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ALICE Data taking status

This document provides an outline of the ALICE experiment's data-taking status, highlighting key aspects such as its physics programme focused on studying quark-gluon plasma through heavy-ion collisions. It discusses recent achievements, including data collection goals and detector performance since 2009, with an emphasis on the 7 TeV data recorded. The report also covers particle identification capabilities and the necessity for baseline collision data. Updates on statistics and UK perspective are presented, detailing the contributions of RAL T1 to ALICE operations.

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ALICE Data taking status

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  1. ALICE Data taking status Lee Barnby L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  2. Outline • Introduction to ALICE • Experiment • Physics Programme • 2009 Data Taking • Detector performance • 7 TeV Data Taking • Latest news • A UK Perspective L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  3. ALICE Detector Cut away view showing central barrel inside L3 magnet (red) and muon tracker to the right. L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  4. Particle ID capabilities L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  5. ALICE Physics Programme • Primary ALICE purpose is to study quark-gluon plasma via heavy-ion collisions • Original plan for √s=5.5 TeV per nucleon collisions • Now 2.75 TeV for obvious reasons • 14/5.5 is A/Z for 208Pb • Few (4?) weeks of Pb+Pb running envisaged for late Autumn • ALICE goal is to collect 1 x 108 Pb+Pb events L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  6. QGP observables • Initial measurements to characterise system • Dynamics (expansion) through differential measures of hadron spectra, interferometry • Detailed measurements of properties • Jet quenching / modification in QCD medium • Direct photons • Quarkonia disassociation L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  7. ALICE Physics Programme: p+p • 1st question: Why? • LHC marks the first time that energy frontier for p+p and A+A is advancing at the same time • Eg RHIC provides 200 GeV collisions since 2000, previously achieved with SppS in 1980s • Therefore need baseline/reference data • OK, energy is higher but we prefer to interpolaterather than extrapolate • ALICE best suited to measure aspects of particle production (soft QCD) in p+p due to • Low field (0.5 T) thus low pT reach • Particle ID capabilities (hadronic and EM) • Low material budget (X/X0 ~ 7%) L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  8. ALICE Physics Programme: p+p • What? • Large minbias sample needed, nominally 109 events. We need sufficient stats to compare to 108 Pb+Pb events • Triggered samples to get better stats for some measurements • Electron trigger (heavy flavour) • High multiplicity p+p events • EMCAL (jet patch) • PHOS (photons) L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  9. 900 GeV Run Statistics • 1st collisions recorded 23/11, continued through 15/12 • ALICE recorded ~1 M events • 500k are ‘good’ events • 100k with field off for alignment • Also 40k at 2.36 TeV L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  10. 900 GeV Detector Performance TOF L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  11. 900 GeV Detector Performance TOF L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  12. L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  13. More 900 GeV plots Conversion photons - radial Conversion photons – x-y L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  14. 900 GeV more statistics • 430 GB raw data – we store 2 replicas (860 GB) • RAW data processed in 6 passes • Due to debugging of both detectors and code • Eg many updates to online conditions database • We store 3 copies of reconstruction output, currently 330 GB • Currently working to reduce this since it works out 115% of RAW • Eg have to stop saving reconstructed points for all events L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  15. 7 TeV Data Recorded Events recorded since 30 March Minbias event rates L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  16. 7 TeV p+p event in ALICE 7 TeV event L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  17. Another 7 TeV event L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  18. Yet another view L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  19. 7 TeV Outlook • Goal is to collect 1.0 x 109 minbias events • In first two weeks we collected 1.0 x 107 ie 1% • BUT this is utilising only one bunch crossing (BX) • A modest increase in the number of colliding bunches would allow ALICE to reach its goal • Continued running for rare triggers depends on limiting luminosity increase at P2 (ALICE) • TPC is limiting factor • Number of overlaid events from one BX • Past and future events during the drift time L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  20. UK Perspective – RAL T1 • ALICE production jobs run at RAL • Small fraction of integrated time but noticeable spikes ALICE Jobs in red L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  21. ALICE jobs on various timescales 1 year 3 months Lots of bursts of activity around Christmas holiday for raw data pass and recently for first pass at 7 TeV 1 month L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  22. L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  23. RAL T1 is important to ALICE 2 months L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  24. RAL T1 is important to ALICE 6 months L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

  25. Conclusion • We are taking data! • There is a lot more to come. • Pass 0 RAW reconstruction is completed within <24 hours • Pass 1(+) reconstruction at T1 sites • We are looking forward to Pb+Pb data later this year L.Barnby@bham.ac.uk - GridPP24 ALICE Data Taking Status

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