Young scientist workshop, Ringberg castle
19-07-14
Impact of sterile neutrinos on
long baseline experiments
Niki Klop
Ludwig-Maximilians University Munich
Max Planck Institute for Physics Munich
Supervisor: Antonio Palazzo
Outline
• ν oscillations in the standard framework
• Motivations for a sterile neutrino
• What I am doing
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Introduction
•
•
•
•
In the Standard Model, neutrinos are massless
Experiments have shown that neutrinos can change
flavour
Spectrum of 3 neutrino mass eigenstates
Flavour states can be written as a superposition of
mass eigenstates (and vice versa)
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Introduction
Transition probability
Only dependent of ∆m2, not of the absolute mass.
The sensitivity to ∆m2 of an experiment is maximal for the values of
∆m2 such that
~1
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Introduction
• The PMNS matrix
• Mixing angles are measured
CP-violating phase still has to be determined
LBL experiments (T2K)
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The T2K experiment
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Introduction
The neutrino mass spectrum:
normal
hierarchy
inverted
hierarchy
Δm2atm
Δm2sol
Δm2atm = Δm223 = 2.4  10-3 eV2
Δm2sol = Δm212 = 7.6  10-5 eV2
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Motivation
Anomalies in short baseline (SBL) experiments:
experiments for which L/E ~ 1 km/GeV ( ∆m2~ 1 eV2 )
νe appearance:
_
• LSND_ measured νe appearance
from νμ beam consistent with
mixing with ∆m2~ 1 eV2
• MiniBoone: rules out part
of the LSND region
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Motivation
νe disappearance
L/E ~ 1 m/MeV
• Reactor anomaly
Mention et al.
arXiv:1101:2755
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Motivation
Introduction of a 4th neutrino with ∆m2~ 1 eV2
• 4th neutrino should be sterile
(must not couple to the standard electroweak current)
• Success of 3ν should be preserved
• 4x4 mixing matrix
• 6 mixing angles, 3 CP-violating phases
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What I am doing
• If sterile neutrinos indeed exist, this will have both positive
and negative effects on the efficiency of the LBL experiments
• Simulation of 3+1 neutrino oscillation
in a LBL experiment (T2K)
•
Goal: put LBL-experiments in a wider perspective.
3+1 case
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3ν probability
0.06
Patm
Psol
Pint
P
0.05
0.04
0.03
0.02
0.01
0
0
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0.05
0.1
0.15
0.2
0.25
0.3
0.35
Sin(2ϑ13)
12
1
"plotje15.txt"
Best fit
0.0008
2.69CL
90%
68% 1CL
NH
3ν (matter)
0.5
0
δcp (π)
-0.5
-1
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
1
"plotje15IH.txt"
Best fit
0.0006
2.69CL
90%
68%1CL
IH
0.5
0
-0.5
-1
0
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0.05
0.1
0.15
0.2
0.25
0.3
0.35
Sin2(2ϑ13)
0.4
13
3ν (vacuum)
1
δcp (π)
"Chi2nieuw1.txt"
Best fit
0.0008
90% CL
2.69
68%1CL
DB
0.5
I I
0
-0.5
-1
0
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0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
2
Sin (2ϑ13)
14
4ν probability
0.06
Patm
Psol
Pstr
P1max
P2max
P3max
P
0.05
0.04
0.03
0.02
0.01
0
0
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0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
Sin(2ϑeμ)
0.2
15
4ν “results” (vacuum)
1
1
"Chi2nieuw1.txt"
Best fit
0.0008
2.69
90%
CL
1
68% CL
0.5
DB
I I
"Chi2nieuw3.txt"
Best fit
0.0008
2.69
90%
CL
68% 1CL
0.5
0
DB
I I
0
δ14 = π/2
δ13 (π)
-0.5
-0.5
-1
-1
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
1
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
1
"Chi2nieuw5.txt"
Best fit
0.0008
2.69CL
90%
68% 1CL
0.5
DB
"Chi2nieuw4.txt"
Best fit
0.0008
90%
2.69CL
68% 1CL
I I
0.5
0
DB
I I
0
δ14 = - π/2
-0.5
δ14 = π
-0.5
-1
0
0.05
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0.1
0.15
0.2
0.25
0.3
0.35
0.4
-1
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Sin2(2ϑ13)
0.4
16
Summary
• The standard 3 ν framework may be not
complete
• Intriguing indications in the favour of light
sterile neutrinos ~ 1 eV
• Large experimental activity on sterile ν
• Large theoretical activity on sterile ν
• I focus on impact of these sterile neutrinos in
LBL experiments
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The T2K experiment
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