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UNIVERSITA’ degli STUDI di LECCEFacoltà di Scienze MM.FF.NNDottorato di Ricerca in Fisica

Presentazione attività di ricercaDottoranda : Anna Karen Calabrese Melcarne

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High Altitude Cosmic RayLaboratory at YangBaJing

Longitude 90° 31’ 50” EastLatitude 30° 06’ 38” North

4300 m above the sea level

Astrophysical Radiation Ground-based Observatory

-ray astronomy Gamma Ray Burst physics Cosmic Ray physics Sun and Eliosphere physics

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Detector layout

10 Pads = 1 RPC (2.80 1.25 m2)

78 m

111 m

99 m

74 m

12 RPC = 1 cluster ( 5.7 7.6 m2 ) 8 Strips = 1 Pad

(56 62 cm2)

104 clusters

in DAQ

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Experiment Hall

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Main detector features and performance

pointing resolution ( < 1°)

detailed space-time image of the shower front

detection of small shower (low threshold energy)

large aperture and high “duty-cycle”

continuous monitoring of the sky (-10°< <70°)

Resistive Plate Chambers (RPC) as active elements

Space information from Strip ( resolution 6.5 62 cm2 )

Time information from 8-strip Pad ( resolution 1 ns)

Large area ( 10,000 m2 ) and full coverage ( 6,000 m2 )

High altitude (4300 m a.s.l.)

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The detector provides a detailed space-time picture of the shower

Space-time view of a shower

with 104 cluster in DAQ

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A.Check of data quality looking at quantities reconstructed with Medea++ code

• distribution of zenith angle

• distribution of azimuth angle

• distribution of director cosines

• 2 of the planar fit

Activity during the first year of PHD

2fitpad

HITtime

2

HIT

2 )t(tN

1δ

N

1χ

It is not a true 2 (ns2 as measure unit)

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January 8-9, 2005

nCl nHit

nHits_pl Chi2_pl

2 is strongly sensitive to data quality

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B. Test of the algorithms for the direction reconstruction

C. Definition of the procedure to calibrate the pad-times

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Calibration method

TDCP

TDCPEPP

TDCPEPE

PPP

TDCP

PPPP

TDCPEE

PE

PE

TDCPE

FITPEPE

tCttt

c

ym

c

xl

tCc

ym

c

xl

tCc

ym

c

xltt

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2

1

residual

residual correction

(repeated twice)

systematic correction

P pad index

E event index

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Assumption : The shower flux has to be uniform in azimuth

Azimuth distribution is flat

The average values of the direction cosines are null

Gaussian fit in a range [-10, +10] ns around the peak

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Corrections for data collected with 42 cluster in DAQ

Azimuth distribution before and after calibration

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Time profile versus distance from center of the carpet

before and after calibration

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An analogous procedure has been implemented by Chinese colleagues of the ARGO collaboration

Difference between

Italian and Chinese

calibrations

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January and February 2006 - STAY in the Institute of High Energy Physics (Chinese

Academy of Science) at Beijing

Many checks in order to understand the differences between Chinese and Italian method

Effect of the cut Nhit > 500

Peak, medium and median values of the TDC distribution

Medea++ and Chinese stand-alone program

Different samples

Actually, the two methods resulted analitically equal

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Italian residuals after calibration

Chinese residuals after calibration

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Italian-Chinese calibration difference(after the addition of the Chinese residuals to the Chinese calibration)

The difference was in the repetition of the procedure

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Constitution of a unique working group for the time-calibration

Now we are working together for

a unique calibration of 104 clusters

Future schedule of time-calibration group

Monitor of the TDC peak values in order to check the stability of the calibration

Hardware calibration

New off-line calibration taking into account the conicity of the showers

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Only MC MC + delay

After 1st correction After 2nd correction

SIMULATIONS with ARGOG

Simulation to check the calibration procedure

20 iterations of 50x103 Corsika proton-induced showers :

106 showers 0.81x106 “triggered” eventson the generation area (100x100 m2)

Zenith range: < 15°

Energy samples: 3 - 10 TeV 10 - 30 TeV 30 - 100 TeV

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Circular symmetry of MC Residual distribution

Residuals vs clusterRMS 0.2 ns

Residuals vs pad position

From planar fitEffect of conical shape

of the shower front

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Simulation

6x106 Corsika proton-induced showers ( = -2.7):

on the generation area (200x200 m2) 1.062 x106 “triggered” events

Zenith range: < 60°

Energy range: 100 GeV – 100 TeV

What effects of the systematicson the direction-reconstruction ?

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Calibration does not introduce systematics in the reconstructed direction either we use planar fit or we use conical fit

figura

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Geomagnetic field on the secondaries

In the geomagnetic field, the secondary charged particles generated in EAS are rotated by Lorentz force, with its lateral distribution stretched.

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2

)(cos2

sin

eE

Bhd

Average shift in the shower plane for a secondary electron

zenithprimary

electron ofenergy average

field cgeomagneti

rajectoryelectron t theofheight verticalaverage

eE

B

h

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2)(cos

sin

g

YBJ - the geomagnetic effect is stronger for showers from North than for showers from South

This difference is more evident for larger zenith angles

H

HH φ)(χ

cossinsincoscosacos

azimuth angle - 0 geomagnetic North

geomagnetic declination

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New shower simulation

Protons and photons

1000 showers

Θ = 20º 0º <Φ< 360º

E = 3 TeV

Geomagnetic field ON

Geomagnetic field OFF

Corsika ARGOG

691 “triggered” protons

999 “triggered” photons

generation on the carpet center

“trigger” = at least 20 fired pads

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protons

photons

Reconstructed core offset

Geomagnetic field OFF/ON

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PRELIMINARY

Azimuth distribution is fitted with a two-harmonic function

)]2cos()cos(1[ IIIIII AAKd

dN

N events from North (161.5º < Φ < 341.5º )

N events from South (161.5º >Φ and Φ >341.5º)

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NS

NS

SIMULATION

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Developments

To complete the started up simulations to understand deeply the azimuthal asymmetry and to distinguish geometric, geomagnetic and calibration effects

To inspect deeply the shower features and phenomenology

To check the compatibility of the shower arrival times with the random cosmic ray flux

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Note interne e pubblicazioni

• P. Bernardini, A.K. Calabrese Melcarne, C. Pino “Time calibration of six clusters”, ARGO-YBJ Internal note 2004-002

• P. Bernardini, A.K. Calabrese Melcarne, H.H. He and C. Pino “Time-Calibration of the ARGO-YBJ detector (42 Clusters)'‘, ARGO-YBJ Internal note 2005-002

• P. Bernardini et al. “Time Calibration of the ARGO-YBJ experiment'‘, Proceedings of 29th International Cosmic Ray Conference (Pune, India) 5 (2005) 147

• A.K. Calabrese Melcarne “Time-Calibration of the ARGO-YBJ detector”, Proceedings of 3rd Workshop on Science with the New Generation of High Energy Gamma-ray Experiments (Cividale del Friuli, 2005)

• P. Bernardini, A.K. Calabrese Melcarne, I. De Mitri and G. Mancarella “Study of the arrival times of cosmic rays”, ARGO-YBJ Internal note 2006-003

G. Aielli et al. (ARGO-YBJ Collaboration) “Performance of RPCs used for cosmic ray experiments'', accepted for publication on Nuclear Instruments and Methods A

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Partecipazione conferenze e scuole

Neutrino Oscillation Workshop, (Otranto, 2004)

Third Workshop on Science with the New Generation of High Energy Gamma-ray Experiments (Cividale del Friuli, May 30 - June 1, 2005)

Scuola Internazionale di Dottorato, ISAPP 2005 (Belgirate 30 Giugno - 9 Luglio 2005)