1. 1 UNIVERSITA’ degli STUDI di LECCE Facoltà di Scienze MM.FF.NN Dottorato di Ricerca in Fisica Presentazione attività di ricerca Dottoranda : Anna Karen Calabrese Melcarne

2. 2 High Altitude Cosmic Ray Laboratory at YangBaJing Longitude 90° 31’ 50” East Latitude 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

3. 3 Detector layout 10 Pads = 1 RPC (2.80  1.25 m 2 ) 78 m 111 m 99 m74 m 12 RPC = 1 cluster ( 5.7  7.6 m 2 ) 8 Strips = 1 Pad (56  62 cm 2 ) 104 clusters in DAQ

4. 4 Experiment Hall

5. 5 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 cm 2 ) Time information from 8-strip Pad ( resolution  1 ns) Large area (  10,000 m 2 ) and full coverage (  6,000 m 2 ) High altitude (4300 m a.s.l.)

6. 6 The detector provides a detailed space-time picture of the shower Space-time view of a shower with 104 cluster in DAQ

7. 7 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 It is not a true  2 (ns 2 as measure unit)

8. 8 January 8-9, 2005 nClnHit nHits_pl Chi2_pl  2 is strongly sensitive to data quality

9. 9 B. Test of the algorithms for the direction reconstruction C. Definition of the procedure to calibrate the pad-times

10. 10 Calibration method residual residual correction (repeated twice) systematic correction P pad index E event index

11. 11 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

12. 12 Corrections for data collected with 42 cluster in DAQ Azimuth distribution before and after calibration

13. 13 Time profile versus distance from center of the carpet before and after calibration

14. 14 An analogous procedure has been implemented by Chinese colleagues of the ARGO collaboration Difference between Italian and Chinese calibrations

15. 15 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 N hit > 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

16. 16 Italian residuals after calibration Chinese residuals after calibration

17. 17 Italian-Chinese calibration difference (after the addition of the Chinese residuals to the Chinese calibration) The difference was in the repetition of the procedure

18. 18 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

19. 19 Only MC MC + delay After 1st correction After 2nd correction SIMULATIONS with ARGOG Simulation to check the calibration procedure 20 iterations of 50x10 3 Corsika proton-induced showers : 10 6 showers  0.81x10 6 “triggered” events on the generation area (100x100 m 2 ) Zenith range:  < 15° Energy samples: 3 - 10 TeV 10 - 30 TeV 30 - 100 TeV

20. 20 Circular symmetry of MC Residual distribution Residuals vs cluster RMS 0.2 ns Residuals vs pad position From planar fit Effect of conical shape of the shower front

21. 21 Simulation 6x10 6 Corsika proton-induced showers (  = -2.7): on the generation area (200x200 m 2 )  1.062 x10 6 “triggered” events Zenith range:  < 60° Energy range: 100 GeV – 100 TeV What effects of the systematics on the direction-reconstruction ?

22. 22 Calibration does not introduce systematics in the reconstructed direction either we use planar fit or we use conical fit figura

23. 23 Geomagnetic effect East-West asymmetry Primary cosmic rays arrive at the near vicinity of the Earth isotropically, having been randomized by interstellar magnetic field. Actually low energy cosmic rays from the east are suppressed compared to those from the west, because the geomagnetic field effectively shadows certain trajectories, which are therefore forbidden.

24. 24 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. Average shift in the shower plane for a secondary electron

25. 25 YBJ - the geomagnetic effect is stronger for showers from North than for showers from South This difference is more evident for larger zenith angles azimuth angle - geomagnetic North geomagnetic declination

26. 26 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

27. 27 protons photons Reconstructed core offset Geomagnetic field OFF/ON

28. 28 PRELIMINARY Azimuth distribution is fitted with a two-harmonic function N events from North (161.5 º < Φ < 341.5 º ) N events from South (161.5 º >Φ and Φ >341.5 º ) SIMULATION

29. 29 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

30. 30 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

31. 31 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)