreds of eV Challenges: small recoil energy and smaller ionization energy • the nucleus recoil energy is • for heavy nuclei, the recoil energy is in the few keVs: • quenching: detectable ionization energy is just a fraction of the recoil energy

6. the cross section increases with neutrino energy: but …there are fewer reactor neutrinos at higher energies • the detectable recoil energy threshold constraints the access to lower neutrino energies, since, to produce an event with energy I, the minimum neutrino energy is Germanium target Challenges: fewer reactor neutrinos at larger energies

7. Uranium yields 65% more neutrinos with E>8MeV than Plutonium 52% Uranium fission produces 67% more events with I> 300eV than Plutonium fission 57% Estimation of Events per eV, day, kg(Ge) vs. the minimum neutrino energy E that produces recoils with Reactor neutrino spectra Neutrinos per MeV fission from Uranium and Plutonium From: Klapdor, Metzinger PLB 112,1 (1982)

8. Sensitivity to NPP fuel composition About 20% variation in total events during a Nuclear Power Plant fuel cycle ~20 %

9. Estimated number of counts/day kg above threshold with a Germanium Detector A 100eV-improvement in detector threshold produces a large reduction in detector size. Scale of a Coherent Scattering Detector

10. Estimated counts/day kg above threshold with Germanium The solar neutrino background is comparable with the reactor neutrino signal at distances >1.5 km from the reactor core. The solar background prevents or at least greatly complicates using coherent scatter detectors as standoff reactor monitors beyond a kilometer or so. Comparison to solar neutrino background Detector

11. Conclusions • Neutrino Coherent Scattering … • is hard to detect since the detectable fraction of the released energy is less than few hundreds of eV, • requires detector with very low noise threshold, • can be used for NPP monitoring since it is sensitive to fuel composition.

12. Muito obrigada.