Mohammad S. Sabra1

Mark J. Christl1, John W. Watts2 11Marshall Space Flight Center, Huntsville AL

222CSPAR, University of Alabama, Huntsville, AL

14/7/2015

Geant4 Simulation of Air Showers using

Thinning Method

APS April Meeting 2015, Baltimore, MD

https://ntrs.nasa.gov/search.jsp?R=20150006841 2020-07-26T15:04:19+00:00Z

Cosmic Rays• High-energy protons and heavy

ions• Very broad range of energies• Galactic and Extragalactic• maximum energy predicted at

60 1018 eV (= 60 EeV) (GZK-cutoff)

24/7/2015

p+ cmb+ p + 0

n + +

Proton Horizon~1020 eV

Extreme Energy Cosmic Rays (EECRs)

• EECRs (E > 60EeV) suffer almost no deflection from magnetic field in extragalactic, galactic, and solar system

• They point back directly to the location of their original sources “Charged Particle Astronomy”

• Detection of EECRs gives us information about their sources

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4

Eleven Science Questions for the New Century*

Question 6:How Do Cosmic Accelerators

Work and What Are They Accelerating?

*”Connecting Quarks with the Cosmos: Eleven Science Questions for the New Century Committee on the Physics of the Universe”, National Research Council , ISBN: 0-309-50569-0 (2003)

4/7/2015

54/7/2015

HiRes (Utah) TA (Utah)

Auger (Argentina)

AGASA (Japan)

Yakutsk (Siberia)

Detecting EECR

Data accumulated

64/7/2015

• EECRs Flux is low of the order of 1 particle/km2/sr/century• At high end of the spectrum reduces to 1 particle/km2/sr/millennium!

Spectra of leading EECRs observations

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Extreme Universe Space Observatory Mission

• A collaboration of 15 countries, 85 institutions and ~ 333 scientists

• It will be the first space-based observatory to use the Earth’s atmosphere to discover the origin of EECRs.

4/7/2015 8

Extensive Air Showers (EASs)• Studies of the nature of EECRs are based on

the measurement of EASs, • EASs are cascades of secondary particles in

the atmosphere as a result of the interaction of EECRs with the Earth’s atmosphere

• Maximum atmospheric depth Xmax depends on:

primary energy, nature of the primary

particle details of the interactions

94/7/2015

Modeling EAS using Geant4• Atmosphere is modeled as cylinder of radius 0.5 km

and divided into 112 layers of 1 km thickness and varying density

104/7/2015

0

0.25

0.50

0.75

1.00

1.25

0.1 1 10 100

Height (km)

Den

sity

(kg/

m3 )

Modeling EAS using Geant4

• Using Geant4 model FTF_BICProton and Iron as primaries

• Time and data size are huge!• Simulating 1 event of 1TeV proton:

Time ~ 20 hrsSize ~ 200GB

• Simulation time for EAS scales with energy of primary particle

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Iron

Proton

Radial distance from core

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Thinning Algorithm• Let Eo be energy of primary particle, and E be

energy of secondary particleThinning level Eth = E / Eo

• All secondaries with energies greater than Ethare followed, BUT if the energy sum of all jsecondaries produced in a certain interaction falls below thinning energy

only one particle is followed 134/7/2015

100TeV ProtonThinning level 1E-2 1E-4 1E-6

Time (min) 17 66 130

144/7/2015

0

200

400

600

800

0 200 400 600 800 1000 1200

Thinning 10-6

Thinning 10-4

Thinning 10-2

Xmax ~ 770 g/cm21 event of 100 TeV Proton

Depth (g/cm2)

Gam

ma

Yie

ld

100TeV/u IronThinning level 1E-2 1E-4 1E-6

Time (min) 21 120 380

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0

200

400

600

800

1000

1200

0 200 400 600 800 1000 1200

Thinning 10-6

Thinning 10-4

Thinning 10-2

Xmax ~ 370 g/cm2

1 event of 100TeV/u Iron

Depth (g/cm2)

Gam

ma

Yie

ld

Geant4 vs CORSIKA100TeV Proton

164/7/2015

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200

0 200 400 600 800 1000 1200

Geant4CORSIKA

100TeV Proton

Depth (g/cm2)

Nor

mal

ized

Gam

ma

Yie

ld

Geant4 vs CORSIKA100TeV/u Iron

174/7/2015

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

0 200 400 600 800 1000 1200

0 200 400 600 800 1000 1200

Geant4CORSIKA

100TeV/u Iron

Depth (g/cm2)

Nor

mal

ized

Gam

ma

Yie

ld

Remarks

• Thinning algorithm cuts simulation time significantly

• Xmax is not affected by thinning level• Location of Xmax depends on primary particle• Preliminary calculations show that Geant4

predicts low Xmax compared to CORSIKA:Magnetic FieldGeometry

4/7/2015 18

Acknowledgement

This work is supported by an appointment to the NASA Postdoctoral Program at Marshall Space

Flight Center, administered by Oak Ridge Associated Universities through a contract with

NASA

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www.orau.org

4/7/2015 20

Thank You!Questions?