2017-03 Tracker summary¶

The tracker group have looked at the reconstruction from digits to tracks for several runs from each configuration and found that the tracker reconstruction is working well. There are some unexplained features which we are looking into but the data looks good and we have seen nothing to suggest new data must be taken so far. A subset of these runs are shown below with explanations of the plots.

https://indico.cern.ch/event/691779/contributions/2839280/attachments/1581579/2499443/VC_TrackerDataQualityJan2018.pdf

Digits¶

After the summer warm up a significant proportions of channels in the were lost. Since there are a number of unused connections hardware changes could be made to reduce the impact of the losses. This resulted in a significant amount of work trying to minimise the spacepoint loss. This sometimes meant increasing the number of dead channels seen in the data in order to group them into certain planes. In the end 9 waveguide swaps were made 5 US and 4 DS and the spacepoint loss was reduced to ~1% and significant recalibration work was also required and successfully completed. However, the effect can be seen in the digits so this should be taken into account when looking at the following plots.

What we do see, is that the digits are stable across many runs of different types, the dead channels are constant while the shape of the distributions may change as a result of the beam and channel settings. The shows that the digit level data is good.

A selection of runs for different cooling channel settings are shown below.

Run 10420 LiH Empty 6-240+M3-Test1¶

Run 10567 Wedge 6-240+M3-Test1¶

Clusters¶

The following series of plots shows a couple of examples of the next stage of comparison, clusters. A track passing through a particular doublet layer produces scintillation light in one or at most two fibre channels. For each channel “hit”, the tracker data acquisition system records the channel number, n, and the pulse height. After calibration, the pulse height is recorded in terms of the number of photo-electrons (n pe) generated in the Visible Light Photon Counter (VLPC) illuminated by the hit channel. Occasionally, showers of particles or noise can cause three or more neighbouring channels to be hit. The term clusters” is used to refer to an isolated hit or a doublet cluster.

Below are a groups of six cluster plots for a selection of varied runs, showing the validation procedure for the clusters.

Cluster NPE shows the reconstructed cluster npe for all clusters, the 2npe bin shows the noise (which is removed in the spacepoints). The features at ~15 and ~22 are the result of increased noise in the DAQ following the warm up. The next two plots on the top[ row show the position of the clusters in the planes for all clusters (left) and with a 3npe cut and hence noise reduced (right). The shapes vary but it is a way to understand which planes are noisiest.

The bottom left plot shows the ration of singlet to doublet clusters, with a 2npe (blue) and a 3npe (red) cut applied. We can calculate the expected ratio of singlet to doublet clusters as 10:1, as is seen.

The central bottom plot shows the npe of each digit in the singlet cluster (blue) and doublet cluster (red) this shows that noise is isolated to the singlets as expected.

Run 10108 LH2 Empty 10-140+M3-Test4¶

Run 10420 LiH Empty 6-240+M3-Test1¶

Run 10567 Wedge 6-240+M3-Test1¶

Kuno Plot¶

A check of the mapping the total should be 318.5 as shown.

Run 9728 LH2 Empty 10-140+M3-Test4¶

Run 10420 LiH Empty 6-240+M3-Test1¶

Spacepoints¶

Spacepoint Beam profiles¶

Triplet spacpoints are formed from 3 overlapping clusters one in each plane. Doublet spacpoints are found when 2 out of three planes record a cluster. Due to the works mentionned above there are an increase in doublet spacpoints and a decrease in triplets after the summer.

The following beam profiles (non normalised by colour) show the x-y position of doublet and triplet clusters for a selection of runs and are used to check that there is not an increase in deadspace.

Run 9728 LH2 Empty 10-140+M3-Test4¶

Run 10420 LiH Empty 6-240+M3-Test1¶

Spacepoint Summary plots¶

In a more general way the spacepoints are compared below.

Run 10108 LH2 Empty 10-140+M3-Test4¶

Run 10420 LiH Empty 6-240+M3-Test1¶

Run 10567 Wedge 6-240+M3-Test1¶

Tracks¶

The number of 4 and 5 spacepoints tracks (ie tracks which have a spacpoint in 4 or 5 out of 5 stations are shown top left. The track p value are then compared. The trackpoint pull should be a spike at 0.

Run 9728 LH2 Empty 10-140+M3-Test4
¶

Run 10420 LiH Empty 6-240+M3-Test1¶

Run 10567 Wedge 6-240+M3-Test1¶

Efficiency¶

The efficiency for a subset of runs has been considered and is being expanded. The efficiency for 3-5 spacepoint tracks looks good but a decrease in efficiency fro 5 spacepoint tracks is seen as is to be expected due to the loss of some channels. The variation between runs is under consideration.