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Solving Vertex Determinant Error with StarSoft Local: Case Study

Investigate a vertex error matrix determinant issue involving ancient bug V, with relevant equations and comparisons between old and new codes. Discover the influence of track multiplicity on error matrix correlations.

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Solving Vertex Determinant Error with StarSoft Local: Case Study

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  1. New ancient bug V. Perevoztchikov Brookhaven National Laboratory,USA

  2. UPC, ancient bug • UPC makes vertex from very small amount of tracks. Two in our case. • Two tracks lead to high XY correlation of vertex error matrix • We got negative determinant of error matrix; • Why? StarSoft local

  3. Look on the code • // A=R*S • double axx = rxx*msxx + rxy*msxy; • double axy = rxx*msxy + rxy*msyy; • double ayx = ryx*msxx + ryy*msxy; • double ayy = ryx*msxy + ryy*msyy; • // S=A*Rt • msxx = axx*rxx + axy*rxy; • msxy = axx*ryx + axy*ryy; • msyy = ayx*ryx + ayy*ryy; • You see, no updating of xz,yz terms. To fix it easy, but what is influence to old data. • Some how is evident, that more tracks, less Xz,Yz correlations. Less correlation, less influence of the bug. Zero correlation, no influence at all. The solution of this is trivial: StarSoft local

  4. PP test The smallest multiplicity in STAR is PP. Jan gave me the file st_physics_adc_7136022_raw_1080005.daq Old and new code gave exactly the same result. When I tell exactly, means exactly. I did not find any difference. When I compare UPC file, the difference is: • Old code events with 2 primary tracks/total event = 0.45 • New code events with 2 primary tracks/total event =0.82 There is still room to investigate, but better. StarSoft local

  5. But life is not easy Yury Gorbunov told me that nothing is perfect. StarSoft local

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