Valerio Verzi INFN Roma Tor Vergata for the Pierre Auger Collaboration

Valerio VerziINFN Roma Tor Vergata

for the Pierre Auger Collaboration

Results on Ultra-High Energy Cosmic Rays from the

Pierre Auger Observatory

l

COSMIC RAYS SPECTRUM (2008)

Flux x E2.5

3E

1Flux

1 particle/km2/century!

~ 1020 eV

UHECR

WHERE DO COME FROM?

B

R

Hillas diagram

B R

E

only few candidates

1018 eV 1020 eV

Centaurus A

AGN at only 3.4 Mpc

•

Trajectory in galactic and inter-galactic B

Back to origin!

AGN

more details in G.Farrar’s talk

Greisen-Zatsepin-Kusmin (GZK)

p CMB→ N

Interaction with CMB Modification of the spectrum

UHECR sources must be closer than 50-100 Mpc!

epe

Nπ

5÷10 Mpc

GZK cutoff

10 i

30 X0

ATMOSPHERIC SHOWERS

at ground millions of particles… detectors in coincidence

AUGER – HYBRID DETECTOR

FD

SD

Surface Detector (SD):•detection of the shower front at ground

(+) Duty cicle ~ 100% (important for UHECR)

(-) Shower size at ground E (systematics) calibration from FD

Fluorescence Detector (FD):•fluorescence light from the N2 de-excitation

(+) Longitudinal shower development calorimetric measurement of E sensitivity to CR mass (Xmax)(-) Duty cicle ~ 10%

PIERRE AUGER OBSERVATORY

FD 4 x 6 fluorescence telescopes

50 km

Malargue - Argentina SD 1600 water Cherenkov detec. on a 1.5 km hexagonal grid

3000 km2

PIERRE AUGER OBSERVATORY

FD 4 x 6 fluorescence telescopes

50 km

Malargue - Argentina SD 1600 water Cherenkov detec. on a 1.5 km hexagonal grid

3000 km2

Installation completed this year

1.5 km

SD TANKS

FLUORESCENCE TELESCOPE

WATER TANK

Solar PanelElectronics enclosure40 MHz FADC, local triggers, 10 Watts

Communication antenna

GPS antenna

Batterybox

Plastic tank with 12 tons of water

three 9”PMTs

diffusive Tyvek• -response ~ track

• e/-response ~ energy

TANK SIGNAL

‘old’ showersignal dominates

‘young’ showerstrong e.m. component

PMT

water

Cerenkovlight

1.2 m ~ 3 X

o

Distance from the core (m)

SD SHOWER RECONSTRUCTION

1.5 km

shower front

Shower front from particle arrival times

Core position and S(1000) from LDF (NGK) fit

Sign

al

(VE

M)



1.5 km

shower front



Sign

al

(VE

M)

Sh

ower

axi

s re

solu

tion

zenit (degrees)

E > 1019 eV~ 10



1.5 km

shower front



Sign

al

(VE

M)S(1000) ~ E

FD calorimetric measurement

No simulations!

Schmidt optics

FD TELESCOPE

Spherical mirror 3.4m radius of curvature

Schmidt optics

FD TELESCOPE

2.2 m diameter diaphragm corrector ring, UV optical filter

Schmidt optics

FD TELESCOPE

Camera (focal surface) - 440 PMT’s 30ox30o FOV pixel = 1.5o spot: 15 mm (0.5o)

bin=100 nsFD EVENT

Nγ

FD ENERGY SCALEdEdX

Energydeposit

Fluorescence yield from laboratory measurements

Shower energy uncertainty ~ 15%

5 photons/MeV at 337 nm

Airflyspectrum

Atmospheric monitoring aerosols, clouds, density profiles(Lidar, Central Laser Facility,Ballons, …)

Atmospheric transmission

Nγat diaphragm

Nγ


FD ENERGY SCALE

Nγat diaphragm

Nγ

PMT’s signal

Drum absolute calibration uniform camera illumination with a calibrated light source


~ 5 /ADC

FD ENERGY SCALE

Xmax~ 810 g/cm2

E ~ 3.5 1019 eVExpected profile:fitted Gaisser-Hillas function

Ecal

EEcal

Ecal Xmax

Log E

dEdX

X

only a 10% model dependent correction

E


FD ENERGY SCALE

SD CALIBRATION USING FD ENERGY

S(1000,=380) with CIC

04.008.1 B

BFD SAE 38

FD syst. uncertainty (22%) dominates

PRL 101, 061101 (2008)

LINEAR FIT

50 VEM ~ 1019 eV

HYBRID SHOWERS

Statistical uncertainty7% at 1019 eV15% at 1020eV

S(1000)

661 events

SPECTRUM

COMPOSITION

SOURCES

AUGER SCIENCE

ENERGY SPECTRUM - <600

PRL 101, 061101 (2008)

Full efficiency above 1018.5 eV 3% uncertainty on aperture

Data up to31/08/07

Aperture7000 km2 sr yr

~ 1 year Auger completed 2 x HIRES4 x AGASA


Exp. Observed> 4x1019 167±3 66

> 1020 35±1 1

Evidence of GZK cutoff

PRL 101, 061101 (2008)

Data up to31/08/07

Aperture7000 km2 sr yr

~ 1 year Auger completed 2 x HIRES4 x AGASA

Full efficiency above 1018.5 eV 3% uncertainty on aperture

γ = 2.69 ± 0.06

HiRes: 5.1 ± 0.7

γ = 4.2 ± 0.4

Fit E-γ

difference with respect to reference shape Js = A x E-2.69

GZK cut off


0-60 degrees 60-80 degrees

Comparison of the three Auger spectra - consistency

ENERGY SPECTRUM

ICRC 07

Different reconstruction

Exposure from simulation

Ankle

Auger combined compared to Hires and Agasa

Fairly agreement within systematic uncertainties

ICRC 07

SPECTRUM

COMPOSITION

SOURCES

AUGER SCIENCE

ELONGATION RATE

Not proton dominated composition at the highest energies

Change of slope

correlation with ankle ?

Systematics< 15 g /cm2

preliminary

(< A> ~ 5)

SENSITIVITY TO PHOTON SHOWERS

Fluorescence Detector

Xmax from shower

longitudinal profile.

A(SD) Shower front curvature

A(SD) Shower front thickness

Surface Detector

Shape of the front of the shower

preliminary

Astro. Ph. 29 (2008), 243. Astro. Ph. 27 (2007), 155.

PHOTON FRACTION LIMIT

HP: Haverah ParkA1,A2: AGASAY: Yakutsk

~ 3 % Top Down models:

Super HeavyDark Matter

Relic of “topologicaldefects”

Signature: very inclined showers with high e.m.signal component

hadronic showers: signal dominated by muon component

87 degrees

NEUTRINO FLUX LIMIT

PRL 100 (2008), 211101.

SPECTRUM

COMPOSITION

SOURCES

AUGER SCIENCE

GALACTIC CENTER ANISOTROPIES

Excess in previous experiments

AGASA 2.5SUGAR 2.9

angular windows:• AGASA and SUGAR • 10° and 20° around the GC (charged CR’s) • 1° around the GC

• 0.1 < E < 1 EeV (photons)• 1 < E < 10 EeV (neutrons)

H.E.S.S.: TeV -ray from Sagittarius A*

No statistically significant excess in Auger data

Auger: • larger exposure• GC lies well in the f.o.v.

GC

EVIDENCE OF ANISOTROPY

Correlation of the Highest-Energy (>5.7x1019 eV)

Cosmic Rays with Nearby (<75 Mpc) Extragalactic Objects

Astro. Ph. 29 (2008), 188.Science 318 (2007), 939.

Centaurus A

Super-galactic plane

galacticcoordinates

Border of the f.o.v. Doublet from Centaurus A

27 eventsE > 57 EeV3.20 radius

Véron &Véron-Cetty catalogue442 AGN (292 in f.o.v.)z<0.017 (71 Mpc)

Relative exposureRelative exposure

EVIDENCE OF ANISOTROPY

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 CR

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 maximum anisotropy (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

CR

RESULTS

1.2 year full Auger

zmax = 0.017 (71 Mpc) E > 57 EeV = 3.20

Absolute minimum

Selected events

Events correlated

Expected for isotropy

27 20 5.6

Isotropy hypothesis rejected with at least 99% confidence level

exploratory scan (01/01/04- 27/05/06) confirmation on an independent data set (27/05/06- 31/08/07)

WHAT ABOUT NOT CORRELATED EVENTS?

CR

closest AGN

Isotropic fluxEvents with lowgalactic latitudes |b| < 120

• catalogue incompleteness

• larger deflections in galactic magnetic field

Selected events

Events correlated

Expected for isotropy

Full data sample 27 20 5.6

|b| > 120 21 19 5.0

6 events less with 5 not correlated

THE ANGULAR SEPARATION • angular resolution ~ 10 < (=3.20)

• determined by galactic and inter-galactic magnetic fields

Simulation including galactic magnetic field

27 observed events

=3.20

simulated protons (isotropy)

THE ANGULAR SEPARATION • angular resolution ~ 10 < (=3.20)

• determined by galactic and inter-galactic magnetic fields

Simulation including galactic magnetic field

deflection E

60EeVZ

correlated events are likely protons

27 observed events

=3.20

simulated protons (isotropy)

but elongation rate suggests a mixed composition at the highest energies …

CONNECTION TO THE GZK CUT OFF

spectrumevents E > 5.7 1019 eV

flux reduced by 50%

sources < 71 Mpc

but …



flux reduced by 50%

sources < 71 Mpc

but …

GZK Horizon is ~200 Mpc

maximum distance of the sources from which 90 % of the protons arrive on Earth with energy above a given value.

90%



flux reduced by 50%

sources < 71 Mpc

but …



90%

For an +30% energy estimator the Horizon would be ~100 Mpc



flux reduced by 50%

sources < 71 Mpc

but …



90%

Uncertainty on energy scale ~ 25%

For an +30% energy estimator the Horizon would be ~100 Mpc

CONCLUSIONS• Auger is fully operational: exposure ~ 1 year of Auger completed

angular distribution similar to that of AGN within ~ 70 Mpc sources are of extra-galactic originprimaries are likely protons which interact with CMB radiation (GZK)

• UHECR anisotropy




• evidence of GZK cut-off in the spectrum confirming HIRES data

• no photon and neutrino candidates (disfavour TOP-DOWN models)




• evidence of GZK cut-off in the spectrum confirming HIRES data

• no photon and neutrino candidates (disfavour TOP-DOWN models)

Consistency or not with the GZK horizon?

Two events from CenA, none from Virgo. Why?

but …

Xmax studies disfavour a proton dominated composition at the highest energies

• Need more statistics (~ 70 events/year above 4x1019 eV)

and better control of systematics

Auger North (Colorado, US)(talk of prof. J.Bluemer)

Array: 8000 square miles ≈ 20000 km2 ≈ 7 x Auger South)

Full sky coverage

FUTURE DEVELOPMENT

Auger South: ~ 70 events/yearAuger North: ~ 500 events/year

events above 4x1019 eV (GZK cutoff)

BACK UP SLIDES

diffusive Tyvek

TANK CALIBRATION PMT

water

Cerenkovlight

1.2 m ~ 3 X

o

scintillator

Vertical

1 VEM ≈ 100 p.e.

Online calibration with background muons (2 kHz)

muon peak VEM peak

Dia Noche

11m

Doublets Low energy events (~ 1017 eV) used to compare the time measurement of each tank

Time precision of each individual tank ~ 12 ns

GPS intrinsic time resolution 8 ns

TIME RESOLUTION

SD-TANK TRIGGERThreshold Trigger~ 20 Hz

Time Over Threshold Trigger~ Hz

5 s

hottest tank surrounded by 6 working stations

SD-EVENT TRIGGER

Lateral distribution function (LDF)

NGK

1700

700

1000)1000()(

rrSrS

size parameter

slope parameter

S(1000) and the core position from the fit

core

distance from the core

S(1000)

distance from the core (m)

Sign

al

(VE

M)

34 tanks


(β) 2-2.5)


ground

Xg Xg/cos

vertical shower inclined shower for the same energy and massS(1000;0)> S(1000

for each shower determine

the signal that would have had at 380

Attenuation curve derived with constant intensity cut technique

S38 = S(1000,380)


PRL 101, 061101 (2008)

LINEAR FIT19%

measurement of the energy resolution

16%-S38

8%-EFD

SD APERTURE

(t)dtareatriggerAperture

Full efficiency above 3x1018 eV

Aperture 7000 km2 sr yr (3% error) ~20.000 events above 3 1018 eV

ELONGATION RATE

Comparison with PAO data, without and with acceptance

ELONGATION RATE

ELONGATION RATE

Fe - EPOS

p - EPOS

Fe - QGSJETIIp - QGSJETII

• The mass spectrum is not proton dominated at the highest energies

• Ambiguous interpretation: uncertainties of hadronic interactions at highest energies

proton

iron

p0pmax clnAE/ElnDX

GALACTIC CENTER ANISOTROPIES

1.30 (G) 192.1 / 191.2 1.00 ± 0.07 ± 0.01

100 5663 / 5657 1.00 ± 0.02 ± 0.01

200 22274 / 22440 0.99 ± 0.01 ± 0.01

0.80 (G) 16.9 / 17.0 0.99 ± 0.17 ± 0.01

100 1463 / 1365 1.07 ± 0.04 ± 0.01

200 5559 / 5407 1.03 ± 0.02 ± 0.01

Angular window Nobs/Nexp Ratio (err.: stat, syst)

GC lies well in the Auger f.o.v.

Windows centred in the GC:

0.1 < E < 1 EeV

1 < E < 10 EeV

search for photons

search for neutrons

ANISOTROPYEvents Events

correlatedExpected for

isotropy

Exploratory scan1 Jan 04- 27 May 06

zmax = 0.018

E > 56 EeV = 3.10

15 12 3.2

Test on an independent data set 27 May 06- 31 Aug 07 **running prescription

13 8 2.7

Full data set 1.2 year full Auger *

zmax = 0.017 (71 Mpc)

E > 57 EeV = 3.20

27 20 5.6

Full data set excluding region of the galactic plane(|b| > 120)

21 19 5.0

*Probability to see such anisotropy with an isotropic flux = 10-5

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

** 1.7 10-3

Red dots: 13 HiRes events (claim consistent with isotropy)

Black dots: 27 Auger events

GZK and mass composition

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

Documents

Valerio Verzi INFN Roma Tor Vergata for the Pierre Auger Collaboration