E895 Meeting Minutes at LBNL

taken by Dieter Best

May 20th 1997

• Attending: Gulshan Rai (GR), Nathan Stone (NS), Dieter Best (DB), Heng Liu (HL), James Symons (JS), Dough Olson (DO), Mike Heffner (MH), Jerry Chance (JC), Isaac Huang (IH), Ron Soltz (RS), Mike Lisa (ML)

• GR
  • What is the status of the calibration and tracking?
• NS on calibration
  • We have now a 1D hit finder that is able to read in t0pad, gain and badpad tables.
  • However, the badpad table is not applied. The problem has been identified in the 1D hit finder (variable overwritten somehow) and I will track it down. The 2D hit finder must have the same problem, since the 2D hit finder uses the arrays filled there.
  • It is another question whether the calibration is ok or not. I contacted Chris Pinkenburg in Stony Brook and he says, that the files from the Web page for 2 and 4 AGeV are ok, the 6 and 8 not.
  • He needs the t0pad etc values that have been applied during the 6 and 8 AGeV beam time in order to decalibrate first.
  • HL: I know where the files are.
• DB on track finding
  • A first version of the new track finder has been released, it is a new directory/module in CVS called btf and has its own switch table btf-sw. A kumac with documentation is in CVS.
  • The new track finder is up to 5 times faster, has a much higher hit removal efficiency and the track are on the average much longer.
  • One of the reasons why it is much faster is the fact that a homogeneous magnetic filed is assumed.
  • There have been concerns whether this is justified. We have made extensive studies with the fast simulator and it turns out that this is ok. The momentum resolution is dominated by the spatial resolution.
  • We have studied the momentum resolution as a function of momentum and it turns out that up to 2 GeV the momentum is on the average reconstructed better than 1%, than the momentum is systematically underestimated. The dependency is linear and reaches 20% at 10GeV. This is true for the old track finder too.
  • Comment GR: We have made a new module that enables us to fill the hits table with well defined hits generated from a given set of track parameters which can be set via a switch table. The same time we have the spatial resolution fully under control. It turns out that for perfect resolution the momenta are perfectly reconstructed. When we smear out the points with the experimental resolution we get the experimentally observed momentum resolution.
  • Comment ML: Do we have PID in this momentum range? - No? So it might be not so important.
  • Question NS: Did you use the 2D hit finder? - No. Up to now the 1D hit finder has been used only for the new track finder.
• NS on track merger
  • I am working on the track merger. Now the track merger is a separate module. There are 2 merge, Marvin's and Dean's code. I have been working with Marvin's code so far.
  • At the beginning the merger did not work and it turned out that certain values were not updated. This has been fixed. Now the merger works as a module together with Marvin's track finder. It does not work with Dieter's track finder since the merger uses tracking internal common blocks which are not used by Dieter. The merger has to be changed, so that the track tables and hit tables are used only as input. Then it should work with Dieter's track finder too.
  • However, the merger is less effective as a module if one looks at the number of merged tracks only. This is not yet understood.
  • Comment DB: We need to understand the merge code better. There must be internal cuts that control which track is merged.
  • I agree, we need to remove hard wired cuts and put them in a merger switch table.
• GR: I think we are close to the software for the final dst production.
• DO: If you want to have accounts on NERSC in order to have access to the new mass storage system (1TB), contact Jeff Porter. The software to list, put and get dst/raw data files from/to PDSF should work now on the SUNs and HPs.
• Mike Heffner from UC Davis gives a report about distortion studies with the Laser system.
  • Laser in EOS days was good. In E895 not as good, fewer beams.
  • Look at one Laser beam with magnetic field off: S shape in x-vs-z plot.
  • Apply distortion correction: Moves beam and S shape does not disappear.
  • If one looks at Laser beams during the run (with B field), the S shape comes and goes. This is not understood.
  • Comment: the audience is mystified.
  • Comment RS: Do you see that in beam data too? - We need to look into this, good idea.
• Ron Soltz from E910 gives a report about E910 software. E910 inherited the E895 software.
  • E910 has written a new hit finder and track finder in C++.
  • The new hit finder is a 2D hit finder and 4 times faster than the E895 1D hit finder. We have improved spatial resolution and energy resolution
  • The new track finder is a Kalman filter (only circle tracking) and assumes homogeneous magnetic field.
  • E910 has also very good momentum resolution, a 18GeV proton beam is on the average reconstructed with a resolution of 5%.
  • Comment GR: This momentum resolution is better than what we have, we need to go back and look why our momentum resolution is worse.
• Isaac Huang gives a report about flow at NA49.
• Heng Liu shows transparencies he intends to present in Gatlinburg.