1. VELO Beamtest Trigger VELO meeting 08/12/2005 Jianchun (JC) Wang Syracuse University

2. 01/07/02Jianchun (JC) Wang2 Event Category  The testbeam data will be used to align the telescope.  The 450 GeV/c proton beam hits the detector sensor instead of the center of circle.  We need interaction events, which benefit the alignment. p  Beam p SignalBackground

3. 01/07/02Jianchun (JC) Wang3 Scintillation Trigger ABC Trigger = A  C  B

4. 01/07/02Jianchun (JC) Wang4 Simulation On Scintillation Trigger  MC sample of 120 GeV/c  beam at (30, 10) mm (by Tomas Lastovicka).  Scintillation counter B (veto): size=20  20mm 2, at 2m downstream from first station.  The beam is assumed to be perfect: 0 in size, no dispersion. The scintillation efficiency is 100%.  The trigger efficiency is about 50%. With 450 GeV/c proton beam the efficiency will be less.  The size of scintillation counter will be decided once we have more realistic beam condition. The rejection rate will be estimated then. The hardware will be provided by Syracuse group.  Advantage: hardware, at L0 trigger. Disadvantage: very strict on beam condition.

5. 01/07/02Jianchun (JC) Wang5 Alternative Trigger  The number of hits can be used in L1 trigger.  Example: Sum of maximum number of R hits per station and maximum number of  hits per station is required to be > 20.  Same MC sample used. The noise level is about 0.1%. All 21 stations are included. The efficiency is more than 50%.  With 450 GeV/c proton beam the effect will be more significant.  We can also use hits per sector, or total number of hits of all station and so on.  Advantage: simple, not rely on alignment. Disadvantage: strict on common mode noise.

6. 01/07/02Jianchun (JC) Wang6 Vertex Trigger  Use vertex trigger, similar to that of official L1 trigger ( see Tomas’ presentation on 07/22/05).  The pattern recognition is complicated due to that the tracks are not from the designed beam axis.   R/  Z  constant  Tomas is working on the algorithm.  I will implement the algorithm. Currently I am still on the learning curve of LHCb software.  Advantage: more close to final trigger; The pattern recognition is needed anyway for analysis. Disadvantage: CPU time, … !!!