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Status of ZEUS

Status of ZEUS. Rainer Mankel DESY Hamburg --for the ZEUS collaboration-- PRC Public Session 26-May-2005. Outline. Data-taking & detector status Data processing & simulation Physics highlights heavy flavours QCD fits &  s determination diffractive final states. HERA-II Luminosity.

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Status of ZEUS

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  1. Status of ZEUS Rainer Mankel DESY Hamburg --for the ZEUS collaboration-- PRC Public Session 26-May-2005

  2. Outline • Data-taking & detector status • Data processing & simulation • Physics highlights • heavy flavours • QCD fits & s determination • diffractive final states R. Mankel: Status of ZEUS

  3. HERA-II Luminosity • HERA-II finally at cruising speed • almost reached integrated luminosity of HERA-I • Instantaneous luminosity in e–p running surpassed e+p R. Mankel: Status of ZEUS

  4. ZEUS Data-Taking [nb-1] • Series of daily gated luminosity records (1.2 pb-1) • Remarkable improvement in ZEUS data-taking efficiency • in general above 80% • MVD on 95% of time • 62 pb-1 of new e–p data on tape R. Mankel: Status of ZEUS

  5. Detector Status • Calorimeter: stable with low number of bad channels • MVD: signal & noise are stable • CTD: low trip rate. No signs of premature ageing • Increased use of Global Track Trigger at global SLT level • Efficiency improvements: • comprehensive monitoring via web statistics pages • pre-luminosity test trigger runs • complete rebuild of TLT farm hardware & software • Detector is in good shape R. Mankel: Status of ZEUS

  6. Straw Tube Tracker (STT) add insulation & cooling FDET/STT • STT presently off because of insufficient cooling, which otherwise interferes with stable operation of solenoid • Preparing repair that does not break beam vacuum • additional cooling & insulation • Decision within next weeks GO magnet R. Mankel: Status of ZEUS

  7. Data Processing • Central reconstruction & analysis facility for ZEUS • Presently farm of 150 Intel Xeon processors • >600 000 analysis batch jobs in one year • Up to 22000 jobs per week • Average data throughput 10 TB/day R. Mankel: Status of ZEUS

  8. ZEUS Reconstruction Performance • Daily production (#events) during reprocessing of 2004 e+ data: • Peak production: 3 M events/day • at HERA-I times, peak rate was 500 k events/day • reconstruction of HERA-II events is 6x more CPU-intensive than with HERA-I • Sizable increase in processing performance • Fast turnaround Events reconstructed per day 3 M events/day 3 M 2 M 1 M 17-Oct 9-Nov Date R. Mankel: Status of ZEUS

  9. Gap HERA-II MC Production • Assessment of Monte Carlo simulation needs in 2003 revealed opening of a huge gap • Reasons: • HERA-II luminosity • additional demand from new detector components • considerable increase in simulation demand during HERA-II • Solution: Computing Grid Technology R. Mankel: Status of ZEUS

  10. WN WN WN WN WN WN WN WN WN WN WN WN SE SE CE CE GRID GATEWAY SE dCache MSS Solution: ZEUS Grid • Built on top of LHC Computing Grid software • Transparent integration of traditional funnel sites and grid sites • Reuse of existing ZEUS-specific middleware • “ZEUS Grid Toolkit” • Brings the grid to the end user DESY CE RLS RB UI Padova Classical funnel sites Tel Aviv Zeus Integrated MC Production System KEK Rutherford R. Mankel: Status of ZEUS

  11. ZEUS Grid-Based MC Production Totals • by time of last PRC: 600,000 events • first non-LCG2 site: Univ. Wisconsin (joined last month) • more than 200 million events produced • 29 grid sites in 7 countries on 2 continents • >60% of MC produced on grid R. Mankel: Status of ZEUS

  12. ATLAS LHCB ZEUS Grid: ZEUS & Other Experiments • In January, ZEUS production amounted to 16% of total CPU power in all UK grid sites • running at very low priority (“opportunistic mode”) R. Mankel: Status of ZEUS

  13. Physics Highlights • Many essential results still coming from HERA-I data • 8 papers published since last PRC • HERA-II data are under analysis • still less statistics than HERA-I, but increasing • also first results from fresh e– data R. Mankel: Status of ZEUS

  14. First Impact of New e-p Data: D* D*+ D0+  (K-+)+ • About equal sample sizes of e+ and e- data in HERA-II • Already 2x as much integrated e-p luminosity compared to HERA-I • Time to revisit an old puzzle… e+p 40 pb-1 e-p 33 pb-1 m(D0+) - m(D0) R. Mankel: Status of ZEUS

  15. D* in New Data (cont’d) • There is no obvious mechanism that should lead to different D* cross sections for e+p and e-p scattering • Still, an indication of such an asymmetry was seen in the HERA-I data • r(e-p)/ r(e+p)=1.670.21 (Q2>40 GeV2) • statistical fluctuation, or mysterious anomaly? Charm production by boson-gluon fusion R. Mankel: Status of ZEUS

  16. D* in New Data (cont’d) • HERA-II data with increased e-p statistics do not show this anomaly any more R. Mankel: Status of ZEUS

  17. Total bb Cross Section HERA-I Data • Traditional analysis tags single B hadrons (e.g. with ) • example: ptrel study • sensitive to fast B hadrons • strong cuts into phase space to suppress background • Tagging of both B’s • makes use of the correlation • allows low ptμ thresholds • is sensitive to B hadrons that are practically at rest • measures total bb cross section double tag R. Mankel: Status of ZEUS

  18. non-isolated, ET>8 GeV Di-Muons: Data vs MC • Same-charge combinations used to normalize light-flavor background • Good overall description with MC • bb contribution ~2000 events, purity ~43% R. Mankel: Status of ZEUS

  19. bb Cross Section from Di-Muon Events (cont’d) • NLO QCD predictions:PHP: 5.8 nb (FMNR,CTEQ5M)DIS: 1.0 nb (HVQDIS,CTEQ5F4)  6.8 nb • NLO prediction lower than the data • applied first time at HERA this analysis +3.0 –1.7 D*μ PHP D*μ DIS R. Mankel: Status of ZEUS

  20. s Determination From NLO QCD Fits Gluon distribution: relative uncertainty in bins of Q2 • Recently, parton distribution functions have been obtained by a rigorous fit to combined inclusive DIS & jet data • uncertainty of the mid-to-high x gluon distribution in inclusive DIS is very effectively constrained by the jet cross sections • sufficient sensitivity to determine PDFs entirely in one experiment R. Mankel: Status of ZEUS 10

  21. s Determination From NLO QCD Fits (cont’d) • This method can also be used to determine s(MZ) as a free parameter in the fit s(MZ) = 0.1183 0.0028 (exp.)  0.0008 (model)  0.0050 (th.) • in agreement with world averages(MZ)=0.1182  0.0027 • first precise determination of s from HERA data alone world average (Bethke 2004): R. Mankel: Status of ZEUS

  22. Strong Coupling Constant C. Glasman, DIS2005 • Comprehensive average of s(MZ) measurements at HERA • conservative assumptions on correlations of theoretical uncertainties (higher order, PDFs, hadronisation) • s(MZ)=0.11860.0011 (exp)0.0050 (th) • experimental uncertainty ~0.9%, theoretical ~4% • Need for NNLO calculations R. Mankel: Status of ZEUS

  23. NC Cross Section at High x • High-x region is hard to measure • for current jet at very low angle, had is either badly resolved, or the jet is not detected at all • x range ends at 0.65 • limits determination of PDF at large x R. Mankel: Status of ZEUS

  24. NC Cross Section at High x (cont’d) e+ One jet • New approach beyond classical “double angle method”: • use jet finder & determine x from Ejet and jet • x  Ejet good resolution • if no jet distinguishable, classify event into integrated bin (xmax<x<1) Zero jet e+ R. Mankel: Status of ZEUS

  25. NC at High x: Data vs. Theory • Good agreement with PDFs • This method applied first time at HERA R. Mankel: Status of ZEUS

  26. Rapidity Gaps at High Q2 • Interest in diffraction at high Q2 extends far beyond HERA • clean final states at LHC, e.g. for Higgs? • Test factorization of diffractive component of proton • At last PRC, first results for charged currents were shown • statistics did not allow to measure Q2 dependence Large rapidity gap • Look for rapidity gaps in neutral current events • Compare with charged current analysis R. Mankel: Status of ZEUS

  27. Rapidity Gaps in NC Events Rapiditygap Forward Plug Calorimeter (FPC) with FPC veto (at beam pipe) • “Normal” DIS MC (Ariadne) clearly insufficient at low max • Need Ariadne+RAPGAP (diffractive MC) to describe the data R. Mankel: Status of ZEUS 5

  28. For comparison: Low-Q2 Data Rapidity Gaps in NC: Q2 Dependence High -Q2 NC x P<0.05 • Sizable diffractive contribution to NC cross section • drops with rising Q2 • still 2% at Q2=1500 GeV2 • NC and CC compatible R. Mankel: Status of ZEUS

  29. Exclusive Electroproduction of Vector Mesons (new: ) • Very clean final state, large kinematical range • At HERA, observe transition from soft to hard regime • Present set of measurements: , (new), J/ • Differential cross sections show high sensitivity to the gluon density functions • challenge to understand diffractive scattering quantitatively R. Mankel: Status of ZEUS

  30. scattered electron K+K–  Electroproduction: Signature • Reconstructed electron + 2 charged tracks • Otherwise detector completely empty • Scattered proton escapes near beam line • 3642  signal events R. Mankel: Status of ZEUS

  31. VM Electroproduction: W Dependence J/ • Highly sensitive not only to different models, but also to different gluon densities within the same model R. Mankel: Status of ZEUS

  32.  Electroproduction: Q2 Dependence • Clean separation of Land T components challenges models • good qualitative description, in particular T • better overall agreement with FS04 model • Excellent sector for further optimizations of pQCD calculations R. Mankel: Status of ZEUS

  33. Looking forward to a fruitful data-taking period with a huge data sample & post-upgrade detector • and polarization Summary • Encouraging data rates from HERA-II • Detector & data chain in good shape • MC mass production on computing grid • Wealth of new physics results R. Mankel: Status of ZEUS

  34. The End R. Mankel: Status of ZEUS

  35. Backup Slides R. Mankel: Status of ZEUS

  36. More Pieces to Pentaquark Puzzle (1520): both in forward & backward hemisphere +: only in forward hemisphere • +signal mainly from forward pseudo rapidity region • unlike regular baryons (1520) and c • predominantly at medium Q2 • similar to c • no sign of decuplet partners seen in –– and –+ ( NA49) R. Mankel: Status of ZEUS

  37. same B (charm cascade) + J/ different B’s (signal!) + cc + light flavor BG low mass high mass low mass high mass mainly light flavor BG different B’s (charm cascade + BB mixing) + light flavor BG Di-Muon Mass Spectra (Data vs MC) • Good description with MC • bb contribution ~2000 events R. Mankel: Status of ZEUS

  38. bb Cross Section: a Di-Muon Event R. Mankel: Status of ZEUS

  39. bb from Di-Muons: Normalization of BG-MC • cc: normalize to D*mu analysis • Bethe-Heitler, elastic charmonium: normalize to data under isolation cut • Light flavor: use like sign spectrum (minus bb MC) R. Mankel: Status of ZEUS

  40. NC Cross Section at High x (cont’d) • Considerable extension of kinematical region towards high x, in particular for moderate Q2 (zero jet case) • Improved x resolution (one jet case) • Only 99-00 e+ data used so far (65 pb-1) R. Mankel: Status of ZEUS

  41.  Electroproduction: W Spectrum • ~W • Test scaling of  with (Q2+MV2) • J/ is always hard •  hardness increases with Q2 •  shows intermediate behavior R. Mankel: Status of ZEUS

  42. J/ Electroproduction Theory vs Exp shown by T. Teubner at DIS2005 R. Mankel: Status of ZEUS

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