Transcript C2CR, Prague Sep 11, 2005 - Particle Physics and Particle

Recent Results from the
High-Resolution Fly’s Eye
(HiRes) Experiment
ARENA - 2006
Newcastle, UK
Pierre Sokolsky
University of Utah
C2CR, Prague
Sep 11, 2005
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Outline
• The High-Resolution Fly’s Eye (HiRes)
Experiment
• Monocular Energy spectrum and features
• Stereo Energy Spectrum
• Composition
• Anisotropy - BL-Lac correlations
• Telescope Array
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High Resolution Fly’s Eye (HiRes)
Collaboration
S. BenZvi, J. Boyer, B. Connolly, C.B. Finley, B. Knapp, E.J. Mannel, A. O’Neill, M. Seman, S. Westerhoff
Columbia University
Z. Cao
Institute of High Energy Physics, Beijing
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
Rutgers University
N. Manago, M. Sasaki
University of Tokyo
R.U. Abbasi, T. Abu-Zayyad, G. Archbold, K. Belov, A. Blake, Z. Cao, W. Deng, W. Hanlon, P. Huentemeyer, C.C.H. Jui, E.C. Loh, K. Martens,
J.N. Matthews, D. Rodriguez, 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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Detector Design
• Each HiRes detector unit
(“mirror”) consists of:
– spherical mirror w/ 3.72m2
unobstructed collection area
– 16x16 array (hexagonally
close-packed) of PMT pixels
each viewing 1° cone of sky:
giving 5 improvement in S:N
over FE (5° pixels)
– UV-transmitting filter to
reduce sky+ambient
background light
– Steel housing (2 mirrors each)
with motorized garage doors
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Typical HiRes Event
~21019eV event
(3× vertical scale)
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1.)
Reconstruction of EAS
from HiRes Data
•
ti
i
t0
The trajectory of the EAS can be
determined in one of two ways:
1.
2.
Monocular reconstruction using the
arrival time of light signal at the
detector.
By intersecting the shower-detector
planes (SDP) seen from the two
detector sites.
ti  t0 

RP
tan i
c
2
2.)
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Physics with HiRes Data
HiRes-2 mono
• Stereo data: best
resolution, optimized
for E>31018eV
• HiRes-2 monocular:
can reach down to as
low as 1017.2eV
• HiRes-1 monocular profile constrained
data began ~3 years
earlier: largest
statistics,
HiRes stereo
HiRes-1 mono
Tandem Stereo Study
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Measured shower profile.
Measured shower parameters.
Event by event:
• Xmax in g/cm2;
• Total energy of the primary
particle:
• Arrival
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Statistically:
• composition.
• p-air inelastic cross-section;
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Compare Data to Monte Carlo:
Judge success of simulation and
acceptance calculation.
Inputs to Monte Carlo:
Fly’s Eye stereo spectrum; HiRes/Mia and HiRes Stereo composition;
Library of Corsika showers.
Detailed nightly information on trigger logic and thresholds, live mirrors, etc.
Analyze MC with exact programs used for data.
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Result: excellent simulation of the data,
and an accurate aperture calculation.
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UHECR Energy Spectrum -first result
• Combined
HiRes-1 and
HiRes-2
monocular
spectra
published:
Phys. Rev.
Lett. 92,
151101
(2004)
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Monocular Spectra-most recent
HiRes1: 7/97-5/05
HiRes2: 12/99-8/04
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We observe: ankle;
high-energy suppression;
second knee?
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5σ Observation of the GZK Suppression
• Broken Power Law Fits
– No Break Point
• Chi2/DOF = 162/39
– One BP
• Chi2/DOF = 68.2/37
• BP = 18.63
– Two BP’s
• Chi2/DOF = 34.7/35
• 1st BP = 18.63
• 2nd BP = 19.75
– Two BP with Extension
• Expect 51.1 events
• Observe 15 events
• Poisson probability:
P(15;51.1) = 3x10-9
(5.8s)
– Independent statistics:
P(14;44.9)=7x10-8 (5.2σ)
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“Test Beam” of High Energy Events
•
•
•
•
•
•
Laser at Terra Ranch
35 km from HiRes-2
Vertical, 355 nm
Fires at five energies, as bright as
40-125 EeV showers.
Efficiency for good-weather nights.
Excellent trigger + reconstruction
efficiency above 6 x 1019 eV.
• We see high energy events
with good efficiency.
GZK Cutoff
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Integral Spectra
• Want to test E½ with integral
spectra
• Use 2BP Fit with Extension
for the comparison
• log10E½ = 19.73 ± 0.07
• Berezinsky et al.:
log10E½ = 19.72,
for
wide range of conditions.
• Suppression is at the right
energy for the GZK cutoff.
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New Stereo Analysis
• Use nightly atmospheric data base for hourly
corrections to aerosol scattering
• IR sensor cloud detection ( data base still being
implemented)
• Nightly radiosonde molecular atmosphere density
profiles from SLC airport
• Geometric cuts to define “fully efficient” stereo
aperture
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Checks on Aperture Simulation
• Stereo aperture calculation uses same atmospheric
data base as data reconstruction.
• Input Fe and p showers from Corsika QGS-jet and
generate “simulated” events
• “Simulated” events reconstructed with same
programs as real data
• Compare distributions and input/output
resolutions and offsets
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MC vs. Data: Rp distribution (proton)
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Rp1 (km)
Rp2 (km)
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MC vs. Data: zenith angle distribution
Iron
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θ
( rad )
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MC vs. Data: Xmax distribution
Data seems to favor protons
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Xmax (g/cm2)
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Defining a “fully efficient” aperture
• HiRes I and II are fully efficient at triggering on a
shower out to a certain Rp distance for a given
energy. Lower energy showers will have a smaller
aperture
• Use MC simulation to determine minimum energy
for a given Rpmax to have a a flat aperture.
• Aperture dependence on aerosol concentration is
then also minimized!
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Energy and Rp continuus cut
•
•
•
•
•
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E: 18.25~18.65 Rp<10km
E: 18.65~19.05 Rp<15km
E: 19.05~19.45 Rp<20km
E: 19.45~19.85 Rp<30km
E: 19.85~
Rp<75km
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Aperture (Fully Efficient)
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New Stereo Spectrum (Preliminary)
no cloud cuts yet!
1
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Most recent Mono spectrum
(with cloud cuts)
New “fully efficient” stereo
Spectrum - no cloud cuts
Monocular Spectra
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HiRes and Other Experiments
HiRes, Fly’s Eye Stereo, and HiRes/MIA
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HiRes, AGASA, Auger(2005)
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Summary of Spectrum Results
• Monocular Spectrum
• Using the latest monocular data, HiRes has observed the GZK suppression
• Ankle at ~1018.6eV
• Stereo Spectrum
•
•
•
•
Shape consistent with monocular spectrum at 2.5x AGASA statistics
“Fully efficient” aperture produces more reliable results
Resulting aperture largely independent of aerosol corrections
Normalization of stereo spectrum consistent with monocular spectrum
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HiRes Composition Measurement
• Astrophysical Journal 622
(2005) 910-926
• Higher statistics needed to extend
analysis up to the GZK Threshold!
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Additional Data - Thru 2005-5
• 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 - Xmax
new HiRes
“golden
events”
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Log10(E)
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Stereo Xmax Measurement
• Two simultaneous measurements of the Xmax allows
for direct verification of the MC resolution
Data
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MC
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QGS-protons vs data
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QGS-FE vs data
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Composition as measured by Xmax
• New data indicates continuing light compostion to
GZK cutoff
• Overall, FE and HiRes data consistent within
quoted systematic errors
• Rapidity of transition from a heavy to a light
composition near 1 EeV needs better data
• Width of Xmax distribution consistent with
protons above 1 EeV
• Composition at highest energies constrains the
neutrino flux calculations!
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The GZK cutoff is present.
We see the Ankle clearly.
What’s next?
• Where is the galactic/extragalactic transition?
• Composition gives an indication.
• Is there a sign of e+e- pair production?
• What are the properties of the extragalactic sources?
– Power law?
– Distribution of Emax values?
– Evolution of the sources?
• Fit the spectrum to a model which contains both galactic and
extragalactic sources.
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Implications of Composition change and
spectral features
 Galactic/Extragalactic Transition
•
•
•
•
•
•
There is a 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.
Fits, plus QGSJet predictions, yield model of
proton fraction as a function of energy.
All fluorescence measurements of Xmax are
consistent.
Only fluorescence experiments SEE Xmax.
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Fit Spectrum and Composition Simultaneously
•
Fit composition and spectrum
simultaneously.
– Heavy = nuclei, inert propagation
– Light = extragalactic protons.
•
Extragalactic proton model:
–
–
–
–
•
Spectral index γ,
Emax = 1021 eV,
ρ=const*(1+z)m.
Energy loss from interactions with
CMBR and uniform expansion.
Best fit:
– m = 1.95
– g = -2.47
– Chi2 = 49.7/41
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Interpretation of Extragalactic Spectrum
• Pion-production pileup
causes the bump at 1019.5
eV.
• e+e- pair production
excavates the ankle.
• Pileup from e+e- production
below ankle.
• Fractionation in distance
and energy; e.g., z=1
dominates at second knee.
• Evolution of the sources is
important.
D. Bergman’s plot of shells in z
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The Ankle is Important
• Ankle is due to e+e- pair
production:
– Berezinsky: better evidence of
CMBR interactions than GZK.
– Shows that composition is
mostly protons
[+ some Helium (Hillas);
or “light” (Allard et al.)].
• Astrophysics: tells about
cosmic ray sources.
– Ankle region  spectral index
at source.
– fall to ankle  evolution
parameter, m.
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Stereo point spread function
HiRes Anisotropy
Results
Monocular Anisotropy Results
•
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)
•
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)
•
•
Point source search: null result
Submitted to Astropart Phys.
Search for cross-correlation with
AGASA doublets and triplet:
– Observed overlap no greater than
that expected by chance from an
isotropic
Submitted to Astropart Phys.
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Stereo Anisotropy Results
• Stereo angular resolution ~0.6
•
HiRes stereo data (E > 1019 eV) is
consistent with isotropy at all small
angular scales
Astrophys. J. Lett. 610 (2004)
L73
•
Search for Point Sources of Ultra-High
Energy Cosmic Rays above 4.0 1019 eV
Using a Maximum Likelihood Ratio Test
Astrophys. Journal 623 (2005) 164
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Maximum Likelihood Point Source Search
Qi ( xi , xs )
Introduced here as a way to
search for a single point
source among events with
different errors.
Qi(xi,xs) is the probability for an
event observed at xi to have a
true arrival direction at xs. Qi
depends on the angular
resolution of the event.
Ri(x) is the probability
distribution for the event to be
observed anywhere in the sky.
Ri depends on the detector
acceptance and exposure.
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Ri (x)
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Maximum Likelihood Point Source Search
The test hypothesis is that ns events arrived from a source located at xs,
and the remaining N-ns events are background.
Under this hypothesis, the probability
associated with a given event is the weighted
sum Pi of the source and background
probabilities.
The product of Pi for all events gives the
likelihood L for a particular choice of ns. The
best estimate for ns is the value which
maximizes L.
In practice, we maximize ln(R), the log of the
ratio of the likelihood of ns relative to the
likelihood of the null hypothesis: ns = 0.
ns
N  ns
Pi ( x, xs )  Qi ( x, xs ) 
Ri ( x)
N
N
N
L(ns , xs )   Pi ( xi , xs , ns )
i 1
L ( ns , x s )
ln(R)  ln
L(0, xs )
ln(R) is the measure of deviation from the null hypothesis of
no source events.
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Correlation with BL Lacertae Objects
•
BL Lacertae Object - special type
of blazar, active galaxy with jet
axis aligned with our line of sight.
•
Blazars are established sources of
TeV gamma-rays
Candidates for accelerating cosmic
rays to EeV energies
•
Somewhat controversial recent history regarding correlations of
UHECR with BL Lac objects:
Tinyakov and Tkachev, JETP 74 (2001) 445.
Tinyakov and Tkachev, Astropart. Phys. 18 (2002) 165.
Gorbunov et al., ApJ 577 (2002) L93.
Evans, Ferrer, and Sarkar, Phys.Rev. D67 (2003) 103005.
Torres et al., Astrophys.J. 595 (2003) L13.
Gorbunov et al., JETP Lett. 80 (2004) 145.
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Stern and Poutanen, ApJ 623 (2005) L33.
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Confirmed BL Lacs m>18 (10th Veron)
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+ HiRes Events E>1019 eV
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Summary of BL Lac Correlation:
• “BL”, m<18, all HiRes events (no E cut): F = 2×10-4
• “BL+HP” with m<18, HiRes E>10 EeV: F = 10-5
• Confirmed TeV blazars, all HiRes events (no E cut): F = 10-3
• These are not independent results: the samples overlap.
• Analysis has been a posteriori, so above F values are not true
chance probabilities.
• Correlations must be tested with independent data before any
claim can be made.
• Arrival directions of past year of data have not been analyzed. Data
taking through March 2006 will yield an independent data set
~70% of the current sample size: Independent test of BL Lac
correlations should be possible
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TeV BL Lac Correlation
• Six BL Lacs are confirmed sources of TeV g-rays. Five are in
the northern hemisphere and well observed by HiRes.
• We perform the maximum likelihood analysis on each source
individually using all HiRes events:
Name
Mrk 421
H1426+428
Mrk 501
1ES1959+650
1ES2344+514
z
0.03
0.13
0.03
0.05
0.04
V Mag
12.9
16.5
13.8
12.8
15.5
ns
0.3
0
3.3
2.0
0
F
0.2
0.4
610-4
810-3
0.7
• For the TeV blazars taken as a set, the ML analysis yields:
All energies:
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ns = 5.6 with F = 10-3
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BL Lac Correlation: Sensitivity of Future Data
We estimate the sensitivity which future HiRes data will have by
resampling the real HiRes events (Bootstrap resampling)
We simulate 1, 2, 3 years of new data to estimate the distribution of
possible signal strengths if the observed correlations are real.
(Arrival directions of past year of data have not been analyzed.)
HiRes can perform “typical”
mountain tau neutrino search
nt
energy losses
t
showe
r
calorimeter
target mass
Use ANIS program to predict sensitivity
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Improvments on ANIS:
• atmosphere:
- decay volume
• local surface topology:
600km x 600km
HR2
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SLC
HR1
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Where the t come from:
n interaction points for t decaying in atmosphere
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What sensitivity can be achieved?
HiRes???
from:
APS Multidivisional Neutrino Study
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(Neutrino Astrophysics and Cosmology Working Group)
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Future Prospects
• HiRes has ceased operation at the end
of March 2006
• Analysis of major topics to be
completed by summer of 2007 (30th
ICRC)
• Subgroups of HiRes have joined the
Telescope Array (Delta, UT, USA)
– Grond array of 576 (1.2km spacing)
scintillation counters
– Three fluorescence sites looking
inward
• US contribution: Third fluorescence
site and low-energy extension down to
1016.5 eV
• TA is now funded (Japan and NSF
funds)
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Conclusions
• The HiRes experiment has completed data taking.
• Monocular spectra strongly support GZK cutoff and ankle
structure - 5 sigma level
• New stereo analysis is consistent with monocular data in
shape and normalization and confirms ankle structure
• Xmax method is consistent with light composition to the
cutoff
• BL-Lac correlations do not appear to be easily ruled out
yet.
• Next generation TA experiment is under construction
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Estimating Systematics
• Highest energy data is best measurements
- most complete profile
- minimum Cherenkov subtraction
Energy scale for all three experiments is consistent
(location of ankle and second knee).
Use HiRes stereo average Xmax and Fly’s Eye stereo
average Xmax above 1018 eV.
Require a 13 gm/cm2 upward shift for Fly’s Eye to bring
means into agreement
Shift all Fly’s eye Xmax data points by the same amount.
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Elongation Rate
• Simple shift of Fly’s Eye data brings all date into
reasonable agreement.
• Fly’s Eye and HiRes data are in excellent
agreement above 1018 eV.
• HiRes/MIA shows earlier transition to “protons”,
but point by point discrepancy is small.
• HiRes/MIA systematics are better understood,
however.
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What about Xmax distributions?
• Are Xmax distribution widths consistent?
• Two overlap regions
– - Fly’s Eye and Hires/MIA in 3x1017 to 5 x 1017 eV bin.
- Fly’s Eye and HiRes stereo in > 1018 eV bin.
No evidence of discrepancy in distribution widths.
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Fly’s Ey vs HiRes/MIA 3-5 x 1017 eV
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Fly’s Ey vs HiRes > 1018 eV
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Normalized Xmax distributions for
3-5 x 1017, 5-10 x 1017 and > 1018 eV.
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• Filled triangles,
Stereo Fly’s Eye
result, scaled up by
13 gm/cm2 (
average shift above
10 EeV)
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Conclusions
• A simple Xmax shift brings all three experiments
into reasonable agreement.
• Widths of Xmax distributions are in agreement.
• Normalized Xmax distribution show jump to
wider distribution above 1018, consistent with
change to protons.
• Interpretation of elongation rate over limited
energy range is problematic - Need large dynamic
range in a single experiment!
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Additional cuts
• Cerenkov cut: Cerenkov < 30% Total Light
• Aerosol cut: VAOD < 0.15
• Profile shape cut: concave - remove “flat” or
“monotonic” events.
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Stereo Spectrum-tight cuts
(Preliminary)
11 10
32
2
18
4
1
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