Pixel Offline Analysis for EndcapA Cosmic Data

This document summarizes the results of the offline analysis for the pixel endcapA system test cosmic data. The setup consists of one pixel endcap of three disks, for a total of 144 modules and 6.6 million channels, about the 8\% of the full detector with the goal of exercising the readout system, data taking and testing the full chain of offline reconstruction. The observed noise occupancy per readout (BCID) is found to be $10^{-10}$ after removing all noisy pixels. Comparison with the detector characterization performed during the detector assembly shows that approximately 90\% of these noisy pixels were already flagged as ``special'' during the production test and that the total fraction of special pixels is below 0.1\%. The tracking studies, especially relating to tracks passing in the overlap regions between adjacent modules in the same disk, have been very useful in spotting problems in our geometry description and can be used for the relative alignment between the adjacent modules with the residuals of overlap hits. The characteristic of pixel clustering in the data are checked and agree well with Monte Carlo simulation. The pixel cluster efficiency has been measured to be $>$99.0\% using the hits in the overlap region. When using the nominal geometry, an initial resolution of 23.0 $\mu m$ is obtained. After a preliminary alignment this improves to 16.0 $\mu m$, which is not far from 14.0 $\mu m$ expected from the Monte Carlo simulation.