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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