Track Reconstruction with iTPC Sector in Run 18

Dmitri Smirnov

March 13, 2019

Updated

<h1>TPC in Run 18</h1> - In Run 18 the inner section of TPC sector 20 trippled the number of layers - 13 TPC layers to 40 iTPC layers resulting in change from 45 to 72 total layers in the sector - It was decided not to use iTPC hits in Run 18 tracking - We would like to know how tracks are affected by missing hits in sector 20

<h1>First Observations</h1> - <a href="https://drupal.star.bnl.gov/STAR/blog/lisa/phi-distributions-not-understood-isobar-runs">Early observations reported by Mike Lisa and Xiaoyu Liu</a> - The data was reconstructed by fast offline during the Run, i.e. early feedback, no fixed release <img style="display: block; margin: 0em auto;" src="graphics/phi_high_pt_xiaoyu.png" width="70%" /> - Claimed: $\sim 75\\%$ of tracks lost at hight $P_T$

<h1>First Observations</h1> - Asked Xiaoyu to analyze recently reconstructed data - The effect is much smaller <img style="display: block; margin: 0em auto;" src="graphics/phi_high_pt_xiaoyu_2.png" width="70%" />

<h1>Our Investigation</h1> - Look at the data reconstructed with SL18h with vetted calibrations - Model the situation in sector 20 by excluding hits in the inner sector 14 - Reconstructed same sample twice: With and without hits in sector 14 - Labeled samples as YES14 and NO14 respectively - We confirm the expected loss of track efficiency around sector 14 for global and primary tracks

<h1>Track Phi vs Eta Distribution</h1> <img style="display: block; margin: 3em auto;" src="graphics/phi_vs_eta_pt_bin_9.png" width="70%" />

<h1>Track Phi vs Eta Distribution</h1> <img style="display: block; margin: 3em auto;" src="graphics/phi_vs_eta_pt_bin_5.png" width="70%" />

<h1>Track Phi vs Eta Distribution</h1> <img style="display: block; margin: 3em auto;" src="graphics/phi_vs_eta_pt_bin_4.png" width="70%" />

<h1>Track Phi Distribution</h1> <img style="display: block; margin: 5em auto;" src="graphics/phi_pt_bin_9.png" width="80%" />

<h1>Track Phi Distribution</h1> <img style="display: block; margin: 5em auto;" src="graphics/phi_pt_bin_8.png" width="80%" />

<h1>Track Phi Distribution</h1> <img style="display: block; margin: 5em auto;" src="graphics/phi_pt_bin_7.png" width="80%" />

<h1>Track Phi Distribution</h1> <img style="display: block; margin: 5em auto;" src="graphics/phi_pt_bin_6.png" width="80%" />

<h1>Track Phi Distribution</h1> <img style="display: block; margin: 5em auto;" src="graphics/phi_pt_bin_5.png" width="80%" />

<h1>Track Phi Distribution</h1> <img style="display: block; margin: 5em auto;" src="graphics/phi_pt_bin_4.png" width="80%" />

<h1>Track Phi Distribution</h1> <img style="display: block; margin: 5em auto;" src="graphics/phi_pt_bin_3.png" width="80%" />

<h1>Track Phi Distribution</h1> <img style="display: block; margin: 5em auto;" src="graphics/phi_pt_bin_2.png" width="80%" />

<h1>Track Phi Distribution</h1> <img style="display: block; margin: 5em auto;" src="graphics/phi_pt_bin_1.png" width="80%" />

<h1>Track Phi Distribution</h1> <img style="display: block; margin: 5em auto;" src="graphics/phi_pt_bin_0.png" width="80%" />

<h1>Estimated Track Efficiency</h1> <img style="display: block; margin: 3em auto;" src="graphics/eff_by_pt_bin.png" width="70%" />

<h1>Hits on Track</h1> <img style="display: block; margin: 5em auto;" src="graphics/nhits_pt_bin_9.png" width="90%" />

<h1>Hits on Track</h1> <img style="display: block; margin: 5em auto;" src="graphics/nhits_pt_bin_8.png" width="90%" />

<h1>Hits on Track</h1> <img style="display: block; margin: 5em auto;" src="graphics/nhits_pt_bin_7.png" width="90%" />

<h1>Hits on Track</h1> <img style="display: block; margin: 5em auto;" src="graphics/nhits_pt_bin_6.png" width="90%" />

<h1>Hits on Track</h1> <img style="display: block; margin: 5em auto;" src="graphics/nhits_pt_bin_5.png" width="90%" />

<h1>Hits on Track</h1> <img style="display: block; margin: 5em auto;" src="graphics/nhits_pt_bin_4.png" width="90%" />

<h1>Hits on Track</h1> <img style="display: block; margin: 5em auto;" src="graphics/nhits_pt_bin_3.png" width="90%" />

<h1>Hits on Track</h1> <img style="display: block; margin: 5em auto;" src="graphics/nhits_pt_bin_2.png" width="90%" />

<h1>Hits on Track</h1> <img style="display: block; margin: 5em auto;" src="graphics/nhits_pt_bin_1.png" width="90%" />

<h1>Hits on Track</h1> <img style="display: block; margin: 5em auto;" src="graphics/nhits_pt_bin_0.png" width="90%" />

<h1>Impact Parameter</h1> <img style="display: block; margin: 0em auto;" src="graphics/imp_pt_bin_9.png" width="90%" />

<h1>Impact Parameter</h1> <img style="display: block; margin: 0em auto;" src="graphics/imp_pt_bin_8.png" width="90%" />

<h1>Impact Parameter</h1> <img style="display: block; margin: 0em auto;" src="graphics/imp_pt_bin_7.png" width="90%" />

<h1>Impact Parameter</h1> <img style="display: block; margin: 0em auto;" src="graphics/imp_pt_bin_6.png" width="90%" />

<h1>Impact Parameter</h1> <img style="display: block; margin: 0em auto;" src="graphics/imp_pt_bin_5.png" width="90%" />

<h1>Impact Parameter</h1> <img style="display: block; margin: 0em auto;" src="graphics/imp_pt_bin_4.png" width="90%" />

<h1>Impact Parameter</h1> <img style="display: block; margin: 0em auto;" src="graphics/imp_pt_bin_3.png" width="90%" />

<h1>Impact Parameter</h1> <img style="display: block; margin: 0em auto;" src="graphics/imp_pt_bin_2.png" width="90%" />

<h1>Impact Parameter</h1> <img style="display: block; margin: 0em auto;" src="graphics/imp_pt_bin_1.png" width="90%" />

<h1>Impact Parameter</h1> <img style="display: block; margin: 0em auto;" src="graphics/imp_pt_bin_0.png" width="90%" />

<h1>Summary</h1> - We do not confirm the initially claimed $\sim 75\\%$ loss in efficiency in iTPC sector 20 - The effect is much less visible in properly calibrated data - We modeled track reconstruction without the inner hits using sector 14 - The average expected loss due to missing hits is $\sim 20\\%$ for global tracks with higher $P_T$ ($\gtrsim 0.4$ GeV) and an additional $\sim 7\\%$ loss for primary tracks - The $\sim 7\\%$ loss in primaries is consistent with the widening of the track impact parameter distribution.<br> As a result the tracks do not pass the 3 cm cut and are not assigned to the vertex - For lower $P_T$ ($\lesssim 0.4$ GeV) tracks we observe an increase in the number of short tracks in the adjacent sectors. The exact reason for such behavior is under investigation