Science Motivations for Northern Auger

At a recent meeting of U.S. collaborators for Auger, the consensus opinion was that we should begin the process of securing major U.S. funding for building the northern Auger site. If the Collaboration supports this initiative, a "letter of intent" would be sent to U.S. funding agencies after the upcoming ICRC meeting, advising them to expect a proposal in 2004 for construction of northern Auger. The hope is to get approval in 2005 for construction to begin early in 2006. This is when we expect completion of the southern site. Completing the southern site is the first priority.

Hans Bluemer circulated a summary of the meeting to the auger_collaboration mailing list. John Harton is writing more detailed minutes of what transpired at the meeting February 28 - March 2 at Colorado State University. Electronic slides from some talks are online at http://www.physics.colostate.edu/users/bauleo/Auger/Meetings/03_AugerUS_CSU/Agenda.htm. These include arguments why observing the entire sky is important for identifying the cosmic ray sources.

Below are some "frequently asked questions" whose answers highlight science issues discussed at the CSU meeting which relate to the need for northern Auger.

A) Full sky map of source locations

A3: Can discrete sources be identified using sub-GZK showers despite greater magnetic bending and a large expected isotropic background?

B) Large-scale anisotropy

B4: Would a non-uniform distribution of cosmic ray sources in our vicinity be detectable in a map of all arrival directions for showers of 10 EeV and above?

C) Spectrum and Composition

C4: Might the cosmic ray spectrum or composition be different if measured at a northern site than if measured at the southern site?

D) More statistics

D2: Is it important to double our sensitivity to high energy neutrinos? According to the recent theoretical predictions, how many and what kind of neutrinos do we expect?