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

2. Sergio Palomares-Ruiz December 18, 2005 THE FACTS

3. Sergio Palomares-Ruiz December 18, 2005 “Non Standard” results Solar neutrino deficit 8 σ effect Atmospheric neutrino anomaly 14 σ effect Neutrino disappearance  m 2 21 = (7.3 - 9.1) 10 -5 eV 2 sin 2  12 = (0.23 – 0.37) |  m 2 31 | = (1.4 – 3.3) 10 -3 eV 2 sin 2 2  23 > 0.90 Neutrino Oscillations Homestake, SAGE, GALLEX, SK, SNO + KamLAND SK and K2K Standard results sin 2  13 < 0.047 M. Maltoni et al., New J. Phys. 6:122, 2004

4. Sergio Palomares-Ruiz December 18, 2005 “Standard” results Bugey ( e → e ) L = 15 m, 40 m, 95 m; E ~ few MeV →  m 2 ~ 0.01 – 1 eV 2 CHOOZ and Palo Verde ( e → e ) [for  13 small] L ~ 1000 m; E ~ few MeV →  m 2 ~ 10 -3 eV 2 CCFR84 (  →  ) L = 0.715 km and 1.116 km (2 detectors) 40 GeV < E < 230 GeV →  m 2 ~ 10 – 100 eV 2 CCFR (  →  ) L = 0.9-1.4 km; 30 GeV < E < 500 GeV →  m 2 ~ 10 – 1000 eV 2 CDHS (  →  ) L = 0.130 km and 0.835 km (2 detectors) E ~ GeV →  m 2 ~ 1 – 100 eV 2 No neutrino disappearance Y. Declais et al., Nucl. Phys. B434:503, 1995 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 F. Dydak et al., Phys. Lett. B134:281, 1984 K. S. McFarland et al., Phys. Rev. Lett. 75:3993, 1995

5. Sergio Palomares-Ruiz December 18, 2005 “Standard” results NOMAD (  → e ) L = 0.635 km; 1 GeV < E < 100 GeV →  m 2 ~ 1 – 100 eV 2 CCFR-NuTeV (  → e ) L = 0.9-1.4 km; 30 GeV < E < 500 GeV →  m 2 ~ 10 – 1000 eV 2 KARMEN (  → e ) L = 17.6 m; 16 MeV < E < 50 MeV →  m 2 ~ 0.1 – 10 eV 2 No neutrino appearance So far, so good! No short baseline neutrino “anomaly” Neutrino anomalies explained by oscillations between 3 neutrinos → 2 independent  m 2 P. Astier et al., Phys. Lett. B570:19, 2003 B. Armbruster et al., Phys. Rev. D65:112001, 2002 A. Romosan et al., Phys. Rev. Lett. 78:2912, 1997

6. Sergio Palomares-Ruiz December 18, 2005 LSND (  → e ) L = 30 m; 20 MeV < E < 52.8 MeV →  m 2 ~ 1 – 10 eV 2 It did see e appearance! Non-Standard result Neutrino appearance But…  m 2 atm +  m sol   m 2 LSND A. Aguilar et al., Phys. Rev. D64:112007, 2001

7. Sergio Palomares-Ruiz December 18, 2005 The LSND experiment A. Aguilar et al., Phys. Rev. D64:112007, 2001 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

8. Sergio Palomares-Ruiz December 18, 2005 3.3 σ effect A. Aguilar et al., Phys. Rev. D64:112007, 2001G. Drexlin, Nucl.Phys.Proc.Suppl.118:146-153,2003 e excess : 87.9 ± 22.4 ± 6.0 P (  → e ) = (0.264 ± 0.067 ± 0.045) %

9. Sergio Palomares-Ruiz December 18, 2005 The near future MiniBooNE

10. Sergio Palomares-Ruiz December 18, 2005 THE SPECULATIONS

11. Sergio Palomares-Ruiz December 18, 2005 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. Sergio Palomares-Ruiz December 18, 2005 4 neutrino models 2+23+1  m 2 sol  m 2 atm  m 2 LSND e   s 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 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

13. Sergio Palomares-Ruiz December 18, 2005 3+2 neutrino models  m 2 sol  m 2 atm  m 2 LSND1  m 2 LSND2 M. Sorel, J. M. Conrad and M. H. Shaevitz, Phys. Rev. D66:033009,2002 Compatibility between SBL (including KARMEN) and LSND of 30%, instead of 3.6 % in the standard 3+1 model O. L. G. Peres and A. Yu. Smirnov, Nucl. Phys. B599:3,2001

14. Sergio Palomares-Ruiz December 18, 2005 CPT violating spectra  m 2 sol  m 2 atm e   The killer: reactor experiments Bugey and CHOOZ: need U e3 ' 1 P KamLAND ' 1  m 2 atm  m 2 LSND  m 2 KamLAND  m 2 LSND,atm H. Murayama and T. Yanagida, Phys. Lett. B520:263-268, 2001 G.Barenboim, L. Borissov and J. Lykken, Phys.Lett.B534:106-113,2002 The killer: atmospheric experiments … for LSND  m 2, antineutrinos signal would wash out the up-down asymmetry produce a deficit of up-going muon events near the horizon Although there is some room for CPT violation with all-but-LSND data… 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

15. Sergio Palomares-Ruiz December 18, 2005 3+1 models - U  4 constrained by CCFR and atmospherics, not CDHS → still some room - U e4 constrained by GALLEX ( e disappearance during test with a 51 Cr 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 4 neutrinos + CPT violation Assuming the same  m 2 for neutrinos and antineutrinos but different mixings V. Barger, D. Marfatia and K. Whisnant, Phys. Lett. B576:303-308,2003

16. Sergio Palomares-Ruiz December 18, 2005 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 KamLANDWith KamLAND G. Barenboim and N. E. Mavromatos, JHEP01:034, 2005 Pure decoherence Pure decoherence both Mixing + decoherence Mixing + decoherence both

17. Sergio Palomares-Ruiz December 18, 2005 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 ) ' |(h eff )  e | 2 L 2 → for LSND |(h eff )  e | 2 ~ (3 x 10 -19 GeV) 2 V. A. Kostelecký and M. Mewes, Phys. Rev. D70:076002, 2004 Unusual dependences for the oscillation phases: a L L and c L L E Predict, e.g., azimuthal dependence for atmospheric neutrinos Constraints (in the  -  sector): a L < few 10 -23 GeV c L < 10 -24 M. C. González-García and M. Maltoni. Phys. Rev. D70:033010, 2004 a L ~ 10 -19 GeV c L ~ 10 -17

18. Sergio Palomares-Ruiz December 18, 2005 LNV muon decay The  L = 2 decay:  + → e + + e +  (  = e, ,  ) could explain LSND data if Scale of new physics relatively low,  ~ 300-400 GeV, → effects on low energy observables, e.g., the SM  parameter in the Michel spectrum These models predict  = 0 for  L = 2 decays → constrained by KARMEN BR KARMEN 0.0021 (90% CL) B. Armbruster et al., Phys. Rev. Lett. 90:181804, 2004 K. S. Babu and S. Pakvasa, hep-ph/0204236 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. Sergio Palomares-Ruiz December 18, 2005 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 V(  )´´ Nucleon number density 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. Sergio Palomares-Ruiz December 18, 2005 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 E res ~ 30 – 100 MeV → no signal in MiniBooNE If E res ~ 200 – 400 MeV → impressive signature in MiniBooNE H. Päs, S. Pakvasa and T. J. Weiler hep-ph/0504096

21. Sergio Palomares-Ruiz December 18, 2005 Neutrino oscillations + decay The decay option: key ingredient to evade CDHS bounds For small U  4 and short baselines 3+1 model with a decay option… …but LSND explained (mainly) by oscillations CDHS compares measurements at two detectors: if D 1 = D 2, no difference This requires  4 / m 4 ~0.03-0.1 and m 4 ~ few eV → g ~ 10 3 -10 4 In contradiction with laboratory bounds g < 10 -2 E. Ma, G. Rajasekaran and I. Stancu, Phys. Rev. D61:071302, 2000

22. Sergio Palomares-Ruiz December 18, 2005 Neutrino decay 3+1 model with a decay option… …but LSND explained by decay As far as g e ´  U el g 4l  0, we expect e and e appearance  produced in  and  decay  4 produced in a fraction given by |U  4 | 2 Subsequently  4 decays into light neutrinos C. W. Kim and W. P. Lam, Mod. Phys. Lett. A5:297, 1990 SPR, S. Pascoli and T. Schwetz, JHEP0509:048, 2005

23. Sergio Palomares-Ruiz December 18, 2005 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 SPR, S. Pascoli and T. Schwetz, JHEP0509:048, 2005 Oscillations:  2 min = 5.6/9 Decay:  2 min = 10.8/9

24. Sergio Palomares-Ruiz December 18, 2005 Spectrum after decay

25. Sergio Palomares-Ruiz December 18, 2005 LSND and KARMEN Compatibility of different data sets: Parameter of Goodness of fit (PG) Oscillations:  2 PG = 5.02 → 8.1% Decay:  2 PG = 4.97 → 8.3% M. Maltoni and T. Schwetz, Phys. Rev. D68:033020, 2003

26. Sergio Palomares-Ruiz December 18, 2005 Global analysis Mixing of e with N 4 is not required → we set U e4 = 0 Only CDHS and atmospherics constrain the model SPR, S. Pascoli and T. Schwetz, JHEP 0509:048, 2005 Best fit: |U  4 | 2 = 0.016 g m 4 = 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%

27. Sergio Palomares-Ruiz December 18, 2005 The MiniBooNE signal 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  beam from  + decay E ~ 700 MeV and L = 540 m Smaller impact of the spectral distortion due to the initial spectrum

28. Sergio Palomares-Ruiz December 18, 2005 Bounds Laboratory bounds –U e4 = 0 → No effect on 0  decay and tritium  decay experiments –2  decay with emission of two scalars→ g eh < O(1) – Pion and kaon decays → g 2 < few 10 -5 Supernova bounds –For g ~ 10 -5, l  ↔ N 4, l N 4 ↔ , … are much faster than weak interactions → N 4 and  are trapped within the neutrinosphere Cosmological bounds –For g ~ 10 -5, N 4 and  are thermalized at BBN→  N =1.57 D. Dassie et al., Nucl. Phys. A678:341, 2000 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 m 4 ~ 1 eV and g ~ 10 -5 → m 4 ~ 100 keV

29. Sergio Palomares-Ruiz December 18, 2005 THE RIGHT ONE

30. Sergio Palomares-Ruiz December 18, 2005 ??

31. Sergio Palomares-Ruiz December 18, 2005 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!