1. ● What a cosmic ray (CR) and a ultra high energy cosmic ray (UHECR) are? ● What do we know and what we would like to know about them? ● How do we detect them? ● First Auger public results and conclusions The Pierre Auger Observatory for the UHECR Federico Sanchez, Dip.Fisica e INFN sezione Milano

2. A cosmic ray is not a ray... subatomic primaries (e, p, He, C, N, O, Fe) and secondaries particles (Li, Be, B) from our galaxy. EAS regimeDirect observation regime ? ? ? Produced by diffusive shock acceleration in SNR (super novae remnants) What: How and where:

3. X particle How far? B intergalactic B galactic B halo B source   CR Relic Nucleons

4. Gaucho

5. SD FD HYB Spectrum

6. Conclusions: ● The Pierre Auger Observatory started regular data taking in January 2004 and released its firsts physics results in August 2005. ● The southern site construction will finish by the end of 2006. ● The northern site is in R&D phase. Thank you,