Measurement of the UHECRs flux and composition with Pierre Auger - PowerPoint PPT Presentation

Measurement of the UHECRs flux and composition with Pierre Auger Observatory OBSERVATORY Ioana C. Mari¸ s for the Pierre Auger Collaboration

Outline • Ultra high energy cosmic rays • Pierre Auger Observatory • Energy spectrum (calibration, combined spectrum) • Composition XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 2

Introduction: Cosmic rays energy spectrum Equivalent c.m. energy s (GeV) pp 3 5 6 10 10 2 10 10 4 10 10 2 10 ] -1 sr HiRes I 1 -1 sec HiRes II AGASA -2 10 -2 E J(E) [m Auger 2007 -4 10 ATIC 10 -6 PROTON -8 RUNJOB 10 KASCADE -10 10 Fly’s Eye Stereo MSU -12 10 Akeno 10 -14 -16 10 13 15 16 17 18 19 20 10 11 10 12 10 10 14 10 10 10 10 10 10 Energy [eV] XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 3

Introduction: Cosmic rays energy spectrum Equivalent c.m. energy s (GeV) pp 3 4 5 6 10 10 10 10 17 HiRes I 10 ] 1.5 HiRes II eV AGASA -1 sr Auger 2007- combined -1 16 10 sec PROTON -2 J(E) [m RUNJOB KASCADE Fly’s Eye Stereo 10 15 Akeno 2.5 Scaled flux E LHC (p-p) 14 10 Tevatron (p-p) 15 16 17 18 19 20 10 10 10 10 10 10 Energy [eV] XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 3

Introduction: Cosmic rays energy spectrum Equivalent c.m. energy s (GeV) pp 3 4 5 6 10 10 10 10 17 HiRes I 10 ] 1.5 HiRes II eV AGASA -1 sr Auger 2007- combined -1 16 10 sec PROTON -2 J(E) [m RUNJOB KASCADE Fly’s Eye Stereo 10 15 Akeno 2.5 Scaled flux E spectral features: change in composition LHC (p-p) 14 10 nature of the sources Tevatron (p-p) transition from galactic to extragalactic origin 15 16 17 18 19 20 10 10 10 10 10 10 Energy [eV] XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 3

Introduction: Cosmic rays energy spectrum Equivalent c.m. energy s (GeV) pp 3 4 5 6 10 10 10 10 17 HiRes I 10 ] 1.5 HiRes II eV AGASA -1 sr Auger 2007- combined -1 16 10 sec PROTON -2 J(E) [m RUNJOB KASCADE Greisen Zatsepin Kuzmin effect Fly’s Eye Stereo • p + γ CMB → ∆ + ( 1232 ) 10 15 Akeno 2.5 → p + π 0 → p γγ Scaled flux E → n + π + → pe + ν LHC (p-p) 14 10 15% energy loss / interaction ⇒ only Tevatron (p-p) nearby universe visible 15 16 17 18 19 20 10 10 10 10 10 10 Energy [eV] XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 3

Introduction: Cosmic rays energy spectrum Equivalent c.m. energy s (GeV) pp 3 4 5 6 10 10 10 10 17 HiRes I 10 ] 1.5 HiRes II eV UHECRs Challenges AGASA -1 sr Auger 2007- combined • energy spectrum -1 16 10 sec PROTON • reduce stat. and syst. -2 J(E) [m RUNJOB uncertainties KASCADE Fly’s Eye Stereo 10 15 • composition Akeno 2.5 Scaled flux E • arrival directions LHC (p-p) 14 10 Tevatron (p-p) Pierre Auger Observatory 15 16 17 18 19 20 10 10 10 10 10 10 Energy [eV] XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 3

Introduction: Measurement Techniques Surface detector(SD) • acceptance geometric • energy scale from air shower simulations • duty cycle ≈ 100 % Fluorescence detector(FD) • energies from longitudinal energy deposit, nearly calorimetric • acceptance from detector and atmosphere simulation • duty cycle ≈ 10 % Pierre Auger Observatory: acceptance and energy from data ! XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 4

Pierre Auger Observatory: hybrid detector XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 5

Surface detector (SD) 3000 km 2 , 1612 tanks deployed, 1584 with water, 1526 working XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 5

Surface detector (SD) GPS antenna communications antenna electronics solar panel three 9 inch PMTs battery 12 tons of water XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 5

Fluorescence detector (FD) Atmosphere monitoring • radio soundings (h, T, P), LED for end to end calibration, LASER shots, horizontal attenuation, IR cloud cameras, star light monitor XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 5

Pierre Auger Observatory: event example 14 S [VEM peak] S [VEM peak] S [VEM peak] 500 10 12 elevation [deg] 30 10 400 8 8 300 6 6 200 4 4 100 2 25 2 0 0 0 150 200 250 300 350 400 450 150 200 250 300 350 400 450 150 200 250 300 350 400 450 t [25 ns] t [25 ns] t [25 ns] S [VEM peak] S [VEM peak] 3.5 S [VEM peak] 5 20 4 3.5 3 4 3 2.5 2.5 3 2 2 1.5 1.5 2 15 1 1 1 0.5 0.5 0 0 0 150 200 250 300 350 400 450 150 200 250 300 350 400 450 150 200 250 300 350 400 450 t [25 ns] t [25 ns] t [25 ns] 10 S [VEM peak] 1.8 S [VEM peak] 4 S [VEM peak] 3.5 1.6 3.5 3 1.4 3 1.2 2.5 2.5 5 1 2 2 0.8 1.5 1.5 0.6 1 1 0.4 0.2 0.5 0.5 0 0 0 150 200 250 300 350 400 450 150 200 250 300 350 400 450 150 200 250 300 350 400 450 0 t [25 ns] t [25 ns] t [25 ns] 150 155 160 165 170 175 180 S [VEM peak] 1.2 azimuth [deg] 1 Footprint on the camera 0.8 FADC traces (25 ns) 0.6 0.4 0.2 0 150 200 250 300 350 400 450 t [25 ns] Detector signal (VEM) vs time y [km] 47.5 47.4 47.3 47.2 47.1 63.5 63.6 63.7 63.8 63.9 Golden hybrid events: SD and FD x [km] XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 6

Pierre Auger Observatory: event example Signal [VEM] χ 2 / NDoF: 6.833/ 7 4 10 3 10 S(1000 m) 2 dE/dX [PeV/(g/cm )] 2 10 10 20 30 40 50 0 10 400 1 500 1000 1500 2000 2500 3000 r [m] 600 slant depth [g/cm 800 Lateral distribution: S(1000 m) χ 2 /Ndf= 167.37/217 Longitudinal profile: energy 2 ] XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 6

Pierre Auger Observatory: event example Transfer the FD energy to the SD high statistics data! Signal [VEM] (no simulations needed) χ 2 / NDoF: 6.833/ 7 4 10 3 10 S(1000 m) 2 dE/dX [PeV/(g/cm )] 2 10 10 20 30 40 50 0 10 400 1 500 1000 1500 2000 2500 3000 r [m] 600 X max ⇒ composition slant depth [g/cm 800 Lateral distribution: S(1000 m) χ 2 /Ndf= 167.37/217 Longitudinal profile: energy 2 ] XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 6

S(1000 m) to Energy From ’Golden Hybrids’ (FD+SD) lateral particle distribution ↓ S (1000m) ↓ zenith angle correction (constant intensity cut method) ↓ S 38 ↓ FD energy ↓ E SD XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 7

S(1000 m)- Attenuation in the atmosphere inclined shower vertical shower ground level inclined S(1000m) < vertical S(1000m) XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 8

Zenith angle correction: S(1000m) ⇒ S 38 S(1000 m) [VEM] 60 55 S 38 50 45 40 35 polynomial 30 exponential 25 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 cos 2 θ S 38 ( 1000 m ) = S ( 1000 m ) / f ( θ ) f ( θ ) = 1 + a · x + b · x 2 , x = cos 2 θ − cos 2 38 ◦ • correct all shower sizes to the same angle 38 ◦ XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 9

Energy Calibration Stat. uncertainties: S 38 ◦ ( ≈ 16 % ) • shower to shower fluctuations • reconstruction E FD ( ≈ 8 % ) • reconstruction • atmosphere E = A · S B 38 ◦ XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 10

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 improved XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 11

Vertical Energy Spectrum E[eV] × 18 19 × 19 20 × 20 3 10 10 2 10 10 2 10 )) -1 sr -13 4128 5165 km 2 sr year until ICRC 2007 -1 2450 s 1631 1185 0.8 × one year complete observatory -2 761 J /(m 560 -14 367 284 178 lg( E 125 79 -15 54 25 14 -16 5 5 Auger ICRC 2007, vertical 1 1 -17 18.5 19 19.5 20 20.5 lg(E/eV) Events (observed/expected) above 4 · 10 19 eV: 51 / ( 132 ± 9 ) above 10 20 eV: 2 / ( 30 ± 2 . 5 ) XLIII nd Rencontres de Moriond- EW, 2008 I. C. Mari¸ s for the Pierre Auger Collaboration 12