Atmospheric Neutrinos
Stefan Söldner-Rembold
University of Manchester
19 December 2013
19 December 2013
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Atmospheric Neutrinos
• Provide complementary
results with other
neutrino sources.
• Increase precision of
global fits of neutrino
parameters.
• Tools to search for new
physics.
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Three Questions
arXiv:1312.2878, see talk by E. Lisi
19 December 2013
1) Is θ23 mixing maximal and which
is the right octant ?
2) Is the mass hierarchy normal or
inverted ?
3) Is δCP > 0 ?
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Neutrino Propagation in the Earth
Preliminary Reference Earth Model
ν
ν
ν
Atmospheric neutrinos interact
with Earth’s mantle and core.
- MSW effect alters oscillation properties
(energy, electron density, MH and flavour dependent).
- “parametric enhancement” at Core/Mantle interface.
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MSW Effect
+: neutrinos
-: anti-neutrinos
CC interactions
Effective mixing angle in matter:
Resonance condition for
- neutrinos in normal hierarchy.
- anti-neutrinos in inverted hierarchy.
depends on energy and density profile.
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MSW Effect in the Earth
SK
cos θ
cos θ
Energy
Distortions for cos θ < -0.5 and at 10 GeV caused by MSW effect
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Energy
arXiv:1310.6677
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Neutrino Energies
10 MeV 100 MeV 1 GeV
10 GeV 100 GeV 1 TeV
Deep
Core
Super-K
IceCube
10 PeV
ANITA
PINGU
fn (GeV-1 cm -2 s-1)
10
1
10-1
10-2
10-3
10-4
10-5
10-6
10-1
Borexino
KamLAND
Double Chooz
Daya Bay
SNO
10 TeV 100 TeV 1 PeV
1
En (GeV)
10
nm
nm
ne
ne
Bartol 3D
Fill gap in intermediate energy region in
region of MSW resonance effects.
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Several future experiments: INO, PINGU,
Hyper-K, LBNE..
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Super-Kamiokande
Water Cherenkov Detector located
in Mozumi Mine, Kamioka, Japan
50,000t of water
11,146 PMTs
19 December 2013
First observation of
muon-neutrino deficit due to
oscillations in 1993
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Super-Kamiokande (SKI-IV)
red: un-oscillated
blue: best oscillation fit
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ντ Appearance (SK)
Phys. Rev. Lett. 110, 181802 (2013)
fitted signal in grey
Unambiguous evidence for oscillations
(νμ  ντ) since not present in source.
2806 day running period.
Energy threshold E > 3.5 GeV.
Reconstruct hadronic tau decays
using neural network.
3.8 standard deviation significance
(complements OPERA result)
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MINOS
see presentation by C. Backhouse
5,400 ton Far Detector
Alternating layers of steel calorimeter and
plastic scintillator.
Magnetized for charge identification
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MINOS Beam/Atmospheric Data
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MINOS Combined Analysis
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Future Experiments
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Indian Neutrino Observatory
Located in Madurai City, Tamil Nadu
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ICAL@INO
Iron sampling calorimeter (ICAL) with
Resistive Plate Chamber (RPCs)
as active component.
50,000 t of iron.
1.3-1.5 T magnetic field for charge identification
and momentum reconstruction
Pre-project activities approved.
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INO Sensitivity
sin2 2θ13 = 0.12, 0.1, 0.08 and sin2θ23 = 0.5.
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arXiv: 1303.2534
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PINGU
Extension of IceCube located
at the South Pole.
40 strings with 60 PINGU
Digital Optical Modules
(PDOMs) per string.
Design still being optimised.
In-fills DeepCore in clearest
ice at bottom centre of
IceCube.
Effective mass about 3Mt for
energies > 5 GeV
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PINGU
μ direction
4.4 GeV νµ
Nγ: circle size
tγ: colour
PINGU Digital Optical Module:
HQE PMT, electronics, pressure vessel.
Very similar to IceCube DOM.
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MH Signature
Energy
Need good energy and
angular resolution.
+
= Pattern A
+
= Pattern B
NH
IH
cos(θ)
19 December 2013
Diagonals are lines of constant L/E
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“Distinguishability”
Parametrized
reconstruction,
PID: tracks
Parametrized
reconstruction,
PID: cascades
With realistic particle identification
No systematics
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PINGU
Consistent results from different
statistical techniques, includes systematics
(mainly energy scale, cross sections).
First vs second octant
First octant only
Expect 1.75 standard deviations
after first year of data.
Reach 3 standard deviations in
roughly 3 years.
19 December 2013
PINGU currently being considered
by P5 in the US – will possibly be
part of a larger NSF facility at South Pole.
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KM3NeT/ORCA
- 1000 optical modules with 6 m spacing,
over 50 strings.
- Semi random pattern in a circular footprint.
- Mean distance between strings is 20 m.
- Instrumented volume: 1.8 Mton
not being pursued ?
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LBNE
LBNE Far Detector
needs to be underground
for atmospheric neutrino
detection.
Data taking to start around 2025
see talk by R. Wilson
Liquid Argon TPC
19 December 2013
ArgoNeuT
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LBNE
Sensitivity (s=ÖDc )
2
6
4
2
0
0
Atmospheric Neutrinos
LAr Detector Simulation
400
600
800
1/2(Dm322 +Dm312 )=±2.4´10 eV2
sin2q =0.4, sin 2q =0.0242, dCP=p
23
13
-3
Input Parameters:
Normal Hierarchy
Inverted Hierarchy
Mass Hierarchy Determination
200
Fiducial Exposure (kt-yrs)
25
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arXiv:1307.7335
35 kt x 10 yrs = 350 kt-yrs
2
350 kt-yrs
Octant Determination
Normal Hierarchy, dCP=p
Normal Hierarchy, dCP=0
Inverted Hierarchy, dCP=p
Inverted Hierarchy, dCP=0
6
4
3s
2
0
0.4
0.5
sin q23
2
Sensitivity (s=ÖDc )
8
Atmospheric Neutrinos
LAr Detector Simulation
2
Sensitivity (s=ÖDc )
LBNE
0.6
Atmospheric Neutrinos
LAr Detector Simulation
6
350 kt-yrs
CP Violation (Exclusion of dCP=0,p)
Normal Hierarchy, sin2q23=0.4
Normal Hierarchy, sin2q23=0.6
Inverted Hierarchy, sin 2q23=0.4
Inverted Hierarchy, sin 2q23=0.6
4
3s
2
0
0
0.5
1
dCP / p
1.5
2
arXiv:1307.7335
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Hyper-Kamiokande
arXiv:1109.3262
8 km south of SK
Total mass: 1 Mt
Fiducial mass: 560 kt
(25 times SK)
99,000 inner detector PMTs (20’’)
Data taking expected to start 2023
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Sensitivity to Mass Hierarchy
10 years of data
Lowest sensitivity for first octant.
arXiv:1309.0184
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Sensitivity to θ23 Octant
10 years of data
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Mass Hierarchy Bottom Line
plus Hyper-K with > 3 sigma around 2033.
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arXiv:1311.1822
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Summary
• Atmospheric neutrinos are a unique source of information,
complementary to neutrino long-baseline beam results.
• Several next-generation experiments based on (frozen) water
(PINGU, Hyper-K), liquid argon (LBNE) or iron sampling
calorimeters (INO) are currently being designed.
• These experiments have potential to determine neutrino mass
hierarchy and to constrain θ23 , providing, among others,
important input for δCP determinations.
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