Auger New Results G. Matthiae Universita’ e Sezione INFN di Roma “Tor Vergata”

Auger New Results

G. MatthiaeUniversita’ e Sezione INFN di Roma “Tor Vergata”

NO – VE Venezia - April 15-18, 2008

“Un altro modo di guardare il cielo”

1 particle/km2/century

LHC c.m.

~ 1 / E3

Cosmic ray spectrum year 2000

Cosmic ray spectrum - 2008

l

AGASA: surface arrayHiRes: fluorescence telescopesAuger: Hybrid

ankle

GZK

e+e–

Interaction length

Attenuation length

Interaction with CMB GZK cutoffAbove E ≈ 6*1019 eV, protons loose rapidly energy via pion photoproduction. Energy loss ≈ 15 % / interaction. Interaction length = 5 – 10 Mpc

Greisen-Zatsepin-Kuzmin

p + γ CMB → n + π+ p + π0

∆+ production

{γ from π0 , ν from π+}

e+ e- pair production isless effective, energy loss

≈ 0.1% / interactionProduces a “dip” in the spectrum (Berezinsky)Nuclei: also photodissociation

protons

1 EeV = 1018 eV

PROTONS

Horizon: maximum distance of the sources from which X % (for example 90 %) of the protons arrive on Earth with energy above a given value.

100 Mpc

Energy (EeV)

Auger hybrid detector Fluorescence Detector (FD)

• Longitudinal development of the shower

• Calorimetric measurement of the energy

Calibration of the energy scale

• Only moonless nights

12% duty cycle !

Surface Detector (SD)

• Front of shower at ground

• Direction and “energy” of the shower

AUGER Observatory

• Very flat region with low population density

• Good atmospheric conditions (clouds, aerosol)

350 S latitude

≈ 1400 m height ≈ 875 g/cm2

1600 Surface detectors (“water tanks”) 1.5 km spacing

24 fluorescence telescopes, 6 in each of 4 buildings

Total area ~3000 km2

nearly completed

Water Tank in the Pampa

Solar PanelElectronics enclosure40 MHz FADC, local triggers, 10 Watts

Communication antenna

GPS antenna

Batterybox

Plastic tank with 12 tons of water

three 9”PMTs

Calibration: Vertical Equivalent Muon (VEM) : ~ 90 p.e.

Selecting vertical muons with telescope scintillation counters

Dia Noche

Time resolution ~ 12 ns

Young & Old Shower ‘young’ shower

strong e.m. component

‘old’ shower

signal dominates

The FD telescope (Schmidt optics)Field of view 30x30 degrees

Spherical mirror

PMT camera

Diaphragm

UV Filter (300-400 nm)

Shutter

Fluorescence Telescope

Spherical mirror (R=3.4 m)Camera with 440 PMTs

FD ABSOLUTE CALIBRATIONDrum: a calibrate light source

uniformly illuminates the FD camera

Dru

m

Mirror reflectivity,

PMT sensitivity etc.,

are all included!

~ 5 photons /ADC 10% error

Laser Mirror DAQ

Backscattering

Elastic bcks. molecular/Rayleigh &

aerosol/Mie

LIDAR

Atmospheric attenuation / shoot on shower technique

FD “TEST BEAM”Central Laser Facility

355 nmSteerable laser

optical fiber

SD tank

Time correlation FD - SD

Longitudinal profile of showers from the FD telescopes Fit with empirical formula of Gaisser-HillasCherenkov light subtractedCalorimetric measurement of the energy.

XX

XX

XXNXN

XX

max

0max

0max exp)(

0max

4 par

Nmax ~ E , Xmax ~ log E

Correction for energy loss (neutrinos, muons)

p / Fe : 8 – 12 % at 1019 eV (10% ± 2%)eventually important to know the composition

XmaxDepth of the maximum

Study of composition – mass of the primaries

Xmax as a function of the energy

Compilationprevious data{

Photon – the experimental method

A(SD) Shower front curvature

A(SD) Shower front thickness

Fluorescence Detector

Xmax from shower

longitudinal profile.

Surface Detector

Shape of the front of the shower

Limits on photon fraction (integral flux)

PRELIMINARY

~ 3 %

HP: Haverah ParkA1,A2: AGASAY: Yakutsk

hmax

10 km

L

W

Neutrinos - Earth skimming

Auger – no neutrino candidates

Xmax measured over two decades of energy

(<A> ~ 5)Syst error on Xmax < 15 g /cm2

Mass composition: protons, light nuclei, Fe ?

HiRes Group: astro-ph/0703099

5.1 +/- 0.7Power law index E-γ

HiRes Final data 2007

V. Berezinski: shallow minimum (“dip”) from e +e- production and pile-up of GZK particles

Lateral Distribution Function

Auger - One event of high energy:~1020 eV, ~60°

34 tanks

LDFFit distance r from the core

S=A [r/rs (1+r/rs)] -β

rs = 700 mA, β from fit (β= 2-2.5)

S(1000) energy estimator

Sign

al (

VE

M)

Energy calibration – hybrid eventsEnergy obtained by the calorimetric measurement of the fluorescence detector. Simulation not needed.

S(1000)Corrected to 380

EFD= a x S b

b = 1.08 ± 0.04

661 events

6x1019 eV

Error on the energy • 19 % statistical• 22% systematic (scale error) fluorescence yield/calibration

Energy spectrum (θ < 600)Exposure 7000 km2 sr yr (3% error) (~ 1 year Auger completed)

Exp. Observed> 4x1019 179±9 75

> 1020 38±3 1

Trigger efficiency =100 % above 3x1018 eV

Detailed features of the spectrum better seen by taking difference with respect to

reference shape Js = A x E-2.69

GZK cut off Slope γ above 4x1019 eV: 4.0 ± 0.4

HiRes:5.1 ± 0.7

γ = 2.69 ± 0.02Fit E-γ

0-60 degrees

60-80 degrees

ENERGY SPECTRUM

Precision of the measurement of the direction

Vertical shower of energy 1019 eV activates 7-8 tanks

EVIDENCE OF ANISOTROPY AT HIGH ENERGY

High-energy events (E > 5.7x1019 eV) are correlated with AGNs

at distance less than about 75 Mpc Angular correlation (~ 30)

9 November 2007

Super-galactic plane

Galactic coordinates

Border of the field of view

Doublet from Centaurus A(nearest AGN at ~ 4 Mpc)

27 events E > 57 EeV20 events correlate with AGN within 3.20

Véron &Véron-Cetty catalogue442 AGN (292 in f.o.v.)z<0.018 (75 Mpc)

RelativeRelativeexposureexposure

Fix candidate sources and maximum angular distance Source

Probability p that one event

from isotropic flux is close (< to at least one source

p = fraction of “Auger sky” covered

by windows centred on sources

Prob. >k of the N events from isotropic flux correlate

by chance with sources (<

ANALYSIS METHOD

Three parameter scan to find the minimum of P

1- Minimum CR energy ( N) minimize deflections in B

2- Maximum source distance zmax GZK

3- Maximum angular

separation deflections in B and angular resolution

Number of events

E > 57 EeV

Correlated with AGN

ψ = 3.1 degree

Expected for isotropy

Exploratory scan1 Jan 04- 27 May 06

15 12 3.2

Second independent set27 May 06–31 Aug 07

13 8 2.7

Full data set (about 1.2 year full Auger)

27 20 5.6

Full data set excluding region of the galactic plane(|b| > 12 degree)

21 19 5.0

Probability of observed configuration if distribution is isotropic: 10-5

5 of the 7 events not correlated are close to the galactic plane

Set of parameters for the minimum P corresponding to maximum correlation with AGN

• Angular separation ψ = 3.10 • Maximum AGN redshift ( 0.018 corresponding to ~75 Mpc)• Energy threshold : 57 EeV

(1.7x10-3)

p = 0.21

CR

AGN

Isotropic fluxThe 6 events at lowgalactic latitudes |b| < 120

ANGULAR SEPARATION FROM THE CLOSEST AGN

• catalogue incompleteness

• larger deflections in galactic B

Deflection in the galactic magnetic field

Simulation(protons 60 EeV)

20 correlated events

Conclusions• Auger observes the GZK steepening of the energy spectrum

confirming HiRes results (very high energy events are of extra-galactic origin).

• Correlation with AGNs (E > 57 EeV). Direct evidence of extra-galactic origin. Identification of the sources. ~ 25 events/year

• Interplay of different observables - Composition at very high-energy: protons or mixture of protons

and light nuclei as indicated by Xmax ? <A>=5 ? - Shape of the GZK steepening.- Energy calibration (22% scale error at present)- Horizon ( calculation gives 75 Mpc 80 – 100 EeV). - Magnetic field deflection (small for protons !)More statistics and better control of the systematic errors needed !

Auger North (Colorado, US) to study northern sky (~ 20000 km2 = 7 x Auger South)FUTURE

Zenith angle dependence of the energy estimator S(1000)

45

Rpt0

χi

χ0

Shower parameters from Fluorescence Detector

(single telescope)

1. Determination of the Shower-Detector Plane (SDP) is good

2. Time fit: t(χi) = t0 + Rp*tan [(χ0 - χi)/2]

Space reconstruction is inaccurate within the Shower Detector Plane.

shower

AttenuationRayleigh attenuation length: 23 km at sea level

Vertical Aerosol Optical DensityVAOD (h) = ∫ α(z) dz

Attenuazione: exp{-VAOD(h)}

Not a good night

Observation of an excess from the region of the Galactic centre at the level of 4.5 σ was reported by AGASA (1.22 ± 0.05) in angular cone of 20 degree radius.

The Auger Observatory is suitable for these studies because the Galactic centre (constellation of Sagittarius) lies well in the field of view of the experiment.

In the Auger data there is no indication of a statistically significant excess

Energy interval (eV) Nobs/Nexp Ratio (errors: stat, syst)

1017.9 -- 1018.3 3179 / 3154 1.01 ± 0.02 ± 0.01

1018 – 1018.4 2116 / 2160 0.98 ± 0.02 ± 0.01

1018.1 – 1018.5 1375 / 1395 0.99 ± 0.03 ± 0.01

Study of excess from the Galactic Center

Effect of interaction with CMBV.Berezinsky et al.

• production of e+ e- pairs• photoproduction of pions

protons

GZK and mass composition

Only protons and not too light nuclei are able to reach the Earth for energies above ~ 60 EeV