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Overview for an European Strategy for neutrino Physics Yves Déclais CNRS/IN2P3/UCBL IPN Lyon

Overview for an European Strategy for neutrino Physics Yves Déclais CNRS/IN2P3/UCBL IPN Lyon. CHIPP – Neutrino CH – June 22th - Neuchatel. Measuring the neutrino mixing matrix Reactor experiments NUMI off axis Combined sensitivity for JPARC, NUMI and reactors Conclusions. θ sol. θ atm.

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Overview for an European Strategy for neutrino Physics Yves Déclais CNRS/IN2P3/UCBL IPN Lyon

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  1. Overview for an European Strategy for neutrino Physics Yves Déclais CNRS/IN2P3/UCBL IPN Lyon CHIPP – Neutrino CH – June 22th - Neuchatel • Measuring the neutrino mixing matrix • Reactor experiments • NUMI off axis • Combined sensitivity for JPARC, NUMI and reactors • Conclusions

  2. θsol θatm θ13, δ Neutrino Oscillation : 3 neutrinos formalism

  3. Oscillation phase • Matter effect sensitive to : • Sign of Δm213 • neutrino versus anti-neutrino 2-3 10-2 The oscillation probability including matter effect All effects are driven by θ13 ! Neutrinos + Anti Nu - dominant « on peak »

  4. Neutrino Mixing Matrix Study : which Road Map

  5. Nuclear reactors are a very intense sources of νe deriving from the b-decay of the neutron-rich fission fragments. • A typical commercial reactor, with 3 GW thermal power, produces 6×1020ne/s From Bemporad, Gratta and Vogel Arbitrary Observable n Spectrum • The observable ne spectrum is the product of thefluxand thecross section. • The spectrum peaks around ~3.6 MeV. • Visible “positron” energy implies ν energy Cross Section Flux Eν = Ee + 0.8 MeV ( =mn-mp+me-1.022) • Minimum energy for the primary signal is 1.022 MeV from e+e−annihilation at process threshold. • Two part coincidence signal is crucial for background reduction. Nuclear reactors as neutrino source

  6. There are two types of background… • Uncorrelated − Two random events that occur close together in space and time and mimic the parts of the coincidence. • This BG rate can be estimated by measuring the singles rates. • Correlated − One event that mimics both parts of the coincidence signal. • These may be caused fast neutrons (from cosmic m’s) that strike a proton in the scintillator. The recoiling proton mimics the e+ and the neutron captures. • Or they may be cause by muon produced isotopes like 9Li and 8He which sometimes decay to β+n. • Estimating the correlated rate is much more difficult! Backgrounds in reactor neutrinos experiment

  7. How to improve the sensitivity • Reactor exp. = Disappearanceexp. • 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... • Basic idea: • use 2 identical detectors to cancel uncertainties on neutrino flux and cross sections • excellent monitoring of calibrations and efficiencies (including analysis cuts) • to reduce the systematics on detectors • large statistics to see small effects

  8. Proposed sites Many Sites have been investigated as potential hosts to a reactor neutrino experiment. This is appropriate since getting the cooperation of the reactor company is the main challenge.

  9. Far detector : using existing infrastructure from the previous experiment @ 1050 m 2 identical detectors goal : σrelative  0.6% Double-Chooz : site • LOI : hep-ex/0405032 • detector cost 7.5 Meuros • civil engineering ~5 Meuros (not studied) • LOI accepted • need for a proposal within 6 months Near detector @100-200 m from the nuclear cores in discussion with EDF

  10. Same concept as CHOOZ : • the target mass is defined by • the Gd loaded scintillator mass • the efficiency is defined by neutron capture • efficiency on Gd 7 m Target cylinder (f = 2.4m, h = 2.8m) filled with 0.1%Gd loaded liquid scintillator (12.7 Tons) Gamma catcher inside Acrylic Vessel, thickness : 60cm Non scintillating buffer new ! mechanical structure to house PMTs Muons VETO of scintillating oil , thickness :60 cm Shielding : main tank , steel thickness 15cm 7 m 7 m existing pit Double CHOOZ : detector structure • Performances (expected): • S/B : 10  100 • target : 5.5  12.7 m3 • analysis errors : 1.5%  0.2% • But the changes would probably worsen the bkgd: • large increase of passive material (including high Z) • active target less protected • due to the increase of the target volume

  11. LENS R&D  new metal β-diketone molecule (MPIK) • Stable: 0.1% Gd-Acac (few months) • Baseline recipe ~80% mineral oil + ~20% PXE + Fluors + wavelenght shifters • In-loaded scintillators (0.1 %, 5% loading) are counting @Gran Sasso • Spare stable recipes available (MPIK, INFN/LNGS) Stability 0,1 % Gd in PXE 3+Gd Gd-Acac molecule • Completion of the R&D first half of 2004 • Choice of the final scintillator • Stability & Material compatibility  Aging tests (MPIK, Saclay) Double CHOOZ : Gd loaded scintillator Warning : long term stability and acrylic vessel damage

  12. ~10-15 m Overburden ~50mwe Dense material Additional water buffer around the detector Double CHOOZ: close detector • similar conditions to PaloVerde (46 mwe) • large dead time for muon veto : 50% • can a massive detector work at such a shallow depth ? • PaloVerde and Bugey was segmented • and used dedicated signature for neutron and positron

  13. Double CHOOZ : Background and signal Ratio at the far detector The baseline is too short to see the L/E pattern • no direct measurement • accidental miscorrection • may mimic or suppress an effect • fake neutron capture signal rate underestimated

  14. The sensitivity may be pushed lower with large detectors sensitive to a shape deformation. sin22θ13 Sensitivity Fit uses spectral shape only 90%CL at Δm2 = 3×10-3 eV2 Statistical error only From Huber, Lindner, Schwetz and Winter Exposure (GW·ton·years) The location of the transition from rate to shape depends on the level of systematic error. Reactor experiment sensitivity

  15. 3 10-2 Double CHOOZ sensitivity To be conclusive a reactor experiment which intend to reach few 10-2 in sin22θ should be able to show an L/E effect according to the value of δm2 ( which will be known at a high level of accuracy ) and to the disappearance rate measured

  16. NUMI off-axis

  17. NOVA detector : TASD 160 M$ νe + n  p + e- + π0

  18. Goals of the NOνA experiment • sensitivity to sin2(2θ13) down to ~0.01 • measurement of sin2(2θ23) to 2% accuracy • contribute to resolution of mass hierarchy via matter effect • contribute to study CP violation in the neutrino sector • NC background reduced by a narrow band beam (off axis) • increase mass with cost/kiloton reduced by a factor 3 • sampling 1/3 X0 per plane for better electron id • choose long baseline to enhance matter effects For 5years @ 4 1020 pot/year, 50kton detector, sin2(2θ13) = 0.1

  19. Nova : tentative schedule MINOS run ? (goal : 16. E20 pot • 5 M$/year to improve proton intensity: • Booster cycle 3  7-10 hz • decrease losses • …

  20. N0νA sensitivity

  21. MassHierarchy

  22. CPViolation

  23. Reactor contribution to CP violation (Shaewitz) • Input: • sin22θ13=0.058 • δCP = 270° • sin22θ23=10.06

  24. Atmospheric neutrino measurements are sensitive to sin22θ23 But the leading order term in νμ→νe oscillations is If the atmospheric oscillation is not exactly maximal (sin22θ23<1.0) then sin2θ23 has a twofold degeneracy sin22θ23 sin2 sin2θ23 θ 45º θ 2θ 90º 2θ The θ23 Degeneracy Problem

  25. Solving the θ23 degeneracy with reactor (Shaewitz) • Input: • sin22θ13=0.058 • δCP = 270° • sin22θ23=10.06

  26. European Strategy (Venice , december 03)4 phases program for q13and d • CNGS/MINOS (2005-2010) • 2) JPARC and Reactor(?) (2008-2013) • 3) Superbeam/betabeam (>2014 ) • 4) Neutrino factory (>2020 ) • Are Phase 3 (and 4) needed in case of a signal seen in JPARC • Can we disentangle all parameters with the superbeam /betabeam option • Should we go directly to phase 4 in case of no signal seen in JPARC • shift in time for Superbeam/betabeam due to funding profile in Europe • is the low energy the optimum choice to measure Θ13 , δ , sign(Δm2) • the choice on the strategy defines not only the needed R&D on accelerators but also for the detectors In any case a MW machine is central

  27. Concluding on european activities (and dreams …) could be provided by Nuclear physics • Concluding remarks by CERN management at MMW • CERN will reimburse LHC loan up to 2011 • in 2008 new round of negotiations with members state • for support for new R&D (not only neutrinos …) • CERN machines (quite old) upgrade will cost • Staff number will decrease from 2500  2000 in 5 years More international coordination is mandatory Cost in Meuros no manpower, no contingencies The choice will imply consequences on Machines AND Detectors R&D

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