# Presentation: 340696

## Astroparticle Physics

- Paul Sommers
- Penn State
- Brookhaven, January 29, 2008

**Astroparticle Physics**

## Slide 2

## Equal Exposure Plot 

**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

**Arrival directions of the 27 highest energy events**

## Veron-Cetty AGNs (red dots)

**Veron-Cetty AGNs (red dots)**
**Supergalactic Plane (blue line)**
**Swift x-ray galactic black holes (blue circles)**

## Mollweide Projection

**Mollweide Projection**
**With AGN marks shaded by exposure**

## Full-Sky Aitoff Projection

**Full-Sky Aitoff Projection**
**(Observatory exposure shaded)**

## The exploratory discovery of the AGN correlation

**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.)

## Slide 11

## 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.*

##       Auger North

**AGN correlation**
**Observatory description**
**Hadronic interactions in air showers**
**Energy spectrum**
**Photon limits**
**Neutrino limits**
**In development:**
**     ****HEAT**
**      ****AMIGA**
**      ****Radio detectors**
**      ****Auger North**

## Auger Water Cherenkov Detector

**Auger Water Cherenkov Detector**

## Slide 15

## Slide 16

## Slide 17

## Slide 18

## Slide 19

## 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.

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

## 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.  

_**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

**Auger Energy Spectrum**

## Spectrum with multiplicative factor

**Spectrum with multiplicative factor**

## Gamma rays develop deeper in the atmosphere

**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

**Signal risetime and shower front curvature are different for gamma ray showers**

## 2% upper limit at 

- 2% upper limit at
- 10 EeV using surface detector shower measurements

## Earth Skimming 

****

**

**Auger exposure to **
**tau Neutrinos**

- zenith angle ~ 90-92o

**Pierre Auger **_**Neutrino**_** Observatory**

## Slide 31

##       Auger North

**AGN correlation**
**Observatory description**
**Hadronic interactions in air showers**
**Energy spectrum**
**Photon limits**
**Neutrino limits**
**In development:**
**     ****HEAT**
**      ****AMIGA**
**      ****Radio detectors**
**      ****Auger North**

## Auger North + Auger South

**5-year Auger Full-Sky Simulation**
**( E > 10****19**** eV and ******** ****< 60****o ****)**
**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”**
**	****X****max**** values stop rising with energy**
**	****Muon richness is greater than predicted by extrapolations**

## Thank you!

**Thank you!**

- Visit  _[www.auger.org](http://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]