Solar Neutrinos: Current Implications and Future Possibilities CENPA Center for Experimental Nuclear Physics and Astrophysics J. F. Wilkerson March 20, 2003 Fermilab -- NUHORIZONS - Solar neutrinos - Reactor antineutrinos - Future Possibilities  -decay  -decay SNO KamLAND solar neutrinos

1854 von Helmholtz postulates gravitational energy Our “accelerator” - the Sun “We do not argue with the critic who urges that the stars are not hot enough for this process; we tell him to go and find a hotter place.” p + p  2 H + e + + e p + e - + p  2 H + e 2 H + p  3 He +  3 He + 3 He  4 He + 2p 3 He + p  + e + + e 3 He +   7 Be +  7 Be + e -  7 Li +  + e 7 Be + p  8 B +  7 Li + p   +  8 B  2  + e + + e SSM Energy Generation 1938 Bethe & Critchfield p + p  2 H + e + + e 1920’s Eddington proposes p + p fusion

1946 Pontecorvo,1949 Alvarez 37 Cl + e  37 Ar + e - Using solar s’ to probe the Sun p + p  2 H + e + + e p + e - + p  2 H + e 2 H + p  3 He +  3 He + 3 He  4 He + 2p 3 He + p  + e + + e 3 He +   7 Be +  7 Be + e -  7 Li +  + e 7 Be + p  8 B +  7 Li + p   +  8 B  2  + e + + e SSM Energy Generation

1946 Pontecorvo,1949 Alvarez 37 Cl + e  37 Ar + e - Using solar s’ to probe the Sun “…to see into the interior of a star and thus verify directly the hypothesis of nuclear energy generation in stars...” 1960’s Ray Davis, builds Chlorine detector John Bahcall, generates SSM & flux predictions

Solar Flux Measurement Results   flux ~ /cm 2 /s

Astrophysical Solutions? p + p  2 H + e + + e p + e - + p  2 H + e 2 H + p  3 He +  3 He + 3 He  4 He + 2p 3 He + p  + e + + e 3 He +   7 Be +  7 Be + e -  7 Li +  + e 7 Be + p  8 B +  7 Li + p   +  8 B  2  + e + + e SSM Energy Generation Hata and Langacker The data are incompatible with standard and non- standard solar models (For a model independent analysis see Heeger and Robertson, PRL 77 (1996) 3720 )

Super-Kamiokande Elastic Scattering:  x + e -  x + e - Data/SSM = ± (stat) (sys.)  ES = 2.32 ± 0.03 (stat) (sys.) (10 6 cm -2 s -1) (hep-ex/ )

Gallium Measurements 71 Ga + e  71 Ge + e - Two independent experiments SAGE Data/SSM = 0.55 ± 0.05 GALLEX Data/SSM = 0.57 ± 0.05 Latest SAGE results (astro-ph/ ) SSM Both Expts Performed  source tests 51 Cr + e -  51 V + e

Gallium Measurements 71 Ga + e  71 Ge + e - Two independent experiments SAGE Data/SSM = 0.55 ± 0.05 GALLEX Data/SSM = 0.57 ± 0.05 Latest SAGE results (astro-ph/ ) SSM Both Expts Performed  source tests 51 Cr + e -  51 V + e

Gallium Measurements 71 Ga + e  71 Ge + e - Two independent experiments SAGE Data/SSM = 0.55 ± 0.05 GALLEX Data/SSM = 0.57 ± 0.05 Latest SAGE results (astro-ph/ ) SSM SAGE Source Test R(  mea /  th )=0.95±.12±.03 Both Expts Performed  source tests 51 Cr + e -  51 V + e

Beyond the Standard Model - mass & mixing Vacuum Oscillations Small splittings in mass can lead to large observable phase differences in Q.M. amplitude.

Sensitivity of experiments to oscillations  m 2 (eV 2 ) Reactor [~MeV] Atmospheric [~GeV] Solar [~MeV] L/E (km/GeV) Accelerator [~GeV]

Sensitivity of experiments to oscillations s in matter can acquire an effective mass through scattering (analogous to index of refraction for light in transparent media) Matter Enhanced Oscillations (MSW) MSW  m 2 (eV 2 ) Reactor [~MeV] Atmospheric [~GeV] Solar [~MeV] L/E (km/GeV) Accelerator [~GeV]

Mikhevev, Smirnov, Wolfenstein Effect s in matter can acquire an effective mass through scattering (analogous to index of refraction for light in transparent media) Matter Enhanced Oscillations Normal Matter contains many electrons, but no muons or taus, so e  can undergo both CC and NC scattering. Have QM two-state level crossing and flavor change. MSW Oscillations are dependent on the energy and the density of the material, hence one can observe spectral energy distortions. e e ee ee x x ee ee W Z

Matter Enhanced Oscillations LMA LOW SMA MSW gives a dramatic extension of oscillation sensitivity to potential regions in  m 2 Solar data are consistent with the MSW hypothesis. But only circumstantial evidence Need definitive proof Appearance measurement Independent of SSM

G. Milton, B. Sur Atomic Energy of Canada Ltd., Chalk River Laboratories S. Gil, J. Heise, R.J. Komar, T. Kutter, C.W. Nally, H.S. Ng, Y.I. Tserkovnyak, C.E. Waltham University of British Columbia J. Boger, R.L Hahn, J.K. Rowley, M. Yeh Brookhaven National Laboratory R.C. Allen, G. Bühler, H.H. Chen * University of California, Irvine I. Blevis, F. Dalnoki-Veress, D.R. Grant, C.K. Hargrove, I. Levine, K. McFarlane, C. Mifflin, V.M. Novikov, M. O'Neill, M. Shatkay, D. Sinclair, N. Starinsky Carleton University T.C. Andersen, P. Jagam, J. Law, I.T. Lawson, R.W. Ollerhead, J.J. Simpson, N. Tagg, J.-X. Wang University of Guelph J. Bigu, J.H.M. Cowan, J. Farine, E.D. Hallman, R.U. Haq, J. Hewett, J.G. Hykawy, G. Jonkmans, S. Luoma, A. Roberge, E. Saettler, M.H. Schwendener, H. Seifert, R. Tafirout, C.J. Virtue Laurentian University Y.D. Chan, X. Chen, M.C.P. Isaac, K.T. Lesko, A.D. Marino, E.B. Norman, C.E. Okada, A.W.P. Poon, S.S.E Rosendahl, A. Schülke, A.R. Smith, R.G. Stokstad Lawrence Berkeley National Laboratory M.G. Boulay, T.J. Bowles, S.J. Brice, M.R. Dragowsky, M.M. Fowler, A.S. Hamer, A. Hime, G.G. Miller, R.G. Van de Water, J.B. Wilhelmy, J.M. Wouters Los Alamos National Laboratory J.D. Anglin, M. Bercovitch, W.F. Davidson, R.S. Storey * National Research Council of Canada J.C. Barton, S. Biller, R.A. Black, R.J. Boardman, M.G. Bowler, J. Cameron, B.T. Cleveland, X. Dai, G. Doucas, J.A. Dunmore, H. Fergani, A.P. Ferrarris, K. Frame, N. Gagnon, H. Heron, N.A. Jelley, A.B. Knox, M. Lay, W. Locke, J. Lyon, S. Majerus, G. McGregor, M. Moorhead, M. Omori, C.J. Sims, N.W. Tanner, R.K. Taplin, M.Thorman, P.M. Thornewell, P.T. Trent, N. West, J.R. Wilson University of Oxford E.W. Beier, D.F. Cowen, M. Dunford, E.D. Frank, W. Frati, W.J. Heintzelman, P.T. Keener, J.R. Klein, C.C.M. Kyba, N. McCauley, D.S. McDonald, M.S. Neubauer, F.M. Newcomer, S.M. Oser, V.L Rusu, S. Spreitzer, R. Van Berg, P. Wittich University of Pennsylvania R. Kouzes Princeton University E. Bonvin, M. Chen, E.T.H. Clifford, F.A. Duncan, E.D. Earle, H.C. Evans, G.T. Ewan, R.J. Ford, K. Graham, A.L. Hallin, W.B. Handler, P.J. Harvey, J.D. Hepburn, C. Jillings, H.W. Lee, J.R. Leslie, H.B. Mak, J. Maneira, A.B. McDonald, B.A. Moffat, T.J. Radcliffe, B.C. Robertson, P. Skensved Queen’s University D.L. Wark Rutherford Appleton Laboratory, University of Sussex R.L. Helmer, A.J. Noble TRIUMF Q.R. Ahmad, M.C. Browne, T.V. Bullard, G.A. Cox, P.J. Doe, C.A. Duba, S.R. Elliott, J.A. Formaggio, J.V. Germani, A.A. Hamian, R. Hazama, K.M. Heeger, K. Kazkaz, J. Manor, R. Meijer Drees, J.L. Orrell, R.G.H. Robertson, K.K. Schaffer, M.W.E. Smith, T.D. Steiger, L.C. Stonehill, J.F. Wilkerson University of Washington The SNO Collaboration

The Sudbury Neutrino Observatory NC xx    npd ES --    e e xx -Low Statistics -Dominant contribution (5/6) from e,, smaller (`1/6) contributions from  &  -Strong directional sensitivity -Good sensitivity to e energy spectrum -Weak directional sensitivity  1-1/3cos(  ) - e only. - Measure total 8 B flux from the sun. - Equal cross section for all types MeV Threshold, Integrated E > E th CC - epd  e p

Key signatures for unexpected Flavors  cc  es = e e (  +     cc  nc e e +  +   = June 2001 April 2002  day  night vs Measure total flux of solar neutrinos vs. the pure e flux Direct Evidence for flavor change Potential signal For oscillations

The SNO Detector during Construction

Reactions in SNO NC xx    npd ES --    e e xx -Low Statistics -Mainly sensitive to e,, some sensitivity to  and  -Strong directional sensitivity -Good measurement of e energy spectrum -Weak directional sensitivity  1-1/3cos(  ) - e only. - Measure total 8 B flux from the sun. - Equal cross section for all types MeV Threshold, Integrated E > E th CC - epd  e p Produces Cherenkov Light Cone in D 2 O Produces Cherenkov Light Cone in D 2 O n captures on deuteron 2 H(n,  ) 3 H Observe 6.25 MeV  D 2 O Only Phase

Extraction of CC, ES, NC Signals To extract the CC, ES, NC signal SNO performs a Max- likelihood statistical separation of these signals based on distributions of the SNO observables.

CC ES NC #EVENTS Shape Constrained Signal Extraction Results First result E th of 6.75 MeV

SNO NC in D 2 O Conclusions  ssm =  sno = ~ 2/3 of initial solar e are observed at SNO to be  Rule out null hypothesis - no flavor change - at 5.3  level.

SNO Signal Extraction in  CC,  NC,  ES E tn = 5 MeV e (  +  ) e SSM e +  +  CC shape unconstrained Neutral Current (NC) Elastic Scattering (ES) Charged Current (CC) CC shape constrained June 2001 ES SNO CC SNO NC SNO April 2002 CC SNO ES SNO 8 B from CC SNO +ES SK 5.3  Neutrino Signal (SSM BP00)   cc ( e ) = 1.76 x10 6 cm -2 s   NC ( e ) = 5.09 x10 6 cm -2 s   es ( e ) = 2.39 x10 6 cm -2 s

SNO Conclusions First NC flux measurements - clear evidence that the majority of e produced in the Sun are transformed to  and/or  Null hypothesis - “No Weak Flavor Mixing” ruled out at 5.3  Lowest Detection threshold yet for a real-time solar detector Total 8 B flux measurement agrees well with Solar Models Data in good agreement with previous SNO - SK CC/ES result First measurements of the Day-Night Asymmetries SNO Data consistent with MSW oscillation interpretation combined with global solar neutrino data favors LMA solution “Dark side” solutions not allowed, indicating m 2 > m 1 nucl-ex/ , nucl-ex/ Combining All Experimental and Solar Model information

Reactor e oscillation searches 1956 Reines & Cowan + enp   e Chooz hep-ex/ Disappearance experiments

Solar neutrino LMA implication Reactor experiments optimum at ~180 km Solar LMA best fit prediction

G.A.Horton-Smith, R.D.McKeown, J.Ritter, B.Tipton, P.Vogel California Institute of Technology C.E.Lane, T.Miletic Drexel University Y-F.Wang IHEP, Beijing T.Taniguchi KEK B.E.Berger, Y-D.Chan, M.P.Decowski, D.A.Dwyer, S.J.Freedman, Y.Fu, B.K.Fujikawa, K.M. Heeger, K.T.Lesko,K-B.Luk, H.Murayama, D.R.Nygren, C.E.Okada, A.W.Poon, H.M.Steiner, L.A.Winslow LBNL/UC Berkeley S.Dazeley, S.Hatakeyama, R.C.Svoboda Louisiana State University J.Detwiler, G.Gratta, N.Tolich, Y.Uchida Stanford University KamLAND Collaboration K.Eguchi, S.Enomoto, K.Furuno, Y.Gando, J.Goldman, H.Ikeda, K.Ikeda, K.Inoue, K.Ishihara, T.Iwamoto, T.Kawashima, Y.Kishimoto, M.Koga, Y.Koseki, T.Maeda, T.Mitsui, M.Motoki, K.Nakajima, H.Ogawa, K.Oki, K.Owada, I.Shimizu, J.Shirai, F.Suekane, A.Suzuki, K.Tada, O.Tajima, K.Tamae, H.Watanabe Tohoku University L.DeBraeckeleer, C.Gould, H.Karwowski, D.Markoff, J.Messimore, K.Nakamura, R.Rohm, W.Tornow, A.Young TUNL J.Busenitz, Z.Djurcic, K.McKinny, D-M.Mei, A.Piepke, E.Yakushev University of Alabama P.Gorham, J.Learned, J.Maricic, S.Matsuno, S.Pakvasa University of Hawaii B.D.Dieterle University of New Mexico M.Batygov, W.Bugg, H.Cohn, Y.Efremenko, Y.Kamyshkov, Y.Nakamura University of Tennessee

KamLAND - Kamioka Liquid Scintillator Anti-Neutrino Detector 16 complexes - 10% of world’s nuclear power 3 GW reactor: ~ e /s L ~ km

KamLAND - Kamioka Liquid Scintillator Anti-Neutrino Detector 16 complexes - 10% of world’s nuclear power 3 GW reactor: ~ e /s L ~ km

KamLAND first results (hep-ex/ ) Data summary –145.1 live days –Observed: 54 –Expected: 86.8 ± 5.6 –Background 1 ± 1 Measured survival probability differs from 1 by 4.1  Probability that result is consistent with no oscillation hypothesis < 0.05%

Evidence of e oscillations KamLAND with LMA shown Global fit (de Holanda and Smirnov) hep-ph/ hep-ex/ CL: 1 , 90%, 95%, 99%, 3  CL: 95%

Current situation Atm., Solar  & KamLAND provide compelling evidence for oscillations. LSND awaits confirmation by miniBoone. Big surprise - unlike quark sector (CKM), lepton sector has large mixing angles. Osc. Results yield a LOWER BOUND on m  ; tritium beta decay, astrophysical data set UPPER BOUND e         s   e Solar & KamLAND What’s next?

physics - issues & questions accurate determinations of  ij,  m 2 ij –especially  13 CP violation phases Majorana/Dirac character of the neutrinos absolute scale of neutrino mass magnetic and other neutrino moments existence of, constraints on sterile neutrinos inverted or regular hierarchy? role of neutrinos in nucleosynthesis, supernova explosions, BBN lepton number violation baryogenesis via leptogenesis

Non-accelerator  physics - future possibilities Solar neutrinos –More accurate determination of  12 –potential independent observation of oscillations day/night effect low energy 7 Be & pp shape effects –Astrophysics (pp flux, CNO cycle) Single  -decay(endpoint measurement) –absolute scale of neutrino mass 0  -decay –Majorana/Dirac character of the neutrinos –absolute scale of neutrino mass –inverted or regular hierarchy? Atmospheric neutrinos - covered by Kearns Reactor neutrinos - will be covered by Gratta

Future Possibilities for Solar Neutrinos Solar neutrinos - immediate future –SNO entering precision phase of experiment Salt measurements underway since June He proportional neutral current detectors (Fall 2003) Some possibility of observing day/night effect - and hence direct oscillation signature

SNO - Current Status and Future Plans Neutral Current Detectors n  3 He  p  t The Salt Phase n  35 Cl  36 Cl   …  e  (E   = 8.6 MeV) Higher n-capture efficiency Higher event light output Event isotropy differs from e - Running since June 2001 Event by event separation Different systematics

Impact of precision SNO de Holanda and Smirnov hep-ph/ Improved NC/CC measure- ment will yield an improved  12 value (red ---- lines) D 2 O: unconstrained ~30% Salt: perhaps 10-15% NCD: potentially ~5 % Note KamLAND should improve on  m 12 Possible chance to observe Day/Night asymmetry and hence direct oscillation siganl

MSW and Day-Night Fluxes A x = 2*(  N,X –  D,X ) (  N,X +  D,X ) Certain MSW oscillation solutions predict s can change flavor while passing through the earth Define Asymmetry

Signal Extraction in  e,  total,  A total = 0  e =  e sk = Signal Extraction in  CC,  NC,  ES.  cc =  nc = SNO A e and A tot Measurements

Impact of precision SNO de Holanda and Smirnov hep-ph/ Improved NC/CC measure- ment will yield an improved  12 value (red ---- lines) D 2 O: unconstrained ~30% Salt: perhaps 10-15% NCD: potentially ~5 % Note KamLAND should improve on  m 12 Possible chance to observe Day/Night asymmetry and hence direct oscillation siganl (blue -- lines) –limited by statistics –Depends on real solution

Future Possibilities for Solar Neutrinos Solar neutrinos - immediate future –SNO entering precision phase of experiment Salt measurements underway since June He proportional neutral current detectors (Fall 2003) Some possibility of observing day/night effect - and hence direct oscillation signature –KamLAND solar and Borexino (2004?) real-time 7 Be ( KamLAND initial backgrounds look promising for solar measurements) Independent confirmation of LMA solution Confirmation of solar model, slight improvement on CNO limit Next generation experiments (pp in real-time)

Next generation Solar Neutrinos Charged-Current Experiments: LENS, MOON Goal: Measure e component of p- p ( 7 Be) with 1-3% (2-5%) accuracy Elastic Scattering Experiments: CLEAN, HERON, TPC XMASS (Japan) Goal: Measure e / ,  component of p-p ( 7 Be) with 1-3% (2-5%) accuracy Projected

Future Possibilities for Solar Neutrinos Solar neutrinos - immediate future –SNO entering precision phase of experiment Salt measurements underway since June He proportional neutral current detectors (Fall 2003) Some possibility of observing day/night effect - and hence direct oscillation signature –KamLAND solar and Borexino (2004?) real-time 7 Be ( KamLAND initial backgrounds look promising for solar measurements) Independent confirmation of LMA solution Confirmation of solar model, slight improvement on CNO limit Next generation experiments (pp in real-time)  12 to 1% CPT- potentially more sensitive than kaon system ~10 x improvement on neutrino magnetic moment sensitivity Confirmation of solar model, slight improvement on CNO limit “…to see into the interior of a star and thus verify directly the hypothesis of nuclear energy generation in stars...”

The absolute scale of masses Addresses key issues in particle physics –hierarchical or degenerate neutrino mass spectrum –understanding the scale of new physics beyond SM –potential insight into origin of fermion masses Impacts cosmology and astrophysics –early universe, relic neutrinos (HDM), structure formation, anisotropies of CMBR –supernovae, r-process, origin of elements –potential insight on understanding the origin of UHE cosmic rays

sub-eV absolute mass measurements hierarchicaldegenerate Given the surprise of large mixing in the lepton sector, there is limited theoretical insight into which scenario occurs in nature.

Probes of absolute mass Indirect methods –Cosmology CMB Galaxy clusters Lyman-  forest Galaxy large scale structure –Astrophysics UHE cosmic-rays Supernovae generation mechanisms –Neutrinoless  -decay Direct techniques –time of flight (supernovae) –particle decay kinematics

Past: history of direct mass measurements ( flavor eigenstates) points without error bars represent upper limits m e < 2.2 eV (95% CL) (Mainz 2000) m  < 18.2 MeV (95% CL) (ALEPH 1998) m  < 170 keV (90%CL) (PSI 1996)

Past: history of direct mass measurements ( flavor eigenstates) points without error bars represent upper limits m e < 2.2 eV (95% CL) (Mainz 2000) m  < 18.2 MeV (95% CL) (ALEPH 1998) m  < 170 keV (90%CL) (PSI 1996) But oscillations with large mixing angles - forces one to consider direct techniques in terms of mass eigenstates!

 -decay endpoint measurement Essentially a search for a distortion in the shape of the b-spectrum in the endpoint energy region dN(E) = K|M| 2 F( Z,R,E ) p e E (E 0 -E)  |U ei | 2 { (E 0 -E) 2 -m i c 4 } 1/2 dE 2 i For 3 mass spectrum, with degenerate states, the beta spectrum simplifies to an “effective mass” : m  2  =  |U ei | 2 m i

Karlsruhe Tritium Neutrino Experiment (KATRIN) arXiv:hep-ex/ ~.2 eV sensitivity

Crucial Challenge - measuring extremely rare decay rates: T 1/2 ~ years  (0 ) relationship to neutrino mass nuclear matrix elements uncertainty on mass ~  -decay

0  -decay - next generation probe lepton number violation and the charge conjugation properties of s best sensitivity to neutrino mass Theoretical caveats: Requires that neutrinos be Majorana particles Key requirements for next generation experiments: Sufficient mass, ~ 1 ton Extremely low backgrounds Good energy resolution

0 bb-decay status Current situation is a bit “muddled” Heidelberg-Moscow Klapdor-Kleingrothaus et al. Eur. Phys. J. A (2001). For 76 GeT 1/2 > 1.9  y (90% CL) < 0.39 eV (90% CL). Klapdor-Kleingrothaus et al. (Klapdor-Kleingrothaus et al. Mod. Phys. Lett (2001). reported a non-zero result with a best value of 1.5  y (~2.2  ) = eV See hep-ex/ and hep-ph/ for comments

0  -decay prospects

The need for a national underground laboratory? Compelling forefront science with a broad impact –the nature of neutrinos, astrophysics, supernova, dark matter, nucleon decay, nuclear astrophysics, origin of elements, biology... Opportunity to establish the world’s deepest and most extensive science laboratory within the United States aimed at the future generations of underground science experiments. –Shortage of space in existing facilities. –Several existing experiments would be “better” if deeper. –Success of SNO cleanliness demonstrates that one can build ultra clean detectors deep underground. –New generation experiments will gain from depth. –Establishment would indicate a clear leadership role for the US in underground science –Range of scientific fields and “cutting edge” research will facilitate learning opportunities for K-Ph.D. students in a multitude of academic disciplines as well as affording excellent outreach opportunities to the American public.

Making the Science Case for NUSEL Nuclear Science Advisory Committee (NSAC) Long Range Plan Committee on an Underground Scientific Laboratory (Community committee, NSF & DOE) HEPAP Sub-panel on Long Range Planning NRC Committee on the Physics of the Universe (CPU) NRC - Neutrino Facilities Assessment Committee March - December 2002

Summary Solar, reactor and atmospheric demonstrate that neutrinos have mass and the Standard Model of Nuclear and Particle Physics is incomplete. –Unlike the Quark Sector where the CKM mixing angles are small, the lepton sector exhibits large mixing –The masses and mixing may play significant roles in determining structure formation in the early universe as well as supernovae dynamics and the creation of the elements Future possibilities –Solar neutrinos improve  12, further confirmation of LMA astrophysics –Single beta decay - direct neutrino mass measurements KATRIN should reach ~0.2 eV sensitivity –0  -decay - discovery potential of Majorana neutrinos Next generation should reach meV sensitivity