Time structure of the Extensive Air Shower Time structure of the Extensive Air Shower front with the ARGO-YBJ experiment front with the ARGO-YBJ experiment 1 - INFN-CNAF, Bologna, Italy 2 - Università del Salento and INFN Lecce, Italy 3 - INFN Lecce, Italy A.K Calabrese Melcarne A.K Calabrese Melcarne 1 , L. Perrone , L. Perrone 2,3 2,3 , A. Surdo , A. Surdo 3 for the ARGO-YBJ Collaboration for the ARGO-YBJ Collaboration XXXI International Cosmic Ray XXXI International Cosmic Ray Conference, ICRC 2009 Lodz, Conference, ICRC 2009 Lodz, Poland, July 7-15, 2009 Poland, July 7-15, 2009
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Time structure of the Extensive Air Shower front with the ARGO-YBJ experiment 1 - INFN-CNAF, Bologna, Italy 2 - Università del Salento and INFN Lecce,
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Time structure of the Extensive Air Shower Time structure of the Extensive Air Shower
front with the ARGO-YBJ experimentfront with the ARGO-YBJ experiment
1 - INFN-CNAF, Bologna, Italy
2 - Università del Salento and INFN Lecce, Italy
3 - INFN Lecce, Italy
A.K Calabrese MelcarneA.K Calabrese Melcarne11, L. Perrone, L. Perrone2,32,3, A. Surdo, A. Surdo33
for the ARGO-YBJ Collaborationfor the ARGO-YBJ Collaboration
XXXI International Cosmic Ray Conference, XXXI International Cosmic Ray Conference, ICRC 2009 Lodz, Poland, July 7-15, 2009ICRC 2009 Lodz, Poland, July 7-15, 2009
High Altitude Cosmic Ray Laboratory @ YangBaJing,Tibet, ChinaSite Altitude: 4,300 m a.s.l. , ~ 600 g/cm2
The ARGO-YBJ experimentThe ARGO-YBJ experiment
ARGO-YBJ
Cosmic ray physics: spectrum and composition above few TeV (HE 562, 407, 411)
study of the shower space-time structure (HE 424, 682)
p-Air cross section measurement (HE 319)
anti-p / p ratio at TeV energies (HE 431)
VHE -Ray Astronomy: search for point-like (and diffuse) galactic and extra-galactic sources at few hundreds GeV energy threshold (OG 399, 398)
Search for GRB’s:
full GeV / TeV energy range (OG 391, 567, 683)
The Physics CaseThe Physics Case
Strip = space pixel
Pad = time pixel
Time resolution ~1.8 ns
10 Pads (56 x 62 cm2)for each RPC
8 Strips (6.5 x 62 cm2) for each Pad
78 m
111 m
99 m
74 m
(43 m2)1 CLUSTER = 12 RPC
RPC
analog charge read-out in progressdynamical range up to ~ 104 TeV (HE 1388)
Num
ber
of
Fire
d S
trip
s
Full coverage, high time and space resolution provide a
detailed view of shower front
Data SelectionData Selection
- Quality cut on S2
Reconstruction
Time sequence and position of hit pads used to reconstruct the CR
arrival direction and core position
- Using a plane (α=0)
- Using a conical correction (α0)
- Core reconstructed within the central carpet
contamination of mis-reconstructed events less than 10% at low multiplicity, rapidly decreasing at higher multiplicity
Average Curvature:Average Curvature: the mean of time residuals Δt(R) with respect to a
planar fit
Time profileTime profile
- larger than 10 ns for particles landing further than 50 m from the core.
- no significant dependence on pad multiplicity observed.
3.5 108 events
zenith < 15°
Shower ThicknessShower Thickness
Average Thickness: the RMS of time residuals σ(R) with respect to a
conical fit
- about 8 ns at 40 m from the core (intermediate multiplicity).
- thinner for increasing multiplicities.
3.5 108 events
zenith < 15°
Data vs SimulationsData vs Simulations
Very good agreement at the level of time profile
curvaturecurvature
Shower thickness systematically underestimated (about 1.5 ns, likely due to the missing contribution of heavier nuclei not yet included in simulation)
Shower generatorShower generator
Corsika 6.720 with
SIBYLL+FLUKA as hadronic interaction models at high and low energies