1. Recent Results from the HiRes Experiment Andreas Zech ( Rutgers University & LPNHE, Université de Paris ) for the High Resolution Fly’s Eye Collaboration HEP2005 in Lisbon

2. A. Zech for HiRes, HEP20051 Cosmic Ray Energy Spectrum knee ankle second knee At lower energies, spectrum of cosmic rays is almost featureless –except for “knee” at 10 15.5 eV –Information about galactic sources. More features expected at higher energies (>10 17 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.

3. A. Zech for HiRes, HEP20052 HiRes Experiment has the Highest Exposure for UHECR Stereo: best reconstruction, covers E > 10 18.5 eV. Mono: wider energy range (E > 10 17.2 eV ), best statistics. HiRes is a fluorescence experiment studying UHE cosmic rays. –Charged particles excite N 2 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.

4. A. Zech for HiRes, HEP20053 HiRes-I consists of one ring of 22 mirrors. Coverage in elevation is from 3 to 17 deg. Sample & Hold Electronics are used to record pulses. (5.6 µs window) HiRes-II has two rings of 21 mirrors each. Coverage in elevation from 3 to 31 deg. Flash ADC electronics record signals at a frequency of 10 MHz.

5. A. Zech for HiRes, HEP20054 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

6. A. Zech for HiRes, HEP20055 2. Reconstruction of the geometry within the shower-detector-plane monomono stereostereo

7. A. Zech for HiRes, HEP20056 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 Č erenkov light. Multiply by mean energy loss rate  => calorimetric energy Add ‘missing energy’ (muons, neutrinos, nuclear excitations; ~10%) => total energy

8. A. Zech for HiRes, HEP20057 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

9. A. Zech for HiRes, HEP20058 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

10. A. Zech for HiRes, HEP20059 Monocular Spectra Features: ankle at ~10 18.5 eV flux suppression at ~10 19.8 eV hint of the second knee below 10 17.5 eV ? HiRes1: 7/97-5/05 HiRes2: 12/99-5/03

11. A. Zech for HiRes, HEP200510 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 1 st BP = 18.46 2 nd 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

12. A. Zech for HiRes, HEP200511 HiRes Stereo Composition Measurement The depth of shower maximum X max depends on the primary particle type. (proton showers develop deeper in the atmosphere than iron showers) Galactic - extragalactic transition complete by 10 18 eV. Our measurement is ~10g/cm 2 below of QGSJet protons (radiosonde correction of atmospheric density coming up).

13. A. Zech for HiRes, HEP200512 Uniform Source Density Model Fits Fit composition and spectrum simultaneously. –Heavy = galactic, –Light = extragalactic. Extragalactic model: –Spectral index , –E max = 10 21 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 10 19.8 eV. Best fit: m = 2.25  = -2.385 Chi2 = 63/37

14. A. Zech for HiRes, HEP200513  p-air Measurement with HiRes stereo New technique for extracting cross- section from X max distribution.  inel. p-air has been measured: 456 ± 17 (stat) + 39 (sys) -11 (sys) mb plot shows  total p-p Agrees with extrapolation of Block-Halzen fit to accelerator data.

15. A. Zech for HiRes, HEP200514 BL Lac Correlation: Test of Previous Claims 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.

16. A. Zech for HiRes, HEP200515 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.

17. A. Zech for HiRes, HEP200516 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 EnergiesE > 10 EeV “BL” Objects, m < 18 (157) 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

18. A. Zech for HiRes, HEP200517 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

19. A. Zech for HiRes, HEP200518 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 10 19 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

20. A. Zech for HiRes, HEP200519

21. A. Zech for HiRes, HEP200520 Test of the HiRes Mono Energy Reconstruction Comparison of energies from mono and stereo reconstruction for a subset of HiRes-I (left) and HiRes-II (right) events that were seen in stereo. HiRes-I HiRes-II

22. A. Zech for HiRes, HEP200521 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.

23. A. Zech for HiRes, HEP200522 Systematic Uncertainties in 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 %

24. A. Zech for HiRes, HEP200523 HiRes-2 Composition Measurement We can extend composition analysis down to about 10 17.5 eV with HiRes-2 data. Preliminary HiRes-2 Composition HiRes/MIA & HR stereo Composition.

25. A. Zech for HiRes, HEP200524 Interpretation of Extragalactic Spectrum Pion-production pileup causes the bump at 10 19.5 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

26. A. Zech for HiRes, HEP200525 Second Knee at 10 17.6 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!

27. A. Zech for HiRes, HEP200526 Fitting to Learn about UHECR Sources Earlier spectrum fits: two problem areas. –Fit might be bad in 10 19.6 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 10 19.6 eV region. Collaboration with P. Biermann to include his study of extragalactic source E max distribution in our model. 2004 2005

28. A. Zech for HiRes, HEP200527 Integral Spectra Want to test E ½ with integral spectra Use 2BP Fit with Extension for the comparison log 10 E ½ = 19.76 -0.04 +0.12 Berezinsky: log 10 E ½ = 19.72, for wide range of conditions.

29. A. Zech for HiRes, HEP200528 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.

30. A. Zech for HiRes, HEP200529 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.

31. A. Zech for HiRes, HEP200530 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.

32. A. Zech for HiRes, HEP200531 Some Confirmation of Akeno/AGASA Large-Scale Structure HiRes-II mono anisotropy data: 10 17.5 < E < 10 18.5 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

33. A. Zech for HiRes, HEP200532 BL Lac Correlation: Source Sample Summary of statistically independent results: 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.

34. A. Zech for HiRes, HEP200533 TeV BL Lac Correlation Six 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: For the TeV blazars taken as a set, the ML analysis yields: All energies: n s = 5.6 with F = 10 -3 Above 10 EeV: n s = 2 with F = 2×10 -4

35. A. Zech for HiRes, HEP200534 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.)

36. A. Zech for HiRes, HEP200535 TA - the “Telescope Array” SD: 576 scintillation counters, each 3 m 2 area, 1.2 km spacing. 3 fluorescence stations, each covering 108 o in azimuth, looking inward. Central laser facility. Millard County, Utah, flat valley floor for SD, hills for fluorescence, low aerosols. A 10 20 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.

37. A. Zech for HiRes, HEP200536 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