Telescope Array Experiment:Status and Prospects

Pierre SokolskyUniversity of Utah

Cosmic Ray Spectrum

5σ Observation of the GZK Suppression (mono)

HiRes/Auger spectra comparison

Auger confirms all spectral features of HiRes spectrum

UHECR Status and Issues

• GZK cutoff exists – HiRes and PAO observe at 5-6 sigma level

• Anisotropy ( sources ) remain unclear- 2-3 sigma correlation in South with AGN’s (PAO), no correlations in North (HiRes).

• Composition – light (proton) favored by HiRes. Light-heavy-light(?) favored by PAO

• >>> A lot more work is required• >>> Unravelling galactic/extragalactic transition

Motivation for TA

• AGASA and HiRes give conflicting results on GZK. Why?

• Increase SD by 10 x. Coincident event observation with FD.

• Keep AGASA and HiRes energy scales • Hybrid events > calibrate SD• SD 10 x higher statistics than HiRes

Motivation for TALE

• Sources of cosmic rays above knee (1015 eV) are unknown.

• What is the Emax of the galactic accelerator?• Connect energy scale established by GZK to all

the other structures in the cr spectrum ( ankle, second knee etc.)

• Study the composition change from galactic to extragalactic cosmic rays.

TALE Proposal under consideration by PASAG

Thank You!