Increasing Field Integral between Velo and TT S. Blusk Sept 02, 2009 SU Group Meeting

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 q 2  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

TT in LHCb  Four layers of silicon  X1, U(+5 o ), V(-5 o ), X2  ~200 um pitch:  hit ~50  m

A view from inside the magnet TT Beampipe (10 mrad) BellowsFlanges IT-1 OT1

Efficiency “Turn on” for p T >1 GeV vs p T resolution  1/p / (1/p) = 10%  1/p / (1/p) = 20%  1/p / (1/p) = 30% E.g:  With ~10% resolution in 1/p T, almost no tracks with p T < GeV would pass trigger.  With 30% resolution, ~6-7% of tracks at p T <0.5 GeV would be accepted. 67% have p T <0.5 GeV 91% have pT<1 GeV 96% have pT<1.5 GeV Min Bias at 5 TeV

Efficiency “Turn on” for pT>1.5 GeV vs pT resolution E.g:  With ~10% resolution in 1/p T, almost no tracks with p T <1.0 GeV would pass trigger.  With 30% resolution, ~2% of tracks at p T <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 cm and 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 material description.

Comparison of p T Resolutions For comparison, long tracks have a resolution of 0.5% By shifting the field by ~50 cm upstream, we get about a factor of 2 improvement in pT resolution.  10% resolution attainable by 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!

Summary Reduce pT uncertainty by ~ 2X by moving magnet 50 cm upstream Other things to do: –Remove RICH-1 from “default” and “shifted” –Simulation at – 25 cm –Look at rejection power after pT cuts and IP cuts at different luminosities. –…