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Beauty 2005 in Assisi, June 2005. Sascha Caron. for the D collaboration. Tag. beauty. fast ... Including beam spot size 35 m. and 15 m SMT resolution. page 11. The ...

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The Silicon Track Trigger STT at D


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    1. The Silicon Track Trigger (STT) at DØ Beauty 2005 in Assisi, June 2005 Tag fast … beauty Sascha Caron for the DØ collaboration

    2. The Silicon Track Trigger at DØ • OUTLINE • - D0 detector • D0 trigger • What is the STT? • dataflow • clustering and tracking • B identification • Performance • Summary page 1 Sascha Caron

    3. The Silicon Track Trigger at DØ D0 in Run II The Silicon Track Trigger is based on information of the : Silicon Microstrip Tracker Central Fiber Tracker page 2 Sascha Caron

    4. The Silicon Track Trigger at DØ D0 in Run II The Silicon Track Trigger is based on information of the : Silicon Microstrip Tracker Central Fiber Tracker • 50 μm pitch strips (parallel to beam) • 800000 readout channels • Only axial strips used for STT tracks • Scintillating fibers • Coverage: |Rapidity| < 1.7 page 3 Sascha Caron

    5. The Silicon Track Trigger at DØ Events per second QCD ET>30 GeV dijet production Aim: High ET Z->bb, HZ->bbvv, H->bb, etc. Hopefully B physics 10 1 b-jets ET>30 GeV Find b-events early to keep high efficiency at an acceptable rate 0.1 0.01 Z-> b bbar 0.001 Higgs->b bbar Events for L=100 E30 cm-2/s = about 8 pb-1/day 0.0001 ZH-> bbvv, bH->bbb etc. page 4 Sascha Caron

    6. The Silicon Track Trigger at DØ Principal Idea B decay products B decay length is mm Interaction point is mean beam spot Impact parameter (2d in x-y plane) • Silicon Improved Tracks with • 2d impact parameter • Select events with large impact parameter tracks page 5 Sascha Caron

    7. The Silicon Track Trigger at DØ Trigger System p p bunch crossing frequency ¯ L1 Trigger decision time about 4 μs (1500) 5000 Hz L2 Trigger decision time about 200 μs (700) 1000Hz L3 Trigger decision time about 50 ms 2.5MHz 50 Hz • Hardware based • CTT tracks, calorimeter towers, muons • Hardware/Software • simple jets, electrons, muons, taus • Silicon Microvertex improved tracks (STT) • global processor to combine information • (e.g. STT tracks for Bid) • Software based • partial event • reconstruction page 6 Sascha Caron

    8. The Silicon Track Trigger at DØ other L2 pre- processors Data flow chart L2 tracks L2 CTT L2 Global Central Fiber Tracker L1 CTT L2 STT Silicon Micro Detector Detector Detector Level 1 Level 1 Level 2 page 7 Sascha Caron

    9. The Silicon Track Trigger at DØ How is the tracking improved? • Tracks found at L1 with the Central Fiber Tracker are used to define roads into the Silicon • Silicon hits are clustered • Track is re-fit within the road page 8 Sascha Caron

    10. The Silicon Track Trigger at DØ Silicon Track Trigger cards Road data to Fiber Road Card Fitting done in Track Fit Card Done in parallel for each of the 12 sectors 2 sectors in 1 crate -> 6 Crates with 1 Fiber Road Card 9 Silicon Trigger Cards 2 Track Fit Cards SMT data to 9 Silicon Trigger Cards L2CTT page 9 Sascha Caron

    11. The Silicon Track Trigger at DØ Silicon Track Trigger cards Road data to Fiber Road Card • - Receives and distributes L1 tracks • Communicates with Trigger • framework SMT data to Silicon Trigger Cards Fitting done in Track Fit Card - Perform clustering and cluster-road matching - Clusters SMT hits + pedestal correction - Axial clusters are matched to the roads • - receives road and axial clusters • convert to physics coordinates via LUT • perform track fit φ(r)= b/r+kr+φ0 • beam spot correction • output tracks to L2CTT page 9 Sascha Caron

    12. The Silicon Track Trigger at DØ Performance studies STT tracks Impact Parameter resolution Correlation to RECO Resolution in μm pT(GeV) Purity Including beam spot size 35 μm and 15 μm SMT resolution page 10 Sascha Caron

    13. The Silicon Track Trigger at DØ B identification Signal to Background ratio Ri Store 2d signal (b events) to background (light quarks) ratio into a lookup table 1.5 mm b/db - Fast, simple and efficient technique - Time needed is 2 operations per track and goes linear with the number of tracks -> about 1-5 μs - Degrades bad tracks without cutting them page 11 Sascha Caron

    14. The Silicon Track Trigger at DØ Performance studies L2 B-id likelihood efficiency Z->bb Red : Simple Cut Blue/Green: B-id Very well separation of signal and background events Large background reduction with L2 b-ID algorithms page 12 Sascha Caron

    15. The Silicon Track Trigger at DØ First studies using data Using MC pdfs DØ preliminary Jet data Offline B-tagged data DØ preliminary Likelihood shifted to higher values due to e.g. min bias effects Max IP Significance Likelihood L2 data well correlated with offline data -> proof of b-id principle -> Much more studies on their way page 13 Sascha Caron

    16. The Silicon Track Trigger at DØ Summary • The STT is operating routinely and smooth • High Impact Parameter resolution • Data is understood • Very fast L2 b-id is (almost) implemented • We expect a high potential for • Z->bb and Higgs physics now and at L=200E30cm-2/s Outlook • Implementation of new Layer 0 (r=22mm) into STT • -> further increase in precision and stability page 14 Sascha Caron