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B triggering

B triggering. Fabrizio Palla INFN Pisa. Consorzio CMS Italia Firenze 7 Sept. 2001. DAQ TDR. Deadlines : November 2002 Milestone March 2002 concentrate on (a) Algorithms (b) CPU needed A preliminary document available. B objects. There are NOT LVL1 b objects

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B triggering

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  1. B triggering Fabrizio Palla INFN Pisa Consorzio CMS Italia Firenze 7 Sept. 2001

  2. DAQ TDR Deadlines : November 2002 Milestone March 2002 concentrate on (a) Algorithms (b) CPU needed A preliminary document available

  3. B objects • There are NOT LVL1 b objects • but LVL1 muons and jets will give objects in which b hadrons can be searched for • Very demanding for the HLT is to design trigger tables for • INCLUSIVE B • Background from QCD • EXCLUSIVE B • Background from other b’s Fabrizio Palla Firenze 7 Sept. 2001

  4. Framework • Start from LVL1 Trigger primitives • Study 1) the amount of data volumeneeded 2) to achieve a givensignalselection efficiency 3) for a desiredbackgroundlevel 4) for the number of operationsof the algorithm • Philosophy is based on ACTION ON DEMAND Fabrizio Palla Firenze 7 Sept. 2001

  5. Partial Tracking Reconstruction • Track reconstruction using only a small number of DetUnits around a given portion of ROI (a jet, a muon etc) and stopped when certain conditions are matched • Example • start from pixel seeds and add one Silicon hit at the time • compute pT and ask for more hits if pT>1 GeV/c • can stop for whatever condition reached • e.g. impact parameter smaller than 2, or anything else • Can also start from LVL2 muon seeds Fabrizio Palla Firenze 7 Sept. 2001

  6. Preliminary studies to be done • How to define the ROI? • Precision of the impact parameter measurements (and significance) as a function of the number of hits along the track compared to the full reconstruction • Is any sorting of the pixel seeds in pT or I.p. helping? • Is vertexing feasible? • … Fabrizio Palla Firenze 7 Sept. 2001

  7. Inclusive b triggers 1) Soft leptons based (the “easiest” part) • A soft lepton from LVL2 trigger • might match with a track • validate muon LVL2 pT • use pT relative to the jet direction • ask for minimum i.p. significance • How many tracks are matched? • Is the jet direction from LVL2 well defined? • Can one look for other b-tracks around the muon? Fabrizio Palla Firenze 7 Sept. 2001

  8. Inclusive b triggers (cont’d) 2) Track based (the real challenge!) • inclusive jet triggers • biased in pT of the tracks or in their multiplicity • ask for minimum i.p. significance • ask for vertices • How many tracks need to be investigated? • Is the jet direction from LVL2 well defined? • Is there a compromise between the number of tracks to be analyzed and their quality? • Study several tracking strategies (Kalman vs Riemann etc) Fabrizio Palla Firenze 7 Sept. 2001

  9. Impact parameters • Problems in the partial reconstruction • impact parameter depends on the precision of the closest measurement point to the beam • technically needs to “smooth” the track back to that RecHit • SLOWER wrt simple pT computation • How to select track candidates? • How fast one could go? Fabrizio Palla Firenze 7 Sept. 2001

  10. Exclusive b triggers • 2 Leptons • main issue is J/y • need to prove that is feasible • Fully hadronic • more problematic • B pp • Dsfp • Common problem: • precision on the invariant mass as a function of the partial track reconstruction Fabrizio Palla Firenze 7 Sept. 2001

  11. Actions • Set-up a LVL1 Triggers for inclusive and exclusive B events • Preliminary studies using partial reconstructed tracks on • tracks impact parameters • invariant masses resolutions • vertexing Fabrizio Palla Firenze 7 Sept. 2001

  12. Actions • common framework for generating B events • identify few decay modes and estimate number of events to be generated • BsJ/yf • fully hadronic Fabrizio Palla Firenze 7 Sept. 2001

  13. Actions • Find volunteers for the highest priority studies and inclusive triggers! • Exclusive B triggers • Already a small group of people interested • Propose to have a meeting on on Sept. 19 • Real challenge to have some preliminary answers for Dec. 2001 Fabrizio Palla Firenze 7 Sept. 2001

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