1 / 20

High Level Trigger – Applications

High Level Trigger – Applications. Open Charm physics Quarkonium spectroscopy Dielectrons Dimuons Jets. Assumptions. Detector readout rate (i.e. TPC) >> DAQ bandwidth  mass storage bandwidth Physics motivation for a high level trigger

guinevere-church
Download Presentation

High Level Trigger – Applications

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. High Level Trigger –Applications • Open Charm physics • Quarkonium spectroscopy • Dielectrons • Dimuons • Jets

  2. Assumptions • Detector readout rate (i.e. TPC) >> DAQ bandwidth  mass storage bandwidth • Physics motivation for a high level trigger • Need for an online rudimentary event reconstruction for monitoring

  3. Data volume and event rate TPC detector data volume = 300 Mbyte/event, data rate = 200 Hz bandwidth 60 Gbyte/sec front-end electronics 15 Gbyte/sec realtime data compression & pattern recognition PC farm = 1000 clustered SMP parallel processing DAQ – event building < 2 Gbyte/sec < 1.2 Gbyte/sec permanent storage system

  4. Data rate reduction • Volume reduction • regions-of-interest and partial readout • pile-up removal in p+p • data compression • entropy coder • vector quantization • TPC-data modeling • Rate reduction • (sub)-event reconstruction and (sub)-event rejection before event building

  5. Fast pattern recognition Essential part of Level-3 system • crude complete event reconstruction  monitoring • redundant local tracklet finder for cluster evaluation  efficient data compression • selection of (,,pT)-slices  ROI • high precision tracking for selected track candidates • dielectrons, ...

  6. Level-3 system structure TRD trigger PHOS trigger Dimuon trigger Trigger detectors Level-1 Pattern Recognition TPC: fast cluster finder + fast tracker Hough transform + cluster evaluator Kalman fitter Dimuon arm tracking Level-3 Extrapolate to ITS ... Extrapolate to TOF Extrapolate to TRD (Sub)-event Reconstruction

  7. TPC Rate limitations

  8. Open Charm Physics (1) • Hadronic charm decays • D0 K– + + • B.R. = 3.86% • c = 124 m • high pT of the decay products: • 75% of decay pions have pT > 0.8 GeV/c

  9. Open Charm Physics (2)Charm Filter • HLT momentum filter • subevent rejection • subevent = low- pT tracks • 11% of charged particles have pT > 0.8 GeV/c

  10. Open Charm Physics (3) Charm Filter • Trigger strategy • find high-pT tracks in outer sector of TPC (based on seeds from TRD) • extrapolate track back to vertex • record raw data along trajectory • Problem of overlapping clusters • for deconvolution of high-pT track clusters the knowledge of track parameters of crossing tracks is necessary • Solution • reconstruction of all tracks in the neighborhood (same/neighboring sector and  )

  11. Open Charm Physics (4) Charm Filter • Trigger efficiency • signal loss: <25% • data volume reduction to 7 Mbyte/event (factor 10) • pT > 0.8 GeV/c vs. all pT

  12. Open Charm Physics (5) Charm Filter • Trigger efficiency • signal loss: <35% • data volume reduction to 10 Mbyte/event (factor 5)

  13. Open Charm Physics (5)Event Abortion • Level-3 trigger: event abortion • Trigger strategy • high-precision reconstruction of high- pT tracks (Kalman + PID) • extrapolation to ITS • cuts on impact parameters, invariant mass etc. • Trigger efficiency • signal/event = 0.0027* • background/event = 0.15* • event rejection rate of 85% (new result incl. PID and pt-cut: factor 10 higher) * A. Dainese, ALICE-PR-2001-04

  14. TPC tracking

  15. Tracking in the ITS:PbPb central event,q slice83o-87o • - primary vertex - secondary vertices => for Hyperons => for Charm and Beauty • - dE/dx for particle identification (@low momenta) • - improve TPC momentum resolution • - stand-alone tracking for low-Pt particles

  16. Heavy Quark Physics • Detectors involved: • TRD, TPC, ITS • Dimuon arm, ITS • Quarkonium spectroscopy • J/,  • D, B

  17. Quarkonium spectroscopy - dielectrons (1) • Trigger rates ptsingle > 1 GeV/c ptsingle > 0.8 GeV/c ptpair > 3 GeV/c J//event 0.007 0.0006 background/event 0.39 0.15 HLT system TPC @ 150 Hz TRD @ 1kHz Online track reconstruction: 1) selection of e+e—pairs (ROI) 2) analysis of e+e—pairs (event rejection)

  18. Quarkonium spectroscopy - dielectrons (2) • Trigger strategy • precise tracking of dielectron candidates in TPC • additional PID by dE/dx • rejection of background tracks (mainly misidentified pions) by combined (TRD+TPC) PID • rejection factor • 5 (singles) • 25 (pairs) • HLT output rate: 1- 40 Hz (full events or ROIs)

  19. Quarkonium spectroscopy - dielectrons (3):event flow

  20. Quarkonium spectroscopy- dimuons • Sharpening of pt-cut • Trigger rate reduction: >4

More Related