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The status of SVD-2 experiment on the search of charm production in pA -interactions at 70 GeV/c

The status of SVD-2 experiment on the search of charm production in pA -interactions at 70 GeV/c. V.Popov for SVD-2 collaboration (SINP Moscow, IHEP Protvino, JINR Dubna). SVD-2 experiment. Physics motivation : Measurement of total cross sections and comparison with QCD predictions

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The status of SVD-2 experiment on the search of charm production in pA -interactions at 70 GeV/c

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  1. The status of SVD-2 experiment on the search of charm production in pA-interactions at 70 GeV/c V.Popov for SVD-2 collaboration (SINP Moscow, IHEP Protvino, JINR Dubna)

  2. SVD-2 experiment • Physics motivation: • Measurement of total cross sections and comparison with QCD predictions • Differences in the fragmentation ( D°, D±,) • Search for the "intrinsic charm" • Experimental goals: • total cross sections • differential cross sections over xF and pt • A-dependence

  3. SVD-2 experiment • Current estimate ofpp cc + X cross section • (E-161 experiment, 5 events) :( 1.6+1.1-0.7 )b • Expected number of charm events within a total of • 5107 hadronic events (current experiment statistics) • For (c,c) ~A113,000 events • For (c,c) ~ A0.75,300 events

  4. SVD-2 experiment • Charm creation cross sections for different energies

  5. SVD-2 experiment • Beam: • (Protvino U-70 accelerator): p, 70 GeV/c • (x,y): 1 ... 1.25 mm • Intensity: 0.5×106 protons/spill • Target • 5 active(trigger) Si planes, 1 Pb plane and 1 C plane • Total "hadronic" thickness ~ 0.5%

  6. SVD-2 experiment Active Target layout

  7. SVD-2 experiment • Trigger-I • Based on energy depositions in 58 Si active target strips • Basic idea:to look for the >2...3 MIPs depositions in consecutive planes • Decision time: 220 ns • "Non-hadronic" events contamination: < 10% • Trigger-II • Not implemented yet... • Basic idea - a search of "secondary" activity • A simplified "fast" information from vertex tracking detector to be used

  8. K-     P-beam K-    1.a p+  1 2 3 5 4 1 High precision microstrip vertex detector. 1a Active target with Si, C and Pb planes 2 Multiwire proportional chambers. 3 Magnet ( 1.18 T over 3m long region). 4 Multicell threshold Cherenkov counter. 5 Gamma detector.

  9. SVD-2 detector • Vertex detector • beam telescope • tracking detector: • MIP/noise ratio ~ 10:1, registration threshold ~ 3.5 noise • Dead/noisy channels : < 5% • Planes configuration: • Orientation Strip pitch Number of strips • X,Y 25 640 • X,Y 50 640 • X,Y 50 1024 • X+10.5 50 1024 • X 50 1024 • Y+10.5 50 1024 • Y 50 1024

  10. SVD-2 detector • Spectrometer • Magnet: • Length : 3m (along the beam) • Field in the centre: up to 1.18 Tl • MWPC: • Number of planes - 18 (15 inside the magnet) • Acceptance: 220 mrad(X) * 170 mrad(Y) • Wires orientation: Y-10.5, Y, Y+10.5 • Wires step: 2 mm • Average efficiency: 80%

  11. SVD-2 detector • Cherenkov detector: • Measured efficiency: 70% for the  withp>5 GeV • Gamma-detector (DEGA): • 1500 channels, Cherenkov glass • Energy resolution for 15 GeV electrons • ~ 12% • mass resolution ~ 13% (preliminary)

  12. SVD-2 detector • Monitoring and data collection • 5 “detector component” PCs • read information from CAMAC electronics of sub-detectors • The “Collector” PC • synchronizing data within a spill, • creating and saving the unified data file • The monitor workstation • Partial reading of data file • Analyzing beam, detector and readout state • Simplified vertexing (also to check the trigger state)

  13. SVD-2 run - April '2002 • 80 “accelerator shifts” • > 50,000,000 triggers • Suggesting that… • 20% of events are discarded, • pp(cc) = 1.6b, • A-dependence as A1, • Identification efficiency is 10%, • gives an estimate for the number of charms to be identified: 1500…

  14. SVD-2 data analysis • Preliminaries: • General analysis of the formal events quality and the “indexing” • Amplitude analysis of the vertex detector data • Checks of the readout consistency • Geodetic analysis and alignment • Evaluation and testing of different algorithms for tracks and vertex reconstruction • Defining the methods of tracks selection by impact parameter • Different methods of momentum reconstruction.

  15. SVD-2 data analysis • Current status of reconstruction software: • FORTRAN code • Based on vertex+spectrometer data • Track finding starts in the vertex detector • Pre-generated tables for the momentum calculations • GEANT3 detector simulations • detailed geometry • geometry configuration file is the same as for reconstruction software (alignment…) • interfaces to • Pythia(…) at input • Raw data file format at output

  16. SVD-2 data analysis • Estimates of accuracies: • X,Y-resolutions for >3 hits tracks fitted: 8…10 m • Z-resolution • for the primary vertex: 70… 130 m • for the secondary vertex: 200… 300 m • Impact parameter resolution: ~ 17 m • Momentum resolution for the beam tracks (70 GeV): 3% • Effective mass resolution: • For K0: 3.9 MeV • For : 1.6 MeV

  17. SVD-2 data analysis Run I (april 2002) ~ 53 millions of inelastic pN-events on Si, C and Pb targets. Si – 300m; Pb – 220 m; С12 – 500 m Pb C12 Si Si Si Si Si sz = 70÷130µm, sx,y = 7÷10µm Fig 2. Primary vertex Z-coordinate in SVD-2 active target.

  18. Effective masses K0 

  19. Plans for the next run (fall ’2004) Vertex detector – changes in configuration and electronics to rise the efficiency and lower the multiple scattering effects Installation of 9 double planes of drift chambers (straw tubes 6mm, resolution <200m) 3 more chambers in the spectrometer  Better tracking and effective mass resolution Better magnetic field screening for Cherenkov detector PMTs  Rising the efficiency (up to 90%) New electronics in gamma detector  no event losses, 0 mass resolution 6…7% Level-II trigger and moving beam intensity to 2*107 p/spill  Increasing statistics 5-10 times Reconstruction software: moving to ROOT/C++  A nice trick to attract students

  20. A new project (with JINR) • The study of high multiplicities in hadronic events • Ncharged = 21…35? • H2 target to be used • SVD-2 modifications (+trigger) • Multiplicity distributions and different + , -, 0 correlations • Beam intensity up to 107 p/spill •  = 10 pb

  21. SVD-2 April '2002 run Number of events Number of charged particles

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