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

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

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

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

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

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

Muon spectra in bundles and zenith angle 11/15/2018 Muon spectra in bundles and zenith angle average muon spectra from 1018-1019 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

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 2008-11 data consistently indicates iron data log N events proton 2008 data log NPE > 3.5 cos za

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 …

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

11/15/2018