The following block of plots show the z position of TPC hits from laser data during days 74-81 of Run 17. One can see the following features:

1. Lasers lead to peaks at specific z positions.
2. The west side (z>0) lasers appear to have more signal than the east side lasers.
3. There are numerous runs, particularly from 18075079 through 18079031, where no laser peaks are discernable.
4. The laser runs without beam (laser_localclock) are obviated by the lack of collision backgrounds: 18075021 and 18079033.

(you may open the below images in a new browser tab/window to see it with higher resolution)



The absent laser data has led to failed drift velocity calibration jobs, and a gap in the drift velocity data in the middle of March (visible on the right side of the following plot):



This was discussed at today's TPC meeting.

-Gene




Here is the shell script I used to generate the plots of z hit positions:

set rdir = /star/data10/calib/tpcDriftVelocity/runs

cd $rdir
set runs = `/bin/ls`
cd $owd
unset rstr
foreach run ($runs)
  mkdir $run
  cd $run
  ln -s ${rdir}/${run}/st*.laser.root .
  cd ..
  if ($?rstr) then
    set rstr = "${rstr},${run}"
  else
    set rstr = "$run"
  endif
end
@ nruns = $#runs
echo $nruns
echo $rstr

root -l << EOF
    int runs[${nruns}] = {${rstr}};
    gStyle->SetPalette(1);gStyle->SetGridColor(kGray);gStyle->SetOptDate(0);gStyle->SetOptStat(0);
    TCanvas c1("c1","plots",1500,1000);
    c1.Divide(5,8);
    TText aa;
    aa.SetTextSize(0.18);
    aa.SetTextColor(4);
    TChain laser("laser");
    for (int i=0; i<${nruns}; i++) {
      printf("Working on %d\n",runs[i]);
      laser.Add(Form("%d/st_laser_*.laser.root",runs[i]));
      c1->cd(i+1);
      laser.Draw("fHits.xyz.mX3");
      aa.DrawTextNDC(0.30,0.7,Form("Run         %d",runs[i]));
      laser.Reset();
    }
    c1->SaveAs("plot.png");
    .q
EOF