Phenomenology of Light Sterile Neutrinos Carlo Giunti INFN, Sezione - - PowerPoint PPT Presentation

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Phenomenology of Light Sterile Neutrinos Carlo Giunti INFN, Sezione - - PowerPoint PPT Presentation

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Phenomenology of Light Sterile Neutrinos Carlo Giunti INFN, Sezione di Torino, and Dipartimento di Fisica, Universit` a di Torino mailto://giunti@to.infn.it Neutrino Unbound: http://www.nu.to.infn.it Technische Universit at M unchen

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SLIDE 1

Phenomenology of Light Sterile Neutrinos Carlo Giunti

INFN, Sezione di Torino, and Dipartimento di Fisica, Universit` a di Torino mailto://giunti@to.infn.it Neutrino Unbound: http://www.nu.to.infn.it

Technische Universit¨ at M¨ unchen Garching, M¨ unchen, Germany 11 December 2013

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 1/38
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SLIDE 2

Fermion Mass Spectrum

m [eV]

10−1 1 10 102 103 104 105 106 107 108 109 1010 1011 1012

νe e u d νµ µ s c ντ τ b t ν1, ν2, ν3

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 2/38
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SLIDE 3

Neutrino Oscillations

◮ 1957: Bruno Pontecorvo proposed Neutrino Oscillations in analogy with

K 0 ⇆ ¯ K 0 oscillations (Gell-Mann and Pais, 1955)

◮ Flavor Neutrinos:

νe, νµ, ντ produced in Weak Interactions

◮ Massive Neutrinos:

ν1, ν2, ν3 propagate from Source to Detector

◮ A Flavor Neutrino is a superposition of Massive Neutrinos

|νe = Ue1 |ν1 + Ue2 |ν2 + Ue3 |ν3 |νµ = Uµ1 |ν1 + Uµ2 |ν2 + Uµ3 |ν3 |ντ = Uτ1 |ν1 + Uτ2 |ν2 + Uτ3 |ν3

◮ U is the 3 × 3 Neutrino Mixing Matrix

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 3/38
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SLIDE 4

|ν(t = 0)=|νe = Ue1 |ν1 + Ue2 |ν2 + Ue3 |ν3

νe

ν3 ν2 ν1 source propagation

νµ

detector

|ν(t > 0) = Ue1 e−iE1t |ν1 + Ue2 e−iE2t |ν2 + Ue3 e−iE3t |ν3=|νe E 2

k = p2 + m2 k

at the detector there is a probability > 0 to see the neutrino as a νµ Neutrino Oscillations are Flavor Transitions νe → νµ νe → ντ νµ → νe νµ → ντ ¯ νe → ¯ νµ ¯ νe → ¯ ντ ¯ νµ → ¯ νe ¯ νµ → ¯ ντ transition probabilities depend on U and ∆m2

kj ≡ m2 k − m2 j

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 4/38
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SLIDE 5

Two-Neutrino Mixing and Oscillations

|να =

2

  • k=1

Uαk |νk (α = e, µ)

ν1 νe ν2 νµ ϑ

U = cos ϑ sin ϑ − sin ϑ cos ϑ

  • |νe = cos ϑ |ν1 + sin ϑ |ν2

|νµ = − sin ϑ |ν1 + cos ϑ |ν2 ∆m2 ≡ ∆m2

21 ≡ m2 2 − m2 1

Transition Probability: Pνe→νµ = Pνµ→νe = sin2 2ϑ sin2 ∆m2L 4E

  • Survival Probabilities:

Pνe→νe = Pνµ→νµ = 1 − Pνe→νµ

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 5/38
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SLIDE 6

Experimental Evidences of Neutrino Oscillations

Solar νe → νµ, ντ    

SNO, BOREXino Super-Kamiokande GALLEX/GNO, SAGE Homestake, Kamiokande

    VLBL Reactor ¯ νe disappearance

(KamLAND)

               →    ∆m2

S ≃ 7.6 × 10−5 eV2

sin2 ϑS ≃ 0.30 Atmospheric νµ → ντ  

Super-Kamiokande Kamiokande, IMB MACRO, Soudan-2

  LBL Accelerator νµ disappearance

(K2K, MINOS, T2K)

LBL Accelerator νµ → ντ

(Opera)

                   →    ∆m2

A ≃ 2.4 × 10−3 eV2

sin2 ϑA ≃ 0.50 LBL Accelerator νµ → νe

(T2K, MINOS)

LBL Reactor ¯ νe disappearance

  • Daya Bay, RENO

Double Chooz

      →    ∆m2

A

sin2 ϑ13 ≃ 0.023

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 6/38
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SLIDE 7

Three-Neutrino Mixing Paradigm

νe νµ ντ ∆m2

A

∆m2

S

ν2 ν1 ν3 m2 Normal Spectrum m2 ∆m2

S

ν2 ν1 ∆m2

A

ν3 Inverted Spectrum ∆m2

S = ∆m2 21 = 7.50 ± 0.20 × 10−5 eV2

uncertainty ≃ 2.6% ∆m2

A = |∆m2 31| ≃ |∆m2 32| = 2.32+0.12 −0.08 × 10−3 eV2

uncertainty ≃ 5%

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 7/38
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SLIDE 8

U =

    c12c13 s12c13 s13e−iδ13 −s12c23−c12s23s13eiδ13 c12c23−s12s23s13eiδ13 s23c13 s12s23−c12c23s13eiδ13 −c12s23−s12c23s13eiδ13 c23c13         1 0 eiλ2 eiλ3    

=  

1 c23 s23 0 −s23 c23

 

ϑ23 = ϑA sin2 ϑ23 ≃ 0.4 − 0.6     c13 0 s13e−iδ13 1 −s13eiδ13 0 c13     Chooz, Palo Verde T2K, MINOS Daya Bay, RENO sin2 ϑ13 = 0.023 ± 0.002     c12 s12 0 −s12 c12 0 1     ϑ12 = ϑS sin2 ϑ12 = 0.30 ± 0.01     1 0 eiλ2 eiλ3     ββ0ν

δ sin2 ϑ23 sin2 ϑ23 ≃ 40% δ sin2 ϑ13 sin2 ϑ13 ≃ 10% δ sin2 ϑ12 sin2 ϑ12 ≃ 5%

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 8/38
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SLIDE 9

Open Problems

◮ ϑ23 ⋚ 45◦ ?

◮ Atmospheric ν, T2K, NOνA, . . . . . .

◮ Mass Hierarchy ?

◮ NOνA, Atmospheric ν, Day Bay II, RENO-50, Supernova ν, . . .

◮ CP violation ?

◮ NOνA, LAGUNA-LBNO, LBNE (USA), HyperK, . . .

◮ Absolute Mass Scale ?

◮ β Decay, Neutrinoless Double-β Decay, Cosmology, . . .

◮ Dirac or Majorana ?

◮ Neutrinoless Double-β Decay, . . .

◮ Beyond Three-Neutrino Mixing ? Sterile Neutrinos ?

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 9/38
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SLIDE 10

Absolute Scale of Neutrino Masses

Lightest mass: m1 [eV] m1, m2, m3 [eV] 10−3 10−2 10−1 1 10−3 10−2 10−1 1

m1 m2 m3

∆mS

2

∆mA

2

95% Kinematical Limit 95% KATRIN Sensitivity 95% Cosmological Limit

Normal Hierarchy Quasi−Degenerate

Normal Spectrum m3 m2 m1

m2

2 = m2 1 + ∆m2 21 = m2 1 + ∆m2 S

m2

3 = m2 1 + ∆m2 31 = m2 1 + ∆m2 A

Lightest mass: m3 [eV] m3, m1, m2 [eV] 10−3 10−2 10−1 1 10−3 10−2 10−1 1

m3 m1 m2

∆mA

2

95% Kinematical Limit 95% KATRIN Sensitivity 95% Cosmological Limit

Inverted Hierarchy Quasi−Degenerate

Inverted Spectrum m2 m1 m3

m2

1 = m2 3 − ∆m2 31 = m2 3 + ∆m2 A

m2

2 = m2 1 + ∆m2 21 ≃ m2 3 + ∆m2 A

Quasi-Degenerate for m1 ≃ m2 ≃ m3 ≃ mν

  • ∆m2

A ≃ 5 × 10−2 eV

95% Cosmological Limit: Planck + WMAP9 + highL + BAO

[arXiv:1303.5076]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 10/38
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SLIDE 11

Effective Neutrino Mass in Beta-Decay

m2

β = |Ue1|2 m2 1 + |Ue2|2 m2 2 + |Ue3|2 m2 3

mmin [eV] mβ [eV]

NS IS

∆mA

2

Current 95% Bound KATRIN 95% Sensitivity 95% Cosmological Limit 10−3 10−2 10−1 1 10 10−3 10−2 10−1 1 10

1σ 2σ 3σ

◮ Quasi-Degenerate:

m2

β ≃ m2 ν

  • k |Uek|2 = m2

ν ◮ Inverted Hierarchy:

m2

β ≃ (1 − s2 13)∆m2 A ≃ ∆m2 A ◮ Normal Hierarchy:

m2

β ≃ s2 12c2 13∆m2 S + s2 13∆m2 A

≃ 2 × 10−5 + 6 × 10−5 eV2

◮ mβ 4 × 10−2 eV

⇓ Normal Spectrum

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 11/38
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SLIDE 12

Majorana ν: Neutrinoless Double-Beta Decay

76 32Ge 76 33As 76 34Se

Germanium Arsenic Selenium β− β+ β−β−

(T 0ν

1/2)−1 = G0ν |M0ν|2 m2 ββ

Effective Majorana Mass mββ =

  • 3
  • k=1

U2

ekmk

  • d
u W
  • k
m k U ek U ek W d u e
  • e
  • EXO + KamLAND-Zen

136 54Xe → 136 56Ba + e− + e−

[PRL 109 (2012) 032505; PRL 110 (2013) 062502]

|mββ| 0.12 − 0.25 eV (90%C.L.) GERDA

76 32Ge → 76 34Se + e− + e−

[arXiv:1307.4720]

|mββ| 0.2 − 0.6 eV (90%C.L.)

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 12/38
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SLIDE 13

Effective Majorana Neutrino Mass

mββ = |Ue1|2 m1 + |Ue2|2 eiα2 m2 + |Ue3|2 eiα3 m3

mmin [eV] |mββ| [eV]

NS IS

95% Cosmological Limit 90% EXO+KLZ 90% GERDA 10−4 10−3 10−2 10−1 1 10−4 10−3 10−2 10−1 1

1σ 2σ 3σ

◮ Quasi-Degenerate:

|mββ| ≃ mν

  • 1 − s2

2ϑ12s2 α2 ◮ Inverted Hierarchy:

|mββ| ≃

  • ∆m2

A(1 − s2 2ϑ12s2 α2) ◮ Normal Hierarchy:

|mββ| ≃ |s2

12

  • ∆m2

S + eiαs2 13

  • ∆m2

A|

≃ |2.7 + 1.2eiα| × 10−3 eV m1 10−3 eV⇒cancellation? |mββ| 10−2 eV = ⇒ Normal Spectrum

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 13/38
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SLIDE 14

Beyond Three-Neutrino Mixing: Sterile Neutrinos ν1 m2

1

log m2 m2

2

ν2 ν3 m2

3

νe νµ ντ νs1 · · · ν4 ν5 · · · m2

4

m2

5

νs2 3ν-mixing ∆m2

ATM

∆m2

SBL

∆m2

SOL

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 14/38
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SLIDE 15

Sterile Neutrinos from Physics Beyond the SM

◮ Neutrinos are special in the Standard Model: the only neutral fermions ◮ In extensions of SM neutrinos can mix with non-SM fermions ◮ SM:

LL = νL ℓL

  • Φ = iσ2 Φ∗ =

φ0 φ−

  • Symmetry

− − − − − − →

Breaking

  • v/

√ 2

  • ◮ SM singlet LL

Φ can couple to new singlet chiral fermion field νR (right-handed neutrino) related to physics beyond the SM

◮ Known examples: SUSY, new symmetries, extra dimensions, mirror

world, . . .

[see http://www.nu.to.infn.it/Sterile Neutrinos/]

◮ Dirac mass term ∼ LL

ΦνR + Majorana mass term ∼ νc

RνR ◮ Diagonalization of mass matrix

= ⇒ massive Majorana neutrinos

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 15/38
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SLIDE 16

Light Sterile Neutrinos

◮ Light anti-νR are called sterile neutrinos

νc

R→νsL

(left-handed)

◮ Sterile means no standard model interactions

[Pontecorvo, Sov. Phys. JETP 26 (1968) 984]

◮ Active neutrinos (νe, νµ, ντ) can oscillate into light sterile neutrinos (νs) ◮ Observables:

◮ Disappearance of active neutrinos (neutral current deficit) ◮ Indirect evidence through combined fit of data (current indication)

◮ Short-baseline anomalies + 3ν-mixing:

∆m2

21 ≪ |∆m2 31| ≪ |∆m2 41| ≤ . . .

ν1 ν2 ν3 ν4 . . . νe νµ ντ νs1 . . .

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 16/38
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SLIDE 17

◮ In this talk I consider sterile neutrinos with mass scale ∼ 1 eV in light of

short-baseline Reactor Anomaly, Gallium Anomaly, LSND.

◮ Other possibilities (not incompatible):

◮ Very light sterile neutrinos with mass scale ≪ 1 eV: important for solar

neutrino phenomenology

[Das, Pulido, Picariello, PRD 79 (2009) 073010] [de Holanda, Smirnov, PRD 83 (2011) 113011]

◮ Heavy sterile neutrinos with mass scale ≫ 1 eV: could be Warm Dark

Matter

[Kusenko, Phys. Rept. 481 (2009) 1] [Boyarsky, Ruchayskiy, Shaposhnikov, Ann. Rev. Nucl. Part. Sci. 59 (2009) 191] [Drewes, arXiv:1303.6912]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 17/38
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SLIDE 18

LSND

[PRL 75 (1995) 2650; PRC 54 (1996) 2685; PRL 77 (1996) 3082; PRD 64 (2001) 112007]

¯ νµ → ¯ νe L ≃ 30 m 20 MeV ≤ E ≤ 200 MeV

  • ther

p(ν

_ e,e+)n

p(ν

_ µ→ν _ e,e+)n

L/Eν (meters/MeV) Beam Excess

Beam Excess

2.5 5 7.5 10 12.5 15 17.5 0.4 0.6 0.8 1 1.2 1.4 10

  • 2

10

  • 1

1 10 10 2 10

  • 3

10

  • 2

10

  • 1

1 sin2 2θ ∆m2 (eV2/c4)

Bugey Karmen NOMAD CCFR 90% (Lmax-L < 2.3) 99% (Lmax-L < 4.6)

3.8σ excess ∆m2

LSND 0.2 eV2

(≫ ∆m2

A ≫ ∆m2 S)

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 18/38
slide-19
SLIDE 19

MiniBooNE

L ≃ 541 m 200 MeV ≤ E 3 GeV νµ → νe

[PRL 102 (2009) 101802]

LSND signal

¯ νµ → ¯ νe

[PRL 110 (2013) 161801]

LSND signal

◮ Purpose: check LSND signal. ◮ Different L and E. ◮ Similar L/E (oscillations). ◮ LSND signal: E > 475 MeV. ◮ Agreement with LSND signal? ◮ CP violation? ◮ Low-energy anomaly!

Energy reconstruction problem?

[Martini et al, PRD 85 (2012) 093012; PRD 87 (2013) 013009]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 19/38
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SLIDE 20

New Reactor ¯ νe Fluxes

[T. Lasserre, TAUP 2013]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 20/38
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SLIDE 21

Reactor Electron Antineutrino Anomaly

[Mention et al, PRD 83 (2011) 073006] [update in White Paper, arXiv:1204.5379]

new reactor ¯ νe fluxes

[Mueller et al, PRC 83 (2011) 054615] [Huber, PRC 84 (2011) 024617]

∼ 2.8σ anomaly

[see also: Sinev, arXiv:1103.2452; Ciuffoli, Evslin, Li, JHEP 12 (2012) 110; Zhang, Qian, Vogel, PRD 87 (2013) 073018; Ivanov et al, arXiv:1306.1995] 20 40 60 80 100 0.7 0.8 0.9 1.0 1.1 1.2

L [m] R = N exp N no osc. R = 0.930 ± 0.024

Reactor Rates Bugey3−15 Bugey3−40 Bugey3−95 Bugey4−15 ROVNO−18 Gosgen−38 Gosgen−45 Gosgen−65 ILL−9 Krasno−33 Krasno−92 Krasno−57 Average Rate

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 21/38
slide-22
SLIDE 22

Gallium Anomaly

Gallium Radioactive Source Experiments: GALLEX and SAGE Detection Process: νe + 71Ga → 71Ge + e− νe Sources: e− + 51Cr → 51V + νe e− + 37Ar → 37Cl + νe Anomaly supported by new 71Ga(3He, 3H)71Ge cross section measurement

[Frekers et al., PLB 706 (2011) 134]

0.7 0.8 0.9 1.0 1.1

R = N exp N no osc.

Cr1 GALLEX Cr SAGE Cr2 GALLEX Ar SAGE

R = 0.84 ± 0.05

E ∼ 0.7 MeV LGALLEX = 1.9 m LSAGE = 0.6 m ∼ 2.9σ anomaly

[SAGE, PRC 73 (2006) 045805; PRC 80 (2009) 015807] [Laveder et al, Nucl.Phys.Proc.Suppl. 168 (2007) 344; MPLA 22 (2007) 2499; PRD 78 (2008) 073009; PRC 83 (2011) 065504; PRD 86 (2012) 113014] [Mention et al, PRD 83 (2011) 073006]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 22/38
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SLIDE 23

Effective SBL Oscillation Probabilities in 3+1 Schemes

P

(−)

να→

(−)

νβ

= sin2 2ϑαβ sin2 ∆m2

41L

4E

  • sin2 2ϑαβ = 4|Uα4|2|Uβ4|2

No CP Violation! P

(−)

να→

(−)

να

= 1 − sin2 2ϑαα sin2 ∆m2

41L

4E

  • sin2 2ϑαα = 4|Uα4|2

1 − |Uα4|2 Perturbation of 3ν Mixing: |Ue4|2 ≪ 1 , |Uµ4|2 ≪ 1 , |Uτ4|2 ≪ 1 , |Us4|2 ≃ 1 Ue4 Uµ4 Uτ4 Us4 Uτ3 Ue3 Uµ3 Us3 Uµ2 Uτ2 Ue2 Us2 Uτ1 Ue1 Uµ1 Us1 U = SBL sin2 2ϑαα ≪ 1 ⇓ |Uα4|2 ≃ sin2 2ϑαα 4

[Okada, Yasuda, IJMPA 12 (1997) 3669-3694] [Bilenky, Giunti, Grimus, EPJC 1 (1998) 247]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 23/38
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SLIDE 24

Effective SBL Oscillation Probabilities in 3+2 Schemes

φkj = ∆m2

kjL/4E

η = arg[U∗

e4Uµ4Ue5U∗ µ5]

P

(−)

νµ→

(−)

νe

= 4|Ue4|2|Uµ4|2sin2 φ41 + 4|Ue5|2|Uµ5|2sin2 φ51 + 8|Uµ4Ue4Uµ5Ue5|sin φ41sin φ51cos(φ54

(+)

− η) P

(−)

να→

(−)

να

= 1 − 4(1 − |Uα4|2 − |Uα5|2)(|Uα4|2sin2 φ41 + |Uα5|2sin2 φ51) − 4|Uα4|2|Uα5|2sin2 φ54

[Sorel, Conrad, Shaevitz, PRD 70 (2004) 073004; Maltoni, Schwetz, PRD 76 (2007) 093005; Karagiorgi et al, PRD 80 (2009) 073001; Kopp, Maltoni, Schwetz, PRL 107 (2011) 091801; Giunti, Laveder, PRD 84 (2011) 073008; Donini et al, JHEP 07 (2012) 161; Archidiacono et al, PRD 86 (2012) 065028; Conrad et al, AHEP 2013 (2013) 163897; Archidiacono et al, PRD 87 (2013) 125034; Kopp, Machado, Maltoni, Schwetz, JHEP 1305 (2013) 050; Giunti, Laveder, Y.F. Li, H.W. Long, arXiv:1308.5288; Girardi, Meroni, Petcov, arXiv:1308.5802]

◮ Good: CP violation ◮ Bad: Two massive sterile neutrinos at the eV scale!

4 more parameters: ∆m2

41, |Ue4|2, |Uµ4|2,

  • 3+1

∆m2

51, |Ue5|2, |Uµ5|2, η

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 24/38
slide-25
SLIDE 25

Global νe and ¯ νe Disappearance

[Giunti, Laveder, Y.F. Li, Q.Y. Liu, H.W. Long, PRD 86 (2012) 113014] sin22ϑee ∆m41

2 [eV2]

+

10−2 10−1 1 10−2 10−1 1 10 102

+ + +

95% CL Gallium Reactors νeC Sun Combined 95% CL Gallium Reactors νeC Sun Combined

νe + 12C → 12Ng.s. + e− KARMEN + LSND

[Conrad, Shaevitz, PRD 85 (2012) 013017] [Giunti, Laveder, PLB 706 (2011) 200]

solar νe + KamLAND ¯ νe + ϑ13

[Giunti, Li, PRD 80 (2009) 113007] [Palazzo, PRD 83 (2011) 113013; PRD 85 (2012) 077301] sin22ϑee ∆m41

2 [eV2]

10−2 10−1 1 10−1 1 10

+

GAL+REA+νeC+SUN 68.27% CL (1σ) 90.00% CL 95.45% CL (2σ) 99.00% CL 99.73% CL (3σ) GAL+REA+νeC+SUN 68.27% CL (1σ) 90.00% CL 95.45% CL (2σ) 99.00% CL 99.73% CL (3σ)

GoF = 62% PGoF = 4% No Osc. excluded at 2.7σ ∆χ2/NDF = 10.1/2

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 25/38
slide-26
SLIDE 26

Mainz and Troitsk Limit on m2

4

[Kraus, Singer, Valerius, Weinheimer, EPJC 73 (2013) 2323] [Belesev et al, JETP Lett. 97 (2013) 67; arXiv:1307.5687]

−8 −6 −4 −2 2 4 6 8

T − Q [eV] K(T) ∆m41

2 = 16 eV2

sin2ϑ14 = 0.4 sin22ϑee ∆m41

2 [eV2]

10−1 1 1 10 102 103 104

95% CL SBL Mainz+Troitsk SBL+Mai.+Tro. 95% CL SBL Mainz+Troitsk SBL+Mai.+Tro.

m4 ≫ m1, m2, m3 = ⇒ ∆m2

41 ≡ m2 4 − m2 1 ≃ m2 4

2σ : 0.85 ∆m2

41 43 eV2

= ⇒ 6 cm Losc

41

E [MeV] 3 m

[Giunti, Laveder, Y.F. Li, H.W. Long, PRD 87 (2013) 013004]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 26/38
slide-27
SLIDE 27

KATRIN Sensitivity

[Formaggio, Barrett, PLB 706 (2011) 68]

102 101 1 102 101 1 10 20 Sin22Θs m41

2 eV2

Bugey4Rovno , 99 C.L. Bugey3 , 99 C.L. global fit , 90 C.L. m1 2 eV , 90 C.L. m1 1 eV , 90 C.L. m1 0 , 90 C.L.

[Esmaili, Peres, PRD 85 (2012) 117301] [see also: Sejersen Riis, Hannestad, JCAP (2011) 1475; Sejersen Riis, Hannestad, Weinheimer, PRC 84 (2011) 045503]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 27/38
slide-28
SLIDE 28

Neutrinoless Double-β Decay

2 4 6 8 10

mββ

(4) [eV]

∆χ2 10−3 10−2 10−1 1 EXO+KLZ 90% CL KK GERDA 90% CL

68.27% 90% 95.45% 99% 99.73%

SBL SBL + Mainz SBL + Mainz + Troitsk

|mββ| =

  • 4

k=1 U2 ek mk

  • m(4)

ββ = |Ue4|2

  • ∆m2

41

caveat: possible cancellation with m(3ν−IH)

ββ

[Barry et al, JHEP 07 (2011) 091] [Li, Liu, PLB 706 (2012) 406] [Rodejohann, JPG 39 (2012) 124008] [Girardi, Meroni, Petcov, arXiv:1308.5802]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 28/38
slide-29
SLIDE 29

3+1: Appearance vs Disappearance

◮ νe disappearance experiments:

sin2 2ϑee = 4|Ue4|2 1 − |Ue4|2 ≃ 4|Ue4|2

◮ νµ disappearance experiments:

sin2 2ϑµµ = 4|Uµ4|2 1 − |Uµ4|2 ≃ 4|Uµ4|2

◮ νµ → νe experiments:

sin2 2ϑeµ = 4|Ue4|2|Uµ4|2 ≃ 1 4 sin2 2ϑee sin2 2ϑµµ

◮ Upper bounds on sin2 2ϑee and sin2 2ϑµµ =

⇒ strong limit on sin2 2ϑeµ

[Okada, Yasuda, IJMPA 12 (1997) 3669-3694] [Bilenky, Giunti, Grimus, EPJC 1 (1998) 247]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 29/38
slide-30
SLIDE 30

3+1 Global Fit

[Giunti, Laveder, Y.F. Li, H.W. Long, arXiv:1308.5288]

sin22ϑeµ ∆m41

2 [eV2]

10−4 10−3 10−2 10−1 1 10−1 1 10

+

10−4 10−3 10−2 10−1 1 10−1 1 10

+

3+1 − GLO 68.27% CL 90.00% CL 95.45% CL 99.00% CL 99.73% CL 3+1 − 3σ νe DIS νµ DIS DIS APP

MiniBooNE E > 475 MeV GoF = 29% PGoF = 9%

◮ APP νµ → νe & ¯

νµ → ¯ νe: LSND (Y), MiniBooNE (?), OPERA (N), ICARUS (N), KARMEN (N), NOMAD (N), BNL-E776 (N)

◮ DIS νe & ¯

νe: Reactors (Y), Gallium (Y), νeC (N), Solar (N)

◮ DIS νµ & ¯

νµ: CDHSW (N), MINOS (N), Atmospheric (N), MiniBooNE/SciBooNE (N) No Osc. excluded at 6.2σ ∆χ2/NDF = 46.2/3

[different approach and conclusions: Kopp, Machado, Maltoni, Schwetz, JHEP 1305 (2013) 050]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 30/38
slide-31
SLIDE 31

MiniBooNE Low-Energy Excess?

sin22ϑeµ ∆m41

2 [eV2]

10−4 10−3 10−2 10−1 1 10−2 10−1 1 10 102

* + + + +

νeDIS νµDIS νe&νµDIS ICARUS OPERA

MiniBooNE 68.27% CL (1σ) 90.00% CL 95.45% CL (2σ) 99.00% CL 99.73% CL (3σ) MiniBooNE 68.27% CL (1σ) 90.00% CL 95.45% CL (2σ) 99.00% CL 99.73% CL (3σ)

−0.2 0.0 0.2 0.4 0.6 0.8

E [MeV] Excess Events / MeV

200 400 600 800 1000 1200 1400 3000

MiniBooNE − νe Data − Expected Background sin22ϑ = 0.98, ∆m2 = 0.04 eV2 (bf) sin22ϑ = 0.013, ∆m2 = 0.35 eV2 sin22ϑ = 0.0017, ∆m2 = 0.47 eV2 sin22ϑ = 0.0022, ∆m2 = 0.85 eV2 sin22ϑ = 0.0023, ∆m2 = 3 eV2

◮ No fit of low-energy excess for realistic sin2 2ϑeµ 5 × 10−3 ◮ APP-DIS PGoF = 0.1% ◮ Neutrino energy reconstruction problem?

[Martini, Ericson, Chanfray, PRD 85 (2012) 093012; PRD 87 (2013) 013009]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 31/38
slide-32
SLIDE 32

MiniBooNE Impact on SBL Oscillations?

with MiniBooNE

sin22ϑeµ ∆m41

2 [eV2]

10−4 10−3 10−2 10−1 1 10−1 1 10

+

10−4 10−3 10−2 10−1 1 10−1 1 10

+

3+1 − GLO 68.27% CL 90.00% CL 95.45% CL 99.00% CL 99.73% CL 3+1 − 3σ νe DIS νµ DIS DIS APP

GoF = 29% PGoF = 9% No Osc. excluded at 6.2σ ∆χ2/NDF = 46.2/3 without MiniBooNE

sin22ϑeµ ∆m41

2 [eV2]

10−4 10−3 10−2 10−1 1 10−1 1 10

+

10−4 10−3 10−2 10−1 1 10−1 1 10

+

3+1 68.27% CL 90.00% CL 95.45% CL 99.00% CL 99.73% CL 3+1 − 3σ νe DIS νµ DIS DIS APP

GoF = 19% PGoF = 8% No Osc. excluded at 6.3σ ∆χ2/NDF = 47.1/3 Without LSND: No Osc. excluded only at 2.1σ (∆χ2/NDF = 8.3/3)

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 32/38
slide-33
SLIDE 33

3+2

◮ 3+2 should be preferred to 3+1 only if

◮ there is evidence of two peaks of the probability corresponding to two ∆m2’s

  • r

◮ there is CP-violating difference of νµ → νe and ¯

νµ → ¯ νe transitions

◮ 2008 ν + 2010 ¯

ν MiniBooNE data indicated ν–¯ ν difference ⇓ reasonable and useful to consider 3+2

◮ ν–¯

ν difference almost disappeared with 2012 ¯ ν data

◮ Okkam razor: 3+1 is enough! ◮ Different approach and conclusions:

◮ Kopp, Machado, Maltoni, Schwetz, JHEP 1305 (2013) 050:

Use all MiniBooNE data. No 3+1 global fit. 3+2 slightly preferred? Small allowed region.

◮ Conrad, Ignarra, Karagiorgi, Shaevitz, Spitz, AHEP 2013 (2013) 163897:

Use all MiniBooNE data. 3+2 strongly preferred. Very small allowed regions.

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 33/38
slide-34
SLIDE 34

MiniBooNE Low-Energy Excess?

−0.2 0.0 0.2 0.4 0.6 0.8

E [MeV] Excess Events / MeV

200 400 600 800 1000 1200 1400 3000 MiniBooNE − νe Data − Expected Background 3+1 3+2 −0.1 0.0 0.1 0.2 0.3

E [MeV] Excess Events / MeV

200 400 600 800 1000 1200 1400 3000 MiniBooNE − νe Data − Expected Background 3+1 3+2

◮ 3+1:

GoF = 6% PGoF = 0.2%

◮ 3+2:

GoF = 8% PGoF = 0.1%

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 34/38
slide-35
SLIDE 35

νe and νµ Disappearance

sin22ϑee ∆m41

2 [eV2]

10−2 10−1 1 10−1 1 10

+

DIS

3+1 − GLO 68.27% CL 90.00% CL 95.45% CL 99.00% CL 99.73% CL DIS 95.45% CL (2σ) 99.73% CL (3σ)

sin22ϑµµ ∆m41

2 [eV2]

10−2 10−1 1 10−1 1 10

+

DIS

3+1 − GLO 68.27% CL 90.00% CL 95.45% CL 99.00% CL 99.73% CL DIS 95.45% CL (2σ) 99.73% CL (3σ)

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 35/38
slide-36
SLIDE 36

Many Exciting New Experiments and Projects

◮ Reactor ¯

νe Disappearance:

◮ Nucifer (OSIRIS, Saclay), Stereo (ILL, Grenoble) [arXiv:1204.5379] ◮ DANSS (Kalinin Nuclear Power Plant, Russia) [arXiv:1304.3696],

POSEIDON (PIK, Gatchina, Russia) [arXiv:1204.2449]

◮ SCRAAM (San Onofre, California) [arXiv:1204.5379] ◮ CARR (China Advanced Research Reactor) [arXiv:1303.0607] ◮ Neutrino-4 (SM-3, Dimitrovgrad, Russia), SOLID (BR2, Belgium),

Hanaro (Korea) [D. Lhuillier, EPSHEP 2013]

◮ Radioactive Source νe and ¯

νe Disappearance:

◮ SOX (Borexino, Gran Sasso, Italy) [arXiv:1304.7721] ◮ CeLAND (144Ce@KamLAND, Japan) [arXiv:1107.2335] ◮ SAGE (Baksan, Russia) [arXiv:1006.2103] ◮ IsoDAR (DAEδALUS, USA) [arXiv:1210.4454, arXiv:1307.2949] ◮ SNO+, Daya Bay, RENO [T. Lasserre, Neutrino 2012]

◮ Accelerator

(−)

νµ →

(−)

νe Appearance:

◮ ICARUS/NESSIE (CERN) [arXiv:1304.2047, arXiv:1306.3455] ◮ nuSTORM [arXiv:1308.0494] ◮ OscSNS (Oak Ridge, USA) [arXiv:1305.4189, arXiv:1307.7097]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 36/38
slide-37
SLIDE 37

Effects of light sterile neutrinos can be also seen in:

◮ Solar neutrinos

[Dooling et al, PRD 61 (2000) 073011, Gonzalez-Garcia et al, PRD 62 (2000) 013005; Palazzo, PRD 83 (2011) 113013, PRD 85 (2012) 077301; Li et al, PRD 80 (2009) 113007, PRD 87, 113004 (2013), JHEP 1308 (2013) 056; Kopp, Machado, Maltoni, Schwetz, JHEP 1305 (2013) 050]

◮ Atmospheric neutrinos

[Goswami, PRD 55 (1997) 2931; Bilenky, Giunti, Grimus, Schwetz, PRD 60 (1999) 073007; Maltoni, Schwetz, Tortola, Valle, NPB 643 (2002) 321, PRD 67 (2003) 013011; Choubey, JHEP 12 (2007) 014; Razzaque, Smirnov, JHEP 07 (2011) 084, PRD 85 (2012) 093010; Gandhi, Ghoshal, PRD 86 (2012) 037301; Esmaili, Halzen, Peres, JCAP 1211 (2012) 041; Esmaili, Smirnov, arXiv:1307.6824]

◮ Supernova neutrinos

[Caldwell, Fuller, Qian, PRD 61 (2000) 123005; Peres, Smirnov, NPB 599 (2001); Sorel, Conrad, PRD 66 (2002) 033009; Tamborra, Raffelt, Huedepohl, Janka, JCAP 1201 (2012) 013; Wu, Fischer, Martinez-Pinedo, Qian, arXiv:1305.2382]

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 37/38
slide-38
SLIDE 38

Conclusions

◮ Short-Baseline νe and ¯

νe 3+1 Disappearance:

◮ Reactor ¯

νe anomaly is alive and exciting.

◮ Gallium νe anomaly strengthened by new cross-section measurements. ◮ Many promising projects to test short-baseline νe and ¯

νe disappearance in a few years with reactors and radioactive sources.

◮ Independent tests through effect of m4 in β-decay and (ββ)0ν-decay.

◮ Short-Baseline ¯

νµ → ¯ νe LSND Signal:

◮ MiniBooNE experiment has been inconclusive. ◮ Better experiments are needed to check LSND signal! ◮ If |Ue4| > 0 why not |Uµ4| > 0? =

⇒ Maybe LSND luckily observed a fluctuation of a small ¯ νµ → ¯ νe transition probability with amplitude sin2 2ϑeµ = 4|Ue4|2|Uµ4|2, which has not been seen by other appearance experiments.

◮ Cosmology:

◮ Important effects of sterile neutrinos. ◮ Implications depend on theoretical framework and considered data set. ◮ Cosmological indications must be checked by laboratory experiments.

  • C. Giunti − Phenomenology of Light Sterile Neutrinos − TUM − 11 Dec 2013 − 38/38