Testing the HiRes Detector Simulation

against UHECR Data

Andreas Zech( Rutgers University)

for the HiRes - Fly´s Eye Collaboration

ICRC 2003 in Tsukuba

HiRes CollaborationHiRes Collaboration

J.A. Bellido, R.W. Clay, B.R. Dawson, K.M. Simpson

University of Adelaide

J. Boyer, S. Benzvi, B. Connolly, C. Finley, B. Knapp, E.J. Mannel,

A. O’Neil, M. Seman, S. Westerhoff

Columbia University

J. Belz, M. Munro, M. Schindel

Montana State University

G. Martin, J.A.J. Matthews, M. Roberts

University of New Mexico

D. Bergman, L. Perera, S. Schnetzer, G.B. Thomson, A. Zech

Rutgers University

N. Manago, M. Sasaki

University of Tokyo

T. Abu-Zayyad, J. Albretson, G. Archbold, J. Balling, K. Belov, Z. Cao, M. Dalton,

A. Everett, J. Girard, R. Gray, W. Hanlon, P. Hüntemeyer, C.C.H. Jui, D. Kieda, K. Kim, E.C. Loh, K.

Martens, J.N. Matthews, A. McAllister, J. Meyer, S.A. Moore, P. Morrison, J.R. Mumford, K. Reil,R.

Riehle, P. Shen, J. Smith, P. Sokolsky, R.W. Springer, J. Steck, B.T. Stokes, S.B. Thomas,

T.D. Vanderveen, L. Wiencke

University of Utah

J. Amann, C. Hoffman, M. Holzscheiter, L. Marek, C. Painter, J. Sarracino, G. Sinnis, N. Thompson, D. Tupa

Los Alamos National Laboratory

The HiRes FADC Detector (HiRes-2)

The newer one of the 2 HiRes air fluorescence detectors 2 rings with 21 mirrors each Located on Camel’s Back Ridge in Dugway (Utah) Started taking data in fall 1999

The HiRes FADC Detector (HiRes-2)

256 photomultiplier tubes per mirror. Flash ADC electronics record at a frequency of 10 MHz.

The Role of Monte Carlo Simulations in the HiRes

ExperimentWe need M.C. to calculate the acceptance of our detectors for the flux measurement:

M.C. is also a powerful tool for resolution studiesand for tests of our reconstruction programs. This requires a simulation program that describes the shower development and detector response as realistically as possible.

We want our code to simulate events under the exact data-taking conditions.

HiRes Simulation Programs

HiRes FADC detector Monte Carlo choose energy & composition from measured

distributions; choose random geometry pick one shower from the library and scale it to energy choose trigger & atmosphere from databases generate detector response for this shower

CORSIKA & QGSJet Generation of Air Showers G.H. Fits to the Shower

Profiles

Shower Library one entry for each shower: energy primary particle zenith angle depth of first interaction 4 G. H. fit parameters

Database with Trigger Conditions Nightly ontime Trigger Gains Trigger Logic Dead Mirrors

Atmospheric Database Hourly Information about the Aerosol Profile of the Atmosphere from Laser Shots.

MC Output File in the same format as

real data

M.C. Input Energy & Composition

The composition is chosen from our HiRes Stereo and HiRes/MIA measurement.

The Fly’s Eye Stereospectrum is used as aninput for the M.C.

CORSIKA Shower Library (proton & iron)

Gaisser-Hillas fit to the shower profile:

Fit parameters scale with primary energy:

Adding Noise to the M.C.

Ambient light level (low amplitude) can be measured from the width of the FADC pedestals.

Additional sky noise (high amplitude) is added to the M.C. to get agreement with data of a certain period.

FADC counts in all trigger channelsblack: datared: M.C.

total noise tubes distributionblack: datared: M.C.

A few Data / Monte Carlo Comparisons

or: Testing how well we understand our experiment ...

HiRes-2 data shown from 12/99 until 09/01. ~ 556 Hours of good weather data. average atmosphere used for consistency with

HiRes-1. Statistics:

– rec. geometry: 6309 events– after all cuts: 2274 events

M.C. : ~ 4 x data statistics

Signal tubes / χ of linear time fit

2

Light per Track Length / Čerenkov Fraction

Rp / Rp Resolution

Energy / Energy Resolution

HiRes-2 Exposure

Flux:

HiRes-2 Energy Spectrum

HiRes-2 data from 12/’99 until 09/’01

HiRes Mono Energy Spectra

HiRes-1 data from 06/’97 until 02/’03

HiRes-2 data from 12/’99 until 09/’01

Conclusions Our data analysis relies on a realistic M.C.

simulation for the aperture calculation and for resolution studies.

We have generated air showers and detector response for the HiRes FADC detector under the exact data-taking conditions.

We have tested our simulation successfully against data taken by HiRes-2.

Our M.C. simulation provides a realistic and detailed model of our experiment.

HiRes and Fly’s Eye Stereo

HiRes-1

HiRes-2

Fly’s Eye Stereo

HiRes and Fly’s Eye Stereo

HiRes-1

HiRes-2

Fly’s Eye Stereo

Energy rescaled by - 6 %

HiRes and HiRes / MIA

HiRes-1

HiRes-2

HiRes Prototype & MIA muon array ( hybrid )

HiRes and AGASA

HiRes-1

HiRes-2

AGASA

Cuts

Track length Number of signal

tubes Zenith angle Track angle Psi angle Error in Psi angle Pseudodistance

Good weather conditions

Time tangent fit Chi Squared

Profile fit Chi Squared

Čerenkov light fraction

‘Bracketing’ cut

Čerenkov Light Simulation

The Longitudinal Profile calculated in the M.C. is in good agreement with results from

CORSIKA.

Lateral Profile: - we fit CORSIKA density

profiles to the sum of 3 exponentials.

- fits are parametrized with zenith angle and distance between detector and Xmax.

black: CORSIKA long. Čerenkov profile vs. atmospheric depthred: our M.C. simulation

red: CORSIKA lateral Čerenkov density vs. radial distance in meterblack: our fit using the sum of 3 exp.

Shower Geometry

Pseudodistance / Angle of shower axis in shower-detector plane