ν?? Solar & Atmospheric Oscillation Experiments Greg Sullivan University of Maryland Aspen Winter Conference January 21, 1999 )Past )Present )Future

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1 Solar & Atmospheric Oscillation Experiments Greg Sullivan of Maryland Aspen Winter Conference January 21, 1999 ν?? e )Past z Neutrino Mass Mass & Oscillations )Present z Atmospheric neutrinos z Solar Solar neutrinos )Future

2 )Can we detect them? z In 1934 Bethe & Peierls calculated the cross section for neutrino interaction of cm 2. ˆNature (London) 133, 532(1934) It is therefore absolutely impossible to observe processes of this kind with neutrinos created in nuclear transformations one can conclude that there is no practically possible way of observing the neutrino. and it is not necessary to assume interaction in order to explain the function of the neutrino nuclear transformations... z In fact, it was some 20 years before they were detected using a nuclear reactor as a source.

3 Solar Neutrino Spectrum

4 Solar Neutrinos detected )R. Davis and his 37 Cl detector z same principle used to try and detect antineutrinos from a nuclear reactor in z measured the flux of neutrinos from the sun almost continuously since about 1970!

5 Solar Neutrino Rate in Cl Detector is 1/3-1/2 expected Explanations? )Astrophysics - Standard Solar Model z Neutrinos from 7 Be and 8 B z Very sensitive to Sun s core temperature )Particle Physics Solutions --- Neutrino properties are not what we think! z Electron Neutrinos don t make it to earth ˆMagnetic properties of ν ˆν e change flavor in transit - Neutrino Oscillations! z Non zero neutrino mass! z Lepton flavor mixing!

6 Neutrino Mass & Neutrino Oscillations? )What is the mass of the neutrino? z Is it identically zero? z If not, Why is it so small? see-saw mechanism The most general mass Lagrangian for one neutrino flavor is: ( ) c c L = m ν ν + ν ν + m ν ν + m ν ν + h. c. m D L R R L L L L R R where m D, m L, m R represent the Dirac, left-handed M ajorana and right-handed M ajorana m asses. This can be written in m atrix form as: R L m = S M S where, S = ν ν L R + + ν ν c L c R M m L m D = m m D R The physical mass eigenstates are found by diagonalizing the mass matrix. If we assume m L = 0 we get: m 2 R 4 m D m 1, 2 = 1 ± m R For a heavy right-handed scale m R >> m D, w e get tw o m ass eigenstates m m ( heavy ν ) 50 MeV 500 m m H R W 2 m D 6 ν ( light ν ) 10 10' s ev m R

7 Neutrino Oscillations ) If ν mass is not 0 and flavor is not absolutely conserved then mixing may occur between different type of neutrinos. Weak eigenstates of the neutrino are mixtures of the neutrinos with definite mass. For two neutrino species ν e and ν µ we have: ν e = ν 1 cosθ + ν sinθ ν µ = ν1 sinθ + ν 2 cosθ where ν 1 and ν 2 are the mass eigenstates. 2 In a weak decay one produces a definite weak eigenstate ( ) ν t = = ν 0 e.. At a later time the probability of the final state will be: ν ie1t ie2t () t = ν e cosθ + ν e sinθ 1 2 The survival probability is: P m 2 ev km ( ν ) = ( ) e ν e; L 1 sin 2θ sin EGeV 2 L.

8 Solar Neutrino Experiments )Homestake -- Radiochemical z Huge Huge tank tank of of Cleaning Fluid Fluid zν e Cl Cl e Ar Ar z Mostly Mostly 8 8 B neutrinos + some some 7 7 Be Be z years years at at <0.5 <0.5 ev/day ev/day z 1/3 1/3 SSM SSM )Sage/Gallex -- Radiochemical z All All neutrinos zν e Ga Ga e Ge Ge z 4 years years at at ~0.75 ~0.75 ev ev /day /day z ~2/3 ~2/3 SSM SSM )Kamiokande-II and and -III -III z 8 8 B neutrinos only only zν e Elastic Elastic Scattering z years years at at ev ev /day /day z ~1/2 ~1/2 SSM SSM

9 Summary of Results Before Super-K )Four experiments measured versus predicted from solar model Experiment SSM(BP92) DATA DATA/SSM GALLEX (Ga) SAGE (Ga) Homestake (Cl) Kamioka (H 2 O) 132 ± 7 70 ± ± 11 8 ± ± ± ±

10 BP95 FROM Langacker -Allowed regions at 95% CL from individual experiments and from the global fit. The Earth effect is included for both timeaveraged and day/night asymmetry data, full astrophysical and nuclear physics uncertainties and their correlations are accounted for, and a joint statistical analysis is carried out. The region excluded by the Kamiokande absence of the day/night effect is also indicated.

11 Atmospheric Neutrinos ν µ + ν µ ν + ν e e 2 Ratio predicted to ~ 5% Absolute Flux Predicted to ~20% : primary CR spectrum geomagnetic cutoff hadron production modeled from accelerator data

12 Atmospheric Neutrino Anomaly )The Observed Ratio of ν µ /ν e is too low z Produced when pions generated in the upper atmosphere by cosmic rays decay. P + N π + π + + X + µ + µ + ν e µ + + ν µ + ν e z Predicted Ratio of ν µ /ν e ~ 2 z Observed Ratio is ~ 1 )Particle Physics Solutions --- Neutrino properties are not what we think! z Muon Neutrinos don t make it to earth ˆν µ change flavor in transit - Neutrino Oscillations! z Non zero neutrino mass! z Lepton flavor mixing!

13 Worldwide Results on R Before Super-Kamiokande

14 Two Suggestions of Neutrino Transformation )Solar Neutrinos (~1-15 Mev ν e ) z Davis experiment (Cl) saw ~30% of expected flux of ν e from 8 B & 7 Be z Galium experiments showed less than expected flux of ν e from all processes z Kamiokande saw ~40% ν e from 8 B z These results can not be reconciled with the standard solar model )Atmospheric Neutrinos (~.1-3 GeV) z IMB and Kamiokande saw less than expected ratio of ν µ / ν e )One Proposed Explanation was: Neutrino Oscillations z Solar neutrinos might be ν e ν µ z Atmos. neutrinos might be ν µ ν τ

15 Super-Kamiokande The Next generation Underground Neutrino Detector. Super-Kamiokande is a 50,000 ton water Cerenkov detector at a depth of 1000 meters in the Kamioka Mozumi mine in Japan. )Detector Characteristics z 41 m h x 39 m dia. z 50,000 tonne total/22,000 tonne fiducial z 11, PMTs inner detector z 1,850 8 PMTs anti-detector z 40% photocathode coverage )Trigger Threshold ~5 MeV )Resolution z Energy 16%/(E) 1/2 at 10 MeV z Position ~50 cm at 10 MeV z Angular ~30 degrees at 10 MeV

16 SuperKamiokande Collaboration ) Institute Institute for for Cosmic Cosmic Ray Ray Research, Research, of of Tokyo Tokyo ) Gifu Gifu ) Institute Institute for for Nuclear Nuclear Study, Study, of of Tokyo Tokyo ) National National Laboratory Laboratory for for High High Energy Energy Physics, Physics, KEK KEK ) Kobe Kobe ) Miyagi Miyagi Education Education ) Niigata Niigata ) Osaka Osaka ) Tokai Tokai ) Tohoku Tohoku ) Tokyo Tokyo Institute Institute of of Technology Technology ) Boston Boston ) Brookhaven Brookhaven National National Laboratory Laboratory ) of of California, California, Irvine Irvine ) California California State State,, Dominguez Dominguez Hills Hills ) Cleveland Cleveland State State ) George George Mason Mason ) of of Hawaii Hawaii ) Los Los Alamos Alamos National National Laboratory Laboratory ) Louisiana Louisiana State State ) of of Maryland Maryland ) State State of of New New York, York, Stony Stony Brook Brook ) of of Warsaw Warsaw ) of of Washington Washington

17 The Super-K Detector

18 The Super-Kamiokande Tank During Filling in 1996

19 Stopping Muon

20 Electron from decay of stopping muon

21 Muon - Electron Identification

22 Sub-Gev (535 days) E vis < 1.33 GeV P e > 100 MeV/c P µ > 200 MeV/c Data MC 1 Ring e-like µ-like Multi-ring ( µ / e) ( µ / e) MC 0.63±.026( stat) Data = ±.05( syst)

23 Multi-Gev (535 days) E vis > 1.33 GeV Fully Contained Data MC 1 Ring e-like µ-like Multi-ring Partially Contained Data MC Total = µ-like ( µ / e) ( µ / e) Data = ± ± MC ( stat ).08 ( syst )

24 Worldwide Results on R )Detectors continue to run z MACRO upward going muons z Soudan II z Super-K muons

25 If the muon ν s oscillate, what it look like? )Depletion of ν µ relative to ν e z double ratio R R = ( µ / e) ( µ / e) data MC < 1 )L dependence of ν µ flux z Zenith angle dependence

26 Zenith Angle Dependence Survival Probability vs. Distance (1GeV,.003 ev^2) Probability Distance (km) P m Lkm ( ν L) = µ ν µ ; 1 sin 2θ sin EGeV

27 Zenith Angle Dependence

28 Zenith Angle Dependence

29 L/E Distribution of Atmospheric Neutrinos The dashed lines show the expected shape for ν µ ν τ at m 2 =2.2 x 10-3 ev 2 and sin 2 2θ = 1.

30 Atmospheric Results

31 East-West Effect

32 Zenith Angle Distribution (736 Day Sample)

33 Zenith Angle Dependence (736 day sample)

34 MACRO Detector )Data collected 89 - Dec 97 z ~3 live-years with 6 full SM z ~480 Upward Going Muon events R(data/MC)= 0.74 ±.036 sta ±.046 sys ±.13 theo z Probability for no oscillations P(null) = 14% z Best fit mass assuming maximal mixing: m 2 ~ 2 x 10-3 ev 2

35 MACRO upward-going muons )Probabilities Number + Shape z Probability of no oscillations P(null) 0.1% z Best fit oscillation parameters sin 2 2θ = 1.0, m 2 2 x 10-3 ev 2 P(best fit) 17%

36 A Picture of the Sun using Neutrinos in Super-K

37 10 MeV Electron in Super-K

38 Super Low Energy (SLE) Data

39 Solar Neutrino Flux (New 708 Day Sample) Data SSM BP98 = 0.471± 0.008( stat) ± 0.013( syst)

40 Day-Night Results 708 day Sample D D + N N = ± ( stat) ± 0.013( syst)

41 Energy Spectrum 708 day day SLE

42 Spectrum and Oscillations? z Data favors Vacuum solution (red) z small angle MSW (blue) starting to get squeezed by flatness with SLE data

43 Hep Neutrinos? )Set limit on hep flux from data z integral of events between E thres & E end z E thres = 17 MeV, E end = 25MeV Hep flux < 8 SSM at 90% C.L. z E thres = 19 MeV, E end = 20 MeV Hep flux < 20 SSM at 90% C.L.

44 Seasonal Variation

45 Energy Dependence of Seasonal Variation for Just-so solution

46 Seasonal Variation in High Energy Data

47 Summary of Super-K Results )Atmospheric Neutrinos z Strong Evidence for ν µ ν τ (ν s ) Oscillations z New results consistent z Higher statistics may allow separation of (ν τ )(ν s ) )Solar Neutrinos z No evidence for Day/Night Effect ˆSqueezes Large Angle Solution z Super Low E and more statistics somewhat flattens energy spectrum ˆStarting Squeeze Small Angle Solution z Vacuum (Just-So) solution is still alive z Continue to Run ˆPostponed the scheduled June 99 shutdown

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49 Future ~2000 )Atmospheric Neutrinos z Continued running of of Super-Kamiokande ˆNeutral Currents? ˆ Distinguish ν µ ν µ ν τ from τ from ν µ ν µ ν s s z MACRO muons muons & neutrinos z Soudan II II z KEK KEK to to Super-K (K2K) (K2K) )Solar Neutrinos z Spectral Distortion at at High High Energy z Instrumental Effect? ˆEnergy Scale Scale & Resolution LINAC LINAC limitations ˆD-T ˆD-T Generator to to make make N as as calibration source source (NSF) (NSF) z Hep Hep Neutrinos? ˆNeed times times predicted flux flux ˆUse ˆUse Super-K data data >18 >18 MeV MeV to to set set limit limit on on hep hep flux?? flux?? z Statistics? z Seasonal Variation needs needs more more data data

50 Future )Atmospheric Neutrinos z Accelerator Experiments (FNAL, (FNAL, CERN, CERN, KEK) KEK) ˆKnown Neutrino Direction ˆBetter Neutrino Energy Measurement z Appearance Experiment???? )Solar Neutrinos z Continued Super-Kamiokande Running z New New Experiments Soon Soon -- should should settle settle the the solar solar neutrino problem z Sudbury Neutrino Observatory (SNO) (SNO) ˆCanada,US,UK institutions ˆ Fill Fill Apr, Apr, Feb, Feb, 99 99? ˆ6 ˆ6 mo. mo. Debug Debug & Calibration ˆ1 ˆ1 Yr. Yr. pure pure D 2 O 2 z Borexino z ICARUS

51 SNO Detector tonnes of D 2 O feet Underground -10,000 pmts )Detector Performance z Threshold 5MeV - 8 B neutrinos z Energy Resolution 14% at 10 MeV z Charged Current off D ev/day ˆmeasure NEUTRINO energy - look for spectral distortion with high sensitivity - seasonal variation over entire spectrum z Neutral Current 7.7 ev/day ˆCC/NC ratio smoking gun z Electron Scattering 3.0 ev/day

52 SNO Sensitivity 1) CC/NC Ratio 2) Spectrum

53 Borexino -300 Tonnes of Scintillator Pmt s -Gran Sasso )Detector Performance z Electron Threshold low enough to observe 7 Be (863 kev) neutrinos z Real time measurement of 7 Be & 8 B z 46 events/day in 100 ton fiducial volume z First Measurement of only the 7 Be flux ˆfinal ingredient

54 Solar Neutrinos in Near Future Possible Solutions * No Solar Osc Small Angle MSW Large Angle MSW Vacuum Osc Small Angle Sterile Super-K (Boron) Flux low No spec No D/N No Seas Spectral Distortion? Day/Night Spectrum Season? Spectrum? SNO (Boron) Flux low? No Spec CC/NC OK Spectrum CC/NC low Day/Night CC/NC low Spectrum Season CC/NC low Spectrum CC/NC OK Borexino (Be)* Meas/exp 1 Boone (Acc) Possible signal ~1/4 No Signal ~1/2 No Signal ~1/2 No Signal ~.01 Possible signal *Bahcall Phys Rev D 58 (

55 Atmospheric Neutrino Oscillations )Need Confirmation of Evidence z Further Running of Super-k, Soudan, MACRO z Accelerator Experiments planned ˆMINOS at FNAL ˆCERN to Gran Sasso - Disappearance experiments? )Future Possibilities z Megaton underground Atmospheric Neutrino detector z Appearance Experiment? ˆ5 GeV Neutrinos ˆ L/E ~ 1 x 10 3 L ~ 5000 km