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Q 13 Measurement with Double Chooz

n e  n x. Q 13 Measurement with Double Chooz. ...chasing the missing mixing angle. IDM 2004. m 3. D m atm. m 2. D m solar. m 1. Disappearance ~ sin 2 (2  ik )sin 2 (  m 2 ik L/4E). CHOOZ. KAMLAND.

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Q 13 Measurement with Double Chooz

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  1. ne nx Q13 Measurement with Double Chooz ...chasing the missing mixing angle IDM 2004

  2. m3 Dmatm m2 Dmsolar m1 Disappearance ~ sin2(2ik)sin2(m2ikL/4E) CHOOZ KAMLAND • ne mixes via small mass difference Dmsolar and large mixing angle to other flavors • does it also mix via large mass difference (~Dmatm) mixing angle must be small (CHOOZ), but is it zero or not?

  3. ne nx Why reactors? The actual best limit is coming from a reactor experiment ! Chooz, Paolo Verde sin22Q < 0.2 Dm2 = 2 10-3 eV2

  4. Experimental method • Nuclear reactors are a powerful source of low energy (up to ~ 8 MeV) electron anti-neutrinos • Detection via inverse beta decay: • Q-value ~ 1.8 MeV • Ee~ En - Q (n spectroscopy) • suppress background via delayed coincidence method

  5. How to improve the sensitivity? • The problem: Reactor exp. = Disappearance exp. • compare total flux (and spectrum) with the • no- oscillation hypothesis • one depends on systematic uncertainties, like: • absolute source strength, • cross section, • detection efficiency, • fuel development over time...

  6. The basic idea: • Use 2 identical detectors • oscillation frequency basically known • monitor the reactor with the close detector (100m) (cancels also uncertainties like cross section, efficiencies etc.) Dm2 = ( 2.0 - 2.5 ) 10-3 eV2 • choose the right distance for the signal with the far detector L/2 ~ 1.0 km - 2.0 km osc.length L

  7. Improve sensitivity on sin2(2Q13) • to 0.02 – 0.03 • Statistics N(far) ~ 5 104 • energy uncertainty s(E) < 1% • normalization uncertainty srel < 1% • number of target protons • efficiencies (positron, neutron) srel excellent calibrations required...

  8. Additional uncertainties: • shape (~ 2%) • cross section (~ 1.9%) • should cancel ! • fuel composition (235U, 238U, 239Pu, 241Pu) • should cancel ! Bugey; comparison with spectrum deconvoluted from exp. determined beta spetra Feilitzsch, Schreckenbach; used for analysis of the Gösgen experiment

  9. Approach towards an experiment... • 3 workshops on „Future Low Energy n-Experiments“ • spring 2003 Alabama, USA • fall 2003 Munich, Germany • spring 2004 Niigata, Japan • White paper • thanks toMaury Goodman. • paper available hep-ex/0402041 • (or http://www.hep.anl.gov/minos/reactor13/white.html)

  10. Daya Bay

  11. Requirements on the Site for the Experiment: • Strong power plant • Shielding (300m.w.e. or better) for at least the far detector • Only one (or two) cores (=sources) preferred • Support from the power plant company

  12. CHOOZ Site

  13. Chooz (site of far detector)

  14. d~1.05 km • P~8.4 GW • 300mwe far detector • no excavation for far detector

  15. Detector design, Double-Chooz 6.7m 5.5m ) g-catcher, scintillator buffer, non-scintillating Muon Veto, scintillator ) ) PMs n-target Gd-scintillator 2.8m ) ) ) 2.4m 3.6m

  16. Sensitivity ? • sensitivity between 0.02 and 0.03 • for sin2 2Q after ~3 years (for Dm2 = 2.0 10-3 eV2 ) P. Huber et al. hep-ph/0403068

  17. Comparison to LBL-projects? P. Huber et al. hep-ph/0403068 • uncertainty in Q13 for LBL projects • - MSW effects in the earth • CP phase

  18. Background? • accidentalbackground • single rate, radio purity experiences from CTF, Chooz, KamLAND • not critical, determine online • correlated background (muon induced) • fast neutrons • beta - neutron cascades • in Chooz signal/background ~ 25 -> 100 (aim) • larger target (12m3) , better muon veto,

  19. Background Double-Chooz • Correlated background events: • Monte-Carlo simulation of fast neutrons, generated by cosmic muons • expected rate far detector (300mwe) ~ 0.15 / day • (lower than 0.3 / day at 90% cl) • signal / background far det. > 100 • expected rate close detector (60mwe) ~ 2 / day • signal / background close det. > 500 • (if distance is ~ 150m) • spectral shape of background quite flat (unequal to signal spectrum)

  20. Conclusions Search for Q13 with a new reactor experiment is very promising Double-CHOOZ sensitivity: sin2(213)<0.025-0.03, 90% C.L. (m2 = 2.0-2.5 10-3 eV2) Current limit: CHOOZ : sin2(213)<0.2  discovery potential ! „next future“ experimentsStrong Support for the EDF power company & local authorities to perform a 2nd experiment at ChoozApproved in France (2.2 – 2.5 M€,, detector costs 7M€ + civil engineering near site (EDF)) Large expertise available from low energy, low background projects (Chooz, CTF/Borexino, KamLAND) Collaboration: Saclay, APC, Subatech, TUM, MPIK, Tubingen Univ. Hamburg Univ., Kurchatov, Univ. Alabama, Univ. Tennessee, Univ. Lousiana, Univ. Drexel, Argonne,+ Italian groups soon …  (maxi-)letter of intent (May 2004)  final proposal end of 2004 Aim for start data taking ~ 2008

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