Title: A Measurement of the UltraHigh Energy Cosmic Ray Flux with the HiRes FADC Detector
1A Measurement of the Ultra-High Energy
Cosmic Ray Flux with the HiRes FADC Detector
- PhD Defense Presentation
- September 15th, 2004
- Andreas Zech
2Outline
- A Brief Introduction to UHECR Physics
- The HiRes Experiment
- Unfolding the Cosmic Ray Spectrum
- Results of the HiRes-2 Analysis
- Conclusions
3A Brief Introduction to Ultra-High Energy Cosmic
Ray Physics
4Energy Spectrum
- differential flux dN / (dE A O dt)
- follows roughly E-3 power law
- direct observation not possible above 1 PeV
- three features
- knee at 1015.5 eV
- 2nd knee ( 1017.5 eV)
- ankle at 1018.5 eV
5Extensive Air Showers
- main channels
- p(-) µ(-) ?µ ( ?µ )
- po 2 ?
- main e.m. processes
- bremsstrahlung
- pair production
- ionization
6HiRes-2 Composition Measurement
- Indirect Composition Measurement using depth of
the shower maximum. - Shift from heavy to light composition at around
1017 eV to 1018 eV.
7HiRes-2 Skymap
- UHECR arrival directions agree with isotropic
distribution. - AGASA claims to see small-scale anisotropies
(clusters of events) at ultra-high
energies.
8Propagation Effects
- magnetic fields (galactic, extragalactic)
- red-shifting
- ee-- pair production with CMBR (at 1017.8 eV)
- photo-spallation of cosmic ray nuclei
- GZK effect with CMBR (at 1019.8 eV)
- ? (2.7 K) p ?(1232) p
n - ? (2.7 K) p ?(1232) p o
p -
- Strong flux suppression for
extra-galactic sources.
9The HiRes Experiment
10Air Fluorescence Detectors
- Detection of longitudinal shower profile via UV
fluorescence light. - Reconstruction of geometry from recorded shower
track. - Using the atmosphere as a calorimeter.
11(No Transcript)
12- Mirror area 5 m2 .
- 256 (16x16) PMT per mirror.
- One PMT sees 1 degree of the sky.
131. Reconstruction of the shower-detector plane
- project signal tubes onto sky
- fit tube positions to a plane through the center
of the detector - reject tubes that are off-track (and off in
time) as noise - shower axis lies in the fitted shower-detector
plane
142. Reconstruction of the geometry within the
s-d-plane (HiRes-2)
153. Shower Profile Energy Reconstruction
- Reconstruct charged particle profile from
recorded p.e. - Fit profile to G.H. function.
- Subtract Cerenkov light.
- Multiply by mean ionization loss rate ?
calorimetric energy - Add missing energy (muons, neutrinos, nuclear
excitations 10) total energy
16Phototube Calibration
- Relative calibration at the beginning and end of
each nightly run. - using YAG laser.
- optical fibers distribute the laser signal to all
mirrors.
- Conversion of recorded FADC signals to photon
flux. - Absolute calibration using a portable
light-source (RXF) of known intensity that is
carried to both sites.
17Atmospheric Calibration
- attenuation of light by two main processes
- Rayleigh (molecular) scattering
- Mie (aerosol) scattering
- Rayleigh contribution is quite stable and well
known. - Aerosol profile of the atmosphere has to be
monitored during the run. -
- Monitoring with an array of vertical Xenon
flashers between the two detector sites. - Detailed monitoring with steerable lasers on
both sites. - Additional vertical laser outside of Dugway
(Terra).
18Atmospheric Database
- Atmospheric data of the selected nights in
this analysis - 27 km
- 0.035
19Unfolding the Cosmic Ray Spectrum
20Deconvolution of the UHECR Spectrum
- We observe the spectrum convoluted with detector
acceptance and limited resolution. - Deconvolution with help of a correction factor
- D(Ei)S Rij T(Ej) T(Ei)
Gmc(Ei)/Rmc(Ei) D(Ei) - We need M.C. to simulate acceptance (
resolution) of our detectors
for the flux measurement
- This requires a simulation program that describes
the shower development and detector
response as realistically as possible.
21HiRes Monte Carlo Simulation
22CORSIKA Shower Library (proton iron)
- Fit parameters scale with primary energy
- Gaisser-Hillas fit to the shower profile
23Data / Monte Carlo Comparisons
- Testing how well we simulate our experiment...
- HiRes-2 data shown from 12/99 until 09/01.
- 531 hours of good weather data.
- average atmosphere used for consistency with
HiRes-1. - Statistics
- rec. geometry 6262 events
- after all cuts 2666 events
- M.C. 5 x data statistics
24Rp (Distance to shower axis)
25 of p.e. / degree of track
26Energy Distribution Resolution
27Acceptances Exposure
- Rmc(Ei) / Gmc(Ei)
- Acceptances from simulations broken up into
3 datasets.
A O t Rmc(Ei) / Gmc(Ei)
Smoothed exposure
(in 104 km2 sr s).
28Results of the HiRes-2 Analysis
29The HiRes-2 UHECR Spectrum
30The HiRes monocular UHECR Spectra
31Systematic Uncertainties
- Systematic uncertainties in the energy scale
- absolute calibration of phototubes /- 10
- fluorescence yield /- 10
- correction for misssing energy /- 5
- aerosol concentration
- uncertainty in energy scale /- 16
- atmospheric uncertainty in aperture
- total uncertainty in the flux /- 31
What are the uncertainties due atmospheric
variations and due to the MC input composition ?
32Systematics due to MC Input Composition
- Detector acceptance at low energies depends on
c.r. composition. - MC uses HiRes/MIA measurement as input
composition. - Relevant uncertainties
- detector calibration
- atmosphere
- fit to HiRes/MIA data
- /-5 uncertainty in proton fraction
33Systematics due to Atmospheric Variations
- Repeated HiRes-2 analysis using the atmospheric
database. - Regular Analysis
- 25 km, 0.04
- in MC generation
- in data MC reconstr.
- Systematics Check
- HAL VAOD from database (hourly entries)
- in MC generation
- in data MC reconstr.
34Fits to the HiRes-2 Spectrum
J E -3.33/-0.01
J E -2.81/-0.02
35Spectrum Fit
- Fit to the HiRes monocular spectra assuming
- galactic extragalactic components
- all propagation effects (ee-, red-shift,
GZK) - Details of the fit procedure
- Float normalization, input spectral slope (g) and
m - Extragalactic component
- 45 protons at 1017 eV
- 80 protons at 1017.85 eV
- 100 protons at 1020 eV
- Use binned maximum likelihood method
36HiRes and Flys Eye
37HiRes and Haverah Park
38HiRes and Yakutsk
39HiRes and AGASA
40Conclusions
41- We have measured the UHECR spectrum from
1017.2 eV to the highest energies with HiRes-2 in
monocular mode. - A simulation of the exact data taking conditions
was used to determine the acceptance and
resolution of the detector. - The simulation was tested in detailed data-MC
comparisons and proven to be realistic. - Systematic uncertainties due to atmospheric
variations and MC input composition were shown to
be small.
42- We observe the ankle in the HiRes-2 spectrum
at 1018.5 eV. - The HiRes-2 result is in close agreement with
HiRes-1 and Flys Eye. - The HiRes-2 spectrum is consistent with the
second knee and GZK flux suppression. - The combined monocular HiRes spectra show
evidence for a break above 1019.8 eV. The Poisson
probability for continuation of the spectrum with
unchanged slope from the HiRes monocular data is
1 x 10-4 .
43The HiRes Collaboration
THANK YOU !
- 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
- 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. ONeil, 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, G. Hughes,
- S. Stratton, D. Ivanov,
- S. Schnetzer, G.B. Thomson, A. Zech
- Rutgers University
44The Truth about Ultra-High Energy Cosmic Rays
- Weve established a clear link between UHECR
program related activities and evildoers
in Iraq.