Neutrino oscillations with IceCube

Neutrino oscillations with IceCube

State of the art measurements Andrii TERLIUK

DESY, Zeuthen

for the IceCube Collaboration

H2020 oscillations workshop

Valencia, Spain

Digital Optical Module

IceCube Neutrino Observatory

A cubic kilometer detector

> IceCube detector:

 5160 DOMs with 10” PMTs

 Ice as optical medium

 Cherenkov light detection

> DeepCore sub-detector:

 The clearest ice

 Denser instrumentation

 +35% higher quantum efficiency

 IceCube as active veto against atmospheric muons

[ m ] Hor. Vert.

[ m ] Threshold [ GeV ]

IceCube 125 17 ~100 GeV

DeepCore 40-60 7 ~5 GeV

μ ν

Cherenkov

light

IceCube Neutrino Observatory

What events do we measure

MeV GeV TeV

Solar Atmospheric

Accelerators

Reactor Astrophys.

IceCube/DeepCore

ν ℓ

p,n

Hadrons

ν ℓ

ℓ – charged current (CC) interaction – neutral current (NC) interaction

> Secondary particles emit Cherenkov light

> Track like events:

 ν

CC interactions

> Cascade like events:

 all NC interaction, CC of ν

, ν

Time [ μs ]

Events in DeepCore

> Events below 50 GeV:

 Dim and produce little light

 More affected by detector uncertainties

 Challenging to select

 Challenging to reconstruct

Careful treatment of systematic uncertainties is a key

IceCube Neutrino Observatory

We are doing great physics!

> A broad range of breakthrough physics studies:

 Astrophysics:

▻ Neutrino sources, diffuse fluxes, transients, cosmic rays...

▻ Multi-messenger astronomy

 Neutrino properties:

▻ Atmospheric neutrino oscillations

▻ Sterile neutrinos, non-standard interactions

▻ Cross sections, neutrino fluxes

 Beyond standard physics:

▻ Dark Matter, monopoles, Lorentz violation...

 Glaciology, Earth tomography

> A lot of studies in progress!

th is ta lk

Picture: DESY, Science Communication Lab

IceCube Neutrino Observatory

Atmospheric neutrino oscillations

Multi-baseline measurement

> Main effect: transition between muon and tau neutrinos

> Different arrival directions

cos(θ

)

→ different baselines:

 Range between 25 and 12760 km

> Disappearance and appearance channels accessible with neutrino telescopes

L ≈ 12 74 0 km

Atmospheric neutrino oscillations

A unique way to probe oscillations at the highest energies

Atmospheric neutrino oscillations

Muon neutrino → tau neutrino transition

* studies are done using full three-neutrino model in IceCube

L ≈ 5

00 k m

L ≈ 1 270 0 km

energy → amplitude →

Main survival minimum:

IceCube/DeepCore

energies

Measuring oscillations in IceCube

Rejecting the background

Atmospheric muons

Depth [ m ]

> Most complicated muon events:

 corridors formed by detector geometry

 “dust layer” above DeepCore

> Dedicated time/space algorithms to reject

> O(10

) muons per 1 neutrino event

> Vetoing techniques:

 Signals in outer regions of IceCube

 Containment in DeepCore

 Simple cuts + machine learning techniques

Measuring oscillations in IceCube

Reconstruction the events

> Reconstruction:

 8 parameters as for ν

CC interaction

 Total neutrino energy

 Neutrino direction = muon direction

 Matching light expectation with signal in every OM simultaneously

> Caveats:

 Tabulated light expectation for every position/direction in the detector

 Very complicated likelihood space

p,n

E

L

, θ , φ (x,y,z,t)

Time P M T s ig na l

Predicted signal

Bin 1 Bin 2 Bin 3 Bin 4

Observed signal

Bin 5 ...

For every DOM:

> Time consuming reconstruction

> Complicated minimization algorithms

(nested sampling alogrithms)

Measuring oscillations in IceCube

Identifying muon neutrinos

> Particle identification = difference between full and cascade-only fits

p,n

E

L

, θ , φ (x,y,z,t)

p,n

θ, φ, E

(x,y,z,t)

VS.

Measuring oscillations in IceCube

What does the signal look like

> No oscillations > With oscillations

> Typically considered systematic parameters:

 Neutrino fluxes: CR properties, hadronic physics in showers, overall rate

 Cross-section: axial masses, NC normalization

 Detector uncertainties: DOM efficiency and angular acceptance, ice optical properties

 Atmospheric muon contamination

O sc ill a tio ns

Disappearance

Measuring oscillations in IceCube

L/E projection

> Data clearly prefers oscillations

> Down-going neutrinos for normalization

Muon neutrino disappearance

The results with 3 years of data

> Approaching precision of dedicated accelerator experiments!

PRL. 120, 071801 (2018)

> Three years of data:

 2012-2014 data seasons

> Performed on 3D histograms

 E

: [6, 56 ] GeV

 cos θ

: [ –1, +1]

 PID: track- or cascade-like

> All studies are performed in blind way:

 Strict internal review process

 Good data/MC is ensured

 Minimal bias of physics-

related parameters

Neutrino mass ordering

Heavy or light?

> First measurements of ordering by IceCube

> Testing statistical tools and analysis techniques

> Normal ordering is marginally preferred

Presented at Neutrino 2018

Physics beyond the three-neutrino model

Is three a magic number?

> Standard PMNS matrix:

 3 mass states

 3 flavour states

 Matrix is unitary

> Non-unitarity of three-neutrino PMNS matrix → new physics

> Ways to probe:

 Normalization of appeared tau neutrinos

 Effects induced by sterile neutrino mixing

Standard mixing

New physics

PRD 93, 113009 (2016)

Tau neutrino normalization

Is the same amount appeared as disappeared?

> Very few tau neutrinos observed/

identified ever

> Can hide new unexpected physics

> Search in DeepCore:

 Statistical way

 Cannot identify tau neutrinos on

event-by-event basis 1.0

ν

norm.

Less

appearance:

oscillations to hidden physics

More

appearance:

Non-physical – completely new physics

S ta n d a rd o sc ill a tio n s

0.0 ∞

Tau neutrino normalization

The results

> First results for tau neutrino appearance with IceCube

> 3 years of data (2012-2014)

> Two independent analysis chains:

 PRL 2018 sample (Analysis 1)

 Parallel analysis (Analysis 2)

> Paper in preparation:

 Details about systematics, statistical approach, event selection, reconstruction etc.

 Both ν

disappearance and ν

appearance

> Results in agreement with standard three-neutrino oscillations

Presented at Neutrino 2018

Sterile neutrinos with IceCube

anti-neutrinos

Mixing in 3+1 model

> Existence of new species suggested by short baseline anomalies

> Simplest extension:

 +1 sterile neutrino

 New parameters:

▻

1 mass

▻

2 CP violating phases

▻

3 mixing angles

[ ν ν ν ν

] = [ U U U U

U U U U

U U U U

U U U U

] [ ν ν ν ν1324] | | | U U Uμe44| |22=sin =sin22θ θ1424⋅ cos2θ14

τ4

|

=sin

θ

⋅ cos

θ

⋅ cos

θ

Standard PMNS matrix

symmetry mag

> Modifies detected

atmospheric neutrino flux

> Assumptions:

 δ

= 0

Sterile neutrinos with IceCube

Effects of the sterile neutrino

> Effects above 100 GeV:

 Mantle-core-mantle resonance transition to sterile state

 Affects muon antineutrinos

 Resonance energy

 Sensitive to angle θ

(|U

|

)

∼Δ m

Expected signature:

anti-neutrinos

Search at TeV energies

Sterile neutrinos with IceCube

Results of the TeV search

> No sterile neutrino signal found

> Only one year of data used

> Constraining limits on sterile neutrino mixing with muon state

PRL 117, 071801 (2016)

Sterile neutrinos with DeepCore

Searching for matter-induced effects

> Effects below 100 GeV:

 Modifications of standard oscillations

▻

shifts of oscillations minimum

▻

changes of amplitude

 Independent of sterile neutrino mass (for )

 Sensitive to the angles θ

and θ

 Effect proportional to matter density

Δ m

> 0.3 eV

Effects of

the sterile

neutrino

Sterile neutrinos with DeepCore

The results

> Observed oscillations are in agreement with standard oscillations

> Constraining limits on sterile neutrino mixing in muon and tau sectors

PRD 95, 112002 (2017)

Future with DeepCore

What do we do now?

> Current studies use only 1-3 years of detector data

 7 years of data are available

> Current progress in:

 New PMT charge response simulation

 New model for ice optical properties

 Extended energy range

 Analysis/selection optimization

> Main sensitivity limitations:

 Statistically limited

 Systematically limited

 Manpower limited

> Main reason:

 See next slide Our case

IceCube

Preliminary

IceCube Upgrade

New tool for studies of atmospheric neutrinos

> Few GeV detection threshold

> New types of sensors

> Additional calibration devices

> Approved by NSF

IceCube Upgrade Modules

Goals with new sensors

> Upgraded electronics

> Better UV sensitivity

> Smaller module diameter

> Better angular sensitivity

> Larger/pixelated photo-cathode area

IceCube Upgrade

Calibration campaign

> Integrated devices

 LED flashers

 Acoustic sensors

 Optical cameras

> Stand-alone sources

 Precision Optical Calibration Module (POCAM)

 “Movable” sub-ns pulsed LEDs with small opening angle

> Reduce systematic uncertainties:

 Calibration of new and existing sensors

 Improved knowledge of glacial

ice CCD CMOS

Piezo-module POCAM

Cameras

DOI:10.1051/epjconf/

201713506003

DOI:10.22323/1.301.1040

DOI:10.22323/1.301.0934

IceCube Upgrade

What we can achieve

> Muon neutrino disappearance > Tau neutrino appearance

> Precision frontier with atmospheric neutrinos!

> Current sensitivities do not include expected improvement of systematic

uncertainties

Summary

Highlights from IceCube DeepCore measurements

> IceCube – major neutrino oscillation experiment

> Key results using atmospheric neutrinos

 Muon neutrino disappearance

 Tau neutrino appearance

 Sterile neutrino mixing

> Mainly using only 3 years of data

 Not systematically limited

 Ongoing work to use full detector live time

 7 year studies are expected very soon

 New calibration is under way

 Stay tuned and keep an eye on conferences and arXiv

> IceCube Upgrade is expected in 2022/2023

Our improvement in less than 3 years!

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