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Neutrino Ocillations and Astroparticle Physics (2)

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  1. Neutrino Ocillations and Astroparticle Physics (2) John Carr Centre de Physique des Particules de Marseille (IN2P3/CNRS) Pisa, 7 May 2002  Neutrino Oscillations - Solar Neutrinos - Atmospheric Neutrinos - Reactor and Accelerator data Experiments - Super-Kamiokande - SNO - LSND/KARMEN - Opera/ Icarus - ANTARES

  2. Time dependence: 2(t) = exp(-iE1t) 2(t) (t) 2 = 1 – sin2 (2 ) sin2 (E2 –E3 )/2 t Neutrino Oscillations Neutrino weak eigenstates (e,, ) are mixtures of mass eigenstates (12,3, ) If masses m1, m2, m3 non-degenerate get mixing eg. for 2 flavours:   cos 23 – sin 23 sin 23 cos23 2 3 = where 23 is mixing angle Probability oscillation   = 1 – sin2 (2 ) sin2 (m2 L /4 E ) where m = (m2 –m3) is neutrino mass difference L is distance travelled, ‘oscillation length’ E is average energy

  3. History of Neutrino Oscillations Theory 1967 Predicted by Pontecorvo Experiments 1968 - ‘ Solar Neutrino Problem ’ 1988 - ‘ Atmospheric Neutrino Anomaly ’ 1970 - Searches at accelerators and nuclear reactors >2004 ‘ Long Baseline Experiment ’ >2010 ‘ Neutrino Factories ’ Only in past couple of years has the situation become clear and situation understood

  4. Oscillation Length Oscillation probability: P(1  2 )= sin22q sin2(1.27 m2L /E), m mass difference, mixing angle E energy of , L oscillation length sin22q L = 4 E/ m2 Source Energy, E Oscillation Length, L m2=1eV m2=10-3 eV m2=10-11 eV 100 GeV 5 GeV 30 MeV 4 MeV 0.2-10 MeV 1-10 GeV 250 km 13 km 75 m 10 m 2.5  105 km 1.3  104 km 75 km 10 km 1.3  104 km 2.5  1013 km 1.3  1012 km 7.5  109 km 1.0  109 km 1.5  108 km Accelerator beam Reactor Sun Atmosphere

  5. Neutrino Oscillations in MatterMSW effect Mikheyev-Smirnov-Wolfenstein: enchancement in matter Evolution in vacuum: Neutrino interactions in matter: depends on Ne electron number density Evolution in matter:

  6. MSW effect for constant Ne Oscillations in matter: Oscillations length scale change: Oscillations amplitude modified: Resonance condition: Maximum oscillation amplitude:

  7. MSW effect: Variable Ne P(1  2 ) E/m2 Modifications different for different energies

  8. Present Situation (Last Year !) Excluded regions Allowed regions

  9. Solar Neutrinos

  10. Solar Neutrino Reactions

  11. Standard Solar Model Experiments have different E thresholds Sensitive to  from different reactions

  12. ‘ Solar Neutrino Problem’ HOMESTAKE e + 37Cl  37Ar + e : threshold 0.8 MeV, sensitive to Be and B solar neutrinos  0.3 of Standard Solar Model GALLEX e + 71Ga  71Ge + e : threshold 0.2 MeV, sensitive to pp solar neutrinos  0.6 of Standard Solar Model

  13. Super-Kamiokande 1) Size:Cylinder of 41.4m (h) x 39.3m (d) 2) Mass:50,000 tons of pure water 3) Light Sensitivity:11,200 photomultiplier tubes 4) Energy Resolution : 2.5% (at 1 GeV) at 16% (at 10 MeV) 5) Energy Threshold:5 MeV 6) Location:Kamioka-cho, Yoshiki-gun, Gifu-ken (1,000m underground at the Mozumi mine of the Kamioka Mining and Smelting Co.)

  14. Super-Kamiokande: Solar Neutrinos x + e  x + e : threshold 5 MeV, sensitive to B solar neutrinos Image of sun with neutrinos Excellent angular resolution

  15. Super-Kamiokande: Solar Neutrinos x + e  x + e : threshold 5 MeV, sensitive to B solar neutrinos  0.5 of Standard Solar Model

  16. Summary of Solar Neutrinos

  17. Believe SSM ? Structure of sun ? - helioseimology data precise - experts convinced OK Nuclear Cross-Sections - not all well known - new experiments in prgress Many Calculations Agree

  18. Solar Neutrino Oscillation Summary ( 1 year ago) Vacuum Solutions MSW Solutions

  19. Sudbury Neutrino ObservatoryFirst results 2001, New results April 2002

  20. Sudbury Neutrino Observatory 2092 m to Surface (6010 m w.e.) 17.8 m Diameter Support Structure for 9456 20 cm PMTs ~55% coverage within 7 m 12 m Diameter Acrylic Vessel 1000 Tonnes D2O 1700 Tonnes Inner Shielding H2O 5300 Tonnes Outer Shield H2O Urylon Liner and Radon Seal

  21. Typical SNO event

  22. D2O Backgrounds Target Level • Equivalent of 7% SSM neutrons Measurement Techniques • Radiochemical assays • In-situ Cerenkov measures Status  at or below target level

  23. Different Reactions in SNO Charged-Current (CC) e only e + d  e- + p + p Elastic Scattering (ES) x, but enhanced for esince (e)  7 () x+ e-  x + e- Neutral-Current (NC) all x x+ d  x+ n + p

  24. SNO Run Sequence I. Pure D2O CC, ES some NC n+d  t+  ... (E= 6.25 MeV, n~24%) II. D2O+NaCl CC, ES (added salt) enhanced NC n+35Cl  36Cl+ ∑ (E ∑= 8.6 MeV, n~45% above threshold) III. D2O+NCDs Concurrent CC, NC, ES (3He proportional counters) n+3He  p+t  event by event separation (n~37%)

  25. First Solar Neutrino Results from SNO Solar Angle Distribution Teff≥6.75 MeV and Rfit≤550 cm Energy Spectrum Teff≥6.75 MeV and Rfit≤550 cm derived from fit without constraint on 8B shape CC Spectrum Normalized to Predicted 8B Spectrum Teff≥6.75 MeV and Rfit≤550 cm With correlated systematic errors

  26. New Solar Neutrino Results from SNO Fluxes from fit:

  27. Flavour Composition of 8B Flux SNOCC = 1.76 ± 0.06 ± 0.09 SNOES = 2.39 ± 0.24 ± 0.12 SKES = 2.32 ± 0.09 SNONC = 5.09 ± 0.44 ± 0.45 e= 1.76 ± 0.05 ± 0.09 ,= 3.41 ± 0.45 ± 0.46 Evidence for appearance of e   at significance of 5.6 ( All previous evidence for disappearance e  ? )

  28. SNO Day-Night Effect Signal Day-Night Asymmetry (%) CC + 14.0 ± 6.3 ± 1.4 ES  17.4 ± 19.5 ± 2.3 NC  20.4 ± 16.9 ± 2.4 Supports MSW LMA oscillation solution

  29. Allowed Oscillation Solutions night day

  30. Effect of SNO Data on Allowed Oscillations

  31. MC data n n n + + + n n n m m m m m m n n n + + + n n n e e e e e e p Atmospheric neutrinos p   L= down10-30 km nm nm ne L=up to 13000 km Ratio : at low energy, higher at high energies (less  decay ) = ~ 2 error in absolute flux ~20%, but   / e ratio~5% Neutrino oscillations : 1 R = - measured ~ 0.6 by IMB and Kamiokande

  32. Zenith angle distribution(1D) Vary oscillation length L by varying zenith angle  En=0.5GeV En=3GeV En=20GeV For En> a few GeV, Upward / downward = 1 (within a few %) Up/Down asymmetry for neutrino oscillations

  33. Event Types in Super-Kamiokande Contained events Upward through-going muons Upward stopping muons Interaction in the rock Contained events Stopping muons through-going muons

  34. Zenith angle distributions SK Multi-ring event analysis No oscillation Best fit (Dm2=2.0x10-3eV2, sin22q=1.00) Sub-GeV multi-ring m-like sample 0.6 GeV < E < 1.33 GeV cosq Multi-GeV multi-ring m-like sample E > 1.33 GeV cosq

  35. Upward through-going muons SK Data 1416 events / 1268 days No oscillation: c2(shape)=18.7 / 10 d.o.f. (prob.=0.044) Osc. best fit (Dm2=5.2x10-3eV2,sin22q=0.86) Upward stopping muons 345 events / 1247 days No oscillation: (Bartol, GRV94) R = 0.65  0.04  0.09 << 1 clear oscillations Oscillation (Dm2=3.2x10-3eV2,sin22q=1.00)

  36. Super-K Allowed Region (Global fit all event types) 79.3 kt . yrs Within physical region; 2 minimum = 157.5/170 dof at sin22q = 1.0, Dm2 = 2.510-3 eV2 With unphysical region; 2 minimumu = 157.4/170 dof at sin22q = 1.01, Dm2 = 2.510-3 eV2

  37. No Oscillations but Neutrino Decay? Fit with neutrino decay 2 = 221/153 dof oscillations = 147/153 clearly favoured ( Also sterile neutrinos disfavoured by 0 data )

  38. Super-Kamiokande Damaged 2001 80% of photomultipliers broken, will be repaired by Nov 2002

  39. SNO Atmospheric Neutrino Analysis So far only preliminary, no conclusion …..

  40. K2K

  41. K2K Event K2K event selection at SK • No pre-activity in 30msec • p.e. in 300ns window > 200 • OD Nhit in largetst cluster<10 • Deposite Energy > 30MeV • Fiducial cut (distance from wall>2m)

  42. K2K Data

  43. K2K Observed vs Expected K2K consistent with Super-Kamiokande

  44. Reactor and Accelerator Experiments Excluded region from Karmen Allowed region from LSND

  45. Medium baseline neutrino oscillation searches LSND: MeV decay at rest MeV decay in flight Final results, 1993-98 data event excess, evidence for oscillations KARMEN: MeV decay at rest Results based on 75% of expected data, Feb 97 - Mar (Nov) 00 experiment ended March 2001 no excess, does not confirm LSND, but does not rule it out either MiniBooNE: MeV Under construction first data summer 2002 8 GeV protons, 3 GeV

  46. LSND and KARMEN experimental scheme muon decay at rest appearance experiment detect prompt e track, 20<Ee<60 MeV neutron capture: 2.2 MeV, 8 MeV g correlated in position and in time with e no B-field, e and g sequence distinguishes e+ from e-

  47. LNSD Results Evidence for oscillations

  48. KARMEN Results

  49. MiniBooNE At Fermilab starting soon….. Search for appearance disappearance With L/E~1 (same as LSND) but at order-of-magnitude higher energies

  50. Medium Baseline Summary LSND observes appearance of oscillations at relatively high and low mixing angle KARMEN does not confirm LSND, but does not rule it out. MiniBooNE will start collecting data in summer 2002, and will make a definitive statement about LSND after two years.