History

• TpcRS was updated by fixing some bugs, tuning it better for particles crossing sector boundaries, changes related to iTPC integration, etc.;
• I produced TpcRS package for the pre-iTPC era for particular embedding jobs (SL17d_embed) to include all the fixes but no iTPC part;
• After embedding people working on the sample (e.g. Xianglei) noticed mismatch between simulation and data in tpc hit distributions. In particular there was a noticeable drop in number of tpc hits in the simulation for the inner sector hits on the tracks. This was not observed in the data (in particular dAu27 GeV collision data);
• Investigation from Gene, Xianglei, and myself showed that it was not a software issue, but pointed to the database parameters;
• After more investigation Xianglei found that the Altro thr = 4 was causing the drop and with Altro thr = 3 it was much better;

Investigation and fix

Below is a plot showing the problem in number of hits [for Run2016 dAu  in this case]

Rouchly 25% mismatch could be seen between inner and outer sectors in every sector.

dEdx

Altro thr has been changed from 3 to 4 for runs 16, 1, and 18. Prior doing so we have investigated the effects on track reconstruction and it showed that 4 was a preferable cut;
Looking in this direction I found that dEdx needed to be recalibrated and proper parameters put in TpcResponseSimulator.C.

Run-16 dAu

The above plot shows the significant split in dEdx between inner and outer sectors for the simulation. This is most probably what transpired as the hit loss in inner sectors when the threshold was raised. The issues has been there but did not show up when accepting lower signal due to a lower threshold cut.

The parameter for the inner sector was adjusted according to the plot above. Below is the plot after recalibration:

Cluster Timing

Cluster timing shift has also been checked. It looks like there is a slight offset (difference between generated z position of the cluster and the mean of the timebucket distribution produced by the clusterfinder for this hit) which is different between inner and outer sectors:

After applying the correction:

Timing above was obtained without explicit matching of the MC and RC clusters. Below I show a detailed breakdown of this difference between RC and MC hit timing (without any T0 Offset Correction):

The difference histogram between inner and outer sectors is showing before (there is some strange behavior for the inner sector 24 - perhaps was off for this particular run).

mean and sigma for these distributions for sectors are shown below.

Based on these the (additional, after first trial, which of course will be combined) correction factors were calculated as a mean of the offset in every sector (removing the outliers - 3sigma away, which are sectors where something strange is happening, perhaps something was off or so):

Plot for the number of hits in each padrow seams to match much better with the data after these corrections:

Run-18 AuAu27 

Investigating Hits

The initial look at the hit mismatch has integrated look over all the sectors. Closer look at the hit mismatch shows the following [for Run2016 dAu in this case]:


Below is the same with the Altro threshold = 3: