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b -tagging performance with xKalman and iPatRec

b -tagging performance with xKalman and iPatRec. José E. García. With the help of: S. Correard, I . Gavrilenko , S. González, A. Poppleton, E. Ros, A. Rozanov, J. Sánchez and M. Vos. ATLAS kit release 7.0.0 xKalmanppAtrecon-00-00-89 Reconstruction with default values

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b -tagging performance with xKalman and iPatRec

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  1. b-tagging performance with xKalman and iPatRec José E. García With the help of: S. Correard, I. Gavrilenko, S. González, A. Poppleton, E. Ros, A. Rozanov, J. Sánchez and M. Vos

  2. ATLAS kit release 7.0.0 • xKalmanppAtrecon-00-00-89 • Reconstruction with default values • xKalmanppAthena-00-00-87 • Selectivity = 2 & xKalman field • iPat-02-09-00 • Reconstruction with default values • Saved truth information for all particles • DC1 samples WH(120), WH(400) and WH(400) + pileup • 50 K events: H  uu • 20 K events: H  bb • Reconstruction @ farm Tools S/W Workshop – December 03 b-tagging … Jose E. Garcia

  3. Standard ATLAS 2D b-tagging and the 3D (2D+Z) algorithm (ATLAS Communication, M. Vos et al.) • Significance = impact parameter divided by it error • Track weight calculated depending on significance S • w2D=log [ fb(S)/fu(S)]w3D=log[ fb(Sd ,Sz )/fu(Sd ,Sz)] • Primary vertex reconstruction with a 30 merror assumed • Same events for likelihood and analysis • ATLFAST jets used in the analysis • Jets coinciding with the direction of the parton from the Higgs decay (Rjp < 0.2) Method S/W Workshop – December 03 b-tagging … Jose E. Garcia

  4. ID cuts: • pT > 1 GeV, || < 2.5 Cuts • |d0| < 1 mm • Number of precision hits  9 • Number of pixel hits  2 • At least one hit in the b-layer. Standard b-tag cuts S/W Workshop – December 03 • 2 of the track: 2 < 3 • Longitudinal impact parameter: z0 < 1.5 mm • No shared hits in the b-layer • Maximum two shared hits in Pixels + SCT High quality cuts Very high quality cuts • No ambiguity in the first wafer b-tagging … Jose E. Garcia

  5. Resolution S/W Workshop – December 03 • No difference in the pT resolution between the three algorithms • xKalmanAthena has less resolution in the impact parameter. iPatRec and xKalmanAtrecon have similar performance b-tagging … Jose E. Garcia

  6. Significances • Distribution for u-jets is independent of the algorithm • xKalmanAtrecon and iPatRec distributions have the same shape. • Small difference for the high significance region in the xKalmanAthena algorithm. b S/W Workshop – December 03 u Signed track significance for u and b-jets from H(120) decay b-tagging … Jose E. Garcia

  7. Weights • ATLFAST used for jet reconstruction • Exactly the same jets used for the two Athena algorithms. • No much difference between jets in xKalmanAtrecon and Athena. • Jet weight calculated as the sum of all track weights. b S/W Workshop – December 03 u Jet weights distribution for u and b-jets from H(120) decay b-tagging results Jose E. Garcia

  8. xKalmanAtrecon performance has not changed since release 5.3.0 • xKalmanAthena and iPatRec improve performance with increasing releases (see previous talks from Marseille group) • Performance of xKalmanAtrecon is still better than both Athena algorithms. • Ru for b= 50% is bigger than 100. b-tagging S/W Workshop – December 03 u-jet rejection as function of b-jet tagging efficiency for H(120) sample b-tagging … Jose E. Garcia

  9. WH(120) sample Rejections WH(400) sample S/W Workshop – December 03 b-tagging … Jose E. Garcia

  10. Pt dependency • Rejection for u-jets with combined WH(120) and WH(400) data samples • Athena algorithms have around 25% less rejection than Atrecon • Slightly better performance of iPatRec comparing the two Athena algorithms S/W Workshop – December 03 Rejection of u-jets for b = 60 % versus transverse momentum of jets b-tagging … Jose E. Garcia

  11. Eta dependency • Combined samples WH(120) and WH(400) • For || > 1.5 results from the three algorithms are almost equal • Better performance of xKalmanAtrecon at small || S/W Workshop – December 03 Rejection of u-jets for b = 60 % versus || b-tagging … Jose E. Garcia

  12. WH(400) + pileup • High luminosity: 23 minimum bias events • After cuts up to 30% of tracks in the jet come from pileup • Pileup tracks primary vertices are generally displaced by large distances (~ 5.6 cm) • Z cut becomes more important • More information on the xKalmanAtrecon: The b-tagging performance of the complete ATLAS DC1 layout using WH events, M.Vos et al., ATLAS communication S/W Workshop – December 03 b-tagging … Jose E. Garcia

  13. WH(400) + pileup WH(400) + pileup (II) xKalmanAtrecon S/W Workshop – December 03 iPatRec- PRELIMINARY b-tagging … Jose E. Garcia

  14. xKalmanAtrecon still has better performance than the Athena algorithms • Needed a check with the error parameterization “a la Atrecon” for SiClusters • 3D method improves considerably rejection • Pileup gives a deterioration around 10% in the rejection • iPatRec has less deterioration than xKalmanAtrecon for the 2D method, being a bit worse for the 3D • xKalmanAthena results maybe more sensitive than iPatRec to error in SiClusters Conclusions S/W Workshop – December 03 WAIT for release 7.4.0 b-tagging … Jose E. Garcia

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