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New ancient bug

New ancient bug. V. Perevoztchikov Brookhaven National Laboratory,USA. 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?. Look on the code.

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New ancient bug

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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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