θ at reactor neutrino experiments Non-standard interaction effects for

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Non-standard interaction effects for θ ₁₃ at reactor neutrino experiments

Partikeldagarna

October 16-17, 2008 Contents:

 Neutrino oscillations and non-standard interactions

 NSIs at sources and detectors

 Mimicking effects on θ₁₃

He Zhang

In collaboration with Tommy Ohlsson Royal Institute of Technology (KTH)

arXiv: 0809.4835

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Lepton flavor mixing

Weak

interaction eigenstates

Mass

eigenstates Standard Parametrization



Dirac CP

violating phase

13 13 12 12

23 23 12 12

23 23 13 13

1 0 0 cos 0 sin cos sin 0 0 0

0 cos sin 0 1 0 sin cos 0 0 0

0 sin cos sin 0 cos 0 0 1 0 0 1

i i

i MNS

i

e e

V e

e

 





   

    

   

   

    

     

    

Majorana CP violating phases

NSI Effects for theta_13 at Reactor Neutrino Experiments 17 October 2008 There are now strong evidences that

neutrinos are massive and lepton flavors are mixed. Since in the Standard Model

neutrinos are massless particles, the SM must be extended by adding neutrino masses.

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17 October 2008 NSI Effects for theta_13 at Reactor Neutrino Experiments

Neutrino oscillation parameters

Schwetz, Tortola, Valle, 08

1. θ₁₃ 2. Sign of Δm₃₁²

3. Dirac or Majorana？ 4. Absolute masses 5. Leptonic CP violation? 6. Sterile neutrino?

Unknowns:

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Neutrino oscillation parameters

Schwetz, Tortola, Valle, 08

1. θ₁₃ 2. Sign of Δm₃₁²

3. Dirac or Majorana？ 4. Absolute masses 5. Leptonic CP violation? 6. Sterile neutrino?

Unknowns:

Experimental steps:

Improve present measurements of solar and

atmospheric parameters.

Discover the last mixing angle θ₁₃ (Daya Bay,

Double Chooz)

CP violating phase (δ) in the future Long baseline experiments (ν-Factory, β-beam).

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New physics for neutrino oscillations

• unitarity violation Natural consequence in seesaw models Combined analysis of neutrino

oscillations, W and Z decays, rare LFV modes and lepton universality tests. (Antusch, et al., 06)

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New physics for neutrino oscillations

• non-standard interactions at neutrino sources

• non-standard interactions at neutrino detectors

• unitarity violation Natural consequence in seesaw models

(standard: ) (standard: )

Combined analysis of neutrino oscillations, W and Z decays, rare LFV modes and lepton universality tests. (Antusch, et al., 06)

These effects can be measured even for L=0 (near detector P_μ_e(L=0) ≠ 0)

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New physics for neutrino oscillations

• non-standard interactions at neutrino sources

• non-standard interactions at neutrino detectors

• unitarity violation Natural consequence in seesaw models

(standard: )

These effects can be measured even for L=0 (near detector P_μ_e(L=0) ≠ 0)

Combined analysis of neutrino oscillations, W and Z decays, rare LFV modes and lepton universality tests. (Antusch, et al., 06)

• non-standard interactions with matter during propagation

Constraint by experiments with neutrinos and charged leptons. (Davidson, et al., 03; M.

Blennow, coming soon)

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Neutrino oscillation with NSIs

• The neutrino states produced in the source and observed in the detector are the superpositions of pure orthonormal flavor states.

Normalization factors

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Neutrino oscillation with NSIs

• Effective Hamiltonian in matter

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Neutrino oscillation with NSIs

• Effective Hamiltonian in matter

• Effective mixing matrix and mass squared eigenvalues in matter.

For reactor neutrinos, H₀

»

^Hm & H_NSI

→

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• Amplitude for the process

• Oscillation probability

Neutrino oscillation with NSIs

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• Amplitude for the process

• Oscillation probability Zero-distance effects

Neutrino oscillation with NSIs

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NSIs at reactor neutrino experiments

Far detector

Near detector

(zero-distance effect:

an enhancement of total neutrino flux)

• Only V±A type of NSIs are involved at the source and detector.

• Average energy E≈3 MeV → matter effects are irrelevant.

• ε

^s

=ε

^d

† (ε

^s

<

0.1

, ε

^d

<

0.2 from universality in lepton decay

)

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Short baseline experiments (Daya Bay & D-Chooz)

• Effective mixing angle

• Only

ε

_eμ and

ε

_eτ are involved

• Invariant with respect to the exchange ε_eμ ↔ ε_eτ

• A minimum exists at the position

• CP violating phases enter the oscillation probability explicitly

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Short baseline experiments (Daya Bay & D-Chooz)

• θ₁₃ < 14^o, which is larger than the Chooz bound 10^o

• In despite a very small θ₁₃ , a sizable effective mixing angle can be gained due to the mimicking effects.

• Even if the effective mixing angle is too small to be measured in a reactor experiment, a discovery search of a non-vanishing θ₁₃ may still be carried out at future neutrino factories.

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Short baseline experiments (Daya Bay & D-Chooz)

• Oscillation probabilities for different θ₁₃ .

• The shadings correspond ε<0.05, ε<0.01 and ε<0.001, respectively.

Mimicking oscillation effects

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Medium baseline experiments (KamLAND)

• Effective mixing angle

• Only

ε

_eμ and

ε

_eτ are involved

→

reactor experiments are not sensitive to

ε

_ee

• Since the magnitude of θ₁₂ is more sizable compared to θ₁₃, NSI effects cannot mimic an effective mixing angle with a vanishing θ₁₂ . However, NSIs may significantly modify the observed effective mixing angle.

• To improve the accuracy of current measurement, a baseline length ~ 50 km (the first minimum related with Δm₂₁²) should be taken for next generation experiments.

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Medium baseline experiments (KamLAND)

• The true value of θ₁₂ may be remarkably different from the measured one, i.e., there exists a degeneracy in θ₁₂

• 26^o<θ₁₂ < 42^o, which is close to the bi-maximal mixing for its upper bound and deviates much from the tri-bimaximal

mixing for its lower bound.

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Medium baseline experiments (KamLAND)

• Oscillation probabilities in a medium baseline experiment.

• The shadings correspond ε<0.05, ε<0.01 and ε<0.001, respectively.

• The oscillation behaviors around L≈0 are mainly induced by Δm₃₁² and θ₁₃

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Correlations between θ

₁₃

and θ

₁₂

• The true value of θ₁₂ may achieve the range of Cabibbo angle.

Some hints on the quark-lepton complementary?

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Conclusions

• Mixing angles measured in reactor neutrino experiments could be dramatically modified by NSIs at sources and detectors.

• The mimicking effects induced by NSIs play a very important role in short baseline experiments, especially in the case of a tiny θ

₁₃

. Even for a vanishing θ

₁₃

, the forthcoming Double Chooz and Daya Bay experiments could still perform a discovery search of an

oscillation phenomenon.

• From the phenomenological point of view, two different and

complementary oscillation experiments (e.g. reactor and neutrino

factory) are needed in order to constrain corresponding NSIs.

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Conclusions

• Mixing angles measured in reactor neutrino experiments could be dramatically modified by NSIs at sources and detectors.

• The mimicking effects induced by NSIs play a very important role in short baseline experiments, especially in the case of a tiny θ

₁₃

. Even for a vanishing θ

₁₃

θ at reactor neutrino experiments Non-standard interaction effects for

Non-standard interaction effects for θ 13 at reactor neutrino experiments

Partikeldagarna

He Zhang

Lepton flavor mixing



Neutrino oscillation parameters

Neutrino oscillation parameters

New physics for neutrino oscillations

New physics for neutrino oscillations

New physics for neutrino oscillations

Neutrino oscillation with NSIs

Neutrino oscillation with NSIs

Neutrino oscillation with NSIs

»

→

Neutrino oscillation with NSIs

Neutrino oscillation with NSIs

NSIs at reactor neutrino experiments

• ε

=ε

† (ε

<

, ε

<

)

Short baseline experiments (Daya Bay & D-Chooz)

ε

ε

Short baseline experiments (Daya Bay & D-Chooz)

Short baseline experiments (Daya Bay & D-Chooz)

Medium baseline experiments (KamLAND)

ε

ε

→

ε

Medium baseline experiments (KamLAND)

Medium baseline experiments (KamLAND)

Correlations between θ

and θ

Conclusions

• Mixing angles measured in reactor neutrino experiments could be dramatically modified by NSIs at sources and detectors.

• The mimicking effects induced by NSIs play a very important role in short baseline experiments, especially in the case of a tiny θ

. Even for a vanishing θ

, the forthcoming Double Chooz and Daya Bay experiments could still perform a discovery search of an

oscillation phenomenon.

• From the phenomenological point of view, two different and

complementary oscillation experiments (e.g. reactor and neutrino

factory) are needed in order to constrain corresponding NSIs.

Conclusions

• Mixing angles measured in reactor neutrino experiments could be dramatically modified by NSIs at sources and detectors.

• The mimicking effects induced by NSIs play a very important role in short baseline experiments, especially in the case of a tiny θ

. Even for a vanishing θ

, the forthcoming Double Chooz and Daya Bay experiments could still perform a discovery search of an

oscillation phenomenon.

• From the phenomenological point of view, two different and

complementary oscillation experiments (e.g. reactor and neutrino factory) are needed in order to constrain corresponding NSIs.

Thank you

Non-standard interaction effects for θ ₁₃ at reactor neutrino experiments