Summary of Recent Results from HiRes Tareq AbuZayyad University of Utah.
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Transcript of Summary of Recent Results from HiRes Tareq AbuZayyad University of Utah.
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Summary of Recent Results from HiRes
Tareq AbuZayyadUniversity of Utah
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High Resolution Fly’s Eye Collaboration:
S. BenZvi, J. Boyer, B. Connolly, C.B. Finley, B. Knapp, E.J. Mannel, A. O’Neill, M. Seman, S. Westerhoff
Columbia University
J.F.Amman, M.D.Cooper, C.M.Hoffman, M.H. Holzscheiter, C.A.Painter, J.S.Sarracino, G.Sinnis, T.N.Thompson, D.Tupa
Los Alamos National Laboratory
J. Belz, M. Kirn
University of Montana
J.A.J. Matthews, M. Roberts
University of New Mexico
D.R. Bergman, G. Hughes, D. Ivanov, S.R. Schnetzer, L.. Scott, S. Stratton, G.B. Thomson, A. Zech
Rutgers University
N. Manago, M. Sasaki
University of Tokyo
R.U.Abbasi, T.Abu-Zayyad, G.Archbold, K.Belov, O.Brusova, S.A..Blake, C. Cannon, Z.Cao, W.Deng, R.C.Gray, W.Hanlon, Y.Fedorova, P.Huentemeyer, B.F Jones, C.C.H.Jui, E.C.Loh, M.M.Maestas, K.Martens, J.N.Matthews, S.A.Moore, K.Reil, R.Rehile, D.Rodriguez,,P.Shen, J.Smith, P.Sokolsky, R.W.Springer, B.T.Stokes, J.R.Thomas,
S.B.Thomas, L.Wiencke
University of Utah
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HiRes HiRes is located on the U.S. Army’s Dugway Proving Ground, ~2 hours SW of The University of Utah
The two fluorescence detector sites are located 12.6 km apart at Little Granite Mountain and Camel’s Back Ridge
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The Two HiRes Detectors
HiRes1: atop Five Mile Hill 21 mirrors, 1 ring
(3<altitude<17 degrees). Sample-and-hold electronics
(pulse height and trigger time).
HiRes2: Atop Camel’s Back Ridge
12.6 km SW of HiRes1. 42 mirrors, 2 rings
(3<altitude<31 degrees). FADC electronics (100 ns
period).
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Typical HiRes Event
~21019 eV event seen in 1999 (3× vertical scale)
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Measured Shower Profile
Event by event: Xmax in g/cm2; Total energy of the primary
particle: Arrival direction
Statistically: Mass composition p-air inelastic cross-section
Measured shower parameters.
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HiRes Topics: Spectrum Chemical Composition Anisotropy proton-air Cross-section (Talk by K.Belov) Neutrinos (Talks by K. Martens & L. Scott)
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High Resolution Fly’s Eye (HiRes) Experiment:Has the World’s Highest Exposure (5xAGASA)
HiRes1 Collected data from May 1997 to April 2006 HiRes2 Collected data from Dec 1999 to April 2006 HiRes Collected data on moonless nights: about 10%
duty factor. Mono: wider energy range (1017.2 < E < 1020.5 eV), best
statistics. Stereo: best resolution, 1018.5 < E < 1020.5 eV, fewer
events.
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Physics with HiRes Data HiRes-1
monocular data began ~3 years earlier: largest statistics,
HiRes-2 monocular: can reach down to as low as 1017.2eV,
Stereo data: best resolution, optimized for E>31018eV
HiRes-2 mono
HiRes-1 monoHiRes stereo
Tandem Stereo Study
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Energy Spectrum
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Spectral Shape Almost featureless spectrum at lower energies However, the GZK Cutoff was predicted in 1966 by
K. Greisen, G. Zatsepin, and V. Kuzmin. Photons of CMBR interact with cosmic ray protons
of extragalactic origin. Photoproduction of ’s via Δ resonance Pion carries away 20% of proton’s energy strong
energy-loss mechanism for protons, that travel > 50 Mpc.
Should occur at about 6x1019 eV (10J) causing a strong break in the spectrum
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Previous Experiments Several smaller experiments
saw one super-GZK event each: Volcano Ranch, Haverah Park, Yakutsk, Fly’s Eye.
Akeno Giant Air Shower Array (AGASA) was the first experiment to be large enough to measure the spectrum at the GZK energy; they didn’t see the cutoff.
AGASA main evidence: 11 events above 1020 eV.
This led some to question whether the GZK cutoff exists, and how it might be evaded.
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5σ Observation of the GZK Suppression Broken Power Law Fits
No Break Point 2/DOF = 162/39
One BP 2/DOF = 62.9/37 BP = 18.65
Two BP’s 2/DOF = 39.5/35 1st BP = 18.65 2nd BP = 19.75 2 difference=>4.5
Two BP with Extension Expect 39 events Observe 13 events Poisson probability:
P(13,39) = 4.8
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Confidence Building Tests:
Geometry/Energy Reconstruction Aperture Composition Dependence Atmosphere (Avg vs Hourly) Aperture High Energy Efficiency/Aperture
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Mono versus Stereo Energy Measurements
The HiRes monocular energy is in excellent agreement with stereoscopic measurements !
HiRes-1 mono vs. stereo
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Add the HiRes Stereo Spectrum(absolutely normalized)
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Spectrum with Systematic Uncertainty from Composition
Composition determines whether <Xmax> is in HiRes’ field of view, or above.
Different apertures for Corsika/QGSJet protons and iron; leads to systematic uncertainty below 1018 eV, which is larger than statistical uncertainty.
HiRes can’t say much about the second knee.
The field needs an experiment, with wide enough energy range, which would see all three UHE cosmic ray features with good statistics!
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ATM and the Aperture
Ratio of Apertures:
numerator:
MC w/ATM database
Reconstruction w/
database
denominator:
MC gen w/database
Reconstruction using
Average ATM
log (E)
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Aperture Check HiRes-2 Data:
Artificially cut the data so that you are certain of the aperture.
Cut data with an impact parameter > 15 km
>10 km
Excellent agreement! Confidence in aperture calculation
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Phase SpaceSpace at High Energies
Compare data with high energy MC phase space relations.
Super GZK events are just like those at lower energies.
No surprises HiRes aperture calculation is accurate.
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HE Aperture Test
HiRes 1
HiRes 2
Terra (Laser)
Shower~30 EeV
Laser tests the reach of our HE aperture - 34 km from HiRes-2 Detector.
Light production equivalent to ~6x1019 - 1020 eV air shower
Detectors have no trouble seeing this laser under good to worse than acceptable viewing conditions.
GZK CutoffGZK Cutoff
30 EeV Shower
Terra Laser
profiles recorded by HR2
NP
E/2
De
g
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Composition
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Stereo HiRes Elongation RateWidth is constant from ~1018 eV up
Width and Xmax (elongation) imply constant composition in this energy range
- QGSjet (1) prefers ~80% “protons”
- Sybil prefers ~60%
Application of radio-sonde data (SLC) will move the HiRes Xmax up ~10 gm/cm2 on average, thus lighter
Model-independent break in slope at about 1018 eV.Heavy (galactic) nuclei decrease, give way to light (extragalactic) composition.Galactic/extragalactic transition is complete by about 1018 eV.
•Astrophysical Journal 622 (2005) 910-926
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Composition: Xmax Distribution Width Predictions
Protons: deeper and wider
The distributions overlap
Thus not an event by event measurement
MC with E = 1018 – 1019 eV
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Composition: All-Energy Xmax Distribution
Solid Line: DataSolid Line: Data
Heavy Dots: QGSJet Heavy Dots: QGSJet
Light Dots: SIBYLLLight Dots: SIBYLL
Data v Proton Models Data v Iron Nuclei Models
Stereo Data:Stereo Data:~800 Events ~800 Events 11/1999 – 9/200111/1999 – 9/2001
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Some of the Additional Data Previous result runs out of statistics near 30 EeV Analyze “golden events” above 8 EeV to
increase statistical reach “golden events” are events where Xmax is
clearly observed by HR 2 as determined by manual scan
80% of data above 10 EeV falls into this category
Scan bias is believed to be small
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Open circles: previous HiRes publication
Filled circles: new HiRes “golden events”
Composition appears to remain light approaching 1020 eV
Student’s Thesis on this is taking shape and expect an updated result this summer
Log10(E)
XmaxExtending the Analysis
A first look:
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HiRes Anisotropy Results: BL Lac Correlations
Correlations between UHE cosmic rays’ pointing directions, and BL Lac sources have been found individually in AGASA, Yakutsk, and HiRes stereo data, by P.Tinyakov, I.Tkachev, D.Gorbunov, S. Troitsky et al.
HiRes stereo result: BL with m<18: 10-4 chance probability. Add HP sources: 10-5 chance probability.
The HiRes result should not exist, since the ~0.5o resolution is smaller than expected magnetic deflections.
This is a northern-hemisphere effect, since many fewer sources are known in the southern hemisphere.
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More Northern Hemisphere Anisotropy
The Quartet: AGASA triplet + HiRes stereo high energy event; in Ursa Major.
Dip near galactic anticenter, observed by AGASA and HiRes at lower energies.
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HiRes-1 Anisotropy
• HiRes-1 mono ang. resolution: ~8° within the SD plane.
• Asymmetric error ellipses but with area comparable to AGASA angular resolution
• 2 publications in 2004
Autocorrelation functions (histogram of cos between all possible pairs) for HiRes-1 monocular (left) and AGASA (right) events above ~4x1019eV Astropart. Phys. 22, 139 (2004)
HiRes-1 mono AGASA
Cen. A
=0.020.06
Galactic Ctr.
=0.010.05
M87
=0.010.05
Search for dipole enhancement in the direction of nearby a-priori sources: null results for the Galactic Center, Centaurs A, and M87 Astropart. Phys. 21, 111 (2004)
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Summary Spectrum
The UHECR Spectrum clearly shows structure (ankle, GZK suppression) – there is physics here
Chemical Composition Xmax AND Width important to measuring composition Changing heavy to light - light and constant above ~1018 eV Transition apparently complete BEFORE the Ankle
Anisotropy Tantalizing hints of BL-Lac correlation – needs verification with
independent data Possible Point source with AGASA Triplet
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