UHECRs Energy Spectrumblois.in2p3.fr/2008/transparents/maris.pdf · Cosmic rays energy spectrum Energy [eV] 1011 12 1013 14 1015 16 1017 18 1019 20-1] sr-1 sec-2 E J(E) [m 10-16 10-14

Ioana C. Maris for the Pierre Auger Collaboration

UHECRs energy spectrum

OBSERVATORY

Outline

• Pierre Auger Observatory

• Constant intensity method

• Energy calibration

• Energy spectra: vertical,horizontal and hybrid

• Combined spectrum

XX Rencontres de Blois 2008 Ioana C. Maris for the Pierre Auger Collaboration

Cosmic rays energy spectrum

Energy [eV]

1110 1210 1310 1410 1510 1610 1710 1810 1910 2010

]-1

sr

-1 s

ec-2

E J

(E)

[m

-1610

-1410

-1210

-1010

-810

-610

-410

-210

1

210

(GeV)ppsEquivalent c.m. energy

10 210 310 410 510 610

ATIC

PROTON

RUNJOB

KASCADE

Fly’s Eye Stereo

MSU

Akeno

HiRes I

HiRes II

AGASAAuger 2007



Energy [eV]

1510 1610 1710 1810 1910 2010

]1.

5 e

V-1

sr

-1 s

ec-2

J(E

) [

m2.

5Sc

aled

flu

x E

1410

1510

1610

1710

(GeV)ppsEquivalent c.m. energy 310 410 510 610

Tevatron (p-p)

LHC (p-p)

PROTON

RUNJOB

KASCADEFly’s Eye Stereo

Akeno

HiRes I

HiRes II

AGASA

Auger 2007- combined



Energy [eV]

1510 1610 1710 1810 1910 2010

]1.

5 e

V-1

sr

-1 s

ec-2

J(E

) [

m2.

5Sc

aled

flu

x E

1410

1510

1610

1710


Tevatron (p-p)

LHC (p-p)

PROTON

RUNJOB


Akeno

HiRes I

HiRes II

AGASA


spectral features: change in composition

nature of the sources

galactic to extragalactic origin



Energy [eV]

1510 1610 1710 1810 1910 2010

]1.

5 e

V-1

sr

-1 s

ec-2

J(E

) [

m2.

5Sc

aled

flu

x E

1410

1510

1610

1710


Tevatron (p-p)

LHC (p-p)

PROTON

RUNJOB


Akeno

HiRes I

HiRes II

AGASA


Greisen Zatsepin Kuzmin effect

• p + γCMB → ∆+(1232)

→ p + π0 → pγγ→ n + π+ → pe+ν

15% energy loss / interaction ⇒

nearby universe visible



Energy [eV]

1510 1610 1710 1810 1910 2010

]1.

5 e

V-1

sr

-1 s

ec-2

J(E

) [

m2.

5Sc

aled

flu

x E

1410

1510

1610

1710


Tevatron (p-p)

LHC (p-p)

PROTON

RUNJOB


Akeno

HiRes I

HiRes II

AGASA


UHECRs challenges

• reduce uncertainties

• spectral features

• composition

• arrival directions


Air Showers Measurement Techniques

Surface detector(SD)

• duty cycle ≈ 100%

• acceptance geometric

• energy scale from air showersimulations

Fluorescence detector(FD)

• energies from longitudinal energydeposit, nearly calorimetric

• acceptance from detector andatmosphere simulation

• duty cycle ≈ 10%

Pierre Auger Observatory: acceptance and energy from data !


Pierre Auger Observatory

3000 km2, 1642 tanks deployed, 1619 with water, 1586 working


Surface detector (SD)

3000 km2, 1642 tanks deployed, 1619 with water, 1586 working

three 9 inch PMTs

12 tons of water

electronics

battery

solar panel

GPS antenna

communications antenna


Fluorescence detector (FD)

Atmosphere monitoring• radio soundings (h, T, P), LED for

end to end calibration, LASER shots,IR cloud cameras, star light monitor


Event example

Golden hybrid events: SD and FDXX Rencontres de Blois 2008 Ioana C. Maris for the Pierre Auger Collaboration

Event example

Timing: direction, impact point

azimuth [deg]150 155 160 165 170 175 180

elev

atio

n [

deg]

0

5

10

15

20

25

30

t [25 ns]150 200 250 300 350 400 450

S [V

EM

pea

k]

0

100

200

300

400

500

t [25 ns]150 200 250 300 350 400 450

S [V

EM

pea

k]

0

2

4

6

8

10

12

14

t [25 ns]150 200 250 300 350 400 450

S [V

EM

pea

k]

0

2

4

6

8

10

t [25 ns]150 200 250 300 350 400 450

S [V

EM

pea

k]

0

0.5

1

1.5

2

2.5

3

3.5

4

t [25 ns]150 200 250 300 350 400 450

S [V

EM

pea

k]

0

0.5

1

1.5

2

2.5

3

3.5

t [25 ns]150 200 250 300 350 400 450

S [V

EM

pea

k]

0

1

2

3

4

5

t [25 ns]150 200 250 300 350 400 450

S [V

EM

pea

k]

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

t [25 ns]150 200 250 300 350 400 450

S [V

EM

pea

k]

0

0.5

1

1.5

2

2.5

3

3.5

4

t [25 ns]150 200 250 300 350 400 450

S [V

EM

pea

k]

0

0.5

1

1.5

2

2.5

3

3.5

t [25 ns]150 200 250 300 350 400 450

S [V

EM

pea

k]

0

0.2

0.4

0.6

0.8

1

1.2

x [km]63.5 63.6 63.7 63.8 63.9

y [k

m]

47.1

47.2

47.3

47.4

47.5

Signal (VEM) vs time

(Talk by Pierre Billoir)


Event example

r [m]500 1000 1500 2000 2500 3000

Sign

al [

VE

M]

1

10

210

310

410

/ NDoF: 6.833/ 72χ

S(1000 m)

] 2slant depth [g/cm

400600

800

)]2dE/dX [PeV/(g/cm

0 10 20 30 40 50/N

df= 167.37/217

2χ

Lateral distribution: S(1000 m)

Longitudinal profile: energy


Event example

r [m]500 1000 1500 2000 2500 3000

Sign

al [

VE

M]

1

10

210

310

410

/ NDoF: 6.833/ 72χ

S(1000 m)

] 2slant depth [g/cm

400600

800

)]2dE/dX [PeV/(g/cm

0 10 20 30 40 50/N

df= 167.37/217

2χ

Lateral distribution: S(1000 m)

Longitudinal profile: energy

FD energy ⇒ SD high statistics

(no simulations needed)

Xmax⇒ composition


S(1000 m) to Energy

From ’Golden Hybrids’ (FD+SD)

lateral particle distribution↓

S(1000m)↓

zenith angle correction (constant intensity cut method)↓

S38

↓

FD energy↓

ESD


S(1000 m)- Attenuation in the atmosphere

ground level

inclined showerverticalshower

inclined S(1000m) < vertical S(1000m)


Method of Constant IntensityHypothesis:

cosmic ray flux is isotropic(at least in local coordinates)

Φ =dN

dΩdEdAeff dt

SD data:projection on flat array geometry

Aeff = A · cos θ

intensity: events above a certain energy

dId cos2 θ

= const


Method of Constant Intensityaim: find S(θ) from I = const, ∆ cos2 θ = const

lg( S(1000 m) /VEM)0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

#

1

10

210

310

410

° < 0θ < °25° < 25θ < °37° < 37θ < °47° < 47θ < °59

/VEM)38

lg( S0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4

#1

10

210

310

410

° < 0θ < °25° < 25θ < °37° < 37θ < °47° < 47θ < °59

• ’correct’ all shower sizes to same zenith angle 38


Zenith angle correction: S(1000m) ⇒ S38

θ2cos0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

S(10

00 m

) [V

EM

]

25

30

35

40

45

50

55

60

polynomialexponential

S38

S38 = S(1000 m)/f (θ)f (θ) = 1 + a · x + b · x2 , x = cos2 θ − cos2 38


Energy Calibration

Stat. uncertainties:S38 (≈ 16%)

• shower to showerfluctuations

• reconstruction

EFD (≈ 8%)

• reconstruction

• atmosphere

E = A · SB38


Energy Calibration

Stat. uncertainties:S38 (≈ 16%)

• shower to showerfluctuations

• reconstruction

EFD (≈ 8%)

• reconstruction

• atmosphere

E = A · SB38


Energy Scale Systematics

Absolute Fluorescence Yield 14%Pressure dependence of Fluorescence Yield 1%Humidity dependence of Fluorescence Yield 1%Temperature dependence of Fluorescence Yield 5%

FD absolute calibration 11%FD wavelength dependence response 3%Rayleigh scattering in atmosphere 1%Wavelength dependence of aerosol scattering 1%

FD reconstruction method 10%Invisible energy 5%

Total: 22%

experimental uncertainties to be improvedXX Rencontres de Blois 2008 Ioana C. Maris for the Pierre Auger Collaboration

Trigger efficiency

• cross-checked with hybrid events!


Vertical Energy Spectrum

lg(E/eV)18.5 19 19.5 20 20.5

))-1

sr

-1 s

-2 J

/(m

lg(

E

-17

-16

-15

-14

-13

E[eV]1810×3 1910 1910×2 2010 2010×2

4128

24501631

1185

761560

367284

178125

7954

25

14

5 5

1 1

Auger ICRC 2007, vertical

5165 km2 sr year until ICRC 20070.8 × one year complete observatory

Events (observed/expected) above 4 · 1019 eV: 51/(132 ± 9)above 1020 eV: 2/(30 ± 2.5)


Horizontal and Hybrid Energy Spectra

lg(E/eV)18 18.5 19 19.5 20 20.5

))2 e

V-1

sr

-1 s

-2 J

/(m

3lg

( E

23.5

24

24.5

E[eV]1810×2 1910 1910×2 2010 2010×2

Auger ICRC 2007, horizontal

lg(E/eV)18 18.5 19 19.5 20 20.5

))2 e

V-1

sr

-1 s

-2 J

/(m

3lg

( E

23.5

24

24.5

E[eV]1810×2 1910 1910×2 2010 2010×2

Auger ICRC 2007, hybrid


Auger Energy Spectrum

lg(E/eV)18 18.5 19 19.5 20 20.5

))2 e

V-1

sr

-1 s

-2 J

/(m

3lg

( E

23.5

24

24.5

E[eV]1810×2 1910 1910×2 2010 2010×2

verticalhybridhorizontalcombined

Very good agreement between the three spectra (< 3%)XX Rencontres de Blois 2008 Ioana C. Maris for the Pierre Auger Collaboration

Auger Energy Spectrum: Spectral features

lg(E/eV)18 18.5 19 19.5 20 20.5

-1

2.62

E×J/

A

-1

-0.5

0

0.5

1

1.5

2

E[eV]1810 1810×2 1910 1910×2 2010 2010×2

Auger ICRC 2007, combined

γ1 = 3.30 ± 0.06

γ2 = 2.62 ± 0.03

γ3 = 4.14 ± 0.42


Auger Energy Spectrum: Spectral features

lg(E/eV)18 18.5 19 19.5 20 20.5

-1

2.62

E×J/

A

-1

-0.5

0

0.5

1

1.5

2

E[eV]1810 1810×2 1910 1910×2 2010 2010×2


ankle: (4.46 ± 0.4) · 1018 eV

flux suppression: (56 ± 8) · 1018 eV


Anisotropies- energy spectrum

lg(E/eV)18 18.5 19 19.5 20 20.5

-1

2.62

E×J/

A

-1

-0.5

0

0.5

1

1.5

2

E[eV]1810 1810×2 1910 1910×2 2010 2010×2


• the energy and redshift that maximise the signal are compatiblewith the GZK horizon


Anisotropies- energy spectrum

lg(E/eV)18 18.5 19 19.5 20 20.5

-1

2.62

E×J/

A

-1

-0.5

0

0.5

1

1.5

2

E[eV]1810 1810×2 1910 1910×2 2010 2010×2


Talk by Antoine Letessier-Selvon

• the energy and redshift that maximise the signal are compatiblewith the GZK horizon


Mass composition- energy spectrum


Mass composition- energy spectrum

Next talk by Jose Bellido


Conclusions

• vertical SD spectrum: 5165 km2 sr year (02.2007)

• good agreement between the three energy spectra

• 6σ evidence for flux suppression at high energies

• combined with the anisotropies studies ⇒ GZK effect

• fluorescence yield measurements → dominate the energyuncertainties

• (soon) updated energy spectrum: 8000 km2 sr year

• high statistics above 1019.8 eV needed to constrain models


Extra slides


Energy Spectrum: comparison with other experiments

Energy [eV]

1910 2010

]1.

7 e

V-1

sr

-1 s

ec-2

J(E

) [m

2.7

Sca

led

flux

E

3110

3210

HiRes IHiRes IIAGASAAuger 2007


Horizontal Spectrum: energy calibration

(EeV))FD

(E10

log0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

)19

(N

10lo

g

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2 / ndf 2χ 38.05 / 36 α 0.06± -0.77 β 0.05± 0.96

/ ndf 2χ 38.05 / 36 α 0.06± -0.77 β 0.05± 0.96


Hybrid Energy Spectrum: exposure

lg(E/eV)18 18.5 19 19.5 20

sr

yr]

2ex

posu

re [

km

0

100

200

300

400

500

600

lg(E/eV)18 18.5 19 19.5 20

Sys

tem

atic

Un

cert

ain

ty[%

]

5

10

15

20

25

30

35

τ

atm.⊕ τ

sel.⊕ atm. ⊕ τ


Documents

UHECRs Energy Spectrumblois.in2p3.fr/2008/transparents/maris.pdf · Cosmic rays energy spectrum Energy [eV] 1011 12 1013 14 1015 16 1017 18 1019 20-1] sr-1 sec-2 E J(E) [m 10-16 10-14