TeVPA, July 13-17 2009, SLAC1

Cosmic rays at

the knee and above with

IceTop and IceCube

Serap Tilav

for The IceCube Collaboration

South Pole4 Feb 2009

TeVPA, July 13-17 2009, SLAC2

IceCube Neutrino Observatory Neutrino Telescope & 3D Cosmic Ray Detector

IceTop

IceCube

IceTop • EM component near shower max• shower size & arrival times over 1km2

IceCube • Muonic component @ 1450m-2450m depth in ice• muon bundle energy over 1km

Air shower detection @ 2835m altitude (680 g/cm2)

TeVPA, July 13-17 2009, SLAC3

Motivation for Air Shower Measurementsin Energy Range 3.1014 eV – 1.1018 eV

from Andreas Haungs, Kascade

spectrum & composition around the knee

iron bump ?

2nd knee ?

transition from galactic to extra-galactic

TeVPA, July 13-17 2009, SLAC4

IceTop Tank

Solid block of clear ice

“ Ice Cherenkov Tank”

Single tank detects secondary particles in air showers : -- MeV e± -- converting γ -- ~1 GeV μ

Light yield (Cherenkov and stochastic) for each particle type is derived from a detailed GEANT4 simulation and parameterized

TeVPA, July 13-17 2009, SLAC5

Tank response to VEM and

calibration with Muon telescope

All eventsVertical muons(tagged with muon telescope)

Full SpectrumMuon Peak

VerticalMuon Peak

signals in coincidencewith muon telescope

all particlespectrumof the DOM

L. Demirors et al.,ICRC07arXiv:0711.0353

TeVPA, July 13-17 2009, SLAC6

IceTop Station

• 2 tanks per station• 1 tank hit muon, e or γ• both tanks hit air shower

• 2 DOMs per tank• 1 HG, 1 LG for dynamic range

Photo: James Roth, Dec 8, 2007

TeVPA, July 13-17 2009, SLAC7

IceTop Deployment 2005-2009

2005 4 stations

2006 12 stations

2007 10 stations

2008 14 stations

2009 19 stations

IceTop-26

IceTop-40

IceTop-59

IceTop-26First attempt on Energy Spectrum

IceTop-40First attempt on Composition

14 stations in 2010 7 stations in 2011

TeVPA, July 13-17 2009, SLAC8

IceTop-26 Reconstruction

Lateral shower profile at 125m

S125 : signal at r = 125m

β : slope at r = 125m

κ = 0.303 fixed

Fluctuations extracted from data

Likelihood function from data & simulation-- untriggered stations are also accounted for

Direction reconstruction : curved shower front

m

r

m

rSrS

125log

125

10

125)(

S. Klepser et al.,ICRC07arXiv:0711.0353

TeVPA, July 13-17 2009, SLAC9

IceTop-26 Resolution & EfficiencySimulations: CORSIKA with Sibyll and Fluka for 3 zenith bins [0-30]°,[30-40]°,[40,46]°

S125 Eprimary derived from proton simulations

for zenith range [0-30]°

Direction ~1.5°Core ~9 mEnergy ~ 16%Effective area ~ 0.094 km2

• requires ≥ 5 station triggers• containment criteria• quality cuts

full efficiency reached > 1 PeV

TeVPA, July 13-17 2009, SLAC10

IceTop-26 Detector Response

ProtonIron

Detector response is characterized as

Response Matrix (RM)

measjij

truei FRMF 1

Primary particlePrimary EnergyZenith Angle

ResolutionEfficiency….

+

RM

TeVPA, July 13-17 2009, SLAC11

Unfolded Spectrum

IceTop-26 Energy Spectrum

ResponseMatrix

Raw Energy Spectrum

5 months of data 1 Jun – 31 Oct 20071.1 107 events processed4.106 events passed

Proton only

Iron only

Composition sensitive zenith behaviorF. Kislat et al.,ICRC09

TeVPA, July 13-17 2009, SLAC12

Method• Reconstruct shower direction and core

location with IceTop• fix core, improve direction using IceCube

reconstruction, improve core using the improved direction --- 2 iterations

• Reconstruct muon bundle energy loss using charge flow information at each layer in IceCube

• Muon bundle energy loss is composition sensitive

IceTop-40/IceCube Coincident EventsData collected at 2 Hz rate

TeVPA, July 13-17 2009, SLAC13

IceTop-40/IceCube

Direction Resolution

Core resolution ~ 12-14 m Angular resolution < 1°

TeVPA, July 13-17 2009, SLAC14

IceTop-40/IceCube Muon Bundle Energy Loss & Composition

Data: 28 days Sep 2008Slant depth behavior of muon bundle energy loss

Data and H, Fe simulations

Resolution, efficiency, systematics work in progress

T. Feusels et al.,ICRC09

preliminary

TeVPA, July 13-17 2009, SLAC15

IceTop-40 Near Threshold ~300 TeV

Restrict event selection-- 3 station triggers only nearby stations forming triangle

-- 4 station triggers only nearby stations forming quadrangle

-- use flat shower front-- use the same LDF-- stronger containment

TeVPA, July 13-17 2009, SLAC16

IceTop-40 Near Threshold ~300 TeV

Proton MC

Iron MC

3 stations only

4 stations only

Reconstructedenergy distribution

for H & Fe simulations

3 station events

Data compared with H & Fe simulations

for zenith [0-26]°

TeVPA, July 13-17 2009, SLAC17

SummaryWork in Progress:

IceTop-26 2 PeV < E < 100 PeV-- Unfolded Energy Spectrum using 5 months of data -- Further exploit zenith angle dependence on composition

IceTop-40/IceCube coincidence 1 PeV < E < 50 PeV -- Muon bundle energy loss measured in IceCube is sensitive to composition-- simulations are limited beyond 50 PeV

IceTop-40 at threshold ~ 300 TeV-- use 3 station events only

• upgrade shower simulations start using thinned CORSIKA showers beyond 50 PeV• upgrade detector simulation calibrations better known than 2 yrs ago • re-work systematics