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

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

Fabrizio Palla Firenze 7 Sept B objects  There are NOT LVL1 b objects u 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 u INCLUSIVE B  Background from QCD u EXCLUSIVE B  Background from other b’s

Fabrizio Palla Firenze 7 Sept Framework  Start from LVL1 Trigger primitives  Study 1) the amount of data volume needed 2) to achieve a given signal selection efficiency 3) for a desired background level 4) for the number of operations of the algorithm  Philosophy is based on ACTION ON DEMAND

Fabrizio Palla Firenze 7 Sept Partial Tracking Reconstruction  Track reconstruction using only a small number of DetUnits  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 u Example  start from pixel seeds and add one Silicon hit at the time  compute p T and ask for more hits if p T >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 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 p T or I.p. helping?  Is vertexing feasible?  …

Fabrizio Palla Firenze 7 Sept Inclusive b triggers 1) Soft leptons based (the “easiest” part) u A soft lepton from LVL2 trigger  might match with a track  validate muon LVL2 p T  use p T 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 Inclusive b triggers (cont’d) 2) Track based (the real challenge!) u inclusive jet triggers  biased in p T 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 Impact parameters  Problems in the partial reconstruction u impact parameter depends on the precision of the closest measurement point to the beam u technically needs to “smooth” the track back to that RecHit  SLOWER wrt simple p T computation u How to select track candidates? u How fast one could go?

Fabrizio Palla Firenze 7 Sept Exclusive b triggers  2 Leptons  main issue is J/   need to prove that is feasible  Fully hadronic u more problematic  B    D s    Common problem: u precision on the invariant mass as a function of the partial track reconstruction

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

Fabrizio Palla Firenze 7 Sept Actions  common framework for generating B events  identify few decay modes and estimate number of events to be generated  B s  J/   fully hadronic

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