Jim Matthews

Louisiana State University

Results from the Pierre Auger Observatory

ECRS, Moscow, 4 July 20121

~ E-2.7

~ E-3.1 Above 1020 eV (50 Joules!):

Φ ≈ 1 per km2 per century

Very low flux …

Very big detectors

2

ArgentinaAustralia

Bolivia*

BrasilCroatia

Czech RepublicFrance

GermanyHolland

ItalyPoland Mexico

NetherlandsPortugalRomaniaSlovenia

Spain United Kingdom

USAVietnam*

~ 500 Scientists

20 Countries 3

Aims of the experiment

• Measure the energy spectrum of high energy cosmic rays up to and beyond energies of 1020 eV

• Determine the sources of these cosmic rays• Determine the elemental composition of cosmic

rays• Study extensive air showers -> particle

interactions

4

How to get particles to extreme energy

• Fermi Acceleration (Bottom-Up)

- repeated encounters with strong plasma shocks

- naturally produces power-law with correct index

- maximum energy can be extremely large

- observed in nature

• “Exotic” (Top-Down)

- decay of massive relic particles

- interaction of nu’s w/cosmic background neutrinos (-> Z)

- topological defects, other things ?

- Signature: protons, photons, neutrinos

5

“GZK”

First pointed out in 1966 in two papers, one by Greisen and one by Zatsepin & Kuz’min

p + (2.7oK) p +

6

Nuclei photo-disintegrate at similar thresholds, distances

7

Surface Arrays and Fluorescence Detection

- Arrays: 24/7 operation, very large size (statistics)

- Fluorescence: ‘calorimetry’ = good energy resolution (spectrum)

8

38° South, Argentina, Mendoza, Malargue

9

Surface Array 1650 detector stations 1.5 Km spacing 3000 km2

Fluorescence Detectors 4 Telescope enclosures 6 Telescopes per

enclosure 24 Telescopes total

Design: AGASA spectrum > 100 events/yr above 1020 eV 10

View of Los Leones Fluorescence Site

11

The Fluorescence

Detector

3.4 m spherical mirror

PMT cameraSpherical surface

camera440 PMT with light

collectorsLarge 300x300 field of

view1.5º pixel fov

(spot 1/3 of pixel)

FADC trace

100 s

12

Energy reconstructed from measured maximum size --- calorimetric (minimal MC) 13

Reconstructed longitudinal profiles

14

15

μ

e

16

17

θ~ 48º, ~ 70 EeV (7 x 1019 eV)

Lateral density distribution

18 detectors triggered

km

18

“Deep” shower

(particles per square meter)

“High” shower

R ≈ 1000m

19

SD Energy Calibration

The power of hybrid…..Does NOT rely on shower simulation

FD

SD

ESD = A (S38)b

b ~ 1

SD Energy resolutionbetter than 20%

20

21

Includes hybrid data (See Settimo & Auger Collab, EPJ (2012))

22

“Infill”

23

Here: from 2011 ICRC

Inferring the Primary Mass

Variation of Depth of Shower Maximum with Energy

**********

**********

****Xmax

log E

p

Fe

24

Xmax correlates tightly with the depth of 1st interaction

Nuclear Composition: Shower Depths of Maximum Xmax

These suggest high cross section and high multiplicity at high energy.

Heavy nuclei?

Or protons interacting differently than expected? (See Nellen presentation, this meeting)

Statistics lacking for the (anisotropic) trans-GZK energy regime!

(Crucial for calculation of the diffuse cosmogenic neutrino flux)

Anisotropy Anisotropy

25Physical Review Letters 104 (2010) 091101

26

SD: Development of Muons in Shower

SD: Asymmetry of Shower front thickness

FD: Mean depth of Shower Max

FD: Fluctuations of Shower Max

Spectral “Ankle”

27

Presentation by Nellen: Data show more muons than simulations

28

“Tail” dominated by protons

Proton-Air Cross Section from the Depth of Shower Maximum

29

To appear in Phys. Rev. Lett. 2012

30

To appear in Phys. Rev. Lett. 2012

31

See presentation of Navarro at this meeting …

Photon limits

32

See presentation of Navarro at this meeting …

Summary

• Energy spectrum exhibits ankle and GZK suppression

• The sources are extragalactic, within the “GZK sphere”: (weak) anisotropy persists above ~60 EeV

• The composition is baryonic, appearing to become iron-dominated (or new particle physics … models do not give enough muons)

• p-Air, p-p cross sections beyond the LHC energy

• Few/no photons or neutrinos (disfavors exotic “top down” models) • Photons/neutrinos nearing GZK regime 33

34

What’s Next?

Auger has been “operating” since 2004, fully deployed since 2008. The international agreement runs for 3.5 more years (end of 2015)

We hope to continue after that, are exploring new technologies in use now or can be started very soon …

-- Auger Engineering Radio Array - AERA - see presentation by Fraenkel

-- Microwave, GHz, ... prototypes operating

-- Focus on better composition determination through new muon detectors, new flourescence techniques, … R&D

спасибо

35

спасибо