OBSERVATORY The AMIGA infill detector of the Pierre Auger Observatory: performance and first data Ioana C. Mariş (for the Pierre Auger Collaboration 2 ) Laboratoire de Physique Nucléaire et des Hautes Energies, Paris, France 2 Observatorio Pierre Auger, Malargüe, Argentina (Full author list: http://www.auger.org/archive/authors 20 05.html) AMIGA (F.Sanchez, talk 0742) muon counters (B. Wundheiler, poster 034) infill surface detector (this talk)
AMIGA (Auger Muons and Infill for the Ground Array) 750 m spacing between detectors, construction began in 2008 all 6 stations deployed (53 completely equipped) data analysis based on methods developed for the regular array y [km] 22 Infill array performance 20 8 6 4 2-32 -30-28 -26-24 -22 x [km] trigger rate: (55 ± 6) events/day/hexagon good quality events (T5): currently: (28 ± 3) events/day/hexagon (390±70) T5 events/day acceptance (08/2008 03/20): (26±)km 2 sr yr Ioana C. Mariş (Pierre Auger Collaboration) /
Trigger efficiency From simulations From data 3ToT Efficiency 0.8 0.6 0.4 p infill array Fe infill array / ndof χ 2 0 0.2 p regular array Fe regular array 0 7 7.5 8 8.5 9 log (E/eV) 3 fold trigger, Time-over-Threshold, lateral trigger probabilities parametrization dependency on zenith angle for < 0% 0% at 3 7 ev for zenith < 55 Pierre Auger Collaboration, submitted to Astropart. Phys., 20) 20 30 40 0 [VEM] S 35 test the hypothesis of a flat distribution in cos 2 θ above a shower size (S 35) value 0% at S 35 20VEM ( 3 7 ev) Ioana C. Mariş (Pierre Auger Collaboration) 2 /
Angular resolution Angular resolution o 3 2.5 2.5 3 stations 4 stations 5 stations 6 or more stations 0.5 0 0 20 30 40 50 θ o accidental muons rejection and spherical shower-front assumption adjusted time variance model (flat χ 2 distribution) angular resolution given by the fit uncertainties better than for events with more than 5 stations (E 3 7 ev) Ioana C. Mariş (Pierre Auger Collaboration) 3 /
Lateral distribution function (LDF) Signal [VEM] 0 NKG χ 2 /Ndf: 7.8/ 8 candidates not triggered 400 600 800 00 200 400 600 distance to axis [m] Modified Nishimura-Kamata-Greisen (NKG) S(r) = S(r opt) ( ) β r r +700m r opt r opt +700m Log-log parabola (LLP), to infer systematics Parameters β β,γ determine the shape of LDF, parametrized as a function of θ,s(r opt) r opt distance where the shower-to-shower fluctuations and the statistical uncertainties are minimal S(r opt) used to infer the energy estimator ( r S(r) = S(r opt) r opt ) β+2γ log( r r opt ) NKG sec(θ) Ioana C. Mariş (Pierre Auger Collaboration) 4 /
Optimum distance (r opt ) Two types of events: with a saturated signal and without saturated signals entries 30000 25000 no saturation saturation 50 obtained from varying the LDF shape parameters (D. Newton et al., 20000 5000 Astropart. Phys., 2007, 26:44) no saturation: r opt = (442±40)m 000 5000 saturation: r opt = (640±52)m 0 300 400 500 600 700 800 r opt [m] optimum distance: 450 m Ioana C. Mariş (Pierre Auger Collaboration) 5 /
Signal uncertainties at r opt = 450m σ S(450) /S(450)[%] 30 20 0 - -20 total systematic (sh2sh + LDF) r opt, no saturation statistical, no saturation -30..2.3.4.5.6.7.8.9 2 log (S(450)/VEM) VEM 0 VEM 200 VEM r opt, no saturation [%] ±3 ±0. ±0. statistical, no saturation [%] ±9 ±5 ±3 Total: 22% at VEM, 4% at >40VEM Ioana C. Mariş (Pierre Auger Collaboration) 6 /
Attenuation in the atmosphere and S 35 S(450) [VEM] θ attenuation correction obtained empirically from data (constant intensity hypothesis) reference angle: 35 (median of the angular distribution of events) Ioana C. Mariş (Pierre Auger Collaboration) 7 /
Attenuation in the atmosphere and S 35 S 35 [VEM] 2 3 4 5 6 20 30 0 200 00 2000 dn/ds 35 S 35 4 3 0 < θ < 28 28 < θ < 4 4 < θ < 55 2-0 0.5.5 2 2.5 3 3.5 log (S /VEM) 35 S 35, independent of zenith angle, used as energy estimator Ioana C. Mariş (Pierre Auger Collaboration) 8 /
Energy calibration with golden hybrid events (FD+SD) [VEM] S 35 200 0 Energy calibration event selection to assure an unbiased energy calibration strong quality cuts and fiducial field of view cuts 44 events with 3 7 ev < E FD < 2 8 ev σ E /E [%] 20 0.2 0.3 0.4 2 3 E FD [EeV] 5 0.3 2 3 4 5 6 7 8 E [EeV] E SD = (2.7±2.5) 5 ev S (.0±0.05) 35 Energy uncertainties systematic (fit): 6% at 0.3EeV, 3% at 8EeV statistical (S 35): 6% at 0.3EeV, 4% at 8EeV FD energy systematic: 22% (R. Pesce, poster 60) Ioana C. Mariş (Pierre Auger Collaboration) 9 /
Preliminary energy spectrum ev - )) sr - s - -2 ( J /(m log 4-28 -29-30 -3-32 -33-34 7 3396 2083 208 8 686 396 σ (E ) SD σ (E ) FD 8 2 Preliminary 232 30 87 4 34 6 9 9 2 Auger Infill (preliminary) E[eV] 7.6 7.8 8 8.2 8.4 8.6 8.8 9 9.2 9.4 9.6 log (E/eV) 8 7 9 extends the energy range down to 3 7 ev (No resolution correction!) very good agreement with the combined spectrum (F.Salamida, talk 0893) slope for E < 3 8 ev: 3.33±0.03(stat)±0.(sys) Ioana C. Mariş (Pierre Auger Collaboration) / 3 2
Preliminary energy spectrum ) - 2.60 J/(A E 3 6 5 4 3 2 0-7 8 8 2 Preliminary 9 9 2 20 Auger Infill (preliminary) Auger E[eV] 20 2 7.5 8 8.5 9 9.5 20 20.5 log (E/eV) extends the energy range down to 3 7 ev (No resolution correction!) very good agreement with the combined spectrum (F.Salamida, talk 0893) slope for E < 3 8 ev: 3.33±0.03(stat)±0.(sys) Ioana C. Mariş (Pierre Auger Collaboration) /
Conclusions and outlook Current status Outlook 53 infill stations with a spacing of 750m equipped (6 deployed) trigger efficiency 0% at 3 7 ev (zenith< 55 ) angular resolution better than for events with more than 6 stations preliminary energy spectrum in very good agreement with the Auger energy spectrum energy calibration: HEAT increase statistics at low energies (H.J. Mathes, talk 076) energy spectrum: correct for energy resolution effects deploy stations with a spacing less than 750m Ioana C. Mariş (Pierre Auger Collaboration) /