Transcript PPT

The High Resolution Fly’s Eye
John Matthews
University of Utah
Department of Physics and
High Energy Astrophysics Institute
JNM
Dec. 2001
Annecy, France
Outline
•
•
•
•
•
Questions
Detector
Calibration
Atmosphere
Capabilities
JNM
Dec. 2001
Annecy, France
UHECR Questions
•
•
•
•
Energy Spectrum
Sources, Anisotropy
Composition
Search for neutrinos
JNM
Dec. 2001
Annecy, France
The Cosmic Ray Spectrum
Direct Observation
below about 1014 eV
Indirect Observation
at higher energies
HiRes is optimized
for stereo observations
above 3x1018 eV
JNM
Dec. 2001
Annecy, France
Anisotropy and Composition
• Relatively isotropy
– Slight anisotropy observed by Fly’s Eye and possible sources
observed by AGASA
• Composition
– In the 1012 – 1015 eV energy range, direct measurements are
available. The composition is:
•
•
•
•
~50% protons
~25% alpha particles
~13% C/N/O nuclei
<1% electrons
– At higher energies, Fly’s Eye observed a composition which was
heavy (iron-like) transitioning to lighter (proton-like) around
5x1018 eV
• Neutrino Search
– Search for deeply penetrating or upward going events….
JNM
Dec. 2001
Annecy, France
The Atmosphere as Detector
• The cosmic ray
initiates an
extensive air
shower when it
hits the
atmosphere
• Measure the
resulting
fluorescence
light
JNM
Dec. 2001
Annecy, France
The High Resolution Fly’s Eye (HiRes)
• Spherical Mirrors: Area = 5.1 m2
• 256 PMT pixels/mirror: 1 degree resolution
JNM
Dec. 2001
Annecy, France
Stereo Observation
• Viewing the
shower from
two sites
allows for
precise
measurement
of geometry as
well as a
measurement
of the energy
resolution
JNM
Dec. 2001
Annecy, France
Utah’s West Desert
• HiRes is located
in Utah’s West
Desert at the
Dugway Proving
Ground
• The two sites are
separated by 12.6
km
JNM
Dec. 2001
Annecy, France
HiRes-I: Little Granite Mountain
• 22 mirrors viewing
– ~360 deg azimuth
– 3-17 deg elevation
• S&H electronics
(5.6 ms integration
time)
• Began data
collection in 1997,
completed 1998
• 2947 hrs data,
2314 hrs good
weather
JNM
Dec. 2001
Annecy, France
HiRes-II: Camel’s Back Ridge
• 42 mirrors
viewing ~360
deg azimuth and
3-31 deg in
elevation
• FADC
electronics with
100ns
integration time
• Completed in
Aug. 1999
JNM
Dec. 2001
Annecy, France
Detector Calibration
JNM
Dec. 2001
Annecy, France
Atmospheric Transmission
• Need to know the atmospheric quality
– Clouds
– Haze
– General transmission (horizontal extinction length and
vertical scale height)
JNM
Dec. 2001
Annecy, France
Atmospheric Instrumentation
• Two Steerable YAG Lasers
– Located at each of the HiRes sites
– Computer/GPS controlled
– Operated nightly
• One Steerable Mobile YAG Laser
– Computer/GPS controlled
– Operated as needed
• 10 Vertical Xenon Flashers
– Arrayed between the two HiRes sites
JNM
Dec. 2001
Annecy, France
Better than Standard Desert
• The “Standard Desert” Model uses an aerosol
horizonal extinction length of 12 km and vertical
scale height of 1.2 km. Optical Depth:
OD=VS/HE = 1.2/12 = 0.10
• Dugway Atmosphere is, on average, cleaner with
an aerosol horizontal extinction length of 25 km
and 1.0 km vertical scale height. Optical Depth:
OD=VS/HE = 1.0/25 = 0.04
• In addition, the molecular part of the atmosphere
has a horizontal extinction length of 18 km
JNM
Dec. 2001
Annecy, France
A HiRes Event
Example of a cosmic
ray air shower as
observed by HiRes-I:
Up = North
Right = East
Center of Circle =
Zenith (UP)
Outer Circle =
Horizon
JNM
Dec. 2001
Annecy, France
Capabilities of the HiRes Experment
• Stereo instantaneous aperture grows to 10,000 km2-str at
1020 eV. Factor of ten over Fly’s Eye
• Energy resolution 10%
• Xmax resolution 30 gm/cm2
• Angular resolution better than 0.4 degreees
• Measure Spectrum, Composition, and Anisotropy.
Search for Neutrino flux
• Expect to collect at least 5 years of data
JNM
Dec. 2001
Annecy, France
Measurement of the UHECR
Spectrum and its Structure
John Matthews
University of Utah
Department of Physics and
High Energy Astrophysics Institute
JNM
Dec. 2001
Annecy, France
The HiRes-I Data Set
• Collected June 1997- May 2001
• 2947 hours of monocular data
• 2314 hours of good weather data selected for this
analysis
• Containing 119M triggers (mostly noise and
atmospheric monitoring ie laser shots)
• 4.54M downward “track-like” events selected for
further processing
JNM
Dec. 2001
Annecy, France
HiRes-I Data Cuts
Events were also required to:
• >25 p.e./PMT (on average) – for reliable shower
profile reconstruction – avoid Poisson fluctuation
problems
• angular speed < 3.33 deg/ms (5 km for vertical
tracks)
• 10,683 events selected for reconstruction
JNM
Dec. 2001
Annecy, France
HiRes-I Monocular Fitting
• Profile Constrained Fit (assumed a Gaisser-Hillas
parameterization)
• Assumed
– x0 = 40 gm/cm2 (shower initiation)
 l = 70 gm/cm2 (elongation rate)
• Allowed xmax to vary 680 < xmax < 900 gm/cm2, 35
gm/cm2 steps (expected range for p - Fe primaries)
• Stepped through y in 1 deg steps (angle of shower
in the plane)
JNM
Dec. 2001
Annecy, France
HiRes-I: More Data Cuts
Assuming the profile fit converged, additional
cuts were made. Events were required to have:
• > 8 deg of track length
• First observation < 1000 gm/cm2 (highest
elevation)
• In plane shower angle, y < 120 degrees (avoid
events with significant Cerenkov light)
• No more than 1 bin with >25% Cerenkov light
• 5,264 events remain
JNM
Dec. 2001
Annecy, France
HiRes-I Event Display
JNM
Dec. 2001
Annecy, France
HiRes-I Event Profile Fit
JNM
Dec. 2001
Annecy, France
HiRes-I: Raw Energy Distribution
JNM
Dec. 2001
Annecy, France
Impact Parameter Resolution
JNM
Dec. 2001
Annecy, France
MC Impact Parameter Resolution
JNM
Dec. 2001
Annecy, France
Stereo Impact Parameter Resolution
JNM
Dec. 2001
Annecy, France
MC Plane Angle Resolution
JNM
Dec. 2001
Annecy, France
MC Plane Angle Resolution
JNM
Dec. 2001
Annecy, France
Stereo Plane Angle Resolution
JNM
Dec. 2001
Annecy, France
MC Energy Resolution
JNM
Dec. 2001
Annecy, France
MC Energy Resolution
JNM
Dec. 2001
Annecy, France
Stereo Energy Resolution
JNM
Dec. 2001
Annecy, France
Energy Resolution Comparision
JNM
Dec. 2001
Annecy, France
Energy Correction
JNM
Dec. 2001
Annecy, France
Energy Distribution
JNM
Dec. 2001
Annecy, France
HiRes-I Energy Spectrum
JNM
Dec. 2001
Annecy, France
HiRes-I Spectrum Atm Effects
JNM
Dec. 2001
Annecy, France
HiRes-II Data
• Good weather data Dec. 1999 – May 2000
• Due to longer tracks (two rings of mirrors) and
greater timing information (FADC), HiRes-II
events can be reconstructed using timing
information alone.
JNM
Dec. 2001
Annecy, France
HiRes-II Data Cuts
Required:
• Downward, track-like events
• Angular speed < 11 deg./ms
• Track-length > 10 deg. (ring 2 events)
• Track-length > 7 deg. (ring 1 events)
• Zenith angle < 60 degrees
• Shower maximum observed
• < 60% of signal Cerenkov light subtraction
 781 Events remain
JNM
Dec. 2001
Annecy, France
HiRes-II Event
JNM
Dec. 2001
Annecy, France
HiRes-II Data/MC Comparisons
JNM
Dec. 2001
Annecy, France
HiRes-II Data/MC Comparisons
JNM
Dec. 2001
Annecy, France
HiRes-II Data/MC Comparisons
JNM
Dec. 2001
Annecy, France
HiRes-II Data/MC Comparisons
JNM
Dec. 2001
Annecy, France
HiRes-II Flux
JNM
Dec. 2001
Annecy, France
HiRes-II Energy Spectrum
JNM
Dec. 2001
Annecy, France
HiRes-I Spectrum
JNM
Dec. 2001
Annecy, France
Fly’s Eye Stereo Spectrum
JNM
Dec. 2001
Annecy, France
HiRes-I/HiRes-II Joint Spectra
JNM
Dec. 2001
Annecy, France
Energy Spectra
JNM
Dec. 2001
Annecy, France
Stereo Event
JNM
Dec. 2001
Annecy, France
Preliminary Stereo Results
JNM
Dec. 2001
Annecy, France
Preliminary Stereo Spectrum
JNM
Dec. 2001
Annecy, France
Preliminary Anisotropy Results
JNM
Dec. 2001
Annecy, France
Preliminary Anisotropy Results
JNM
Dec. 2001
Annecy, France
Preliminary Anisotropy Results
JNM
Dec. 2001
Annecy, France
Preliminary Anisotropy Results
JNM
Dec. 2001
Annecy, France
Summary
• Mono HiRes-I and HiRes-II spectra have the same
slope and amplitude as the stereo Fly’s Eye data…
They show the same structure with a kink at ~3E18
eV. This structure is a good cross-calib point.
• There is a disagreement with AGASA as to the
location of this kink.
• The first stereo and anisotropy results are coming
soon (preliminary results shown here)
• Five years of STEREO data to come – proposal
submitted to US NSF.
JNM
Dec. 2001
Annecy, France