10 - ILP

1st “ILP Day”, Paris, 13 March 2014
Search for cosmogenic
photons with the Pierre
Auger Observatory
Mariangela Settimo
LPNHE, Universites Paris VI and Paris VII
The Ultra-High Energy (UHE) range
Knee
E 2.6 F(E) [GeV1.6 m-2 s-1 sr-1]
104
LHC 14 TeV
Grigorov
10
3
102
JACEE
MGU
Tien-Shan
Tibet07
Akeno
CASA-MIA
HEGRA
Fly’s Eye
Ankle
Kascade
10
1
13
10
Kascade Grande 2011
AGASA
HiRes 1
HiRes 2
Telescope Array 2011
Auger 2011
1014
10
15
Pierre Auger
Observatory
16
17
10
10
18
10
19
10
10
20
E [eV]
Mariangela Settimo, “ILP day”, Paris 13 March 2014
1
The Ultra-High Energy (UHE) range
Knee
E 2.6 F(E) [GeV1.6 m-2 s-1 sr-1]
104
LHC 14 TeV
Grigorov
10
3
102
JACEE
MGU
Tien-Shan
Tibet07
Akeno
CASA-MIA
HEGRA
Fly’s Eye
Ankle
Ankle
Flux suppression
Emax @ source or
propagat. effect (GZK) ?
Kascade
10
1
13
10
Kascade Grande 2011
AGASA
HiRes 1
HiRes 2
Telescope Array 2011
Auger 2011
1014
10
15
Pierre Auger
Observatory
16
17
10
10
18
10
19
10
10
20
E [eV]
Mariangela Settimo, “ILP day”, Paris 13 March 2014
2
The Ultra-High Energy (UHE) range
Knee
E 2.6 F(E) [GeV1.6 m-2 s-1 sr-1]
104
LHC 14 TeV
Grigorov
10
3
102
JACEE
MGU
Tien-Shan
Tibet07
Akeno
CASA-MIA
HEGRA
Fly’s Eye
Ankle
Ankle
Flux suppression
Emax @ source or
propagat. effect (GZK) ?
Kascade
10
1
13
10
Kascade Grande 2011
AGASA
HiRes 1
HiRes 2
Telescope Array 2011
Auger 2011
1014
10
15
Pierre Auger
Observatory
16
17
10
10
E [eV]
18
10
19
10
10
photo-pion production (GZK effect)
Cosmogenic photons and neutrinos
p + γCMB
p
γCMB
Mariangela Settimo, “ILP day”, Paris 13 March 2014
20
π0
γ
γ
Δ+
p + π0
EGZK ~ 5 x 1019 eV, λ ~ 6 Mpc
Inelasticity: ~ 20% (10% for each γ)
3
Flux predictions for cosmogenic photons
Photon flux predictions sensitive to:
- source properties (injection spectrum, maximum energy, primary types, source distrib./evol.)
- propagation (electromagnetic cascades in EBL, magnetic fields)
expected flux: ~ 0.1- 1% of the
all-particle spectrum above 1019 eV
max energy,
spectral index
source distance
M.S., M.De Domenico,arXiv:1311.6140
depending on the observations, some astrophysical
scenarios can be constrained/disfavored
Mariangela Settimo, “ILP day”, Paris 13 March 2014
4
The Pierre Auger Observatory: the hybrid design
Based on 2 complementary and
independent techniques
Real Event, E = 7 1019 eV
Argentina
3000 km2
Fluorescence Detector (FD)
Malargü
e
(Argent
ina), 14
00 m a.
s.l.
24 + 3 telescopes in 4 sites
10-15% duty cycle
Hybrid events:
observed at the same time by
at least 1 fluorescence
telescope + 1 SD
Mariangela Settimo, “ILP day”, Paris 13 March 2014
Surface Detector array (SD)
1600 + 60 water Cherenkov
stations, 100% duty cycle
5
Photon identification
Hybrid events (E > 1018 eV):
proton
- Deeper development of the air showers
Xmax
(larger Xmax)
Xmax
- Smaller detected signal in SD and
steeper lateral distribution function
photon
SD events (E > 1019 eV):
Deeper shower development and smaller number of muons
hadrons
larger risetime
of the SD signals
50%
smaller radius of
curvature
Mariangela Settimo, “ILP day”, Paris 13 March 2014
10%
t10 t50
FADC time
Risetime: t1/2 = t50% - t10%
6
Integral Flux E>E0 [km-2 sr -1 y-1]
Upper limits on photon flux
upper limits 95% C.L.
SD (Auger): Astrop. Phys. 29, 2008
A (AGASA), Shinozaki et al., 2002
Y (Yakutsk), Glushkov et al., 2010
TA (Telescope Array), ICRC 2013
1
Y
Y
SHDM
SHDM'
TD
Z-burst
GZK
Gelmini et al., 2008
Ellis et al., 2006
A
10-1
A
Hyb 2011
TA
✓ most stringent limits available in the EeV range
✓ top-down models disfavored
✓ GZK flux region within reach
10-2
SD
10-3
M.S. for the Pierre Auger Collaboration, ICRC 2011, arXiv: 1107.4805
18
19
10
10
20
10
Energy[eV]
Upper limits to the integral photon fraction:
Hybrid: 0.4%,
SD:
0.5%, 1.0%, 2.6% and 8.9% @ E>1, 2, 3, 5 and 10 EeV
2.0%, 5.1%, 31%
Mariangela Settimo, “ILP day”, Paris 13 March 2014
@ E > 10, 20, 40 EeV
7
Expected sensitivity in the near future
A new trigger designed (installed in the stations on June 2013):
‣ select station with small signals, not dominated by the muonic component
‣ especially effective for photons
al
n
Inter
new
Hy 2023, SD 2023:
current analysis
no additional bkg
no candidates
no background
prove the existence of the GZK effect and
constrain astrophysical scenarios
Data analysis in progress
Mariangela Settimo, “ILP day”, Paris 13 March 2014
8
Outlook
Observation/Non-observation of UHE photons:
‣ Independent prove of the GZK effect
‣ Clarify the nature of the observed flux suppression
‣ flux of cosmogenic photons sensitive to source properties (primary mass,
injection spectra, distribution) and extragalactic environment
‣ hints/constraints on astrophysical scenarios for the origin of ultra-high energy
cosmic rays
‣ Disfavor/constrains top-down models
‣ Open the most extreme window for astronomy
‣ Impact on the measurements of energy spectrum, cross sections, mass
composition and possible consequences for fundamental physics (LIV)
Mariangela Settimo, “ILP day”, Paris 13 March 2014
y
a
st
n
u
t
!
ed
3
Thank you
Backup slides
The Ultra-High Energy (UHE) range
E [eV]
1018
1019
1020
1038
1036
17.5
∆E/E = 14 %
proton
Ankle
Flux suppression
Emax @ source or
propagat. effect (GZK) ?
iron
1037
�
E3 J ( E) eV2 km−2 sr−1 yr−1
�
Auger 2013 preliminary
Proton, Ecut = 1020 eV
Proton, Ecut = 1020.5 eV
Iron, Ecut = 1020 eV
Iron, Ecut = 1020.5 eV
18.0
18.5
19.0 photo-pion
19.5 production
20.0
20.5 effect)
(GZK
log10 ( E/eV
)
Cosmogenic
photons and neutrinos
p + γCMB
p
γCMB
π0
γ
γ
Δ+
p + π0
EGZK ~ 5 x 1019 eV, λ ~ 6 Mpc
Inelasticity: ~ 20% (10% for each γ)
Pre-shower: impact on EAS development (II)
• faster shower development
• small shower-to-shower fluctuations
• competition of LPM and preshower
Shower development for different primaries
electrons
Iron
Proton
Photon
muons
hadrons neutrons
vertical showers
E = 100 TeV
A qualitative view
(CORSIKA simulations: http://www-ik.fzk.de/corsika/)
Light primaries develop deeper than
heavy component
Photon induced showers deeper
than hadrons (on average)
Photon search: the hybrid approach ( E > 1EeV)
M.S. for the Pierre Auger Collaboration, ICRC 2011, arXiv: 1107.4805
proton

Xmax
FD:
- Deeper development of the air showers
Larger Xmax

Xmax
photon
SD:
- Smaller detected signal at a given distance
- Fewer triggered stations
Monte Carlo Simulations
Energy = 1018.5 eV
Si : station signal [VEM]
Ri : station distance to the shower axis [m]
details on Sb: G. Ros et al., arXiv 1104.3399
Smaller Sb
Search for photons with SD: E>10 EeV
Radius of curvature
- Events observed by SD-alone
- radius of curvature and risetime t1/2 at
1000 m used for photons identification
Risetime at 1000 m
Mariangela Settimo, LPNHE Paris, 10 January 2014
12
Search for photons with SD: E>10 EeV
Radius of curvature
- Events observed by SD-alone
- radius of curvature and risetime t1/2 at
1000 m used for photons identification
Deviations of data from the mean value of R and t1/2
expected for photon showers combined with a
Principal Component Analysis
Risetime at 1000 m
PCA training on 5% on data
Mariangela Settimo, LPNHE Paris, 10 January 2014
12
Integral Flux E>E0 [km-2 sr -1 y-1]
Upper limits on photon flux
upper limits 95% C.L.
SD (Auger): Astrop. Phys. 29, 2008
A (AGASA), Shinozaki et al., 2002
Y (Yakutsk), Glushkov et al., 2010
TA (Telescope Array), ICRC 2013
1
Y
Y
SHDM
SHDM'
TD
Z-burst
GZK
10-1
A
Hyb 2011
Nᵧ
1
6
8.2 × 10-2
2
0
2.0 × 10-2
3
0
2.0 × 10-2
5
0
2.0 × 10-2
10
0
2.0 × 10-2
[EeV]
Gelmini et al., 2008
Ellis et al., 2006
A
E0
TA
10-2
Impact of systematic uncertainties
SD
(Exposure, ∆Xmax, ∆Sb, Energy scale,
hadronic interaction model and mass
composition assumptions)
10-3
18
10
19
10
20
10
Energy[eV]
Upper limits to the integral photon fraction assuming the Auger Spectrum
0.4%, 0.5%, 1.0%, 2.6% and 8.9% @ E>1, 2, 3, 5 and 10 EeV
M.S. for the Pierre Auger Collaboration, ICRC 2011, arXiv: 1107.4805
Mariangela Settimo, LPNHE Paris, 10 January 2014
18

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