resolving the

Sergio Palomares-Ruiz

December 18, 2005 Resolving the

L S N DSND explained byterile

eutrino

ecayAnomaly

Nu-Mass MeetingGrey College, Durham, UK, December 18-19, 2005


December 18, 2005

THE FACTS


December 18, 2005“Non Standard” results

Solar neutrino deficit8 σ effect

Atmospheric neutrino anomaly14 σ effect

Neutrino disappearance

m221 = (7.3 - 9.1) 10-5 eV2

sin2 12 = (0.23 – 0.37)

| m231| = (1.4 – 3.3) 10-3 eV2

sin2 223 > 0.90

Neutrino OscillationsHomestake, SAGE, GALLEX,

SK, SNO + KamLANDSK and K2K

Standard results

sin2 13 < 0.047

M. Maltoni et al., New J. Phys. 6:122, 2004


December 18, 2005“Standard” results

• 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

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


December 18, 2005“Standard” results

• 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

No neutrino appearance

So far, so good!

No short baseline neutrino “anomaly”Neutrino anomalies explained by oscillationsbetween 3 neutrinos → 2 independent m2

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


December 18, 2005

• LSND ( → e)

L = 30 m; 20 MeV < E < 52.8 MeV → m2 ~ 1 – 10 eV2

It did see e appearance!

Non-Standard resultNeutrino appearance

But…

m2atm + msol m2

LSND

A. Aguilar et al., Phys. Rev. D64:112007, 2001


December 18, 2005The 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


December 18, 2005

3.3 σ effect

A. Aguilar et al., Phys. Rev. D64:112007, 2001 G. 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) %


December 18, 2005The near future

MiniBooNE


December 18, 2005

THE SPECULATIONS


December 18, 2005Classifying 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!


December 18, 20054 neutrino models

24

24 LSND

2

24

24 CDHS

2

24

24BUGEY

2

4 2sin

)1(4 2sin

)1(42sin

UU

UU

UU

e

ee

2+2 3+1

m2sol m2

sol

m2atm

m2atm

m2LSND

m2LSND

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, 1993J. T. Peltoniemi and J. F. W. Valle, Nucl. Phys. B406:409, 1993D. O. Caldwell and R. N. Mohapatra, Phys. Rev. D48:3259, 1993


December 18, 20053+2 neutrino models

m2sol

m2atm

m2LSND1

m2LSND2

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


December 18, 2005CPT violating spectra

m2sol

m2atm

e

E

LmUU

E

LmUUPP eeeeee 4

sin44

sin)1(41)(2

atm222

21

2LSND22

323REACTOR

The killer: reactor experiments

Bugey and CHOOZ: need Ue3 ' 1

PKamLAND ' 1

m2atm

m2LSND

m2KamLAND

m2LSND,atm

H. Murayama and T. Yanagida, Phys. Lett. B520:263-268, 2001G.Barenboim, L. Borissov and J. Lykken, Phys.Lett.B534:106-113,2002

The killer: atmospheric experiments

… for LSND m2, antineutrinos signal would•wash out the up-down asymmetry •produce a deficit of up-going muon events near the horizon

Although there is someroom for CPT violationwith all-but-LSND data…

G. Barenboim, L. Borissov and J. Lykken, hep-ph/0212116A. Strumia, Phys. Lett. B539:91-101,2002M. C. González-García, M. Maltoni and T. Schwetz, Phys. Rev. D68:053007, 2003


December 18, 2005

• 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

4 neutrinos + CPT violationAssuming the same m2 for neutrinos and antineutrinos

but different mixings

V. Barger, D. Marfatia and K. Whisnant, Phys. Lett. B576:303-308,2003


December 18, 2005

CPT violating decoherenceQuatum 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 KamLANDG. Barenboim and N. E. Mavromatos, JHEP01:034, 2005

Pure decoherence Pure decoherence both

Mixing + decoherence Mixing + decoherence

both


December 18, 2005

Lorentz violationIn 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

ppcpa

Eh LLeff )()(

1

P ( → e) ' |(heff)e|2 L2 → for LSND |(heff)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: 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

aL ~ 10-19 GeVcL ~ 10-17


December 18, 2005

LNV muon decay

)%045.0067.0264.0()( LSND PeBr e

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 BRKARMEN < 0.0017 (90% CL), but BRLSND > 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 experimentMeasured = 0.75080 ± 0.00032 ± 0.00097 ± 0.00023

J. R. Musser et al., Phys. Rev. Lett. 94:101805, 2005


December 18, 2005

Mass varying neutrinos

N

Neffi n

mM i

2

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, 2004K. M. Zurek, JHEP 0410:058, 2004V. Barger, D. Marfatia and K. Whisnant, hep-ph/0509163


December 18, 2005

Shortcuts in extra dimesionsIn 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 MiniBooNEIf Eres ~ 200 – 400 MeV → impressive signature in MiniBooNEH. Päs, S. Pakvasa and T. J. Weiler hep-ph/0504096


December 18, 2005

Neutrino oscillations + decay

The decay option: key ingredient to evade CDHS boundsFor small U4 and short baselines

3+1 model with a decay option…

…but LSND explained (mainly) by oscillations

3,2,14int gL

)1(21)2/(cos(121)( 24

24

)2/(24

44 DUELmeUP ELm

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


December 18, 2005

Neutrino decay3+1 model with a decay option…

…but LSND explained by decay

3,2,143,2,14,

int and .. NNchNgLhl

hRlLhl

N

Nlll E

mgNN

32

||)()(

224

444

As far as ge ´ Uel g4l 0 , we expect e and e appearance

• produced in and decay

• 4 produced in a fraction given by |U4|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


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

max )(

)()(

)()(

0

E

Ee

e

e

e

e

e

edE

EdPEdE

dE

EdPEC

dE

dN

SPR, S. Pascoli and T. Schwetz, JHEP0509:048, 2005

Oscillations: 2min = 5.6/9

Decay: 2min = 10.8/9


December 18, 2005

Spectrum after decay


December 18, 2005

LSND and KARMEN

Compatibility of different data sets: Parameter of Goodness of fit (PG)

i

itotPG2min,

2min,

2

Oscillations: 2PG = 5.02 → 8.1%

Decay: 2PG = 4.97 → 8.3%

M. Maltoni and T. Schwetz, Phys. Rev. D68:033020, 2003


December 18, 2005

Global analysis• Mixing of e with N4 is not required → we set Ue4 = 0• Only CDHS and atmospherics constrain the model

4

4

24122

4

2

4

4

4

4

4

22

4

)( ; 4

msin -14-1)(

)( ; 1)( 44

UPPE

LUUP

eUPPeUUP

loscATM

oscSBL

Ll

decATM

LdecSBL

SPR, S. Pascoli and T. Schwetz, JHEP 0509:048, 2005

Best fit: |U4|2 = 0.016g m4 = 3.4 eV

LSND vs restOsc: PG = 0.0018%Dec: PG = 4.6%3+2: PG = 2.1%

LSND+KARMEN vs restOsc: PG = 0.025%Dec: PG = 55%


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


December 18, 2005

Bounds• 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. Dassie et al., Nucl. Phys. A678:341, 2000

D. I. Britton et al., Phys. Rev. D49:28, 1994V. D. Barger, W. Y. Keung and S. Pakvasa, Phys. Rev. D25:907, 1982G. B. Gelmini, S. Nussinov and M. Roncadelli, Nucl. Phys. B209:157, 1982

For g m4 ~ 1 eV and g ~ 10-5 → m4 ~ 100 keV


December 18, 2005

THE RIGHT ONE


December 18, 2005

??


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!

resolving the

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