Evidence for high-energy extraterrestrial
neutrinos at the IceCube detector

K. Mase, Chiba Univ.

K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	 1	
 ■ Why neutrino?

proton	 VHE γ	 ν	
 Neutrinos are rarely interacting particles→ Arrive straight to the Earth from the deep Universe
Hadronic interaction → CR origin 	 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	 2	
 ■ The IceCube experiment² Deployed in the Antarctic glacier

IceTop	

IceCube	² In-ice + IceTop + DeepCore² 86 strings (completed in 2010)² ~ 5,000 photo-multiplier tubes (PMTs)² Detector volume: ~ 1 km3² ATWD 300MSPS
3 different gains (x16, x2, x0.25)² FADC for long duration pulse² Targets for cosmic high energy neutrinos

In-­‐‑ice  detector	
1  km3	

DeepCore	(mainly >~ 100 GeV)

Digital Optical Module(DOM)
K. MasePMT
2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	 3	
 41 institutes and ~280 physists
K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	 4	 ■ The deployment

Use hot water to make a hole	
 2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 K. Mase5	 ■ The construction
2004: project started
2006-2007: IC9
2007-2008: IC22
2008-2009: IC40
2009-2010: IC59
2010-2011: IC79
End of 2010: IceCube completed!
2011~: IC86
IC59 (2009-2010)

K. MaseIC22 (2007-2008)

IC79 (2010-2011)

IC40 (2008-2009)

IC86 = complete IceCube (2011~)

2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	 6	
 ■ The detection principle

Cherenkov lightν", ν"W, Z
hadronic	
  

μ	
  

shower	  interaction

Ø A large volumeØ transparent medium→ Antarctic glacierK. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

νμ	
  
7	
 

■ Particle identificationνμ	
 Muon (track)	
 

μ	
 

νe	
 

e	
 

ντ	
 

τ	
 
ντ	
 

Neutral current events also generate cascades	 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	 8	
 ■ The angular resolution for tracks

IC59 preliminary	
 12.1σ	
 arXiv:1111.2741	
 Ø Systematic angular shift < 0.2°
Ø Angular resolution < 1° (> 10 TeV)

K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	 9	 ■ Backgrounds
dN dN CRA∝
dE
dE 1+ B cosθ Eεθ:	
  zenith	
  angle,	
  ε:	
  cri=cal	
  energy	 Energy spectra @ surface	
 
	
  	
  	
 

² atmospheric	
  μ	
  
	
  
atmospheric	
  μ	
 

dN µ
∝ E −3.7 (> επ = 115 GeV )dE² atmospheric	
  ν	
  
dNν
∝ E −3.7 (> ε π = 115 GeV )dE² prompt	
  ν	
  ² decay	
  from	  charmed	
  par=cles	 dN∝ E −2.7 (< εcharm = 10PeV )dE
PRL	
  110,	
  151105	
  (2013)	
 Ø Three main backgrounds: Atm µ, Atm ν, prompt ν (all CR originated)
K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

10	
 

■ Backgrounds (cont’d)IC40	
  Point	
  source	  analysis	
 ApJ,	
  732,	
  18	
  (2011)	
  	
 Zenith angle distribution @ detector	 up-­‐going	
  (northern	
  sky)	
 down-­‐going	
  (southern	
  sky)	
 

Atm	
  ν	
 

Atm	
  μ	
 

up-­‐going	
  (northern	
  sky)	
 down-­‐going	
  (southern	
  sky)	
 Ø Essentially energy and zenith angle information used for signal searches
K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

11	
 

■ Diffuse neutrino search
Idea to integrate weak neutrino flux
Search for diffuse muon neutrinos by using mainly energy information
Signal slope is harder than background slope

Sensitive: 30 TeV-10 PeV

arXiv:1302.0127	
 

IC59	
 

Waxman-­‐Bahcall	
  bound	
  IC59	
  sensi=vity	 Signiﬁcance:	
  1.8σ	 Ø Sensitivity is below Waxman-Bahcall boundØ Atmospheric neutrinos measured from 100 GeV - 300 TeV→ Consistent with previous measurements	
 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

12	
 

■ The extremely high energy (EHE)
cosmogenic neutrino searchpγ 2.7K → π + + X → µ + + ν µ → e+ + ν e + ν µ + ν µ
EHECRs

π	

µ	

 νµ	

νµ	

 νe	
  
e

Shed light on the EHECR origin² Source position² Composition (proton/iron)?
² Source evolution / when the EHECR
generation started

All flavor sensitive, Energy > 1 PeV
K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

13	
 

$

J
@
@
$

>+'$7 $?=5?$
J4K4)($6(-$?=5?$1,- backgroundbackground (atm.
atm.
) expectation
0.140.14
events(atm.++conventional
conventionalatm.
) expectation
eventsD$@A:$6B8?2C5=
preliminary p-value:(2.36
preliminary
p-value:0.0094
0.0094(2.36
@A:$8B66?2C5=D$@4EF%1$#G$H*(0/+.$I%')#1)$75?$■ Two cascade
like events
found in 2011-2012 data
34'552;D;9:&%'(87<7788?$
34'552;D;9:&%'(87<7788?$
Run118545-Event63733662@4EF%1$#G$H*(0/+.$I%')#1)$7;D$')#1)$75?$
J4K4)($6$?=5?$
J4K4)($6$?=5?$ days), IC86 configuration	 CC/NCinteractionsin the deAugust9 2011
May, 2011 - May,
2012
(350.9
$
PRL	
  
1
11,	
  
0
21103	  (2013)	
 @A:$8B66?2C5==$@A:$8B66?2C5=
NPE
6.9928x10$
Cinteractions
inthedetector@4EF%1$#G$H*(0/+.$I%')#1)$7;D$*(0/+.$I%')#1)$75?$@4EF%1$#G$H*(0/+.$I%')#1)$7;D$(0/+.$I%')#1)$75?$
Either CC interaction
νe or Sensors
NC interactionof any flavor ν 	
 MC
Number ofofOptical
354
$ $
$
$
CC/NC interactions
7,!
$
CC/NC
interactionsininthe
thedetector
detector4-*S(,F(;,(K(."%,*.,9+(>AJ(,6^,(MC$ $‘’Bert’’MC
MC !"#$%&%'()$*+))%,$(-%$)%.%/(0#'$/10(%10+$
Y$A.B,*.,%(0)+',1$),+$%#$I(.*+,.(A")*.$%,_*"',9>cf,h,9>6^,MH0D,7525,x,H0D,7527$$ $$Aug., 9 ,!"#$%&%'()$*+))%,$(-%$)%.%/(0#'$/10(%10+$
2011&%'(78;;8<=;$%'(78;;8<=;$(- (th

D$D$

D$
4

D$

th

2 events/ 672.7/ 672.7days
days-- backgroundbackground (atm.
atm.
) event	  expectation
eventsRun 118545
2 events(atm.++conventional
conventionalatm.
) expectation
even
rate	
   0.140.14-Event 63733662
preliminary p-value:(2.36
preliminary
p-value:0.0094
0.0094(2.36
in	
  615.9	
  days	4
NPE: 7.0 x 10
34'5567589:&%'(78;;8<=;$34'5567589:&%'(78;;8<=;$
Atmospheric	
  34'552;D;9:&%'(87<7788?$
m34'552;D;9:&%'(87<7788?$
uons	
0.038	  ±	  0.004	
Run118545-Event63733662(NDOM: 354
1,(1,J4K4)($6>+'$7 $?=5?$$?=5?$
J4K4)($6$?=5?$
th$?=5?$>+'$7
August92011
D$ D$
1.04±0.16 PeV	 @A:$8B66?2C5=@A:$6B8?2C5=D$D$@A:$8B66?2C5=
4
conven=onal	
  ±	
  0.001	
@A:$6B8?2C5=
NPE
6.9928x100.012	
  @4EF%1$#G$H*(0/+.$I%')#1)$75?$ atmospheric	
  n@4EF%1$#G$H*(0/+.$I%')#1)$7;D$@4EF%1$#G$H*(0/+.$I%')#1)$7;D$eutrinos	
@4EF%1$#G$H*(0/+.$I%')#1)$75?$
Numberof Optical Sensors 354$ $CC/NC interactions
ininthedetector
prompt	  neutrinos*	
0.033	  ±	  0.001	
CC/NC
interactions
thedetector$$.$,7527w,:((,"0-S,JD,=*S(,H*BB(--,0","'*%,#((C.IO,9:;<=>?97527,$ $‘’Ernie’’/$#,80*%%(),

Jan, 3rd, 2012
Run 119316-Event 36556705
NPE: 9.6 x 104
NDOM: 312
1.14±0.17 PeV	 K. Mase

$$

$$

MC
MC26,

2$

total	
  background	$ $2$

0.082	  ±	  0.004	

Significance:
2.8σ
2$* R. Enberg, M.H. Reno, and I. Sarcevic.
PRD78, 043005 (2008).	
 2013.09.03, 高エネルギーガンマ線でみる極限宇宙201314	
 !D0,9%*'0)0O,](A")*.$,7527w,:((,"0-S,JD,=*S(,H*BB(--,0","'*%,#((C.IO,9:;<=>?97527,

K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

15	
 

round (atm.
atm.
) expectation
0.140.14
eventsround(atm.++conventional
conventionalatm.
) expectation
eventseliminary(2.36
eliminaryp-value:
p-value:0.0094
0.0094(2.36

34'552;D;9:&%'(87<7788?$
34'552;D;9:&%'(87<7788?$
Run118545-Event63733662(-$?=5?$(-$?=5?$
J4K4)($6J4K4)($6
August9th 2011
D$ D$@A:$8B66?2C5=@A:$8B66?2C5=
NPE 6.9928x104@4EF%1$#G$H*(0/+.$I%')#1)$7;D$')#1)$75?$@4EF%1$#G$H*(0/+.$I%')#1)$7;D$')#1)$75?$
Numberof Optical Sensors 354$ $C interactionsC
interactionsininthe
thedetector
detector$ $8<=;$;8<=;$■ The deposited energy and geometry reconstruction

MC
MC

$ $

Aug.	
  (“Bert”)	
 1.04±0.16	
  PeV	
 
26,

2$
2$

Ø Energy	
  resolu=on	
  ~15%	
  Ø Energy	
  resolu=on	
  for	  these	  2$ events	
  speciﬁc	  Ø Including	
  systema=cs	
  (ice	
  +	
  
DOM	
  eﬀ.)	
  7w,:((,"0-S,JD,=*S(,H*BB(--,0","'*%,#((C.IO,9:;<=>?97527,/$#,80*%%(),

Ø Energy	
  based	  on	
  total	
  charge	
  2$Ø Shower	
  size	  ~10	  m	  <	
  detector	
  spacing	
  17	
  m	
  
Ø Shower	
  development	
  informa=on	
  is	
  somewhat	
  kept	  Ø Direct	
  photon	
  (forward):	
  	
  	
  	
  
sharp	  wf	  
Ø Scaiered	
  photon	
  (backward):	
  
wide	
  wf	
  
Ø Angular	  resolu=on:	
  10°-­‐15°	
 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙201316	
 ■Limits
Preliminary	
 high	
  evolu=on	
  models	
  (m>4)	
  are	  mostly	  ruled	
  out	  such	  as	
  FRII	 K. Masedifferential limit per one energy decade	
 2013.09.03, 高エネルギーガンマ線でみる極限宇宙201317	 ■ High energy starting event (HESE) searchØ Follow-up of the EHE neutrino searchØ Search contained events (neutrinos) byusing outer layers as vetoØ Reduce backgrounds

atm.	
  μ	
 

νμ	
 

Ø 420 Mton fiducial massØ All flavorØ > 60 TeV
Ø 3 times better than EHE neutrino search@ 1 PeVØ livetime: 662 days (2 years)

μ	
 

	
 

K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

18	
 

■Atmospheric muon backgroundØ Dominant	
  down-­‐going	
  background	  Ø Es=mated	
  by	
  using	
  data	  Ø Second	
  veto	  layer	
  introduced	
  Ø veto	  power:	
  at	
  least	
  3	
  orders	  of	
  magnitude	  Ø Removes	
  also	
  70%	  of	
  down-­‐going	
  atmospheric	
  neutrino	
  background	
  (southern	
  sky)	
  Ø 3	
  muon	
  events	
  passed	
  the	
  inner	  layer	  →	
  6.0	  ±	  3.4	
  events	
  /	
  2	
  years	
  with	  geometrical	
  volume	
  correc=on	
  K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

19	
 

■Atmospheric neutrino backgroundØLow	
  rate	
  at	
  PeV	
  energy	  (0.1	  event/year)	
  ØReduced	  by	
  70%	  by	
  the	
  muon	
  
veto	
  

Ø

Uncertainty	
  ~30%	
  from	  CR	
  composi=on	
  and	
  hadronic	  interac=on	  Ø

Large	
  uncertainty	
  from	  unmeasured	
  charm	  contribu=on	
  Enberg	
  et	
  al.	  (2008)	
  employed	
  (NLO	  perturba=ve	
  QCD)	
  

	
  	
  	
  	
  	
  	
  	
  	
  -­‐>	
  3.4	
  events	  Ø

K. MaseEs=mated	
  bg	
  rate:	
  4.6+3.7-­‐1.2	
  events	  /	
  2	
  years	  2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

20	
 

■Effective volume

only	
  track	
  type	 This	
  analysis	
  is	
  more	  sensi=ve	
  to	
  cascade	
  events	 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

21	
 

■ Charge distribution
Ø 28	
  events	
  observed	
  above	  selec=on	
  criteria	
  Ø Total	
  bg:	
  10.6+4.5-­‐3.9	
  Ø Signiﬁcance:	
  3.3σ	  (HESE	
  analysis	
  alone	  wo	  two	
  PeV	
  events)	
  Ø Including	
  EHE	  result	
  (2.8	  σ):	
  4.1σ	  Ø A	
  posteriori	
  (including	
  two	
  PeV	
  events):	
  4.8σ	  Ø Atmospheric	
  muons	  are	
  largely	
  reduced	  Ø Data	  and	  MC	  agree	
  well	  at	
  low	  charge	 K. Mase6000	
  p.e.	
 2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

22	
 

■Event samples

K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

23	
 

■Event samples

K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

24	
 

■ Coordinate of the first detected lightØ Uniformly	
  distributed	
  K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

25	
 

■Declination vs deposited energyØ21	
  showers	
  vs	
  7	
  tracks	
  Sugges=ng	
  signals.	
  	
  

Ø

In	
  case	  of	
  conven=onal	  atmospheric:	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  	
  
track	  :	  cascade	
  =	
  2:1	
  

Ø

Most	
  of	
  events	
  come	  from	  southern	
  sky	  because	
  events	
  from	
  north	  are	
  absorbed	
  by	
  
the	
  Earth	  ØExcess	  in	
  south	
  is	
  not	
  due	
  to	
  
atm.	
  ν	
  since	
  they	  are	
  reduced	
  in	
  south	  by	
  our	
  muon	  veto	
  

Ø

low	
  energy	
  4	
  tracks	
  look	  atmospheric	
  origin	
  (consistent	
  with	
  the	  predic=on	
  of	
  6±3.4)	
  Ø

Neutrino	
  energy	
  for	  track	  events	  can	  be	  very	  high	  compared	
  to	
  the	
  deposited	
  energy	 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

26	
 

■Deposited energy distributionØ Energy	
  spectrum	  harder	
  than	
  
that	
  of	
  backgrounds	  Ø Data	
  ﬁts	
  well	  with	  the	  predic=on	
  at	
  low	
  energy	  Ø E2φ	
  =	
  3.6	  ±	  1.2	  ×	  10-­‐8	  GeV/
cm2/s/sr	  (3	
  ﬂavours)	
  Ø Best	
  ﬁt:	
  E-­‐2.2±0.4	
  Ø Cut-­‐oﬀ	
  energy	
  above	
  2	
  PeV	  is	
  preferable	
  K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

27	
 

■Zenith angle distribution

Ø Compa=ble	
  with	  isotropic	
  ﬂux	  
Ø Events	
  absorbed	
  by	
  the	  Earth	  from	  northern	
  sky	  
Ø atm.	
  ν	
  is	
  reduced	
  in	
  south	  due	
  to	
  
the	
  muon	  veto	  Ø Excess	
  in	
  southern	
  sky	  is	
  not	  signiﬁcant	 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

28	
 

■ Sky map and the significanceTest	
  null	  hypothesis	
  against	
  the	
  most	  likely	
  	
  
L0:	
  null	  hypothesis	
  L:	
  maximized	
  likelihood	
  	
 

x:	
  track-­‐like	
  events	
  +:	
  shower-­‐like	
  events	
 

G.C.	
 

Not	
  signiﬁcant	 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

29	
 

■Big Bird
Ø Another	
  high	  energy	  event	  found	  in	
  the	  2012	
  test	  sample	  Ø 378	
  hit	
  DOMs	  K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

30	
 

q SummaryØ IceCube completed end of 2010 and performing as expectedØ Two PeV neutrinos were firstly observed in 2012Ø The significance is 2.8σ
Ø 26 additional neutrino candidates observed by a follow-up searchfor high energy starting eventsØ The significance is 4.1σ (combining with the EHE result)Ø We have started to see other than backgrounds!
Ø More events are coming!

K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

31	
 

backups

K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

32	
 

■ Target objects
Explore the universe with neutrinos

 AGNs GRBstalk by M. Ahlers	  Cosmic ray origin

 Cosmogenic
 Supernova
K. Maseneutrinos Dark Matter Particle physics

 Exiotic(monopole etc…)

2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

33	
 

■	
  The	
  South	  Pole	  The	  South	  Pole	  IceCube	  K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

1	
  km	
  

34	
 

■ Point source search
Search for muon neutrinos by using mainly the directions	 Sensi=ve:	
  >	
  ~1	
  TeV	  Test null hypothesis of no
IC40 (375 days) + IC59 (348 days) + IC79 (316 days)	
  signal against one with signals	
 108317 ν + 146018 µ	
 

G.P.	
 

RA: 34.25 deg.
Dec: 2.75 deg.	
 

Atm.	
  ν	
  
up-­‐going	
 

Atm.	
  μ	
  
(down-­‐going)	
 2000-2004

post-trial after
scrambling data

Equatorial	
  coordinate	 → P-value: 56.8%
Not significant	 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

35	
 

■	
  The	
  detector	
  performance	
  check	
  1	
  p.e.	
  distribu=on	
  

Gain	
  check	
  Time	
  resolu=on	  Mul=plicity	
  distribu=on	
  

~1	
  ns	
  

A. Achterberg	
  et	
  al.,	
  Astropart.	
  Phys.,	
  26,	  3,	  155-­‐173	
  (2006)	
  2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 K. Mase36	 ■ The detection principleCRs	
   Atmospheric	
  muons	  µ	

Down-­‐going	
 

µ	

µ,τ	

τ	

τ	

Up-­‐going	 ντ	EHE ν	

²	  EHE neutrino signal (all flavor)² Horizontal (opaque to the earth)² High energy (> 108 GeV)

² Atmospheric muon background

ντ	

µ	

² Down-going² Low energy (the energy spectrum is steep (~E-3.7))

νµ >1PeV

Yoshida	
  et	
  al	
  PRD	  69	  103004	
  (2004)	
  Energy Dist. @ IceCube Depth

K. MaseZenith Dist. @ IceCube Depth

Up-­‐going	 2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 Down-­‐going	
 37	
 q Effect of source evolution and maximum
energy on neutrino flux
eﬀect	  of	
  the	
  maximum	
  energy	
 eﬀect	  of	
  the	
  source	
  evolu=on	 neutrino	
  ﬂux	
  depend	
  on	
  the	
  source	  evolu=on	
  and	
  maximum	
  energy	  -­‐>	
  constraint	
  on	
  the	  parameters	 Kotera	  et	
  al.,	
  JCAP	
  10	
  (2010)	
  013	 38	 q Offline filter level
NPE	
  >	
  103.5	
  &&	
  NDOM	
  >	
  300	  &&	  Coincidence	
  cleaning	 33.4	
  days	Obs.	
  data	GZK	  signal	

all	(5.23±0.02)x104	

0.174±0.001	

proton	iron	

Coin.	

Atm.	
  nu	

(2.53±0.51)x104	
 (9.10±0.52)x104	
 (8.74±0.08)x103	
 0.769±0.032	

Test data

NPE:	
  4.3x104	
  

CORSIKA (iron)zenith	  angle:	
  19	
  deg.	
  	
 CORSIKA (proton)
CORSIKA (coin.)
GZK signal (Yoshida)Atm. Nu (Honda+ knee correction)	
 atmospheric	
  muon	  (data)	
 108 GeV (at surface, GZK spectrum)	
 1010 GeV (CR primary)	
 reasonable	
  MC/data	
  agreement	  Dominated	
  by	
  atmospheric	
  muons	
 39	
 q Final filter levelwith	
  precise	  reconstruc=on	
  algorithms	
  &&	
  further	
  coincidence	
  cleaning	 33.4	
  days	Obs.	
  data	GZK	  signal	

all	(5.22±0.02)x104	

0.170±0.001	

Below	
  horizon	

0±0	

proton	iron	

Coin.	

Atm.	
  nu	

(2.53±0.51)x104	
 (9.10±0.52)x104	
 (8.72±0.08)x103	
 0.769±0.032	

0.0459±0.0004	
 (2.25±0.94)x10-­‐4	
 (1.61±0.80)x10-­‐3	
 (2.35±1.63)x10-­‐3	
 0.383±0.017	

Zenith angle distribution 	
 NPE:	
  4.6x103	
  Test data
CORSIKA (iron)zenith	  angle:	  140	
  deg.	
 CORSIKA (proton)
CORSIKA (coin.)

atmospheric	
  neutrino	
  (MC)	
 GZK signal (Yoshida)Atm. Nu (Honda+ knee correction)	
 v mis-­‐reconstructd	
  events	
  are	  cleaned	
  cos(zenith angle)	
 v atmospheric	
  neutrinos	
  also	  come	  from	
  horizon,	
  but	
  low	
  energy	
 
	
 

40	
 

q Final selection criteria
Model discovery potential method used (4 sigma)
Iron + coin. + atm. nu is used for the background to be conservative	 Background
GZK signal	 (iron + coin. + AtmNu)	
 108 GeV (at surface, GZK)	
 1010 GeV (CR primary)	
 319.2	  days	Obs.	
  data	GZK	  signal	

all	

0±0	

0.978±0.005	

Below	
  horizon	

0±0	

0.0363±0.003	

proton	Coin.	

Atm.	
  nu	

(6.77±1.29)x10-­‐3	
 (3.31±0.25)x10-­‐2	

0±0	(1.59±0.10)x10-­‐2	

(7.88±6.08)x10-­‐4	
 (1.92±1.09)x10-­‐3	

0±0	(1.29±0.09)x10-­‐2	

* 0.57 per 333 days for IC40	
 

iron	

test data	
 
Data	
 

41	
 

/10(%10+$%'()$*+))%,$(-%$)%.%/(0#'$/10(%10+$

2 events/ 672.7/ 672.7days
days-- backgroundbackground (atm.
atm.
) expectation
0.140.14
events2 events(atm.++conventional
conventionalatm.
) expectation
events7) days- background + conventionalatm.
) expectation 0.14 events
expectation
0.14 (atm.
eventspreliminary
p-value:(2.36
preliminary
p-value:0.0094
0.0094(2.36
preliminary p-value: 0.0094 34'552;D;9:&%'(87<7788?$(2.36
34'5567589:&%'(78;;8<=;$34'552;D;9:&%'(87<7788?$
34'5567589:&%'(78;;8<=;$
Run118545-Event63733662
J4K4)($6$?=5?$q The brightest
stringpositions
August9 201134'552;D;9:&%'(87<7788?$@A:$8B66?2C5=(J4K4)($6(th$?=5?$@A:$8B66?2C5=D$4 D$
NPE 6.9928x10(-$?=5?$@4EF%1$#G$H*(0/+.$I%')#1)$7;D$
J4K4)($6@4EF%1$#G$H*(0/+.$I%')#1)$7;D$
Numberof Optical Sensors 354$ $D$@A:$8B66?2C5=
CC/NC interactions
CC/NC
interactionsininthe
thedetector
detector$ $@4EF%1$#G$H*(0/+.$I%')#1)$7;D$

1,1,
>+'$7
$?=5?$>+'$7$?=5?$
67589:&%'(78;;8<=;$@A:$6B8?2C5=D$D$@A:$6B8?2C5=%'(87<7788?$,$?=5?$@4EF%1$#G$H*(0/+.$I%')#1)$75?$@4EF%1$#G$H*(0/+.$I%')#1)$75?$?$B8?2C5=D$ Ernie	 $$D$=%1$#G$H*(0/+.$I%')#1)$75?$
MC
MC
$
$
$ $
0/+.$I%')#1)$7;D$$
CC/NC interactions in the detector
$$

$

MC

(K(."%,*.,9+(>AJ(,6^, $$(-%$)%.%/(0#'$/10(%10+$$(-%$)%.%/(0#'$/10(%10+$.(A")*.$%,_*"',9>cf,h,9>6^,MH0D,7525,x,H0D,7527N,

m. ++conventionalatm.
) expectation
0.140.14
eventsatm.
conventionalatm.
) expectation
eventsyyp-value:(2.36
p-value:0.0094
0.0094(2.36

!D0,9%*'0)0O,](A")*.$,7527w,:((,"0-S,JD,=*S(,H*BB(--,0","'*%,#((C.IO,9:;<=>?97527,

34'552;D;9:&%'(87<7788?$
34'552;D;9:&%'(87<7788?$
J4K4)($6$?=5?$
J4K4)($6$?=5?$
August9th 2011
D$ D$@A:$8B66?2C5=@A:$8B66?2C5=
NPE
6.9928x104@4EF%1$#G$H*(0/+.$I%')#1)$7;D$@4EF%1$#G$H*(0/+.$I%')#1)$7;D$$
Numberof Optical Sensors 354
$ $
tions
in
the
detector
ctions in the detector$ $Run118545-Event63733662
2345647527,(- (-/$#,80*%%(),

2$

Bert	
 

MC
MC

26,

2$

2$

$ $

2$

S,JD,=*S(,H*BB(--,0","'*%,#((C.IO,9:;<=>?97527,/$#,80*%%(),

26,

2$

Well	
  contained	
 42

q IceTop (surface array) veto information² IceTop	
  veto	  informa=on	
  was	
  checked	
  ² hits	
  search	
  in	
  allowed	
  8μs	  =me	
  window	
  ² 0	
  and	  1	  hit	
  observed	
  against	
  2.1	
  noise	
  hits	
  
-­‐>	
  No	
  CR	
  shower	  K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	 43

■ NPE distribution at final level
IC79/86 combined (615.9 days)	
 PRL	
  111,	
  021103	
  (2013)	
 corresponds to ~108 GeV neutrinos at surface with a cosmogenic neutrino spectrum	 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙201344	
 ■ Effective area
AIC79	  ≈	
  AIC86	
  ≈	
  2	
  x	
  AIC40	 for	
  each	  ﬂavor	 Three	
  ﬂavor	
  sum	 IC79	 v Increases	
  with	  energy	  v ~5000	
  m2	
  @	
  EeV	  	
 K. Mase

45	
 

q	
  The	
  ice	
  property	
  Average optical parameters:

K. Mase	

λabs ~ 110 m @ 400 nm

Clear	
  depth	  dependence	  	

λscat ~ 20 m @ 400 nm→	
  taken	
  into	  account	
  in	
  simula=on	
 2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

46	
 

■Effective area (HESE)

K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

47	
 

■ Longitudinal shower development in iceby	
  GEANT	 K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

48	
 

■ Light yield vs. distance for a point-like source

K. Mase2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 

49	
 

voltage [V]76nearest	  DOM	
 Down-­‐going	
  event	 5one	
  lower	 4one	
  upper	
 

3
2
1
0

K. Mase

9900

9950

10000 10050 10100 10150 10200 10250 10300
time [ns]2013.09.03, 高エネルギーガンマ線でみる極限宇宙2013	
 50