Paul Sommers

Penn State

Brookhaven, January 29, 2008

Astroparticle Physics

Equal Exposure Plot

Arrival Directions for E>3 EeV

+25 deg

0 deg

-30 deg

-60 deg RA = 0 deg

Arrival directions of the 27 highest energy events

Veron-Cetty AGNs (red dots)

Supergalactic Plane (blue line)

Swift x-ray galactic black holes (blue circles)

Mollweide Projection

With AGN marks shaded by exposure

Full-Sky Aitoff Projection

(Observatory exposure shaded)

The exploratory discovery of the AGN correlation

Harari et al., May, 2006

3-parameter search scan: minimum energy, circular window radius, maximum redshift for sources.

The GZK energy threshold

For anisotropy is where the spectrum

Is falling rapidly

GZK Horizon

Definition: The distance for which 90% of the cosmic rays above an energy cut should be produced within a volume around us with that distance as radius.

Depends on the fraction (90% horizon in this example)

Depends on the energy cut

Depends on the source energy spectrum (steepness and maximum energy)

Normally assumes homogeneous source distribution

The steeply falling source spectrum makes for a short horizon distance above the threshold for GZK energy loss. (Particles must start with higher energy at larger distances to arrive above the detection energy cut, but the sources do not produce many particles above those higher energies.)

Firm Conclusions

Cosmic rays do not arrive isotropically.

The arrival pattern proves that sources are extragalactic.

The GZK effect is confirmed. [Spectral steepening is not due simply to “sources running out of steam.” We see structure for D<75 Mpc without confusion from more distant sources.]

Extragalactic B-fields are weak enough that they do not mask the structure.

Galactic halo B-fields are weak enough that they do not mask the structure.

Tentative Conclusions

Discrete sources out to ~75 Mpc are being detected.

Charged particle astronomy will be possible with very large exposure.

Halo B-fields are weak. (Point sources smeared less than 3.2 degrees.)

Intergalactic B-fields are interestingly weak.

The highest energy cosmic rays are protons.

Cosmic ray acceleration occurs where supermassive black holes are accreting matter.

Outline

AGN correlation

Observatory description

Hadronic interactions in air showers

Energy spectrum

Photon limits

Neutrino limits

In development:

HEAT

AMIGA

Radio detectors

Auger North

Three 8” PM Tubes

Plastic tank

White light diffusing liner

De-ionized water

Solar panel and electronic box

Commantenna

GPSantenna

Battery box

Auger Water Cherenkov Detector

The Auger Collaboration

Argentina

Australia

Bolivia

Brazil

Czech Republic

France

Germany

Italy

Mexico

Netherlands

Poland

Portugal

Slovenia

Spain

United Kingdom

United States

Vietnam

Jim Cronin

Alan Watson

Jan 28, 2008

Air showers develop faster than expected for protons at high energies.

Universality: The electromagnetic signal depends only on energy and the grammage distance of shower maximum from the ground. Muon lateral distribution and attenuation with slant depth have little dependence on primary particle or interaction assumptions. (Only the normalization is sensitive to those.)

By studying the dependence of signal on zenith angle at fixed energy (fixed intensity), the muonic contribution can be separated (on average) from the electromagnetic part.

The electromagnetic signal tells the energy. This method gives systematically higher energies than the air fluorescence measurements. (Roughly 25%) The inferred muon content is higher than expected even for iron showers.

Auger Energy Spectrum

Spectrum with multiplicative factor

Gamma rays develop deeper in the atmosphere

16% upper limit

derived using measure depths of maximum in hybrid mode.

Signal risetime and shower front curvature are different for gamma ray

showers

2% upper limit at

10 EeV using surface detector shower measurements

Earth Skimming

Auger exposure to tau Neutrinos

zenith angle ~ 90-92o

Pierre Auger Pierre Auger NeutrinoNeutrino Observatory Observatory

Outline

AGN correlation

Observatory description

Hadronic interactions in air showers

Energy spectrum

Photon limits

Neutrino limits

In development:

HEAT

AMIGA

Radio detectors

Auger North

5-year Auger Full-Sky Simulation

( E > 1019 eV and < 60o )

36000 arrival directions

Relative exposure as function of

sin(declination)

Auger North + Auger South

Exposures in AGASA units

1 AGASA = 1630 km2·sr·yr

Auger South

Auger North

South + North

The Auger North site is a 3-hour drive from Denver International Airport.

Major city is Lamar, pop. 10,000

1300 meters above sea-level.

Flat topography.

Semi-arid or dry climate.84 miles

48 miles

84 by 48 miles is one concept, 4000 square miles

Summary

There is anisotropy correlating with extragalactic structure

GZK effect confirmed independent of source spectrum assumptions

Intergalactic magnetic fields are not strong

Charged particle astronomy is coming. We need Auger North!

Some reasons to suppose energies are underestimated (~25% ?)

The apparent GZK horizon is more appropriate at 80 EeV than 60 EeV

AIRFLY measurements suggest lower fluorescence yield

Surface measurements (with universality arguments) suggest it

Hints of interesting hadronic interactions at high energies

Proton “beam”

Xmax values stop rising with energy

Muon richness is greater than predicted by extrapolations

Thank you!

Visit www.auger.org

for other information:

Scientific and technical papers

Event displays (1% of the data)

Google Earth and Google Sky stuff

[Thanks to Stephane Coutu for those]