Introduction• Recall, for the Upgrade, we will read out the full detector at
40 MHz.• Need to quickly reject uninteresting events and select B
events.– MinBias:B event ~ 200:1, but can exploit:
• “Large” B mass large q2 B tracks have larger pT, on average
• Tracks from Min Bias events peak at lower pT, but do have tails out to larger pT.
– Exploit in trigger by requiring N tracks at “high” pT.(cut value to be tuned, but roughly expect ~ 1-2 GeV)
– Also, require that they do not point back to one of the primary interactions. (only want to do this check for a small subset of the tracks)
– Goal: To use TT to get a quick estimate of each particle’s pT. Aim for 10% resolution, in reNeed sufficient
Efficiency “Turn on” for pT>1 GeVvs pT resolution
1/p / (1/p) = 10%
1/p / (1/p) = 20%
1/p / (1/p) = 30%
E.g:With ~10% resolution in1/pT, almost no trackswith pT<0.7-0.8 GeV would pass trigger.
With 30% resolution,~6-7% of tracks at pT<0.5 GeV would be accepted.
67% have pT<0.5 GeV91% have pT<1 GeV 96% have pT<1.5 GeV
Min Bias at 5 TeV
Efficiency “Turn on” for pT>1.5 GeVvs pT resolution
E.g:With ~10% resolution in1/pT, almost no trackswith pT<1.0 GeV would pass trigger.
With 30% resolution,~2% of tracks at pT<0.5 GeV would be accepted.
Momentum Resolution for VeloTT tracks
• Run Standard MC (5 TeV)• Form VeloTT tracks from ALL VELO-3D tracks
– Default would only make VeloTT tracks with VELO 3D tracks that don’t make long tracks
• Shift Magnetic Field upstream by 50 cmand do the same.– Puts more field integral between Velo & TT
• We do the Kalman Track Fit– Assume that track fit can be done relatively fast, ala
the current HLT2 scheme with parameterized materialdescription.
Comparison of pT Resolutions
For comparison, long trackshave a resolution of 0.5%
By shifting the field by ~50 cmupstream, we get about a factorof 2 improvement in pT resolution.
10% resolution attainableby moving the magnet…
Issues
• If we were to move the magnet upstream,might lose some acceptance on outer edges– TT would be more “inside the magnet”– I think we can get adequate coverage though– If you’ve seen a silicon detector inserted into
the bore of CDF, CLEO… you know what “tight space” means!