Study of cosmic ray shower front

and

time structure with ARGO-YBJ

A. Karen C. M., Lorenzo Perrone

NEW FEATURES

Larger statistics simulations

Allows comparison of simulation to data

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 (TS)

….from ICRC07

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

….from Kascade-Grande

Mean arrival time vs distance to shower core

Thickness vs distance to shower core

….from Kascade-Grande

Shower Reconstruction

Conical Fit

2E

PE

PE0

PP

2 )mcyl

cxtt(

EEEEEE sinsinm and cossinl

2PE

PE

PE0

PP

2 )c

Rmc

ylc

xtt(

Planar Fit

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

angle azimuth

angle zenith

E

E

This quantity is not a proper 2 . Indeed the measurement unit is ns2

Data Selection

•A successful reconstruction of the global shower observables is required

•Nhit > 20

•Reconstructed shower core coordinates are within the central carpet

• Sub-sample well reconstructed days 006-007 2009 (new data sample)

•Zenith angle less than 15°

Room left for more accurate event selection and quality cuts

Cuts used for ICRC07

Data

Mean of the time residuals (from Planar fit) profile as a function of the core distance

for different pad multiplicities

Shower curvature

Data

RMS of time residuals (from Conical fit) profile as a function of the core distance

for different pad different multiplicities

Shower thickness

statistical errors :errors on the mean

Larger statistics simulationsLarger statistics simulationsProduction of Corsika showers with Grid

- Corsika 6720- SIBYLL as high energy interaction model- FLUKA as low energy interaction model- dN/dE ~ E-1 300 GeV - 300 TeV- dN/d ~ sincos 0-45°

Used ce :pi.infn.itba.infn.itna.infn.it (only tested)ihep.ac.cn (only tested)cnaf.infn.it (heavyly used)

Used se : ts.infn.it

August 2008 - December 2008

~ 107 showers ~ 2.3 Tera

Generated Sample vs Energy-ZenithGenerated Sample vs Energy-Zenith

10 TeV

100 TeV

1 TeV

Processing through argog at CNAFProcessing through argog at CNAF

Generation area: 200× 200 m2

Each shower is used up to 10 times after re-sampling the core position

Overall simulated data set ~ 107 events

Argog processing time at CNAF: 100 CPU ~36 hours

Motivation: cross checking the dependence on hadronic models for the cross-section analysis and time front structure

100 TeV

10 TeV

Simulated Events vs Energy-AngleSimulated Events vs Energy-Angle

1 TeV

100 TeV

10 TeV

Usage of individual showers vs Energy-AngleUsage of individual showers vs Energy-Angle

1 TeV

Xmax from corsika fit to the longitudinal profiles included in the produced corsika binary files

SummarySummary

- The production on GRID relatively smooth (GRID malfunctioning limited to short time windows)

- Problems with the ``time bomb'' implemented in FLUKA. This periodically requires a new installation if the production takes longer than few months. (FLUKA doesn't distribute the source code. No way to by-pass this ``feature'' in a clean way). It makes almost impossible to reproduce a given shower generated in the ``past''

Common problem for several experiments. The community is considering to move to UrQMD . It behaves similarly as FLUKA at least in the TeV

range (Geisha is not manteined any longer)

Showers available at /storage/gpfs_argo1/Production/MC/Corsika6.7201/storage/gpfs_argo1/Production/MC/Corsika6.7201 2.3 Tb 2.3 Tb

Simulation

Mean of the time residuals (from Planar fit) profile as a function of the core distance

for pad different multiplicities

Shower curvature

Simulation

RMS of time residuals (from Conical fit) profile as a function of the core distance

at different multiplicities

Shower thickness

statistical errors :errors on the mean

Comparison data with MC

Zenith Angle distribution

Comparison data with MC

Mean of the time residuals (from Planar fit) profile: good agreement between data and simulation

Comparison data with MC

Mean of the time residuals (from Planar fit) profile: good agreement between data and simulation

Comparison data with MC

Mean of the time residuals (from Planar fit) profile: sensible differences between data and simulation for lower pad multiplicities

Comparison data with MC

RMS of time residuals (from Conical fit) profile: to be investigated

nhit 200-400

Moderate correlation of conicity with Xmax for protons

What else can we learn of shower phenomenology…..

New fit with alpha free

true value

Observable

What’s more….