The VDS performance Outline: Current reconstruction / analysis Alignment Efficiencies Monte Carlo Masking Usability of runs Time stability New / on raw data visible: The single event killing Occupancy problems Occupancy maps on single event level Summary

Alignment, Efficiencies Done for all periods with hardware changes Alignment was done synchronised and coordinated for all subdetectors Produced sets: 9 for pre-November-runs 7 for the data taking period 4 test files: VDS primaries & secondaries agree in data and MC ! Analysis shows: We have to align the VDS more often. Efficiencies : In C&A for 30 cases, ready to use Based on repro3 /repro0 Done per plane Variations due to hardware changes seen Unmounted channals seen 2 sets of masks: 21249 (open) 20243 (black)

Masking, Usability of runs, Time stability We do not have a masking finer than 1 plane yet operational Due to hardware problems we have an incomplete list of 4..? Runs where the VDS was not well usable Investigations of time stability just started MC / data comparison shows some problems Time stabilty is beeing investigated ! R. Wolf, dipl. thesis Age: 20h ! + 4 planes unstable ! Dez. min bias runs

The single event killing and beyond.. From March meeting: There was a dynamical, unmonitored occupancy-cut applied in all data Unknown effect on data. We may have more ‚surprises‘ on tape, and just be blind to them ! => some parts of your (single) event may be invisible (up to 39 helixes ‚flushed‘) => Call it: „Jet supressor“, „generation of missing energy or pt“ No way to recover in ‚mini‘ Relaxing this reveals a ‚new‘ problem: (but seen by SLT) Occupancies get crazy (SLT confirms) There are too many wrong-sign clusters We can cut but need to understand Might even be usefull => Test by Friday !

Fine Masks Provide bad channal masks, get rid of „gute Seiten, schlechte Seiten“ => Single strip cuts are developed and ready for ARTE ! these are found easily ! New technique.. .. new surprises: part-time bad HELIXES are good but some chans are bad (always) these are never OK, but cause sometimes trouble == bad efficiency for the plane or a bad HELIX! Simply: unmounted !

Masking Channals, Summary Bad channels in VDS: (suggested mask)   plane chips chans bad planes 4 38 4864 number of chans 138240 bad chips 35 4480 number of chips 1080 bad chans 3566 number of planes 119 sum 73 12910 % 3,36 6,76 9,34 First shot might be x2 too strict, Wait till June 1st ! Alignment will become much easier The masks quite are stable (single chans !) Consequences on resolution and efficiency ? Tests will take place this week !

Time stability Micha Time-stability for MB-analysis: Might be Okay The new findings suggest an even better system ‚Helixes in time‘ might be a small problem

From the year 2000 Primary position drifting in run: 4µm/h ! 200 µm observed in this season. The drift can not be corrected with alignment The IP / beam / target relation is untested Checks will come (June)

Summary For the current analysis, we have Efficiencies Alignment (C&A tables for all important time periods existing, not too fine) MC masks (using C&A, ready to use) Per run investigations just started Some problems found & attacked Unknown systematics due to the ´single event-killer´ => dangerous? Single strip hit maps show that problematic chans stay stable over time Some ‚interesting‘, new problmes found Number of hits in (1..10)% of the events looks crazy Countermeasure for this found => will be tested with physics soon Alignment procedure (showstopper was DQ ´by hand´) will improve further Suggested a procedure for a new repro We can improve the current situation quite a bit !