Analysis of GLAST Balloon Experiment Data Annual meeting of the - - PowerPoint PPT Presentation

September 13th, 2002 Tsunefumi Mizuno 1

Analysis of GLAST Balloon Experiment Data

Annual meeting of the Physical Society of Japan

Tsunefumi Mizuno, Hirofumi Mizushima, Akimitsu Ohto, Yasushi Fukazawa, Takashi Ohsugi (Hiroshima University), Tuneyoshi Kamae, Hiroyasu Tajima (SLAC), Masanobu Ozaki (ISAS)

mizuno@hirax6.hepl.hiroshima-u.ac.jp

• GLAST LAT/Balloon Experiment(p.2)
• Instrument simulator/CR models(p.3)
• Data analysis(pp.4-6)
• Summary(p.7)

September 13th, 2002 Tsunefumi Mizuno 2

GLAST Large Area Telescope/Balloon Experiment GLAST Large Area Telescope/Balloon Experiment

Si-Strip Tracker (TKR) CsI Calorimeter (CAL) Anti Coincidence Detector (ACD)

4X4=16tower

GLAST LAT(20MeV-300GeV)

• To achieve high sensitivity aimed by

GLAST, we need to estimate background in orbit accurately.

Balloon Flight Engineering Model (BFEM): single tower eXternal Gamma-ray Target(XGT)

• During the level flight (@38km), we

collected cosmic-ray events (>=100k) to be used for a background database for LAT.

Support Structure

September 13th, 2002 Tsunefumi Mizuno 3

Instrument simulator and Cosmic Instrument simulator and Cosmic-

• ray models

ray models

XGT ACD TKR CAL Pressure Vessel Support Structure

BESS

(magnetic north pole)

AMS

• ur model

(used in Geant4 Simulation) primary with geomagnetic cutoff and solar modulation @ Palestine, 2001 secondary (atmospheric)

0.01 0.1 1 10 100 GeV

A Geant4-based Monte-Carlo instrument simulator

Proton energy spectrum (from zenith) alpha electron/positron atmospheric gamma muon

• particles with underline

are expected in orbit

September 13th, 2002 Tsunefumi Mizuno 4

Count Rate of Each Layer for Count Rate of Each Layer for “ “Charged Events Charged Events” ”

Count rate of each layer for “Charged Events” (hit in ACD) CAL TKR ACD 26 Si layers (13 planes: x-y pair) muon gamma e-/e+ alpha proton Real Data (level flight)

• trigger rate (Data)

~445Hz

• simulation total

(our prediction before the flight) ~350Hz proton : 145Hz alpha : 18Hz e- : 45Hz e+ : 30Hz gamma : 50Hz muon : 62Hz Count rate observed and simulation prediction agree with each other in ~20%

September 13th, 2002 Tsunefumi Mizuno 5

Angular distribution of Angular distribution of “ “Charged Events Charged Events” ” (preliminary) (preliminary)

e-/e+ gamma proton alpha muon Simulation (total)

rms (arbitrary unit)

10-6 10-3 1 103

Data Data proton muon gamma e-/e+ alpha Straightness of the reconstructed track Zenith angles of the straight/single track straight track

horizontal

• Data and simulation agree with each other in ~20%.
• We may need to increase the proton/alpha/muon flux to explain data.

cos (theta) downward

September 13th, 2002 Tsunefumi Mizuno 6

Count Rate of Each Layer for Neutral Events Count Rate of Each Layer for Neutral Events

• trigger rate (Data)

~55Hz

• simulation total

(our prediction before the flight) ~52Hz proton : 3.1Hz alpha : ~0Hz e- : 6.9Hz e+ : 3.9Hz gamma : 35.5Hz muon : 2.4Hz

• Overall agreement is good between data and prediction.
• Count rate in upper layers are smaller than data.

Count rate of each layer (no hit in ACD) muon gamma e-/e+ proton

Real Data (level flight)

thick Lead converters

September 13th, 2002 Tsunefumi Mizuno 7

Summary Summary

• We performed GLAST Balloon Experiment on August 4th, 2001.
• All detector components worked well in high-counting

enviroment.

• We obtained ~100k Cosmic-ray events to be used as a

background database for LAT.

• We have developed a Geant4 based instrument simulator and

Cosmic-ray flux models.

• We have investigated the count rate, straightness of the track and

angular dependence of the flux.

• Data and simulation prediction agree with each other in ~20%,

below uncertainty of CR flux.

• Detailed study is underway.