For the 200 GeV Au+Au data taken in Run14, the MTD group is proposing a two-pass reconstruction scheme for events that are only triggered by di-muon trigger to speed up the production and save the disk space. A schematic overview of the proposal is the following: 


In the first iteration, the following steps are taken:

• Read in trigger data
• StMtdHitMaker: reconstruct the MTD hits
• StMtdTrackingMaskMaker: select the MTD hits that actually fire the trigger, determine the corresponding TPC sectors that most likely host the tracks producing the hits, and output a 24-bit mask for TPC tracking
• Perform the TPC tracking ONLY for the sectors that may contain the muon tracks according to the mask
• StMtdMatchMaker: associate MTD hits and TPC tracks
• StMtdEvtFilterMaker: decide if the event contains two muon candiates, and write out the decision into .tags.root.

In the second iteration, the following steps are taken:

• Read in the decision made in the first interation from .tags.root.
• Throw away events that are triggered by only di-muon trigger and that do not contian two muon candidates
• Perform standard reconstruction chain for the remaining events
• For events that are triggered by multiple MTD triggers and that do not contain two muon candidates, still do the standard reconstruction and record the status in MTD header. This is needed for offline analysis using di-muon events to impose the same bias

For more details, please refer to a presentation given at the collaboration meeting. Link

The source code of newly developed makers, i.e. StMtdTrackingMaskMaker and StMtdEvtFilterMaker, are located at /star/u/marr/mtd/EventFilter/StRoot. And a testing macro to run them can be found here: /star/u/marr/mtd/EventFilter/doEvent.C.

StMtdTrackingMaskMaker

• It runs on both MuDst and StEvent
• For hits in modules 2, 3, 4, the corresponding TPC sectors on both east and west sides are marked for tracking
• Public function getTrackingMask() can be used to extract the 24-bit mask
• The 24-bit mask corresponds to the 24 TPC sectors, with 1 meaning this sector should be used in tracking. The most right bit corresponds to sector 1, while the most left bit to sector 24.

StMtdEvtFilterMaker

• It runs on both MuDst and StEvent
• Public function isRejectEvent() returns the decision if this event should be thrown away in the second iteration
• Public function shouldHaveRejectEvent() returns if this event should have been thrown away but not because it is triggered by mulitple MTD triggers.
• Default event cuts
  • No vertex cut
• Default track cuts
  
  • Use global tracks with pT > 1 GeV/c
  • NHitsFit >= 15
  • NHitsDedx >= 10
  • NHitsFit/NHitsPoss > 0.52
• Default PID cut
  • |dz| < 50 cm
• Default J/pis cut
  • At least two tracks matched, with the leading track above 1.2 GeV/c