1 / 18

Group 3 – Cheryl, Wojtek, and Sandy

Group 3 – Cheryl, Wojtek, and Sandy. Question 14: Reactor Neutrino Experiments and the 3% flux shift. What is the influence of 3% shift in flux on reactor neutrino experiments?. Double Chooz re-evaluated reactor antineutrino flux (arXiv 1101.2663)

maude
Télécharger la présentation

Group 3 – Cheryl, Wojtek, and Sandy

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Group 3 – Cheryl, Wojtek, and Sandy Question 14: Reactor Neutrino Experiments and the 3% flux shift

  2. What is the influence of 3% shift in flux on reactor neutrino experiments? • Double Chooz re-evaluated reactor antineutrino flux (arXiv 1101.2663) • previous procedure used a phenomenological model based on 30 effective beta branches • new analysis used detailed knowledge of the decays of 10,000+ fission products • New calculation results in overall flux increase of 3.5% in reactor anti-neutrinos

  3. Compare old to new flux results The old data used to be up here with the old flux calculation (clustered around 1.0) T. Lasserre INSS 2011 Purple line: ratio neutrinos Nobs/Nexpected = 1.0

  4. Compare old to new flux results This is the set of corrected data T. Lasserre INSS 2011 Purple line: ratio neutrinos Nobs/Nexpected = 1.0

  5. Compare old to new flux results T. Lasserre INSS 2011 Purple line: ratio neutrinos Nobs/Nexpected = 1.0 However, these analyses were NOT blind… EXCEPT Bugey-3 and Bugey-4 (mostly)

  6. "Reactor Antineutrino Anomaly" • Common bias in systems • Scintillator counters • Integral detectors • Neutrons captured • Metal loaded scintillators • Proportional counters • Isotope composition (mostly the same) • Other systematics? • Other physics reasons?

  7. Effects on experiments • Daya Bay & RENO: • Uses near and far detector to calculate ratios • Both detectors are affected by 3% flux change • Flux effect is mostly canceled • Double Chooz: • Single detector experiment = affected • Can "normalize" to another experiment (such as Chooz using Bugey-4 results) • Minimally affected if far detector combined with near detector (in progress) to create ratio

  8. What is effect of flux on Chooz? • Result of experiment (q13) depends upon ratio of actual/expected events • Expected flux is higher -> ratio is lower • Expected flux affects cross section measurements from low-energy experiments

  9. Effect on Chooz (cont) • Chooz had to choose which cross section to use because it didn't have a near/far detector • They originally decided to use Bugey-4 cross section (smallest error, most blind result) • This also agreed with the "averaged" cross section from the short baseline experiments • However, new flux caused 5% change in Bugey-4 cross section value • Thus, Chooz decided to use predicted cross section with bigger errors • Chooz result of ratio actual/expected events changes from 0.98 to 0.96 with reevaluation

  10. Effect on Chooz (cont) NEAR blind analysis? FAR q13 Daya Bay, RENO, Double Chooz T. Lasserre INSS 2011 Red = using cross section expected from new flux Blue = using cross section from measurements

  11. Effect on Chooz (cont) • Reevaluation of low-energy experiments indicates something might be going on • One possibility is there is one (or more?) "sterile" neutrino(s) involved • But, the required |Dm2| for one sterile neutrino is significantly larger than those required by solar and atmospheric experiments • |Dm2| > 1 eV2 New terms

  12. Effect on Chooz (cont) Dotted line = 3 neutrinos with mixing Solid line = 3+1 sterile n with mixing Need more (blind) analyses to determine what is going on Kamland T. Lasserre INSS 2011

  13. Effect on Chooz (cont) Blue = Recalc with 3 neutrinos ->higher upper bound on sin2(2q13) Green = Recalc with 3+1 sterile neutrinos ->more in agreement with the experimental results T. Lasserre INSS 2011

  14. Sterile Neutrino Hypothesis Best X2 fit (95%): sin2(2qnew) ~ 0.14 Dmnew2 > 1.5 eV2

  15. Give arguments for/against reevaluating Chooz limits • Chooz and Double Chooz are (currently) single detector systems (not using near/far ratio) • More affected by flux difference • Chooz used previous experiment result as their baseline for the ratio • Both are affected roughly the same, effect cancels • Chooz experiment already reevaluated their results (thus it must have been a good idea)

  16. Give arguments for/against reevaluating Chooz limits • Chooz and Double Chooz are (currently) single detector systems (not using near/far ratio) • More affected by flux difference • Chooz used previous experiment result as their baseline for the ratio • Both are affected roughly the same, effect cancels • Chooz experiment already reevaluated their results (thus it must have been a good idea) • We students agree with the experts

  17. References • "The Reactor Antineutrino Anomaly", arXiv 1101.2755, March 2011 • "Improved Predictions of Reactor Antineutrino Spectra", arXiv 1101.2663, March 2011 • "Double Chooz: Searching For q13 With Reactor Neutrinos", arXiv 1105.6079, March 2011 • "Evidence of q13 > 0 from Global Neutrino Data Analysis", arXiv 1106.6028, June 2011

  18. Questions?

More Related