John BelzUniversity of Montana Anisotropy Studies of Ultra-High Energy Cosmic Rays Using Monocular Data Collected by the High-Resolution Fly’s Eye (HiRes) 28 th International Cosmic Ray Conference, Tsukuba, Japan John Belz (University of Montana) for J. Bellido, B. Dawson, C. Jui, M. Kirn, B. Stokes and the HiRes Collaboration

John BelzUniversity of Montana To be presented: Upper limits on pointlike sources (> eV) Search for global dipole enhancement(> eV) Clustering studies (> eV)

John BelzUniversity of Montana Pointlike Source Searches (Full Sky) Consider E > eV monocular dataset. Compare with “isotropic” time- shuffled datasets. Use simulated sources to evaluate sensitivities. Flux upper limits determined by integrating exposure-corrected events.

John BelzUniversity of Montana Interpreting Variances Choose “search circle” and count bins with variance above some particular value. Use artificial (pointlike MC) “sources” to tune circle size and variance cuts. Seek 90% signal reconstruction with <10% false-positive probability.

John BelzUniversity of Montana Simulated 25-Event Source

John BelzUniversity of Montana Pointlike Source Flux Upper Limit With HiRes monocular dataset (1,525 events, E > eV), we rule out the existence of northern hemisphere pointlike sources of greater than 25 events at 90% confidence level. < 0.33 events/km 2 *Yr (90% c.l.) < 1.1 x events/cm 2 *sec (90% c.l.)

John BelzUniversity of Montana Pointlike Source Upper Limit (Cygnus X-3) Cygnus X-3 chosen as a priori candidate: –G. Cassiday et al., Phys. Rev. Lett (1989). –M. Lawrence et al., Phys. Rev Lett (1989). –M. Teshima et al., Phys. Rev. Lett (1990). Use simulated sources to evaluate sensitivities. Flux upper limits determined by integrating exposure-corrected events.

John BelzUniversity of Montana >10 18 eV Skymap in CYG-X3 Region

John BelzUniversity of Montana HiRes Data w/ expected background: w/ background + 2 source: w/background + 4 source:

John BelzUniversity of Montana Flux Upper Limit (Cygnus X-3) 90% confidence level flux upper limit for pointlike source > eV (~3,700 events): –< 1.2 x events/cm 2 *sec (4 events) Compare previous results (E > 5x10 17 eV): –( ) x events/cm 2 *sec (Fly’s Eye) –( ) x events/cm 2 *sec (Akeno) –< 4x events/cm 2 *sec (neutrons) (Haverah Park) –< 8x events/cm 2 *sec (gamma rays) (Haverah Park)

John BelzUniversity of Montana Global Dipole Searches Galactic Center — possible effects observed by AGASA and Fly ’ s Eye CEN-A — suggested as a potential source of a dipole effect (Farrar and Piran) M87 — possible weak effects (Biermann)

John BelzUniversity of Montana Dipole source models: Arrival directions of cosmic rays possess a number density n=1+  cos  is the angle w.r.t. dipole source). galactic dipole model,  galactic dipole model, 

John BelzUniversity of Montana Dipole Functions for an Isotropic Source Model and HiRes-I Data Isotropic source modelHiRes Data

John BelzUniversity of Montana The Galactic Center:  / % Confidence Interval: [-0.085,0.090]

John BelzUniversity of Montana The Galactic Center:  / % Confidence Interval: [-0.085,0.090] Centaurus A:  / % Confidence Interval: [-0.090,0.085] M87:  / % Confidence Interval: [-0.080,0.070] (HiRes-1 Monocular, 1525 events > eV)

John BelzUniversity of Montana HiRes-I Monocular Data, E > eV

John BelzUniversity of Montana Sensitivity to small-scale clustering above eV “Autocorrelation” (opening angle distribution)  Null Result HiRes-I Autocorrelation Function Simulated dataset with clustering

John BelzUniversity of Montana But how sensitive is HiRes-I?

John BelzUniversity of Montana HiRes-I Autocorrelation Results HiRes-I-like experiment should be able to distinguish seven doublets from background 90% of the time. Current data set (52 northern-hemisphere events above eV) contains < 4 doublets (90% c.l.)

John BelzUniversity of Montana Conclusions HiRes-I Anisotropy searches have yielded null results: Flux upper limit of 0.33 events/km 2 *Yr (90% c.l.) on pointlike sources with E > eV in northern hemisphere Flux upper limit of 1.2 x events/cm 2 *sec (90% c.l.) on pointlike sources with E > eV centered at Cygnus X-3 Dipole analyses consistent with isotropy for sources at galactic center, Centaurus A, M-87 No clustering observed in highest energy events. Upper limit of 4 doublets (90% c.l.) in HiRes-I monocular dataset.

John BelzUniversity of Montana Other HiRes Anisotropy Presentations: Ben Stokes, Using Fractal Dimensionality in the Search for Anisotropy of Ultra-High Energy Cosmic Rays, HE: Poster Session 2. Chad Finley, Small-Scale Anisotropy Studies of the Highest Energy Cosmic Rays Observed in Stereo by HiRes, HE-1.3, 16.

John BelzUniversity of Montana AGASA

John BelzUniversity of Montana AGASA Autocorrelation Function for Events above 40 EeV

John BelzUniversity of Montana AGASA Sensitivity

John BelzUniversity of Montana AGASA Exposure HiRes Exposure

John BelzUniversity of Montana Flux Upper Limit (Cygnus X-3) 90% confidence level flux upper limit for pointlike source > eV (~3,700 events): –< 5.4 x events/cm 2 *sec (18 events) –< 1.2 x events/cm 2 *sec (4 events) 90% confidence level flux upper limit for pointlike source > ~5x10 17 eV (~5k events) at Cyg X-3: –< 3.7 x events/cm 2 *sec (16 events) Compare previous results (E > 5x10 17 eV): –( ) x events/cm 2 *sec (Fly’s Eye) –( ) x events/cm 2 *sec (Akeno) –< 4x events/cm 2 *sec (neutrons) (Haverah Park) –< 8x events/cm 2 *sec (gamma rays) (Haverah Park)

John BelzUniversity of Montana Compare events in 1.5 degree circle with isotropic background: Determine 90% c.l. upper limit: