recent results from the hires experiment andreas zech ( rutgers university & lpnhe, université...

Recent Results from Recent Results from the HiRes Experimentthe HiRes Experiment

Andreas Zech

( Rutgers University &LPNHE, Université de Paris )

for the High Resolution Fly’s Eye Collaboration

HEP2005 in Lisbon

A. Zech for HiRes, HEP2005 2

Cosmic Ray Energy Spectrum

knee

anklesecond knee

• At lower energies, spectrum of cosmic rays is almost featureless– except for “knee” at 1015.5 eV – Information about galactic

sources.

• More features expected at higher energies (>1017 eV):– Change from galactic to

extragalactic sources.– Expect features due to interactions

between CR protons and CMBR photons (e+e- pair production; pion photoproduction = GZK effect).

– Information about extragalactic sources and propagation over cosmic distances.


HiRes Experimenthas the Highest Exposure for UHECR

Stereo: best reconstruction, covers E > 1018.5 eV.

Mono: wider energy range (E > 1017.2 eV), best statistics.

HiRes is a fluorescence experiment studying UHE cosmic rays.

–Charged particles excite N2 molecules.–Emit ~5 photons/m.i.p./meter.–300-400 nm wavelength.

Two detectors located atop desert mountains in west-central Utah.We collect data on moonless nights: about 10% duty factor.


HiRes-I consists of one ringof 22 mirrors. Coverage in elevation is from 3 to 17 deg.

Sample & Hold Electronicsare used to record pulses.(5.6 µs window)

HiRes-II has two rings of 21 mirrorseach. Coverage in elevation from 3 to 31 deg.

Flash ADC electronics record signals at a frequency of 10 MHz.


• 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

1. Reconstruction of the shower-detector plane


2. Reconstruction of the

geometry within the shower-detector-plane

mono

s t e r eo


3. Shower Profile & Energy Reconstruction : (Using the Atmosphere as a Calorimeter)

• Reconstruct charged particle profile from recorded p.e.

• Fit profile to G.H. function.

• Subtract Čerenkov light.

• Multiply by mean energy loss rate => calorimetric energy

• Add ‘missing energy’ (muons, neutrinos, nuclear excitations; ~10%) => total energy


Monocular Spectra:Deconvolution of the UHECR Spectrum

We observe the cosmic ray spectrum convoluted with detector acceptance and limited resolution.

=> Deconvolution with help of a correction factor determined from Monte Carlo simulations (acceptance aperture).

HiRes-1

HiRes-2

Instantaneous Apertures


Monocular Spectra:Data / Monte Carlo Comparisons

• Inputs to Monte Carlo: • Fly’s Eye stereo spectrum; HiRes/Mia and HiRes Stereo composition. • Library of CORSIKA/QGSJet showers (proton & iron).• Detailed nightly information on trigger logic and thresholds, live mirrors,...

• Analyze MC with exact programs used for data reconstruction.

=> excellent simulation of the data.

HiRes-II: npe / deg

HiRes-II: time fit 2/dof


Monocular Spectra

Features:

• ankle at ~1018.5 eV

• flux suppression at ~1019.8 eV

• hint of the second knee below 1017.5 eV ?

HiRes1: 7/97-5/05

HiRes2: 12/99-5/03


4.8 Evidence for the GZK Suppression

Broken Power Law Fits:– No Break Point

• Chi2/DOF = 120/38

– One BP• Chi2/DOF = 59.3/36

• BP = 18.43

– Two BP’s• Chi2/DOF = 34.7/34

• 1st BP = 18.46

• 2nd BP = 19.75

– Two BP with Extension• Expect 42.8 events

• Observe 15 events

• Poisson probability: P(15;42.8) = 8.9x10-7 (5 = 2.85x10-7)

P(15,42.8)=8.9*10-7


HiRes Stereo Composition Measurement

• The depth of shower maximum Xmax depends on the primary particle type. (proton showers develop deeper in the atmosphere than iron showers)

• Galactic - extragalactic transition complete by 1018 eV.

• Our measurement is ~10g/cm2 below < Xmax> of QGSJet protons (radiosonde correction of atmospheric density coming up).


Uniform Source Density Model Fits• Fit composition and

spectrum simultaneously. – Heavy = galactic,– Light = extragalactic.

• Extragalactic model: – Spectral index , – Emax = 1021 eV, (z) = const * (1+z)m.– Energy loss from

interactions with CMBR (e+ e- & GZK) and uniform expansion (red-shifting).

• Interpretation:– e+ e- pair production

excavates the ankle and leads to pile-up at second knee.

– pion photoproduction leads to pile-up and flux suppression around

1019.8 eV.

Best fit: m = 2.25 = -2.385Chi2 = 63/37


p-air Measurement with HiRes stereo

• New technique for extracting cross-section from Xmax

distribution.

• inel.p-air has been

measured:

456 ± 17 (stat) + 39 (sys) -11 (sys) mb

• plot shows totalp-p

• Agrees with extrapolation of Block-Halzen fit to accelerator data.


BL Lac Correlation: Test of Previous Claims Magnitude Redshift 6cm Radio Flux

#Obj. CR Sample

#CRs

BinSize

#Pairs Prob.

Catalog: Veron (9th Ed.) BL LacsAGASA >48 EeVYakutsk >24 EeV

65 2.5° 8 < 10-4

m < 18 z > 0.1 orunknown S6cm

> 0.17 Jy

22

HiR es > 24 EeV 66 2.5 ° 0 1.00

Catalog: Vero n (10 th E .d ) B L Lacscorrelat ed wi th EGRE T sources

AGASA >48 EeVYakut sk >24 EeV 65 2.9 ° 8 10-4

nocut nocut nocut

14

HiR es > 24 EeV 66 2.9 ° 1 .70

Catalog: Vero n (10 th E .d ) B L Lacs AGASA > 40 EeV 57 2.5 ° 12 .02

m < 18 nocut nocut

157

HiR es > 40 EeV 27 2.5 ° 2 .78

• The observed number of HiRes - BL Lac pairs excludes the claimed correlations at a confidence level greater than 99 % in the first two cases.

• The claimed correlation is excluded at the 90 % confidence level in the third case.


BL Lac Correlation: New Claim

• The 0.8º angular bin size was estimated by Gorbunov et al. to be optimal for the HiRes stereo angular resolution of 0.6º.

• Correlation at the level of our ang. resolution below 40 EeV despite galactic magnetic field => neutral particles ?

• We verify the new claim and extend the search to lower energy events, and to the rest of the confirmed BL Lacs (with m<18), using an unbinned maximum likelihood analysis with event-by-event angular resolution.

Magnitude Redshift 6cm Radio Flux#

Obj. CR Sample#

CRsBinSize

#Pairs Prob.

Catalog: Veron (10th Ed.) BL LacsHiRes > 10 EeV 271 0.8° 10 10-3

m < 18 nocut nocut

157

Nee d t o tes t wit h n ew data


BL Lac Correlations: Results & Discussion

• Caveat: Analysis has been a posteriori, so the quoted probabilities are not true chance probabilities. Correlations can only be confirmed with independent data.

• HiRes will continue observations through the end of March 2006. By then, we will have an independent sample of ~70 % the size of the sample analyzed here to test the new claims.

Source Sample (# Obj.) All Energies E > 10 EeV

“BL” Objects, m < 18 (157) 2 x 10-4 2 x 10-4

“BL” & “HP” Objects, m < 18 (204) 5 x 10-4 10-5

Confirmed TeV Blazars (6) 10-3 2 x 10-4


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

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, L. Perera, 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, Z. Cao, W. Deng, W. Hanlon, P. Huentemeyer, C.C.H. Jui, E.C. Loh, K. Martens,

J.N. Matthews, K. Reil, J. Smith, P. Sokolsky, R.W. Springer, B.T. Stokes, J.R. Thomas, S.B. Thomas, L. Wiencke

University of Utah


Instead of a summary...• Fits to the HiRes energy spectrum:R.U. Abbasi et al., accepted in Physics Letters B. (2005) [astro-ph/0501317]• HiRes composition measurement:R.U. Abbasi et al., Astrophysical Journal 622 (2005) 910-926 [astro-ph/0407622]

• p-air cross-section measurement:K. Belov for HiRes, proceedings of the 28th International Cosmic Ray Conference pp.

1567-1570

• HiRes anisotropy searches:Angular Correlation / Energy Scan for HiRes Stereo Data above 1019 eV

R.U. Abbasi et al., Astrophysical Journal 610 (2004) L73 [astro-ph/0404137]Combined HiRes / AGASA Maximum Likelihood Point-Source Search

R.U. Abbasi et al., Astrophysical Journal 623 (2005) 164 [astro-ph/0412617]HiRes / BL Lac Correlations

R.U. Abbasi et al., submitted to Astrophysical Journal [astro-ph/0507120]

• HiRes webpages: hires.phys.columbia.edu ; www.cosmic.ray.org


Test of the HiRes Mono Energy

Reconstruction

Comparison of energies from mono and stereoreconstruction for a subset of HiRes-I (left) and HiRes-II (right) events that were seen in stereo.

HiRes-I HiRes-II


Phototube Calibration

pe = qe * ce * A * = G * pe

= G * (*pe)

pe = * ( / ) 2

• Relative calibration at the beginning and end of each nightly run.– using YAG laser

– optical fibers distribute the laser signal to all mirrors.

• Absolute calibration using a portable light-source (“RXF”), that is carried to both sites.– calibration of RXF in the lab

using HPDs.

=> +/- 10% uncertainty in energy scale.


Systematic Uncertaintiesin monocular reconstruction

Systematic uncertainties in the energy scale:• absolute calibration of phototubes: 10 %

• fluorescence yield: 10 %

• correction for ‘missing’ energy: 5 %

• modeling of the atmosphere: 15 %

=> uncertainty in energy scale: 21 % + atmospheric uncertainty in aperture

=> total uncertainty in the flux: +/- 31 %


HiRes-2 Composition Measurement

We can extend composition analysis down to about 1017.5 eV with HiRes-2 data.

Prelim

inary

HiRes-2 Composition

HiRes/MIA & HR stereo Composition.


Interpretation of Extragalactic Spectrum

• Pion-production pileup causes the bump at 1019.5

eV.

• e+e- pair production excavates the ankle.

• Pileup at location of second knee.

• Fractionation in distance and energy; e.g., z=1 dominates at second knee.

• Can cosmic ray physicists see evolution of sources ?

D. Bergman’s plot of shells in z


Second Knee at 1017.6 eV

• Yakutsk, Akeno, Fly’s Eye Stereo, HiRes Prototype/MIA all saw flat spectrum followed by a steepening in the power law. The break is called the second knee.

• Correct for varying energy scales: all agree on location of the second knee.

• There are THREE spectral features in the UHE regime.

• We need an experiment, with wide enough energy range, which would see the three UHE cosmic ray features with good statistics!


Fitting to Learn about UHECR Sources

• Earlier spectrum fits: two problem areas.– Fit might be bad in 1019.6 eV region;

not statistically significant.

– Second knee is too weak in model, just where QSO evolution changes.

• Latest spectrum, better statistics: fit is bad in 1019.6 eV region.

• Collaboration with P. Biermann to include his study of extragalactic source Emax distribution in our model.

2004

2005


Integral Spectra

• Want to test E½ with integral spectra

• Use 2BP Fit with Extension for the comparison

• log10E½ = 19.76-0.04+0.12

• Berezinsky: log10E½ = 19.72, for wide range of conditions.


The Ankle is Important

• Berezinsky: ankle due to e+e- pair production.– Better evidence of CMBR interactions than GZK.

– Shows that composition is protons [+ some Helium (Hillas); or “light” (Allard et al.)].

• Astrophysics: tells about cosmic ray sources. – rise from ankle spectral index at source.

– fall to ankle evolution parameter, m.


Cosmology with TA/TALE ?

• Adjust evolution to match QSO’s:

• m=2.6, z<1.6• Lower m, z>1.6• Must extend spectrum

measurement lower by an order of magnitude.


Point Source Search in a combined HiRes/AGASA data set

• No significant point source is found in the combined set of HiRes stereo and AGASA events above 40 EeV.

• If the HiRes threshold is lowered to 30 EeV, one more event lands near the triplet. There are now 57 AGASA events and 40 HiRes events.

The fraction of isotropic MC sets with higher ln(R) is 0.6 %.

This result contains some biases:

• the clustered AGASA events which were originally used to establish the 40 EeV threshold are still included in the sample.

• the HiRes energy threshold has to be changed to include an event that contributes to the cluster.

These biases imply that 0.6 % is a lower bound on the chance probability.


Some Confirmation of Akeno/AGASA Large-Scale Structure

• HiRes-II mono anisotropy data: 1017.5 < E < 1018.5 eV, integrated over 20 deg. circle.

• Deficit of events along an arc in galactic anti-center direction.

• No ridge of events in Cygnus arm region.

• Need more summer data to see galactic center region.

AGASA


BL Lac Correlation: Source Sample

Summary of statistically independent results:

Confirmed BL Lacs HiRes Events< 10 EeV > 10 EeV

Mag. Class ns F ns F“BL” (157) 22 6×10-3 8 2×10-4

m<18 “HP” (47) 0 0.7 3 6×10-3

“B ” (L 193) 0 0.7 0 0.4m≥18

“HP” (21) 0 0.7 0 0.8

The m<18 cut was optimized by Tinyakov et al. to maximize BL Lac correlations with AGASA.

This cut isolates BL Lacs which correlate with HiRes events as well.


TeV BL Lac CorrelationSix BL Lacs are confirmed sources of TeV -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 z V Mag ns F

Mrk 421 0.03 12.9 0.3 0.2

H1426+428 0.13 16.5 0 0.4

Mrk 501 0.03 13.8 3.3 6×10-4

1 1ES 959 +650 0.05 12.8 2.0 8×10-3

PKS2155-3 04 0.12 13.1 - -1 2ES 344 +514 0.04 15.5 0 0.7

For the TeV blazars taken as a set, the ML analysis yields:

All energies: ns = 5.6 with F = 10-3

Above 10 EeV: ns = 2 with F = 2×10-4


BL Lac Correlation: Sensitivity of Future DataWe 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.)


TA - the “Telescope Array”

• SD: 576 scintillation counters, each 3 m2 area, 1.2 km spacing.

• 3 fluorescence stations, each covering 108o in azimuth, looking inward.

• Central laser facility.• Millard County, Utah, flat

valley floor for SD, hills for fluorescence, low aerosols.

• A 1020 eV event (on a night when the moon is down) will be seen by SD and all three fluorescence detectors.

• A powerful detector for hybrid and stereo cross correlation with SD.


HiRes vs. Auger FD • 2 eyes, 22 / 42 spherical

mirrors• azimuth ~360, elevation

3 - 17 / 3-31

• mirror radius 1.3 m• 16x16 PMT per mir.• Pixel size: 1 x 1 • UV filter

• Sample&Hold / FADC @ 10 MHz

• 2 eyes (so far), 6 spherical mirrors each

• azim. 180, el. 28.6

• Schmidt optics

• mirror radius 3.4 m

• 20 x 22 PMT per mir.

• pixel size: 1.5 x 1.5

• UV filter, Winston cones

• FADC @ 10 MHz

recent results from the hires experiment andreas zech ( rutgers university & lpnhe, université...

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