Pierre Auger Observatory

Outline• Cosmic Rays• Pierre Auger Observatory

▫ Description/Status▫ Enhancements▫ Future

• Auger Results• Auger @ LIP

▫ Detector Simulation▫ Measurements ▫ Phenomenology

• Conclusions

M. Pato, P. Assis, P. Brogueira, P. Abreu , P. Gonçalves, B. Tomé, J.

Romão, R. Conceição, M. Pimenta, S.

Andringa, E. Santos, M. C. Espírito Santo, J. Dias de Deus, J. G. Milhano

Ultra-High Energy Cosmic Rays• Cosmic rays with E > 1020

eV arrive on Earth at the rate of 1 particle per km2 per century

• Their composition and their sources are unknown

• Create a shower of particles when they enter the atmosphere▫ Hadronic▫ Electromagnetic

• Can be detected▫ Ground Arrays▫ Fluorescence Detector

Moonless nights

Pierre Auger Observatory• The Auger Observatory is a

"hybrid detector," employing two independent methods to detect and study high-energy cosmic rays:

• Surface detector (SD)▫ 3000 km2 in the Pampa Argentina▫ 1600 pure water tanks▫ 1.5 km spacing

• Flourescence Detector (FD)▫ 4 “eyes”▫ 6 telescopes in each viewing 30º x

30º▫ 4 weather stations (with LIDARs)▫ 2 Laser Facilities

FD

SD20 May 2007 E ~ 1019 eV

Event ReconstructionSurface Detector Fluorescence Detector

• Tank hit time gives shower direction

• Energy is obtained using Nch( distance to the

shower core )

• Evolution in camera gives the shower geometry

• Energy is calculated by integrating a universal longitudinal profile

Hybrid Technique

• Better reconstruction geometry▫ Higher Xmax resolution▫ Better energy

reconstruction

• Calibration of SD with FD▫ Reduce systematics▫ Good correlation between

SD and FD

SD

FD

Auger EnhancementsAMIGA HEAT

• Auger Muons and Infill for the Ground Array

• Study muon component of showers▫ Good variable to check

hadronic models

• – Hexagon (7 x 60 m2)• 2 – Infill array 433m• 3 – Existing tank array 1500m• 4 – Infill array 750m

• High Elevation Auger Telescopes• 3 “standard” Auger telescopes

tilted to cover 30 - 60° elevation

Extend studies to lower energies ~ 1017 eV

FutureAuger North Auger South Extension

▫ Construction 2009-2012 ?

▫ Total area: 20 000 km2

▫ About 7 x Auger South extension 4032 surface detectors

3 FD eyes

• Expansion possibilities for Auger South If a non-compact configuration is acceptable▫ 60 000 km2 ??

• Many possible Upgrades▫ Radio Antenna Array▫ …

1 Linsley = 1 L = 1 km2 sr yr

• Energy Spectrum• Anisotropies• Xmax

Energy Spectrum

• GZK cut-off▫ Interaction

with CMB photons degrades energy

• Ankle▫ Transition from galactic to extra-

galactic sources?

AnisotropiesSearch for Sources ( E > 57 EeV ) positions of (318 visible+164invisible) AGNs at z < 0.018 (D< 75 MPc)

19 out of 27 events are within 3.1º of an AGN !!( The probability of having an isotropic distributions is 10-5 )

Evidence for Proton Primary?

The angular aperture suggests that the particle is a proton!

EnergyE > 57 EeV

Angular aperture

α = 3.1

Distancez < 0.018 → D < 75 MPc

Low EHigh Z

High ELow Z

Xmax – Primary Composition

• Iron showers develop faster than proton

• Slope depends strongly on the interaction models

• Auger data indicates heavier

composition at high energy!!!!!

Particle Physics?!...Particle Physics?!...

• Good understand of the detector• Geant 4 Simulation of the FD• Simulation studies for AMIGA

• New variables from data• 3D Analysis• Čerenkov

•Phenomenological Models

Particle Physics @ Cosmic Rays

FD Simulation with Geant 4

Going into detail...

Geant 4 Simulation

• Good overall agreement with official simulation

• Small differences with some more realistic settings▫ Good tool to find systematics!!

Mirror curvature from database!!

New possibilities…

Simulation studies for AMIGA

•Muon selection effieciencies of 80 to 90%•About 10% of multihits

3D Reconstruction Method• Currently for FD the shower is

being treated as a 1D object but it’s an 3D object

• It is possible to get information about the “width” of the shower taking the arrival time of photons at the detector into account▫ It uses time as a 3rd dimension

Adding Time

3D Reconstruction Method

• This method obtains a good agreement with the simulation

• Longitudinal Profile

• Lateral Profile

• Low statistics

Simulation

Longitudinal Profile

Lateral Profile

Ratio Expected / Observed

3D Reconstruction Method

• 6 Months of data

• Longitudinal Profile shows a good agreement

• Lateral Profile shows a clear disagreement

•Data seems wider

• Detector?• Physics??

Experimental Data

Ratio Expected / Observed

Longitudinal Profile

Lateral Profile

3D Simulation• Currently:

▫ Čerenkov and fluorescence photons are produced from longitudinal profiles (1D)

▫ All photons are propagated to the lens and then spread transversally

• A 3D Reconstruction needs a 3D Simulation!

Auger Simulation and Reconstruction Software

(Offline) with some modifications

3D SimulationAlready a first shower…

Čerenkov

• Shower produce intense colimated beam

• Events with a large fraction of Čerenkov light are interesting because they allow us to:▫ See further away ▫ Improve horizontal ν

search▫ Study Čerenkov

properties A(α) – Lateral

Distribution Function of Čerenkov

FD

Showeraxis

Extensive Air Shower (EAS) Physics • Phenomenological

Approach• Extrapolate from

accelerator energies to several orders of magnitude above

Exploring High Energy Hadronic Models…

Models

New models and possible high energy effects…

String Percolation

• As energy increases the number of sea strings increases

• Strings overlap and fuse creating more energetic strings with higher length in rapidity▫ Create faster particles▫ Change the type of the

leading particle• In EAS:

▫ Change number of muons▫ Change the Xmax

But how important are valence quarks??

Net-Baryon ( Simple Model )• Net-Baryon is • Two step-scenario Model

▫ String Formation Valence quarks Energy obtained from

PDFs Parameter Q2 (√s)

▫ String Fragmentation String decays into a

meson and a baryon Kinematic Constraints

Net-Baryon Results• Usual Models have problems

explaining the data• Effective Q2 obtained from fit

to data• Evolution with energy is a

consequence of QCD evolution of the PDFs and the kinematic constraints in the string fragmentation

• Simple model can reproduce Net-Baryon main features

• Our model shows that the role of the Net-Baryon is not negligible

Conclusions

•Auger opens new windows in:▫Astrophysics▫Particle Physics

•The LIP group has an active and enthusiastic participation!!

A little bonus…