Babar logo
HEPIC E,S & H Databases PDG HEP preprints
Organization Detector Computing Physics Documentation
Personnel Glossary Sitemap Search Hypernews
Unwrap page!
Det. Search
Who's who?
Intern. region
Vertex Tracker
Drift chamber
Run Coordination
Contact Experts
Shift Takers Info
Operations Manual
Electronic Logbook
Ops Hypernews
Shift Signup
Check this page for HTML 4.01 Transitional compliance with the
W3C Validator
(More checks...)
Contents: [L1 TRG Primatives] [L1 TRG Object] [L1 TRG Line] [L3 Output Line] [Trigger Configutation]
A very simplified BaBar Trigger Scheme is here.

L1 Trigger Primitives 

The L1 Triggers (DCT and EMT) get raw data from DCH and EMC, then create L1 Trigger primitives. They are summary data on the position (azimuthal angle) and energy of particles. The DCT primatives are B, A, Z, Zt, Z', and Zk, and the EMT primatives are M, G, E, X, and Y. (The definitions are below.)

Nice diagram of Level 1 DCT/EMT/IFT Trigger Primitives
(1 page eps diagram made by Jason McFall that shows some of the following definitions in a graphical format)

L1 Trigger Objects 

A trigger object is a quantity indicating the presence of a particle. For example, a drift chamber track or a calorimeter energy deposit. Definitions are below.

Object color coding:
     Objects available in both old DCT and new DCZ era
     Objects for old DCT era only
     Objects for new DCZ era only
      DCT/DCZ objects
      Z cut
      B   Short tracks reaching DCH SL5 ~120 MeV N/A
      Long tracks reaching DCH SL10 ~150 MeV N/A
      A'  High Pt tracks reaching DCH SL7
         800 MeV
      Z Standard Z tracks reaching DCH SL7  200 MeV 12 cm
      Tight Z tracks reaching DCH SL7    200 MeV 10 cm
      Z' High Pt tracks reaching DCH SL7
        800 MeV 15 cm
      Zk Tracks reaching DCH SL7 using a charge-asymmetric pT cut. 200 MeV (-e), 800 MeV (+e) 12 cm
      Note:  a) DCZ Z/pT cuts are preliminary and still being optimized. 
                      Cut values are current as of January 05, 2007.
                  b) B, A, A', Z have 16 phi bins. Zt and Z' have 8 phi bins. And, Zk has 4 phi bins.
                  c) The pT cut for "Zk" can be read as "pT cut at 200 (800) MeV for negatively (positively) charged tracks".
                  d) If you want to get the configuration yourself, read this.
      EMT objects
      Energy cut
      M Minimum ionizing clusters 
      130 MeV 
      G Intermediate energy clusters 
      350 MeV 
      E High energy electron/gamma 
      900 MeV 
      X MIP in EMC forward endcap 
      130 MeV 
      Y Backward barrel electron
      1 GeV 
      Note:  a) Cut values are current as of .... 
                  b) M, G, E, X have 20 phi bins. Y has 10 phi bins.
                  c) If you want to get the configuration yourself, read this.
      Back-to-back Objects  
      phi cut 
      B *,A*  back to back short,long tracks 
      > 124o 
      M*,G*  back to back M,G clusters 
      > 117o 
      E-M E vs M clusters back to back   
      E-Z E vs Z track back to back
      DCT+EMT Match objects
      phi cut 
      BM  B and M phi match  
      AM A and M phi match 
      A'M A' and M phi match 
      BMX  M cluster object veto X without BX phi match  

      Compound Trigger Objects
      A+ 1A & 1A'  
      D2  2B & 1A   
      D2*  B* & 1A   
      D2*+  B* & 1A+   
      T 2T with a loose back-to-back azimuthal cut (T is any primitive)   


      • IFT: U-- IFR trigger 3-bit pattern

      • Current definition since Oct/99

                 1= ``2 or more IFT lines'' (or, 2 muons other than U5~U7)
                 2= 1 muon in backward endcap
                 3= 1 muon in forward endcap 
                 4= 1 muon in barrel
                 5= 2 back-back muons in barrel + 1 in forward endcap
                 6= 1 muon in barrel + 1 muon in forward endcap
                 7= 2 back-back muons in barrel or endcap

        Old definition before Oct/99

                 1= 1 high P muon at backward endcap
                 2= 1 high P muon in barrel or forward
                 3= 2 high P muon back-to-back 
                 4= 1 middle P muon
                 5= 2 middle P muon
                 6= 2 or more high P or middle P  muon

       Note:  Actual cut values listed are examples taken from the Aug/27/99 settings.
                    They are mostly configurable and may vary from the listed values. 

    L1 Trigger Lines 

    GLT gets L1 Trigger Objects as input and generate L1 Trigger lines. The Trigger lines are defined to capture minimal event topologies. Here are example lines: 3B&2A&1Z&2M, 3B&2A&2Z, 3B&B*&1G&1Z, 2E, etc. (To see all lines, see Trigger Configuration.)

    A diagram of a few Level 1 Trigger Lines
    (1 page ps diagram made by Jason McFall that shows some of the 24 total L1 trigger lines displayed in a graphical format)

    A detailed description of trigger line configuration naming convention can be found here

    L3 Output Lines 

    The L1 Trigger lines from GLT are sent to FCTS(Fast Control and Timing System). FCTS issues L1 Accept to initiate event readout, if a valid trigger remains. These L1 Accept and data from DCH and EMC are sent to L3. L3 Trigger is part of OEP (Online Event Processing) and acts primarily as filter, and issue L3 Output lines. Some examples are: L3OutDch, L3OutEmc, L3OutBhabha, etc. (To see all lines, see Trigger Configuration.) Their definitions can be found here in a ps file.

    Trigger Configuration 

    How to check Trigger Configuration information is here, and an example output for Run 67676 is here.

Page Maintainer(s): Kim Hojeong
Last significant update: Oct-4-2007 Expiry date: JAN-01-2009