Recent results from IceCube andthe future high energy extension
Aya Ishihara

KEK東海キャンパス
Feburary 20, 2015

COSMIC RAY FLUX [(GeV cm2 sec sr)-1]

Extremely-high energy emission in the Universe
cosmic-rays!
A particle beam injected from Universe
Energies upto 1019.5eV

E-2.7

knee 1015.5eV

E-3.0

second knee 1017.5eV

E-3.3

ankle
1018.5eV

E-2.6
cut off
1019.5eV

Aya Ishihara KEK at Tokai

ENERGY [eV]High energy emission in the Universe

FLUX [(GeV cm2 sec sr)-1]

Atmospheric Neutrinos
cosmic-ray up to knee : n from p and K decay
around and above knee: n from charmed meson decay

Atmospheric neutrino

Decay

𝜋+𝜋0

νμμ+νμν𝑒

Aya Ishihara KEK at Tokai

γ𝑒+𝑒+𝑒−ENERGY [eV]

Air Nuclei

FLUX [(GeV cm2 sec sr)-1]

Ultra-high energy neutrinos in the Universe

Atmospheric neutrino

Astrophysical neutrino
p+p or p+
astrophysicalphoton ormatter

Aya Ishihara KEK at Tokai

ENERGY [eV]Extremely-high energy neutrinos in the Universe

Decay

𝜋+𝜋0

FLUX [(GeV cm2 sec sr)-1]νμμ+νμν𝑒γ𝑒+𝑒+∆CMBphoton

𝑒−kneeCosmogenic neutrinos neutrino
induced by the off-source (<50Mpc) interactionsof cosmic-ray and CMB photons via GZK(Greisen-Zatsepin-Kuzmin) mechanism

Aya Ishihara KEK at Tokai

ENERGY [eV]ankle

Questions for the ultra-high energy neutrinos
-ray＞１００TeV

Cosmic Microwave Backgrounde+e－e－Charged Particles

Aya Ishihara KEK at Tokai

Multi-Messenger detections and constraints
Still in the same origin, it is critical to observe them as multi-messengers!

𝒑 + 𝒑 → 𝝅+ , 𝝅− , 𝝅𝟎𝒑 + 𝜸 → 𝝅+ , 𝝅𝟎

𝝅𝟎 → 𝟐𝜸𝝅+ → 𝝁+ 𝝂𝝁𝝁+ → 𝒆+ 𝝂𝒆 𝝂𝝁𝝅− → 𝝁− 𝝂𝝁𝝁− → 𝒆− 𝝂𝒆 𝝂𝝁

Aya Ishihara KEK at Tokai𝑬𝝂 ≈𝟏𝟏𝑬𝑷 ≈ 𝑬𝜸
𝟐𝟎𝟐e.g. 10PeV CR – 500TeV n – PeV The Largest Underground Detector in the world:

The IceCube Detector
1km

1.5km

Array of 78 sparseand 8 dense strings
5160
opticalsensors

1km

Aya Ishihara KEK at Tokai

South Pole Dome (old station)

Amundsen-Scott
South Pole station

Digital Optical Module••••••PMT: 10 inch Hamamatsu
Waveforms, times digitized in each DOM
Power consumption: 3 W
Digitize at 300 MHz for 400 ns with custom chip
40 MHz for 6.4 μs with fast ADC• Dynamic range 500 photoelectron/15ns
Flasherboard with 12 LEDsLocal HV

Clock stability: 10-10 ≈ 0.1 nsec / sec
Synchronized to GPS time every ≈10 sec
Time calibration resolution = 2 nsec

25 cm PMT
33 cm Benthosphere

Aya Ishihara

9

Waveform
examplesfrom spe to
10000 pesingle pe level

Digitized
Waveform

25 cm PMT

7VO(10000)pe
SC410Aya Ishihara

NPE = Integrated charge/PMT gain10South Pole
Landing Strip
South Pole Station
IceCube Drill Head& First Hole
Residential Build

IceCube Drill CampAya Ishihara KEK at Tokai

IceCube LabThe IceCube LAB

Aya Ishihara KEK at Tokai

60 photomultipliers/string

Aya Ishihara KEK at Tokai

The IceCube Collaboration
http://icecube.wisc.edu

CanadaUniversity of Alberta

SwedenGermany

Universität Mainz
Uppsala Universitet
Stockholms Universitet DESY-Zeuthen
US
Universität Dortmund
Bartol Research Institute, U. Delaware
Universität Wuppertal
UK
Pennsylvania State University
Humboldt-Universität zu Berlin
University of California - Berkeley
Oxford University
MPI Heidelberg
University of California - IrvineRWTH Aachen
Clark-Atlanta University
Universität Bonn
University of Maryland
Ruhr-Universität Bochum
University of Wisconsin - Madison
BelgiumKorea
University of Wisconsin - River Falls
Université Libre de Bruxelles Sungkyunkwan University
Lawrence Berkeley National Lab.
Vrije Universiteit Brussel
University of Kansas
Universiteit Gent
Southern University, Baton Rouge
Université de Mons-Hainaut
University of Alaska, Anchorage
University of Alabama, Tuscaloosa
Switzerland
Georgia Tech
Australia
Ohio State University
Ecole Polytechnique
University of Adelaide
EPFL, Lausanne
University of Geneva

AyaIshihara KEK at TokaiANTARCTICA
Amundsen-Scott Station

New Zealand
University of CanterburyThe IceCube Construction and Runs
IC86 = full IceCube (2011~)

Very stable full operation since May
2011 - Now taking 4th year physics
run with the full IceCubeconfiguration
IC9 (2006-2007)
IC1(2005-2006)
Aya Ishihara KEK at Tokai

IC79 (2010-2011)

IC22 (2007-2008)

IC59 (2009-2010)

IC40 (2008-2009)

Detection Principle
Dark and transparent material

An array ofphotomultiplier tubes

νlν

l

W,
W, Z
Zl,l,
νlν

l

mte

hadronic
hadronic
showershowerm, t or cascades
Cherenkov light

DigitizedWaveform
Aya Ishihara KEK at TokainIceCube event topological signatures
With 59 strings 2009
νlW,Zl,νlmte

hadronicshower

With 40 strings, 2008 Dec〜100TeV up-going muontrack event

With 22 strings 2007

130TeV
Cascade-like eventhigh energy cosmic-ray induced
atmospheric muon bundle event

Phys. Rev. D 84, 072001 (2011)
Aya Ishihara KEK at Tokai

Searches for diffuse neutrinos
Diffuse neutrino fluxes: Powerful tool to search abandant sources• Advantage: Accumulate neutrinos from many many sources even at very farUniverse, different direction, and of different types• Disadvantage: Accumlate background from all the direction and time (goodunderstanding needed), indirect identification of sourcesν

νν

ννν
ν
Aya Ishihara KEK at TokaiννBackground for cosmic diffuse neutrinos

neutrinos
Atmospheric Neutrinos
cosmic-ray up to knee : n from p and K decay
around and above knee: n from charmed meson decay

Decay

Atmospheric neutrino νμνμν𝑒𝜋+𝜋0

Air Nuclei

μ+γ𝑒+𝑒−𝝁, 𝝁-bundle

Atmospheric muons
dominant but removable since track-like trajectories of Cherenkov
photons and its directions is able to be reliably reconstructed
Aya Ishihara KEK at Tokai

19

Expected signals in diffuse n search
Conventional
Atm. neutrinos• neutrinos
from decaysof pions andkaons inatmosphere

Prompt Atm.
neutrinos

Astrophysicalneutrinos• neutrinos
from decaysof short-lived
mesons inatmosphere• neutrinos
from decaysof pions inastrophysicalsources“Features” in the energy spectra
promptconventional
astrophysical-
steepening of neutrino spectra:    , ~3.7(+*)  ~2.7(+*)  ~2.0(+**)* is due to cosmic-ray steepening (knee), ** is possible softening at CR acceleration site

Neutrino “flavor”
flavor changes with energy:

conventional

nm

prompt nm + ne  nm + ne + nm (?)
astrophysical

Event “directions”
zenith angle distribution changes with energy:
conventional

promptastrophysicalhorizontal enhanced  isotropic  isotropic (?)
This is true at surface, after propagation in Earth, high energy n is highly reduced in
the upward-going region
Aya Ishihara KEK at TokaiAtmospheric n measurements
nm
Data: 2008-2009
100 GeV to 400 TeV
Phys. Rev. D 83, 012001 (2011)by IceCubeneData: 2010-2011
DeepCore
80 GeV to 6 TeV
Phys. Rev. Lett. 110, 151105 (2013)by IceCube

Aya Ishihara KEK at TokaiUp-Track astrophysical nm search
CRup-going muon
neutrino sample

Trigger rates:
Atm. muons: ~3 kHz,~200 atm. ν /day(with E >100 GeV in IceCube)m

Mis-reconstructed atms. mmnm

Downgoing atms. m

Atmospheric n

North

TeV astrophysical n
PeV – EeV GZK n

Aya Ishihara KEK at TokaiAstrophysical and Atmospheric nm
MC expectations

Data:2010-2012 (2 years) fit results

Aya Ishihara KEK at TokaiExtraterrestrial neutrino search with nm
Data:2010-2012 (2 years)• Best fit results of astro∝E-2 for nm
E2=(1.01+0.36-034)x10-8 [GeV cm-1 s-1 sr-1]• background-only hypothesis disfavored at 3.9s

Aya Ishihara KEK at TokaiExtraterrestrial neutrino search with cascades
νlW,Z

Data:2008-2009

mtel,
νl

cascade-likesignatures

hadronicshower

Data:2009-2010

arXiv:1312.0104
Phys. Rev. D 89, 102001 (2014)

3 additional events
2.7 sigma excess
over background only

no event above 10TeV

3 flavor upperlimiton astro∝E-2 (43TeV - 6.3PeV)

E2=1.7x10-8 [GeV cm-1 s-1 sr-1]

Aya Ishihara KEK at Tokai

The extremely high energy neutrino search‘Very bright’ is an important condition
Select both type of events with a ‘brightness’ of events

400TeV

2 EeV

log # photo electrons (NPE)

below ~PeV, upwardgoing tracks andcascade-like topology isimportant

350TeV
200 PeV2 EeV
Aya Ishihara KEK at Tokai

from MC simulation

IceCube EHE Event NPE Distributions
PhysRevD.88.112008 (2013)

NPE > 3000 (10% test sample)

Aya Ishihara KEK at TokaiExtremely high energy neutrino search above PeV
Phys. Rev. Lett. 111, 021103 (2013)
2..8sigma excess over 0.08+0.04-0.06 events of default atmospheric background2010-2012 (2 years)

1.0PeV

1.1PeV

Number of photoelectrons: NPE ∝ Visible Energy

Aya Ishihara KEK at TokaiAre these 2 events cosmogenic in origin?
the Kolmogonov-Smirnov test implies that the estimatedenergies (assuming GZK spectra on surface) can not be
explained by the cosmogenic neutrino models
No!
“Standard” GZK

The predicted En cumulative
probability“Low Energy Enhanced” GZKData

The test tells that they are very (at 90%CL) inconsistent

Aya Ishihara KEK at TokaiModel independent quasi-differential upper limit• Including Energy PDF of thetwo events•

PeV region upperlimits are
weaken by the 2 eventobservation• Significantly improved from theprevious upperlimits• IceCube becoming more andmore sensitive to cosmogenic
fluxes above 100 PeV (108GeV) and started to constrain
the highest energy comsic-ray
source evolutions• E-2flux integrated limit takinginto 2 observations
E2φ(νe+νμ+ντ)= 2.5×10−8GeV
cm−2s−1sr−1(1.6 PeV – 3.5 EeV)Aya Ishihara KEK at Tokai

Constraint on the highest energy neutrino
fluxes and cosmic-ray sources
𝑝 𝑚, 𝑧𝑚𝑎𝑥 = 1 + 𝑧 𝑚 (𝑧 < 𝑧𝑚𝑎𝑥 )• Highly evoloving source
models of the highest energy
cosmic-ray protons can be
excluded

FRIIGRBSFR• Disfavoring a genericexpression of the evolution
parameter m larger than ~4
which includes radio loudactive galaxies (FRII)

Aya Ishihara KEK at Tokai

High Energy Starting Event Analysis• Followup analysis on the UHE cascade-like events• Atmospheric muon/neutrino background largely reduced byvetoing events with initial photons in outer layers•

Events with NPE > 6000 (the case for EHE, NPE > 60000), sensitivity
extended down to 30TeVAya Ishihara KEK at TokaiAtmospheric muon and neutrino vetosignal neutrinos

Rejectedbackground events• Down-going atmospheric neutrinos are also reduced by vetoing
atmospheric muon events• This changes atmospheric neutrino zenith angle distributions toupward-going dominated
Aya Ishihara KEK at Tokai

Effective AreasPropositional to expected event rates
Area x n flux x 4p x livetime = event rate

IC79+IC86 livetime 670.1 days

Aya Ishihara KEK at Tokai

Starting event energy distribution
IceCube:Science 342, 1242856 (2013)2010-2012 (2 years) results 26 new events found(19 cascades, 7 with tracks)
 over background expectation of
10.6-3.6+5 total atmospheric muons(6.0 ±3.4) and atmospheric+ .
neutrinos (4.6−1.2 3 7)

 Best fit results
E2=(1.20.4)x10-8 [GeV cm-2 s-1
sr-1] with a hard cut off at 1.6PeV

Aya Ishihara KEK at Tokai

Starting Events in 3 year sample
2010-2013 (3 years)

Physical Review Letters 113 (2014) 101101;
arXiv:1405.5303
 9 new events found 7 cascades, 1 with tracks,and 1 coincident muon
event (not plotted)
 5 from southern sky and 3
from northern sky
 the highest energy 2PeV
event in the test sample
 28+9 over backgroundexpectation of 15.0+7.2-4.5
atmospheric muons 8.4 ±4.2 and atmospheric
neutrinos 6.6+5.9-1.6

Aya Ishihara KEK at TokaiExtraterrestrial neutrino search with starting events
 atmospheric background13.0+7.2-4.5
 Inconsistent withbackground only model at
4.1s with 28 events (science2013) and 5.7s with additional
7 events (preliminary) Event features (reconstructedenergy, zenith angle andtopology) consistent withbackground + astrophysical(astro∝E-2) fluxes

 Best fit flux

E2=(0.950.3)x10-8 [GeV cm2 s-1 sr-1] with a hard cut off
around 2.0 PeV or a softer
spectra with a spectral index
2.30.3

Aya Ishihara KEK at Tokai

Zenith angle distributions• Low energy atmosphericmuons in downward-goinggeometry

atm. matm. n• Atmospheric neutrinos inhorizontal to upward-goingregion• High energy astrophysicalcomponent dominant in thedownward-going region
signal + background

Veto method suppress a large
fraction of southern atmospheric
neutrino background but not theastrophysical neutrinos
Aya Ishihara KEK at Tokaibackgroundsystemic uncertainty

Diffuse neutrino flux summary
IceCube preliminary

From upgoing muon analysis:
E2=(1.01+0.36-034)x10-8 [GeV cm-1 s-1 sr-1]

From starting event analysis with a 2 PeV cut off:E2=(0.950.3)x10-8 [GeV cm-2 s-1 sr-1]

Aya Ishihara KEK at Tokai

2 years data cascade channel results soon to comeHigh energy starting event clustering

all events
p-value = 84%

cascadesp-value = 7%
No evidence of (significant) spatial clustering
Aya Ishihara KEK at Tokai

More quests for n point sources• all-sky through-going muons unbinned point source analysis• 4 years (IC40+IC59+IC79+IC86) 1373days

Hottest spot:
RA 29.25, DEC 10.55-log10(pre trial p-value) =5.32

All sky search: post-trial p-value 23% no evidence for a neutrino source
Aya Ishihara KEK at TokaiNeutrinos in coincidence with gamma-ray bursts?
•••

4 years (IC40 + IC59 + IC79 + IC86-1)
506 GRBs
No significant event observedνUpperlimit on a double
broken power law type of
GRB neutrino fluxes
𝑑𝑁= 𝜙𝜈𝑑𝐸

𝐸 −1 𝜀𝑏 −1 𝐸 < 𝜀𝑏𝐸 −2 𝜀𝑏 < 𝐸 < 10𝜀𝑏𝐸 −4 𝜀𝑏 2 10𝜀𝑏 < 𝐸

Gamma-raysatellitesγ, νGRB timing/localization informationfrom correlations among satellites
distant
GRB plus time (10-100s) cuts reduces background significantly• Direction• Upperlimits are below theWaxman Bahcall model
Aya Ishihara KEK at TokaiImplication to the neutrino-nucleus cross sectionssνsRate
V
T
NA

(En)
expNA
X
Aperture:
Detector+
Geometry

Interaction

Absorption

Astro n flux
Gamma-raysatellitesγ, νGRB timing/localization informationfrom correlations among satellites
distant GRB
Aya Ishihara KEK at TokaiImplication to the neutrino-nucleus cross sectionsRate
VT
NA

(En)
expNAXss

Sandra Miareckiν<miarecki@berkeley.edu>

distant GRB
Aya Ishihara KEK at TokaiImplication to the neutrino-nucleus cross sections
Reference model ‘CSMS’: A. Cooper-Sarkar, P. Mertsch, and S. Sarkar, JHEP p.
1108:42 (2011) using HERAPDF1.5

νtarget energy

distant GRB
Aya Ishihara KEK at Tokai

Raj Gandhi, Chris Quigg,
Mary Hall Reno, and Ina
Sarcevic. Phys. Rev. D,
58(9):093009 (1998)

What’s beyond IceCube?
IceCube found:• Working well at South Pole
• High level of astrophysical neutrino flux cosmic ray sources are efficient neutrino sources• Neutrinos above 1 PeV from Southern sky (3events/3years)• Spectral indices and shape, E-2.3 at high energies

We need more:• Discoveries– neutrino point sources, PeV tau neutrinos, 𝑣𝑒 𝑒 − → 𝑊 − Glashow
resonance events, GZK neutrinos (E>10PeV)• Precision measurements– cosmic neutrino spectra, flavors, anisotropy• Particle physics• And more…
Aya Ishihara KEK at Tokaithe Next Generation IceCube:
IceCube-Gen2

High Energy extension
Scale: 100 strings, 10,000 PMT
volume 5 ~ 10 km3, area 5 ~ 8 km2• optimal spacing under study
Surface component a la IceTop
A large surface extension for vetoing
downgoing background
Up to 6 km from detector• optimal size and density under study47

A baseline configuration• more statistics at high energy• increase volume with more strings

IceCube100 new strings
240 m spacing

PINGU: extra strings
inside original IceCube

Aya Ishihara KEK at Tokai

IceCube-Gen2 Geometry
120 more strings
78 strings for HE n

240m string spacing“benchmark”

300m string spacing

verticalNeutrino Frontier Workshop 2014

horizontal

49

New Optical Modules design proposal fromChiba for IceCube-Gen2: “D-EGG”
300mm

8” SBA PMT R5912-100

to observe• More signal events• Better angular resolution• Better muon veto
534mm

• Realize higher
photon detection
efficiency• Up/down symmetric
PMT configuration
Neutrino Frontier Workshop 201450

PMT + Glass measurement
Glass + PMT

ref. PMT
LED/splitter

Neutrino Frontier Workshop 2014

51

PMT + Glass photon detection efficiency
detection eff. @ 340nm

bare PMT 27%
PMT + glass 24 %detection efficiency~24%@340nm

The present IceCube DOM

8% @ 337nm

Neutrino Frontier Workshop 201452Summary• IceCube has been fully operational since 2011, accumulated
3-full year samples + 4 years of partial operation data (22,40, 59, and 79 strings• Observed extraterrestrial diffuse neutrinos from different
analysis methods as an excess from background only
hypothesis
omore than 3s with muon neutrino upgoing track channel andmore than 5s level achieved with the starting event search withmuon veto technique• No indication of transient/continuous point sources yet• High energy extension of the IceCube proposed – 5 times ormore signal events to study the nature of neutrino fluxes anddetect point sources. Improvements on the hardwares.
• Stay tuned!
Aya Ishihara KEK at Tokai