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Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande Fabiana Cossavella 27 October 2009 Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 1

Outline • overview of the KASCADE-Grande experiment • air shower measurement and reconstruction • cosmic ray spectrum • composition study Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 2

Cosmic Ray Energy Spectrum 19 10 direct data Akeno KASCADE-Grande EAS-TOP AGASA 18 KASCADE (QGSJET 01) 10 KASCADE-Grande (QGSJET II) Nch-N µ HiRes I ) 1.5 HiRes II eV 17 10 AUGER 2008 (PRL) -1 sr -1 s 16 10 -2 J(E) (m 15 10 2.5 E 14 10 13 10 4 5 6 7 8 9 10 11 12 10 10 10 10 10 10 10 10 10 Energy (GeV) • break in the single elemental spectra at E ∝ Z · E knee Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 3

Detection: Extensive Air Showers • interaction primary-air → mainly π -mesons • secondary products interact (hadrons) or decay (muons, electrons) • particles reach ground in a shower disc • longitudinal profile → N particles as function of the atmospheric depth • lateral profile → distribution at ground of the shower particles as a function of the distance from the shower axis Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 4

Different primaries • dominated by electromagnetic component Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 5

Different primaries • N µ / N e larger as compared to proton Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 5

The KASCADE Experiment Physics Observables • electron • gammas • muons • hadrons The detectors • Array stations: liquid scintillator for e /γ detection and plastic scintillator for µ detection above 230 MeV • Muon Tracking Detector for E µ ≥ 800 MeV • MWPC/LSTs for muon detection above 2.4 GeV • Calorimeter, for hadron detection Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 6

KASCADE-Grande KASCADE extension to 700 × 700 m 2 • energy spectrum and composition from • iron knee ? 10 16 eV to 10 18 eV • origin of the knee ? • galactic to extragalactic transition? • Anisotropies • Testing hadronic interaction models Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 7

KASCADE-Grande Physics observables • ≈ 10 m 2 of plastic scintillator per station • arrival time and energy deposit by charged particles in each detector • light detected and coverted into ⇒ particle densities electronic signal by PMTs • muons from the KASCADE detectors Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 8

-500 36 25 26 27 28 29 30 31 32 33 34 35 37 23 Trigger-Cell฀17(18) -700 -600 KASCADE -400 -300 -200 -100 0 100 -600 -500 -400 -300 -200 -100 24 22 100 8 Piccolo-Stations Grande-Stations x-coordinate฀ [ m ] y-coordinate฀ [ m ] 1 2 3 4 5 6 7 9 21 10 11 12 13 14 15 16 17 18 19 20 0 Trigger efficiency trigger efficiency 1 0.9 0.8 0.7 proton - 7/7 iron - 7/7 0.6 all - 7/7 trigger all - 4/7 trigger 0.5 0.4 0.3 0.2 6 6.2 6.4 6.6 6.8 7 7.2 7.4 7.6 log (E /GeV) 10 0 • based on air shower simulation • full efficiency at E = 10 16 eV , for • fiducial area of ∼ 192,000 m 2 (orange area), both proton and iron primaries • trigger by 7/7 coincidence Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 9

Shower reconstruction Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 10

Shower reconstruction shower core: impact position of the shower axis at ground level = ⇒ Grande measurements arrival direction = ⇒ Grande measurements electron shower size N e : total number of electrons arriving at observation level = ⇒ Grande measurements muon shower size N µ : total number of muons arriving at observation level = ⇒ KASCADE measurements Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 10

Reconstruction procedure Time (ns) 4845 3 Charged (Grande) 100 5 4 2 10 2 1 11 µ (KASCADE) 0 10 8 7 6 9 µ ( + e) -100 µ 14 ) Lagutin ( ) 15 13 16 12 2 10 *m Y (Meters) -200 21 ρ 20 19 18 17 ( 22 10 -300 log 26 24 25 23 -400 27 1 -500 30 29 28 33 32 31 -600 37 36 35 34 -1 10 -700 -700 -600 -500 -400 -300 -200 -100 0 100 100 200 300 400 500 5554 X (Meters) Distance From Shower Axis [m] (x,y)=(-115 m, -223 m), ( θ , φ )=(11 ◦ , 338 ◦ ) log 10 ( N e ) = 7, log 10 N µ = 5 . 7 Core position and total number of charged particle ( N ch ) by fitting the lateral distribution with a modified NKG function: � r � s − 1 . 6 � s − 3 . 4 � 1 + r ρ ch = N ch · C ( s ) · r 0 = 30m · r 0 r 0 Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 11

Reconstruction procedure Time (ns) 4845 3 Charged (Grande) 100 5 4 2 10 2 1 11 µ (KASCADE) 0 10 8 7 6 9 µ ( + e) -100 µ 14 13 ) Lagutin ( ) 15 2 16 12 10 *m Y (Meters) -200 21 ρ 20 19 18 17 ( 22 10 -300 log 26 24 25 23 -400 27 1 -500 30 29 28 33 32 31 -600 37 35 36 34 -1 10 -700 100 200 300 400 500 -700 -600 -500 -400 -300 -200 -100 0 100 5554 X (Meters) Distance From Shower Axis [m] (x,y)=(-115 m, -223 m), ( θ , φ )=(11 ◦ , 338 ◦ ) log 10 ( N e ) = 7, log 10 N µ = 5 . 7 Total number of muons ( N µ ) by fitting the muon lateral distribution with a Lagutin function: � r � 2 � − 1 ρ µ = N µ · 0 . 28 � − 0 . 69 r � − 2 . 39 � r � � 1 + 1 + 320 2 · · · 320 320 10 · 320 Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 11

Reconstruction procedure Time (ns) 4845 3 Charged (Grande) 100 5 4 2 10 2 1 11 µ (KASCADE) 0 10 8 7 6 9 µ ( + e) -100 µ 14 ) Lagutin ( ) 15 13 16 12 2 10 *m Y (Meters) -200 21 ρ 20 19 18 17 ( 22 10 -300 log 26 24 25 23 -400 27 1 -500 30 29 28 33 32 31 -600 37 35 36 34 -1 10 -700 -700 -600 -500 -400 -300 -200 -100 0 100 100 200 300 400 500 5554 X (Meters) Distance From Shower Axis [m] (x,y)=(-115 m, -223 m), ( θ , φ )=(11 ◦ , 338 ◦ ) log 10 ( N e ) = 7, log 10 N µ = 5 . 7 Total number of electrons ( N e ) by subtracting the estimated muon content from the estimated charged particles content. Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 11

Reconstruction accuracies sim/data 30 true Core accuracy [m] proton e proton )/N 0.6 iron true 25 e iron -N rec 0.4 e (N 20 0.2 15 0 10 5 -0.2 0 5 5.5 6 6.5 7 7.5 8 8.5 5 5.5 6 6.5 7 7.5 8 8.5 true true log (N ) log (N ) 10 e 10 e • statistical uncertainty for N e at full efficiency around 25 % • systematics change from less than 5% at threshold to 15% • small dependence on primary particle type • core accuracy ≈ 6 m Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 12

3 11 22 21 20 19 18 17 16 15 14 13 12 KASCADE 24 Piccolo-Stations Grande-Stations x-coordinate฀ [ m ] y-coordinate฀ [ m ] 1 2 10 4 5 6 7 23 25 9 -700 100 0 -600 -500 -400 -300 -200 -100 100 0 -100 -200 -300 -400 -500 -600 Trigger-Cell฀17(18) 26 37 36 35 34 33 32 31 30 29 28 27 8 Reconstruction accuracies sim/data 12 0.15 10 0.1 8 Core accuracy 0.05 Size 6 ∆ 0 4 -0.05 2 -0.1 5.8 6 6.2 6.4 6.6 6.8 7 7.2 5.8 6 6.2 6.4 6.6 6.8 7 7.2 log (Size_KASCADE) log (Size_KASCADE) 10 10 • Trigger from Grande • Maximum density in the central station of the cluster overlapping with KASCADE • KASCADE reconstruction used as reference Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 12

Reconstruction accuracies sim/data true 2 Angular accuracy [deg] proton 0.6 µ proton )/N iron true µ iron 1.5 -N 0.4 rec µ (N 1 0.2 0.5 0 -0.2 0 5 5.5 6 6.5 7 7.5 8 8.5 4.5 5 5.5 6 6.5 7 true log (N ) true log (N ) 10 e µ 10 • statistical uncertainty for N µ at full efficiency around 20 % • bias of 10% to -5% in energy (muon) dependence • Angular accuracy < 0 . 5 ◦ up to 40 ◦ Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 13

Spectra SIZE (electron) SPECTRA ] -1 sr -12 ° 10 0-17 -1 ° s 17-24 -13 -2 10 ° [m 24-30 ° e -14 30-35 • 987 days of data taking 10 dI/dN ° 35-40 -15 10 • fiducial area of ≈ 0 . 2 km 2 -16 10 • ≈ 880 , 000 events -17 10 -18 10 -19 10 -20 10 -21 10 6 6.5 7 7.5 8 Log (N ) 10 e Fabiana Cossavella — Measurement of high energy cosmic rays above 10 PeV with KASCADE-Grande 14