1. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania1 THE NA57 CERN EXPERIMENT FOCUS ON

2. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania2 Physics Department, University of Athens, Greece; Dipartimento IA di Fisica dell'Università e del Politecnico di Bari and INFN, Bari, Italy; Fysisk Institutt, Universitetet i Bergen, Bergen, Norway ; Høgskolen i Bergen, Bergen, Norway; University of Birmingham, Birmingham, UK; Comenius University, Bratislava, Slovakia; University of Catania and INFN, Catania, Italy; CERN, European Laboratory for Particle Physics, Geneva, Switzerland; Institute of Experimental Physics Slovak Academy of Science, Kosice, Slovakia; P.J. Safárik University, Kosice, Slovakia; Fysisk institutt, Universitetet i Oslo, Oslo, Norway; University of Padua and INFN, Padua, Italy; Collège de France, Paris, France; Institute of Physics, Prague, Czech Republic; University “La Sapienza'' and INFN, Rome, Italy; Dipartimento di Scienze Fisiche “E.R. Caianiello'' dell'Università and INFN, Salerno, Italy; State University of St. Petersburg, St. Petersburg, Russia; IReS/ULP, Strasbourg, France; Utrecht University and NIKHEF, Utrecht, The Netherlands. THE NA57 COLLABORATION

3. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania3 PLAN Introduction NA57 in Heavy Ion Physics Experimental layout Data sets and analysis status Main steps of data processing Examples of computing Some physics results Summary

4. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania4 INTRODUCTION 1. NA57 – a dedicated CERN experiment for studying strangeness production in Pb-Pb collisions 2. NA57 – continuator of WA97 but: - larger centrality range - data at 40 and 158 GeV/c => energy dependence study 3. Strangeness Enhancement – one of the pillars of evidence for existence of QGP ( CERN announcement of the observation of a NEW STATE of MATTER U.Heinz and M.Jacob, nucl-th/0002042)

5. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania5 Early prediction of Rafelski and Műller abundant production of strange quarks in QGP: _ - gluons are flavor blind (gg => equally probable) - in baryon rich environment Pauli Blocking favors strange quarks production (J.Rafelski and B Műller Phys. Rev. Lett. 48 (1982) 1066) Physics Motivation Strange particles – a detector and diagnosis tool of QGP The only possible way to study QGP in laboratory  high energy HEAVY ION COLLISIONs

6. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania6

7. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania7 APPARATUS (Pb-Pb setup) 1.4 T Target: 1% Pb Scintillator Petals: centrality trigger MSD: multiplicity silicon detector Tracking device: silicon pixel planes (5 x 5 cm 2 cross section) Lever arm: double side  strips 5 cm

8. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania8

9. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania9 SystemBeam energySample sizeData taking year Pb-Pb160 A GeV230+230 x 10 6 evts1998+2000 Pb-Pb40 A GeV240 x 10 6 evts1999 p-Be*40 A GeV60+110 x 10 6 evts1999+2001 DATA SAMPLES AND ANALYSIS STATUS  Both 160 and 40 A GeV Pb-Pb samples analyzed  Enhancement measurements at 160 A GeV completed  Analysis of 40 A GeV p-Be sample ongoing: - event reconstruction fully completed - preliminary signal extraction shows good data quality - correction procedure started  enhancements at 40 GeV coming! IN CASTOR(3-4 Tb)

10. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania10 MAIN ANALYSIS STEPS ALIGNMENT and CALIBRATION (  DATA BASE) GEOMETRICAL RECONSTRUCTION (ORHION  tracks) V0 FINDING (still ORHION)  Λ and K0 candidates (DSTs) CASCADE RECONSTRUCTION (V0s + tracks) : CASNA57  Gold-Plated ntuples (CLEAN) SIGNALS EXTRACTION (selection cuts) EVENT-BY-EVENT WEIGHTING PROCEDURE (or de-convolution) M t – INVERSE SLOPE FITTING ( Max-Log-Likelihood) EXTRAPOLATION TO FULL Pt AND ONE UNIT OF rapidity NORMALIZATION (beam flux,target) YIELDS MULTIPLICITY RECONSTRUCTION  CENTRALITY

11. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania11 EXAMPLE OF ORHION PROCESSING (Pb-Pb 2000 Background) Background data – representative sample of all data (each 200 th event – 5%), 24 files Parallel running at CERN (Linux Batch)  overall 1 day and 1 night human time About 3-4 NCU hours per file 1440-1920 NCU hours of full 2000 data ( 230 Mevents at 158 GeV) ORHION processing (distributed between all labs !!) Slightly less for Pb-Pb at 40 GeV/c, then still less for p-Be (one week)

12. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania12 WEIGHTING PROCEDURE A weight is associated with each selected particle to correct for acceptance and efficiency ( typically few thousands) Weights are calculated by Monte Carlo: - generated hyperons are traced through a GEANT simulation of the NA57 apparatus - track hits are merged with true events - resulting events are processed through the reconstruction and analysis chain - reconstructed hyperons are counted Simulation thoroughly checked against real data

13. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania13 MC vs REAL DATA 30 cm 5 cm    byby byby

14. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania14 WEIGHT STATISTICS at 158 GeV/c Particle weighted collected 3340 2350 2718 6444 936 432 192 x400 x400 x50 x1 x1 x1 x1 Most expensive cascade particles:1-3 NCU hours on LXPLUS, 10000 Λs and 10000 K0s  about 40K NCU hours, alias 1 working month (estimate) 2001 p-Be data weighting ( 4000 Λs only) just in one week at CERN

15. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania15 YIELDS MEASUREMENTS ONE UNIT OF RAPIDITY FULL Pt RANGE

16. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania16 STRANGENESS ENHANCEMENT def. Enhancement E : Needs p-Be measurement !!! YIELD (WA97 at 160 GeV/c, NA57 at 40 GeV/c)

17. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania17 MOST CENTRAL ENHANCEMENTS Most central 5% of Pb-Pb collisions at 158 GeV/c Systematic error INCREASE WITH STRANGENESS CONTENT !

18. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania18 FROM SPS TO RHIC Centrality ranges: 5% for ,  10% for ,  STAR data: C. Adler et al., Phys.Rev.Lett. 89 (2002) 092301 J. Castillo et al., Nucl.Phys. A715 (2003), 518c C. Suire et al., Nucl.Phys. A715 (2003), 470c

19. 4 DECEMBER 2003 Adam Jacholkowski NA57/CERN&Catania19 SUMMARY and CONCLUSIONS  NA57 HAS REACHED ITS MAIN PHYSICS GOALS,  ANALYSIS OF p-Be DATA AT 40 GeV/c DATA NEAR COMPLETION  STRANGENESS ENHANCEMENT (40 GeV/c) COMING SOON (QUARK MATTER CONFERENCE January 2004),  HEAVY DATA PROCESSING (done mainly at CERN) IS OVER  (no reprocessing foreseen, but…),  INCREASE OF WEIGHTED PARTICLES STATISTICS IN 2004  estimated 20-40K NCU hours,  INCREASE OF /afs/cern.ch/exp/na57/ SPACE WELCOME (from 5 actually up to 7 Gbytes for example)