Study of cosmic ray shower front

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Study of cosmic ray shower front and time
structure with ARGO-YBJ
A. Karen C. M., Lorenzo Perrone
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Definition of observables
Shower axis - trajectory of the incident primary
cosmic ray particle towards the obervation
level Shower plane plane perpendicular to the
shower axis R radial distance from the shower
core
The shower disk refers to the curved disk of
secondary shower particles towards earth
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Definition of observables

1. The curvature of the shower front as the mean of
   time residuals with respect to a planar fit (Td)
2. The thickness of the shower front as the root
   mean square (RMS) of time residuals with respect
   to a conical fit

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Projection of R on the shower plane
? zenith and ? azimuth angles of the shower
Rotation of ? in the xy plane
Projection
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Shower Reconstruction
In EAS experiments for an event E the time tEP
can be measured on each fired detector unit P,
whose position (xP,yP) is well known
Primary direction cosines
Planar Fit
Conical Fit
This quantity is not a proper c2 . Indeed the
measurement unit is ns2
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Data Selection
A successful reconstruction of the global shower
observables is required Nhit gt 20 Reconstructed
shower core coordinates are within the central
carpet
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Data
Shower curvature
Mean of the time residuals (from Planar fit)
profile as a function of the core distance
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Data
Shower curvature
Mean of the time residuals (from Planar fit)
profile as a function of the core distance at
different multiplicities
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Data
Shower curvature
Mean of the time residuals (from Planar fit)
profile as a function of the core distance at
different multiplicities
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Data
Shower thickness
RMS of time residuals (from Conical fit) profile
as a function of the core distance
statistical errors errors on the mean
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Simulation
Protons (E-1) Corsika 6720 SIBYLLFluka. ?
showers
ARGOG - area of generation 200x200 m2 130
cluster
                       Theta
0-15E(TeV)          0.3 -1 1-3
3-10        10-30   30-100 N_argog
1800000 840000 210000  270000     
285000                     
   Theta 15-30E(TeV)          0.3 -1
1-3 3-10        10-30  
30-100 N_argog 2700000 600000
210000  210000      135000                    
     Theta 30-45E(TeV) 
        0.3 -1 1-3 3-10  
     10-30   30-100 N_argog 2700000
600000 210000  210000      135000
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Xmax
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H1st
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Comparison data vs MC
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Simulation
Shower curvature
Mean of the time residuals (from Planar fit)
profile as a function of the core distance
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Simulation
Shower curvature
Mean of the time residuals (from Planar fit)
profile as a function of the core distance
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Simulation
Shower thickness
RMS of time residuals (from Conical fit) profile
as a function of the core distance
statistical errors errors on the mean
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Photon Shower
Proton Shower
The study of the shower space-time patterns
can be useful to have higher discrimination
power and then a larger sensitivity
We can use the indicators density lateral
profile, alpha and RMS from the conical fit and
the deviation of time residuals from planar fit
at different cut of multiplicity and angular
range to have information about the age
parameter s ?
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Question Do we expect different structure of the
shower front for protons and photons?
Ad-hoc simulation 5000 proton-induced showers
and 3000 photon-induced showers 3-10 TeV and
0-15 - Corsika 6.501 Fluka 2005 QGSJET2
Preliminary
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Correlazione di alpha con Xmax?
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