Constraining new physics scenarios in neutrino oscillations

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Constraining new physics scenarios in neutrino oscillations

Davide Meloni

Dipartimento di Matematica e Fisica RomaTre

ICHEP2014

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07/04/14

Searching for New Physics

Neutrino oscillation physics is entering a precision era:

 Good knowledge of mixing angles and mass differences

 First hints of a non-vanishing CP phase

 Sum of the neutrino masses bounded from above (around 0.2 eV)

It is time to devote serious efforts to the search of New Physics in the lepton sector, using neutrinos

Mariam's talk

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07/04/14

Two

^(three)

different items

 Large Extra Dimensions

 (Non Standard Interactions)

 Sterile neutrinos Main message of this talk:

Neutrinos can be used as probes for some New Physics scenarios

Discussing new results in details for two examples to show how New Physics shows up in the n sector

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07/04/14

Perturbative approach

 sin² 2q₁₃ is a small parameter

 New effects in oscillations must be even smaller

A ( ν

_α

→ ν

_β

)= A

^SM

( ν

_α

→ ν

_β

)+ δ A

_{α β}

Ex: sin² 2q^eff₁₃ = sin² 2q^SM₁₃ (1+d)

From the interference term one can:

(d² is generally too small)

 set strong bounds on d if the data are precise and very well described by SM physics

 “measure” d if the data are precise and NOT well described by SM physics

interference

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07/04/14

The case of sterile neutrinos

m

₃

m

₂

m

₁

Mass differences Mixing angles

q₂₃ q₁₃

q₁₂

m

₄

m

₅

m

₆

q

₁₄

small

Δ m

₁₂²

Δ m

₂₃²

Δ m

₃₄²

Δ m

²₄₅

standard 3- nu scenario

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07/04/14

The case of sterile neutrinos

U = R

₃₄

R

₂₄

R

₁₄

R

₂₃

R

₁₃

R

₁₂

perturbations

P_ee∼1−s₁₂sin²2θ₁₃sin²( Δ m₃₂² L

4 E_ν )−c₁₂² sin²2θ₁₃ sin²(Δ m₃₁² L 4 E_ν )

−s₁₂sin²2θ₁₄sin²(Δ m₄₂² L

4 E_ν )−c₁₂² sin²2θ₁₄ sin²(Δ m₄₁² L 4 E_ν )

Example: n_e → n_etransition

Standard

Interference

Current upper limit:

sin² 2q₁₄ ~ 0.1

M.C.Gonzalez-Garcia et al., JHEP 1212, 123 (2012)

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07/04/14

Bounds on new parameters require experiments with very low systematic uncertainties

Daya Bay in China:

n_e → n_etransition

neutrinos from reactor plants

Daya Bay Collaboration,

Phys.Rev.Lett.112, 061801 (2014)

Far Hall Near

Detectors

sin² 2q₁₃ = 0.090 (0.009) Dm²₃₁=2.59(0.20) x 10^-3 eV² Standard result:

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07/04/14

The case of sterile neutrinos

New results...

3+1 result

1,2 and 3sconfidence level

allowed

excluded

sin² 2q₁₄ <~ 10^-2

I.Girardi, D.Meloni, T.Ohlsson, H.Zhang and S.Zhou, arXiv:1405.6540 [hep-ph].

New bound:

L/Enu →

Dm² around 10^-2/3eV²

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07/04/14

Large Extra Dimensions

A possible way-out:

● there are d compact extra dimensions

of radius R and M_D is the only fundamental energy scale: M²_PL = R^d M^d+2_D

● at distances less than R gravity propagates in all 4+d dimensions

● Standard Model fields are confined in our 4D world Hierarchy problem:

there exist two fundamental energy scales:

● the electroweak scale M_D~ 1 TeV

● quantum gravity M_PL~ 10¹⁸ GeV

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07/04/14

Right-handed neutrinos in extra dimensions

Since neutrinos are special: massless right-handed neutrinos n_Ralso feel the

whole 5D space

2R n_Rpropagated in the whole 5D

n_{R =}n_R(x^m,y)

ν

_R

( x , y )∼Σ

^+∞_n=−∞

ν

⁽_Rⁿ⁾

( x , y ) e

i n y R

Imposing on the n_Rwave function generates infinite replica of the field

Interaction term:

λ

_{α β}

ν

_L^α

( x) ν

^β_R

( x , 0 ) H ( x )

y= y+ 2π R

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07/04/14

Right-handed neutrinos in extra dimensions

For the mass eigenstates (normal ordering):

n₁

n₂

n₃ n⁽¹⁾₁

n⁽ⁿ⁾₁

n⁽²⁾₁

n⁽ⁿ⁾₂ n⁽ⁿ⁾₃

n⁽¹⁾₂

n⁽¹⁾₃ 1/R

Oscillations can take place among active-active and active-KK (infinite) states Kaluza-Klein

excitations

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07/04/14

Right-handed neutrinos in extra dimensions

A ( ν

_α

→ ν

_β

)=Σ

_j

U

_β _j

U

^∗_α _j

e

−i m²_jL 2E_ν

→ Σ

³_j=1

Σ

_k^∞₌₀

U

_β _j

U

^∗_α _j

∣ W

j

(k)

∣

²

e

−iλ⁽_j^k)²L 2E_νR²

W_j^(k)= Transition between zero modes and KK l_j^(k)= absolute neutrino masses

Depend on the lightest absolute neutrino mass

m₀ and R

Only upper limit on m₀(from S_i m_i < 0.2 eV)

Limits on R from experiments based on the torsion pendulum:

R < 37x10^-6m (95% CL) on the largest extraD

J. Beringer et al. (Particle Data Group

Collaboration), Phys. Rev. D 86, 010001 (2012)

D. Davoudiasl, P. Langacker and M. Perelstein, Phys. Rev. D 65, 105015 (2002)

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07/04/14

First results...

I. Girardi and D, Meloni, 1403.5507

new limits from Daya Bay

R < 0.2 (0.6) x10^-6m @2s

for Inverted (Normal) Ordering

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07/04/14

Conclusions



Neutrino physics is an active field, from both experimental and theoretical point of views



Many and precise data are now available, which are very well described in the context of the SM theory of neutrino

oscillation



As for the hadronic sector, New Physics must pop-up as perturbations of the standard picture



We started to investigate such tiny effects for a variety of

New Physics scenarios...

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07/04/14

Backup

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07/04/14

c

²

analysis

χ

²

(⃗ θ , ⃗ S , α

_r

, ϵ

_d

, η

_d

)=Σ

_d⁶₌₁

[ M

^d

−T

^d

(1 + Σ

^r

ω

^r^d

α

^r

+ ϵ

^d

)+ η

^d

]

²

M

_d

+ B

_d

+ Σ_r α_r²

σ_r² +Σ_d⁶₌₁

[

^σ^ϵ^d²^d² ⁺^σ^η²^B^d²^d

]

⁺ ^priors

SM parameters

NP parameters measured events

background events theoretical predictions

pull parameters

w= the fraction of

InverseBetaDecays contribution of the r-th reactor to the d-th detector

background

uncertainties ~ O(1) detector uncertainties ~ O(0.1%) reactor

uncertainties ~ O(1%)

GLoBES

P. Huber et al., Nucl. Phys. B665, 487 (2003);

P. Huber et al., Comput. Phys. Commun. 167,195 (2005).

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07/04/14

Standard neutrino oscillations

 Neutrinos can also be described in terms of mass eigenstates n_i

 Considering time evolutions of mass eigenstates:

neutrino matrix matrix

∣ ν

_α

⟩=Σ

_i=1³

U

_α_i

∣ ν

i

⟩

P (ν

_α

→ ν

_β

)= ∣ 〈 ν

β

∣ ν

_α

( t )〉 ∣

²

= ∣ Σ

j

U

_β _j

U

_α^∗ _j

e

−i m²_j L 2E_ν

∣

²

U_PMNS=

(

¹⁰⁰ ⁻^c⁰^s²³²³ ^c^s⁰²³²³

)

^×

(

⁻^s^c¹³⁰¹³^e⁻ⁱ^δ ⁰¹⁰ ^s¹³^c⁰¹³^eⁱ^δ

)

^×

(

^−s^c⁰¹²¹² ^c^s⁰¹²¹² ⁰⁰¹

)

atmospheric reactor solar

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07/04/14

Summary of the experimental results

Parameter Fit results q₁₂ 33.36^+0.81_-0.78

q₁₃ 8.66^+0.44_-0.46

q₂₃ 40.0^+2-1_-1.5 d (?) 300⁺⁶⁶_-138

(10^-3eV²) 2.47^+0.07_-0.07

(10^-5eV²) 7.50^+0.18_-0.19

Gonzalez-Garcia et al. JHEP1212,(2012)123

 precision era in the determination of mixing parameters Δ m₁₂²

Δ m₂₃²

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07/04/14

To be determined by oscillation experiments

m

₃

m

₂

m

₁

Mass differences Mixing angles

q

₂₃

q

₁₃

q

₁₂

 And: a possible CP phase d and the absolute order of the mass eigenstates (normal or inverted hierarchy)

Δ m

₂₃²

Δ m

₁₂²

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07/04/14

 The number of active neutrino species is fixed by the Z-boson invisible decay width: N_n = 2.994 ± 0.011

 Extra families (if they exist) must have either very heavy neutrinos (m_N > m_Z/2), or no neutrinos at all

Standard Model singlets allowed:

sterile neutrinos

M.Archidiacono et al., arXiv:1404.1794 [astro-ph.CO]

Renewed interest after the recent Planck and BICEP2 results

extra species

Mass of the extra species

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07/04/14

The case of sterile neutrinos

Effects on the standard parameters

small perturbations on top of the standard results

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07/04/14

First results...

I. Girardi and D, Meloni, 1403.5507

Effects of New Physics

standard results are robust...

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07/04/14

Matrix elements