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SVD software meeting summary Jul. 20 th , 2005

SVD software meeting summary Jul. 20 th , 2005. Alignment status (A.Kibayashi) Hit efficiency (Y.Fujiyama) Cluster size study (D.Heffernan) Other topics (T.Hara ). Alignment (A.Kibayashi). Her detail report is available on http://www.hp.phys.titech.ac.jp/atsuko/post/2005/0711

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SVD software meeting summary Jul. 20 th , 2005

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  1. SVD software meeting summaryJul. 20th, 2005 • Alignment status (A.Kibayashi) • Hit efficiency (Y.Fujiyama) • Cluster size study (D.Heffernan) • Other topics (T.Hara )

  2. Alignment (A.Kibayashi) Her detail report is available on http://www.hp.phys.titech.ac.jp/atsuko/post/2005/0711 She is studying global alignment with magnetic field with the method suggested by Ozaki-san; she merges two upper and lower tracks using chisqure minimization to improve the precision of the track. She finds that the drho shift of ~4um found with the previous method disappears, but the tanl dependence of drho shows up. it is pointed out to use only high momentum track in cosmic ray muons. She will try the second method that is also suggested by Ozaki-san, that aligns the SVD so that drho and dz are minimized.

  3. Hit Efficiency (Y.Fujiyama) He compares hit efficiency vs occupancy with new (b20050311) and old(b20040727) libraries. The new library gives ~5% higher efficiency because the bug in trak has been fixed. He also checks the efficiency with loose cluster size cut in the 1st layer n-side: the default cut is applied at the cluster size of 6, the modified threshold is set to 9. This change increases the efficiency 2~3%. Now the hit efficiency is closed to 1 with the occupancy ~0. He finds that the pivot of the helix had been set to the origin, that makes the selection bias of di-muon events with a tight dr cut. He modifies the pivot to the IP and finds no selection bias.

  4. clustering (D.Heffernan) He is now studying on the improvement of cluster positioning using track information such as incident angle and residuals to clusters. From the incident angle dependence of cluster size and charge division of clusters, he define a likelihood function assuming Gaussian smearing that optimizes the cluster position. He finds that the residual slightly shifts from zero and the position resolution is worse than that of the current cluster position algorithm. He will improve this method by increasing statistics for determining the PDFs, modifying the likelihood function etc.

  5. other topics (T.Hara) T.Hara san checks invariant mass resolution with the modified n-side cluster size cut in TRAK, i.e. the threshold is changed to 5 to 9 to retrieve the clusters that is the part of the cause of the inefficiency. He uses phi(->K+K-), J/psi(mu+mu-), D(->Kpi), D*(Dpi) and Ks. He requires at least 2 SVD hits in reconstructing invariant mass. No difference is found in invariant mass resolution with the TRAK modification, but detection efficiency slightly increases by 3% at most. It is pointed out that the effect of the change is sensitive to the vertexing. Kibayashi-san will volunteer to estimate the IP resolution as a function of occupancy for low momentum region.

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