Joint T2K and reactor experiments analysis within VALOR

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Joint T2K and reactor experiments analysis within VALOR

Maria Antonova Pau Novella

IFIC Valencia

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Joint T2K and reactor experiments analysis within VALOR

Overview

• Motivation

• Study with Double Chooz inputs

• 1D fit study

• Study with Daya Bay inputs

• 2D fit study

• Future plans

• Summary

• Comments on the talk

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sin² θ₁₃ δ_CP

|Δm₃₂² | × sin² θ₁₃

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Motivation

What is used now:

• The penalty term used in current analysis is gaussian ( i.e.

“symmetric”) Proposed idea:

• Combine likelihood surface from T2K and reactor experiment

• More accurate analysis

(reactor likelihood is not exactly symmetric )

• Take advantage of reactor experiments being sensitive to

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| Δm₃₂² |

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Double Chooz (DC): Fit features

• Two ways of taking into account reactor constraint:

• Penalty term using mean and sigma from reactor experiment best fit (same as current analysis, but using DC

instead of PDG average)

•

i.e.get directly from reactor

experiment likelihood surface and sum with T2K one

• 1D likelihood surface

• 2D likelihood surface

• Converting

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χ²

L_T_2K + L_Reactor

Used DC likelihood surface with fixed

|Δm₃₂² |

Δm_ee² → Δm₃₂²

Δm_ee² ≃ cos² θ₁₂|Δm₃₁² | + sin² θ₁₂|Δm₃₂² |

|Δm₃₂² | ≃ |Δm_ee² | ∓ 5.2 × 10⁻⁵eV²

assuming NH (upper sign) or IH (lower sign)

DC best-fit values:

sin² θ₁₃ = 0.025 ± 0.005

|Δm₃₂² | = (2.58 ± 0.46) × 1 −⁻³ eV²

(L_Reactor(θ₁₃, Δm₃₂² )) (L_Reactor(θ₁₃)

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T2K only vs. T2K+ DC BF

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• T2K-only fit :

• 0.024

• [0.021;0.029]

• T2K + DC BF penalty fit

• 0.025

•

[0.022;0.028]

μ

1σ interval

μ

1σ interval

Asimov A

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13) (θ

sin2

10 15 20 25 30 35 40 45 50

−3

×10

ln(L)Δ-2

0 5 10 15 20 25

1σ 2σ

T2K_only 1D_external

T2K Run 1-9 Preliminary T2K Run 1-9 Preliminary

T2K only vs. T2K+DC 1D

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• T2K-only fit :

• 0.024

• [0.021;0.029]

• T2K + penalty term from DC 1D

likelihood surface fit:

• 0.025

•

[0.022;0.028]

μ

1σ interval

μ

1σ interval

• Denoted : 1D_external

Asimov A

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13) (θ

sin2

15 20 25 30 35

−3

×10

ln(L)Δ-2

0 2 4 6 8 10 12 14 16

1σ 2σ

1D_penalty

BF_DC_penalty

T2K Run 1-9 Preliminary T2K Run 1-9 Preliminary

Asimov A

T2K+DC 1D vs. T2K+ DC BF

• T2K + penalty term from DC 1D

likelihood surface fit:

• 0.025

• [0.022;0.028]

• Denoted: 1D penalty

• T2K + DC BF penalty fit:

• 0.025

•

[0.022;0.028]

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μ

1σμ interval

1σ interval

• Denoted : BF_DC_penalty

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• T2K + DC BF Gaussian prior fit:

• -2.07

•

[-3.10;-0.25]

T2K only vs. T2K + DC BF based prior

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• T2K-only fit:

• -1.88

• [-3.10;-0.25]

μ 1σ interval

μ

1σ interval study:

• Use different priors for the Theta 13:

• Gaussian prior based on BF value from

reactor experiment

• Non-Gaussian prior - likelihood surface from reactor experiment

δ_CP Asimov A

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T2K only vs. T2K +DC 1D based prior

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• T2K-only fit::

• -1.88

• [-3.10;-0.25]

• T2K + DC 1D

likelihood surface as a prior fit:

• -1.94

•

[-3.11;-0.26]

μ

1σ interval

μ

1σ interval

Asimov A

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T2K + DC 1D based prior vs. T2K + DC BF based prior

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• T2K + DC 1D

likelihood surface as a prior fit:

• -1.94

•

[-3.11;-0.26]

• T2K + DC BF

Gaussian prior fit:

• -2.07

•

[-3.10;-0.25]

μ

1σ interval

μ

1σ interval

Same difference in

behaviour as for the fits _sin² _θ₁₃

Asimov A

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32

m2

∆

0.002 0.0022 0.0024 0.0026 0.0028

2 χ∆

0 5 10 15 20

7.20e-05 +6.40e-05

=2.47e-03

32

m2

∆

Daya Bay 2D fit

• surface based on official Daya Bay data release *

• Better precision on

• Improving accuracy for (at least ~√2)

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| Δm₃₂² | χ²

sin² θ₁₃

* https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.241805

θ13

sin2

0.014 0.016 0.018 0.02 0.022 0.024 0.026 0.028

2 χ∆

0 5 10 15 20

0.001 +0.001

=0.022 θ13

sin2

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Asimov A

T2K only vs T2K + DB 2D likelihood surface

• Improvement in the BF value

• Will do comparison with gaussian priors ( to be shown at next OA meeting)

• Here may be a problem in T2K only fit -> to be investigated

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T2K only

Asimov A

T2K + Daya Bay

• T2K-only fit :

• T2K + DB penalty fit : sin² θ₁₃ = 0.022

Δm₃₂² = 2.5 × 10⁻³eV² sin² θ₁₃ = 0.028

Δm₃₂² = 2.52 × 10⁻³eV²

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Further steps

• Check the impact on using Daya Bay inputs

• Repeat T2K + Daya Bay analysis for IH

• Focus on the validating new VALOR framework

• Try to implement Daya Bay analysis based on released data within that framework

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δ_CP

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Summary

• A combined T2K+Reactor-experiments fit implemented within VALOR

• Rather than applying a gaussian penalty term (oﬃcial approach), likelihoods are combined

• This new approach accounts for the fact that reactor likelihoods are not symmetric (unlike gaussian penalty term)

• It also takes advantage of the sensitivity to in reactor experiments:

• The implementation has been validated with Double Chooz likelihood (comparison of diﬀerent approaches)

• A combined T2K + Daya Bay analysis is currently being performed (preliminary results presented)

• results on consistent with oﬃcial approach (expected)

• significant improvement in precision (as expected, ~ √2 )

• impact on ?

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δ_CP θ₁₃

|Δm₃₂² |

L_Reactor = L(θ₁₃, Δm₃₂² )

|Δm₃₂² |

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Comments on the talk

• Suggest fits:

• 1D and 2D fits comparison for T2K+PDG vs. T2K+DB

• P-theta and MaCH3 are interested in performing the same study

• Nakajima-san used to work in DayaBay -> willing to answer any of our question related on DB analysis procedure

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