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Pre- n Factory Possibilities

Pre- n Factory Possibilities. Leslie Camilleri CERN, PH Scoping Study Meeting Imperial College May 6, 2005. Plan of talk.

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Pre- n Factory Possibilities

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  1. Pre- n Factory Possibilities Leslie Camilleri CERN, PH Scoping Study Meeting Imperial College May 6, 2005

  2. Plan of talk • The Past: excellent results from Solar, atmospheric, K2K and KAMLAND. • The Future: A Neutrino Factory some time in the future. I will talk about the “bridge” between the past and the nFactory. The interest: q13, the mass hierarchy, the CP phase d. • Near Future: T2K NOvA C2GT Reactors • Intermediate Future: SPL Beta beams But remember two persisting anomalies in n physics: LSND(High massnm to ne oscillations) and NuTeV(3s sin2qW)

  3. Near Future (Accelerators) T2K (Japan) 295km C2GT(CNGS beam) ~1200km NOnA (NUMI beam) 810km They look for nm~ neoscillations by searching for ne appearance in a nm beam. All three projects are Long Baseline Off-axis projects: Can dial energy of beam To maximum of oscillation

  4. Correlations: 8-fold degeneracy From M. Lindner: • q13 - d ambiguity. • Mass hierarchy two-fold degeneracy • q23degeneracy: sin2q23is what enters in the oscillation formula. • For sin2 2q23, say = 0.92, 2q23is 67o or 113 o and q23 is 33.5o or 56.5 (x1.5) • If we just have a lower limit on sin2 2q23: all values in between are possible

  5. Matter effects In vacuum and without CP violation: P(nm-ne)vac = sin2q23 sin2 2q13 sin2 Datm withDatm= 1.27 Dm232 (L/E) For Dm232 = 2.5 x 10-3 eV2 and for maximum oscillation: Must have: Datm = p/2 L(km)/E(GeV) = 495 For L = 800km E = 1.64 GeV, For L = 295km E = 0.6 GeV Introducing matter effects, at the first oscillation maximum: P(nm-ne)mat = [1 +- (2E/ER)] P(nm-ne)vac withER = [12 GeV][Dm232/(2.5x10-3)][2.8 gm.cm-3/r] ~ 12 GeV +-depends on the mass hierarchy. Matter effects grow with energy and therefore with distance. 3times larger (30%) at NOnA (1.64 GeV) than at T2K (0.6 GeV)

  6. T2K Detector 50 ktons (22.5 kton fiducial) Reconstructed Super- K T2K K2K 0.4 % intrinsic ne background at peak Must know it well Data taking: 2009 Near detector at 280m to measure flux before oscillation

  7. q13Sensitivity, correlations But, the limit on sin2 2q13 is much worse if we take into account correlations and degeneracies Sin2 2q13 ~ 0.04 -150 0 dCP150

  8. All degeneracies included T2K II: Hyper-Kamiokande One megaton Water Cerenkov and 4MW accelerator. Improvement by more than an order of magnitude on q13 sensitivity 0.01 sin22q13 0.001 -150o d +150o

  9. T2K II: Sensitivity to dCP Definition: For each value of sin2 2q13: The minimum d for which there is a difference Of 3s between CP and NO CP violation Limited by statistics d 50o 20o Limited because: CP violation asymmetry (n,n) decreases with increasing sin2 2q13 0.0001 0.01 Sin2 2q13

  10. NOnA Detector Given relatively high energy of NUMI beam, decided to optimize NOnAfor resolution of the mass hierarchy Detector: 14mrad (12 km) Off-axis of the Fermilab NUMI beam (MINOS). At Ash River near Canadian border (L = 810km) : New site. Above ground. Fully active detector consisting of 15.7m long plastic cells filled with liquid scintillator: Total mass 30 ktons. Each cell is viewed by a looped WLS fibre read by an APD 760 000 cells n

  11. MINOS Near detector n events, and Beam The NUMI beam is already functional ! MINOS NEAR detector has observed and reconstructed neutrino events. En • Expected proton intensity on target 6.5 x 1020 per year greatly helped by • cancellation of BTeV and foreseen end of collider programme in 2009. • Longer term: 8 GeV proton driver: 25 x 1020 protons per year: Phase II. If approved in 2006, First kiloton: 2009. Full completion: 2011.

  12. 3 s measurement limits for sin2 2q13 • 5 years Phase I (NO proton driver) Dm2 > 0 Dm2 < 0 NOnA Dm2 > 0 Dm2 < 0 T2K • NOnA alwaysMORE sensitive than T2K (about a factor of 1.4)

  13. Mix Neutrinos and Anti neutrinosComparison with Reactor • Neutrinos and anti neutrinos mix to have a more uniform dependence of the sensitivity on d. • Proton driver brings a factor of 2 more sensitivity • Comparison with reactors, shows NOnA always MORE sensitive.

  14. Resolution of mass hierarchy • Fraction of dover which the mass hierarchy can be resolved at 2s. • Equal amounts of neutrino and antineutrino running: 3 years each assuming Phase I. • Near the CHOOZ limit the mass hierarchy can be resolved over 50% of the range of d. • T2K can onlyresolve the hierarchy in a region already excluded by CHOOZ. (Because of its lower energy). • Some small improvement if we combine T2K and NOnA results T2K CHOOZ limit

  15. Looking further ahead • With a proton driver, Phase II, the mass hierarchy can be resolved over 75% of d near the CHOOZ limit. • In addition to more protons in Phase II, to resolve hierarchy a second detector at the second oscillation maximum can be considered: • Datm= 1.27 Dm232 (L/E)= 3p/2. • L/E = 1485, a factor of 3 larger than at 1st max. For ~ the same distance, E is 3 times smaller: matter effects are smaller by a factor of 3 • 50 kton detector at 710 km. • 30km off axis (second max.) • 6 years (3n + 3 n) Determines mass hierarchy for all values of d down to sin2 2q13 = 0.02

  16. CERN to Gulf of TARANTO • The CNGS beam continues SOUTH: beyond the Gran Sasso • Goes over the Gulf of Taranto. • A detector in the Gulf would be 40km OFF-AXIS. • And at a distance of ~1200km would be appropriate for the SECOND oscillation maximum. • Immersed in the sea at a depth of 1000m Required n energy:0.8 GeV Implies a modified lower energy CNGS beam Incompatible with OPERA running

  17. CERN to Gulf of TARANTO: C2GT Viewing distance of ~ 20m. Fiducial mass: 1.5 Mton High pressure glass container • Basic Unit: 380mm diameter HPD with a cube of 5 Si sensors: • One on each of 5 faces of cube :Uniform 110o angular acceptance. Cube 5 Si sensors 10m x 10m Radius 150m Proton intensity(rep. rate of accel.) and Flux (Proportionaltog2) make C2GT less competitive Waiting for OPERA completion also a problem

  18. q13 with Reactors • The best limit comes from a reactor experiment: CHOOZ. • Energetically impossible to produce a m fromnm’s, in an appearance experiment. • Technique: anti-ne disappearance experiment Pee = 1 – sin2 2q13sin2 [(Dm232L)/(4En)] near oscillation maximum Advantage: NO dependence ondCP oron mass hierarchy: No ambiguities. Disadvantage: Cannot determine them! Measured through inverse b decay: ne + p = e+ + n Measure e+ and n (capture in gadolinium or scintillator): Reconstruct n energy Look for Distortion of the ne energy spectrum Effects are SMALL :Must know neenergy spectrum well to control systematics. Solution: Use a FAR detector to search for oscillations (1700m) and a NEAR detector to measure spectrum BEFORE oscillations(170m).

  19. Acrylic Gamma catcher vessel Liquid scint. (R = 1,8m, H = 4 m, t = 8mm) LS + 0,1%Gd LS Muons VETO (shield) Thickness = 150mm Example: Double Chooz detector AcrylicTarget vessel Liquid scint+Gd (R=1,2m,h=2,8m, t = 12mm) Non-scintillating Buffer: Water

  20. Systematics Improvements over CHOOZ • Two detectors: Reactor power and cross sections, Energy per fission : Negligible. • Thicker non-scintillating buffer: Smaller singles rate allows e+threshold of 0.5 MeV wellbelow the lowest possible 1.02 MeV. No Uncertainty due to Threshold. • Target mass: Only Relative mass needed. Will be measured by weighing filling vessel Before and After fill. Total 2.7% 0.6%

  21. Far detector starts Near detector starts 2004 2005 2006 2007 2008 2009 2003 Site Proposal & design Construction ? Data taking Schedule and Sensitivity Near det. ready Far det. ready Importance of Systematics 1% 0.4% 0.02 10 x run time only gains x 2 in sensitivity Near det. ready

  22. Superconducting Proton Linac • Power : 4 MW • Kinetic Energy : 2.2 GeV (3.5 GeV) • Repetition Rate: 50 Hz • Spill Length: 11 msec. • Accumulator needed to shorten pulse length. • Target: Liquid Mercury Jet to cope with stress due to high flux. • Focusing: Horn and Reflector optimized for 600 MeV/c particles • Decay Tunnel: 20m long 1m radius • Neutrino energy to be at oscillation maximum for Dm232 = 2.5 x 10-3 eV2260 MeV • Distance: 130km • Location: New lab in Frejus tunnel • Detector mass: 440 kton fiducial. • Type: Water Cerenkov (Super-K)

  23. Optimization of Proton beam energy J.E. Campagne, A. Cazes hep-ex/0411062 Angle of emission of Pions (0.5 < pp < 0.7 GeV/c)/s 3.5, 4.5 GeV 2.2 GeV 2.2 GeV Horn acceptance < 25o More at 3.5.4.5 GeV. Higher n flux. 20% Increase in significance Better sensitivity at 3.5, 4.5 GeV

  24. Optimization of the neutrino energy • Modify horn • Profitable to go to 350 MeV Instead of 260 MeV 350 MeV

  25. Advantage of mixing neutrino and antineutrino running • 3.5 and 4.5 GeV proton beam • 260 and 350 MeV options • 5 years of n running. • 2 years of n running and 8 years of n running The limit IMPROVES near d = 90o

  26. Idea introduced by Piero Zucchelli. Accelerate radioactive ions decaying via b+ or b-. Because of Lorentz boost, the decay electron neutrinos or antineutrinos will be focused forward into a beam. Look for: Appearance of nm ornm Advantages: “Clean” beams with no intrinsicnmcomponent. Precisely calculable energy spectra. Energy of beam tunable through acceleration of ions. • Accelerate protons in SPL • Impinge on appropriate source • Bunch resulting ions (atmospheric n’s) • Accelerate ions in PS and SPS. • Store in decay ring. 8 bunches. • Favourite scheme: • 6He 6Li + e- + ne 18Ne 18F + e+ + ne Half lives: 0.8 sec and 0.64 sec. Stored together if g(18Ne) = 1.67 g(6He) Detector: Same as for SPL (Frejus) Beta beams

  27. d sensitivity for g = 60,100 M. Mezzetto SPSC Villars Statistics limited 2% Syst. Unc. Limited because CP violation Asymmetry decreases with increasing q13 Down to 30o 2.9 x 10186He ions and 1.2 x 1018 18Ne ions per year decaying in straight sections

  28. Optimization of g • J. Burguet-Castell, hep/ph/0503021 and M. Mezetto. • Not necessary to store the 2 ion types simultaneously: 4 bunches each. • Store 8 bunches of given type at a time and run each type half as long as in joint run. • Frees from g(18Ne) = 1.67 g(6He) constraint. • Assume number of ions stored is INDEPENDENT of energy. • Different schemes tried, all leading to higher energies. This is profitable because: • Higher event rates because of larger cross sections. • Better directionality: lower atmospheric background. • Signal events are in a region of lower atmospheric rate. • Fermi motion relatively less of a problem: better correlation between reconstructed and actual neutrino energy. • Can analyze energy dependence of appearance Events instead of just counting them.

  29. g = 60,100 scheme Fix baseline at Frejus 30o 150 q13 = 8o • 99% CL on d improves from > 30o to > 15ofor a symmetric g > 100 scheme. • The q13sensitivity improves a little. g= 100 d = 90o d = -90o

  30. Fix g at maximum SPS value: 150. d q13 = 8o 300 km • For this g the optimum distance is 300 km • The 99% CL dreach can be improved from 15oto 10o. • and the q13 sensitivity can also be improved substantially But no existing laboratory at this distance! 10o L(km) L( 60,100 130km sin22q13 150,150 300km

  31. Combining SPL and Beta beams SPL + b (130km) SPL b Both • The b beam is more sensitive than an SPL beam. • The b beam only requires the SPL for 10% of its up time. • Can therefore run of an SPL beam at the SAME TIME as the b beams. • The combination improves over the b beam alone.

  32. Systematic uncertainties Must be kept at the 2% level • Most important ones: • Target mass difference between near and far detectors. • Uncertainty on n and n cross sections (will be measured by near detector)

  33. T2K II vs Beta d T2K II b 150 sin22q13 T2K II b 150 sin22q13 d T2K Phase IIandb beam(g = 150)have very similar CP reach and sin2 2q13sensitivity.

  34. (Personal) Conclusions • Accelerator physicists must be encouraged to produce detailed studies of SPL and b beams scenarios. • Many options are still possible. Some optimizations are only days old. Work in progress. • Double Chooz, could be first to go, but its physics is limited. • T2K, will be next, and will include the physics of the reactor experiment. • NOnA, provided it gets an early approval, has the most extensive physics reach, in particular a first look at the mass hierarchy.

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