1. observations of the muon bundles with IceCube
Aya Ishihara
JSPS Research Fellow
Chiba University
Mini-workshop on hadron interaction at ICRR: Oct 12, 2011

2. Project completion, 86 strings
11/15/2018
1km
2011
Project completion, 86 strings
In operation
1.5km ~ 2.5km
below the surface

3. Muon bundle detection detector muon m m m downward -going Cherenkov
11/15/2018
Muon bundle detection CR
muons are from pion and kaon
(+heavier meson) decays
multiple muons are highly centered in the cosmic-ray direction m m
downward
-going m
detector
North
Cherenkov
light cone
muon

4. NPE from muon bundles NPE proportional to dE/dx ~ a*Nm + b SEm
11/15/2018
NPE from muon bundles
NPE proportional to dE/dx ~ a*Nm + b SEm
E.g. a*1500 ~ b*1PeV
Several thousands of muons from the ultra high energy cosmic-rays reach to the IceCube depth

5. NPE distribution and cosmic-ray energies
11/15/2018
NPE distribution and cosmic-ray energies
NPE ∝ dE/dx ~ a*Nm + b SEm
QGSJET-II iron SIBYLL iron SIBYLL proton Data
NPE event rates
Data rates a factor of 10 higher than proton prediction for wide energy range upto 1019eV region

6. Event direction and energy threshold
11/15/2018
Event direction and energy threshold
Horizontal m energy threshold ~100TeV
Inclined m energy threshold ~3TeV
Vertical m energy threshold ~300GeV

7. Muon spectra in bundles and zenith angle
11/15/2018
Muon spectra in bundles and zenith angle
average muon spectra
from eV cosmic-rays
q<10
60<q<70
q>80
# of muons / bin
muon spectra at the IceCube depth
q<10
60<q<70
q>80
spectra at surface muons that reach to the IceCube depth
# of muons / bin
more number of horizontal events
Normalization shifts are artificial

8. Zenith angle distributions
11/15/2018
Zenith angle distributions
QGSJET-II iron
SIBYLL iron
SIBYLL proton
Data
horizontal vertical
higher energy threshold lower energy threshold
data consistently indicates
iron
data
log N events
proton
2008 data
log NPE > 3.5
cos za

9. Observation of muon deficit by Auger
11/15/2018
Observation of muon deficit by Auger
By Ralf Ulrich at TAUP11
While we’re not looking at the same muons …

10. 11/15/2018
Summary
IceCube is a rare tool that can measure muon bundles from CR E > 1018GeV
Several airshower measurements suggest underestimation of muons relative to EM components
IceCube muon rates are between proton and iron - much closer to iron
about 50% less than iron, about one order of magnitude higher than proton
however,
Data rates become much closer to proton IF 20-30% more energies go into muon (pi, K) - e.g. if currently 5% of cosmic-ray energy is going to muon channel, make it 6-7%
zenith angle distribution suggests – iron only primary MCs underestimate high energy muons (or produce too many low energy muons)
SIBYLL and QGSJET-II show similar features

11. 11/15/2018