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Resolving the

SND explained by. Resolving the. terile. L. S. D. N. eutrino. Anomaly. ecay. Nu-Mass Meeting Grey College, Durham, UK, December 18-19, 2005. THE FACTS. Standard results. “Non Standard” results. Neutrino disappearance. Solar neutrino deficit 8 σ effect.

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Resolving the

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  1. SND explained by Resolving the terile L S D N eutrino Anomaly ecay Nu-Mass Meeting Grey College, Durham, UK, December 18-19, 2005

  2. THE FACTS

  3. Standard results “Non Standard” results Neutrino disappearance Solar neutrino deficit 8 σ effect Atmospheric neutrino anomaly 14 σ effect Neutrino Oscillations Homestake, SAGE, GALLEX, SK, SNO + KamLAND SK and K2K sin213 < 0.047  m221 = (7.3 - 9.1) 10-5 eV2 sin212 = (0.23 – 0.37) | m231| = (1.4 – 3.3) 10-3 eV2 sin2 223 > 0.90 M. Maltoni et al., New J. Phys. 6:122, 2004

  4. “Standard” results No neutrino disappearance Y. Declais et al., Nucl. Phys. B434:503, 1995 • Bugey (e→ e) L = 15 m , 40 m, 95 m; E ~ few MeV → m2 ~ 0.01 – 1 eV2 • CHOOZ and Palo Verde (e→ e) [for 13 small] L ~ 1000 m; E ~ few MeV → m2 ~ 10-3 eV2 • CCFR84 (→ ) L = 0.715 km and 1.116 km (2 detectors) 40 GeV < E < 230 GeV → m2 ~ 10 – 100 eV2 • CCFR (→ ) L = 0.9-1.4 km; 30 GeV < E < 500 GeV → m2 ~ 10 – 1000 eV2 • CDHS (→ ) L = 0.130 km and 0.835 km (2 detectors) E ~ GeV → m2 ~ 1 – 100 eV2 M. Apollonio et al., Phys. Lett. B466:415, 1999 F. Boehm et al., Phys. Rev. D64:112001, 2001 I. E. Stockdale et al., Phys. Rev. Lett. 52:1384, 1984 K. S. McFarland et al., Phys. Rev. Lett. 75:3993, 1995 F. Dydak et al., Phys. Lett. B134:281, 1984

  5. “Standard” results No neutrino appearance P. Astier et al., Phys. Lett. B570:19, 2003 • NOMAD (→ e) L = 0.635 km; 1 GeV < E < 100 GeV → m2 ~ 1 – 100 eV2 • CCFR-NuTeV (→ e) L = 0.9-1.4 km; 30 GeV < E < 500 GeV → m2 ~ 10 – 1000 eV2 • KARMEN (→ e) L = 17.6 m; 16 MeV < E < 50 MeV → m2 ~ 0.1 – 10 eV2 A. Romosan et al., Phys. Rev. Lett. 78:2912, 1997 B. Armbruster et al., Phys. Rev. D65:112001, 2002 So far, so good! No short baseline neutrino “anomaly” Neutrino anomalies explained by oscillations between 3 neutrinos → 2 independent m2

  6. Non-Standard result Neutrino appearance • LSND (→ e) L = 30 m; 20 MeV < E < 52.8 MeV → m2 ~ 1 – 10 eV2 It did see e appearance! A. Aguilar et al., Phys. Rev. D64:112007, 2001 But…  m2atm +  msol m2LSND

  7. Neutrinos are produced from pion and muon decays + → + (e+e) - → - (e- e) + → e+e- → e-e e Most + decay at rest (97%) and also most + Very few - decays at rest (DAR) → 0.08% e backgrounds The LSND experiment A. Aguilar et al., Phys. Rev. D64:112007, 2001

  8. e excess : 87.9 ± 22.4 ± 6.0 P ( → e ) = (0.264 ± 0.067 ± 0.045) % 3.3 σ effect A. Aguilar et al., Phys. Rev. D64:112007, 2001 G. Drexlin, Nucl.Phys.Proc.Suppl.118:146-153,2003

  9. The near future MiniBooNE

  10. THE SPECULATIONS

  11. Classifying solutions • With and without sterile neutrinos • With one and with more than one sterile • With and without neutrino oscillations • With and without CPT violation • With non-standard and with standard processes • With and without extra dimensions • With problems and with problems • Those we like and those we don’t like • Those we have proposed and those we haven’t proposed • No solution But if LSND is right, all imply NEW PHYSICS!

  12. 4 neutrino models 2+2 3+1 e   s  m2atm  m2LSND  m2LSND  m2atm  m2sol  m2sol J. T. Peltoniemi, D. Tommasini and J. F. W. Valle, Phys. Lett. B298:383, 1993 J. T. Peltoniemi and J. F. W. Valle, Nucl. Phys. B406:409, 1993 D. O. Caldwell and R. N. Mohapatra, Phys. Rev. D48:3259, 1993 Steriles would participate in solar and atmospheric neutrino oscillations Ruled out at 5.1 σ Disfavored by SBL and atmospheric neutrino experiments M. Maltoni et al., New J. Phys. 6:122, 2004

  13. 3+2 neutrino models O. L. G. Peres and A. Yu. Smirnov, Nucl. Phys. B599:3,2001  m2LSND2  m2LSND1  m2atm  m2sol Compatibility between SBL (including KARMEN) and LSND of 30%, instead of 3.6 % in the standard 3+1 model M. Sorel, J. M. Conrad and M. H. Shaevitz, Phys. Rev. D66:033009,2002

  14. m2LSND m2LSND,atm m2atm m2KamLAND The killer: reactor experiments The killer: atmospheric experiments Although there is some room for CPT violation with all-but-LSND data… • … for LSND m2, antineutrinos signal would • wash out the up-down asymmetry • produce a deficit of up-going muon events • near the horizon Bugey and CHOOZ: need Ue3' 1 G. Barenboim, L. Borissov and J. Lykken, hep-ph/0212116 A. Strumia, Phys. Lett. B539:91-101,2002 M. C. González-García, M. Maltoni and T. Schwetz, Phys. Rev. D68:053007, 2003 PKamLAND' 1 CPT violating spectra e   m2atm m2sol H. Murayama and T. Yanagida, Phys. Lett. B520:263-268, 2001 G.Barenboim, L. Borissov and J. Lykken, Phys.Lett.B534:106-113,2002

  15. 4 neutrinos + CPT violation Assuming the same m2 for neutrinos and antineutrinos but different mixings • 3+1 models • - U 4 constrained by CCFR and atmospherics, not CDHS → still some room • - Ue4 constrained by GALLEX • (e disappearance during test with a 51Cr source) • 2+2 models • Too little sterile content on solar and • atmospheric neutrino oscillations → Ruled out • Hybrid models • (3+1) , (2+2) : no bound from solar neutrino data • (3+1) , (2+2) : similar to (2+2) → excluded V. Barger, D. Marfatia and K. Whisnant, Phys. Lett. B576:303-308,2003

  16. Pure decoherence  Pure decoherence both Mixing + decoherence  Mixing + decoherence both CPT violating decoherence Quatum gravity models involve singular space-time configurations: space-time foam → decoherence is the result of particle propagation due to the fuzzy properties of the background not necessarily related to mass differences between particles and antiparticles Simple model: effects only in the antineutrino sector and diagonal decoherence matrix → No spectral distortions at KamLAND Without KamLAND With KamLAND G. Barenboim and N. E. Mavromatos, JHEP01:034, 2005

  17. Lorentz violation In the minimal Standard Model Extension (SME) with Lorentz violation, neutrinos are massless and oscillations are determined by 102 real constants controlling the Lorentz violation V. A. Kostelecký and M. Mewes, Phys. Rev. D69:016005, 2004 P (→ e) ' |(heff)e|2 L2 → for LSND |(heff)e|2 ~ (3 x 10-19 GeV)2 aL ~ 10-19 GeV cL ~ 10-17 V. A. Kostelecký and M. Mewes, Phys. Rev. D70:076002, 2004 Unusual dependences for the oscillation phases: aL L and cL L E Predict, e.g., azimuthal dependence for atmospheric neutrinos Constraints (in the  -  sector): aL < few 10-23 GeV cL < 10-24 M. C. González-García and M. Maltoni. Phys. Rev. D70:033010, 2004

  18. These models predict  = 0 for L = 2 decays → constrained by KARMEN BRKARMEN < 0.0017 (90% CL), but BRLSND > 0.0021 (90% CL) LNV muon decay The L = 2 decay: + → e+ + e +  ( = e, , ) could explain LSND data if K. S. Babu and S. Pakvasa, hep-ph/0204236 B. Armbruster et al., Phys. Rev. Lett. 90:181804, 2004 Scale of new physics relatively low,  ~ 300-400 GeV, → effects on low energy observables, e.g., the SM  parameter in the Michel spectrum Predicted  = 0.7485 TWIST experiment Measured  = 0.75080 ± 0.00032± 0.00097 ± 0.00023 J. R. Musser et al., Phys. Rev. Lett. 94:101805, 2005

  19. Mass varying neutrinos Matter effects on neutrinos due to the interaction with a very light and weakly coupled scalar particle could give rise to masses and mixings which are enviroment dependent Yukawa couplings Nucleon number density V()´´ • LSND, KamLAND, K2K and Palo Verde are • in matter • Bugey and CHOOZ are in air • KARMEN is 50% in matter and 50% in air • CDHS is 90% in matter • It could accomodate 3+1 models: an experiment • like Bugey but in matter should see disappearance • Limits for 2+2 models are very model dependent D. B. Kaplan, A. E. Nelson and N. Weiner, Phys. Rev. Lett. 93:091801, 2004 K. M. Zurek, JHEP 0410:058, 2004 V. Barger, D. Marfatia and K. Whisnant, hep-ph/0509163

  20. Shortcuts in extra dimesions In some theories with extra dimensions, SM particles propagate only in the brane, but non-SM particles can also do it in the bulk. If the brane is distorted → shortcuts s travel “faster” This induces an effective term in the hamiltonian which introduces resonant mixing driven by , the aspect ratio of the brane deformation The key point: evading CDHS bounds by a resonance in the range 30 - 400 MeV No effect No bound If Eres ~ 30 – 100 MeV → no signal in MiniBooNE If Eres ~ 200 – 400 MeV → impressive signature in MiniBooNE H. Päs, S. Pakvasa and T. J. Weiler hep-ph/0504096

  21. 3+1 model with a decay option… …but LSND explained (mainly) by oscillations Neutrino oscillations + decay The decay option: key ingredient to evade CDHS bounds For small U4 and short baselines CDHS compares measurements at two detectors: if D1 = D2 , no difference This requires 4 / m4 ~0.03-0.1 and m4 ~ few eV → g ~ 103 -104 In contradiction with laboratory bounds g < 10-2 E. Ma, G. Rajasekaran and I. Stancu, Phys. Rev. D61:071302, 2000

  22. As far as ge´ Uel g4l 0 , we expect e and e appearance Neutrino decay 3+1 model with a decay option… …but LSND explained by decay SPR, S. Pascoli and T. Schwetz, JHEP0509:048, 2005 •  produced in  and  decay • N4 produced in a fraction given by |U4|2 • Subsequently N4 decays into light neutrinos C. W. Kim and W. P. Lam, Mod. Phys. Lett. A5:297, 1990

  23. LSND analysis Decay at rest (DAR) • +→ e+ + e +   contributes via helicity-conserving decays (same channel as in oscillations):  • +→+ +   contributes via helicity-flipping decays (not in oscillations): monochromatic initial spectrum, 0 Oscillations: 2min = 5.6/9 Decay: 2min = 10.8/9 SPR, S. Pascoli and T. Schwetz, JHEP0509:048, 2005

  24. Spectrum after decay

  25. LSND and KARMEN Compatibility of different data sets: Parameter of Goodness of fit (PG) M. Maltoni and T. Schwetz, Phys. Rev. D68:033020, 2003 Oscillations: 2PG = 5.02 → 8.1% Decay: 2PG = 4.97 → 8.3%

  26. Global analysis • Mixing of e with N4 is not required → we set Ue4 = 0 • Only CDHS and atmospherics constrain the model Best fit: |U4|2 = 0.016 g m4 = 3.4 eV LSND vs rest Osc: PG = 0.0018% Dec: PG = 4.6% 3+2: PG = 2.1% LSND+KARMEN vs rest Osc: PG = 0.025% Dec: PG = 55% SPR, S. Pascoli and T. Schwetz, JHEP 0509:048, 2005

  27. The MiniBooNE signal  beam from + decay E ~ 700 MeV and L = 540 m Smaller impact of the spectral distortion due to the initial spectrum In addition, extending the model with an extra neutrino and allowing for complex couplings, the signal in the neutrino run might be suppressed due to interference between oscillation and decay amplitudes

  28. Bounds D. Dassie et al., Nucl. Phys. A678:341, 2000 • Laboratory bounds • Ue4 = 0→ No effect on 0 decay and tritium  decay experiments • 2 decay with emission of two scalars→ geh < O(1) • Pion and kaon decays → g2 < few 10-5 • Supernova bounds • For g ~ 10-5 , l↔ N4 , l N4 ↔  , … are much faster than weak interactions → N4 and  are trapped within the neutrinosphere • Cosmological bounds • For g ~ 10-5, N4 and  are thermalized at BBN→ N=1.57 D. I. Britton et al., Phys. Rev. D49:28, 1994 V. D. Barger, W. Y. Keung and S. Pakvasa, Phys. Rev. D25:907, 1982 G. B. Gelmini, S. Nussinov and M. Roncadelli, Nucl. Phys. B209:157, 1982 For g m4 ~ 1 eV and g ~ 10-5→ m4 ~ 100 keV

  29. THE RIGHT ONE

  30. ??

  31. Conclusions • Solar (8σ) and atmospheric neutrino (14σ) anomalies well understood in terms of oscillations • LSND: the only (anti)neutrino appearance experiment with positive signal (3.3σ)… why shouldn’t it be right? • Many possible solutions… • … if LSND is right, (hopefully) one must be right • We propose a new explanation in terms of a heavy (sterile) neutrino, N, mixed with  and coupled to a light scalar and light neutrinos • If so, we might need to forget about our prejudices on sacred principles, modify the Standard Model of Cosmology… • We all will have more fun!

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