1. 1 ttbar events with Atlantis   A lot of jets in this event !   Bjets (1 and 2) close in phi   Muon from semilep decay of b-jet1   Tau jet   Pb 1: Muon ID track bad  -z view   Ex: tt  Wb Wb  udb   b (Evt #7 in first file of #5200 with 11.0.41) E (GeV) p T (GeV)  (deg) u6660-0.45-129 d4944-0.49127 b 1169130-0.75-93 b 279 -0.11-109  98192.3554  2015-0.83127  p T miss j2j1  from j1 u j1 d p T miss u jet d jet  j2  j1 d jetu jet   from j1

2. 2 Primary vertex X-Y plane p T > 5 GeV   Transverse plane: Primary vertex displaced by 20  m, precision ± 15  m   z: Primary vertex displaced by 9cm, precision ± 100  m   Pb: 8 particles (6 , 1  Proton) originated from the MC vertex. FSR from jets? Reconstructed tracks Monte Carlo tracks p K p K Detector center Rec. vertex Monte Carlo vertex Rec. vertex Detector center  -Z plane p T > 5 GeV Monte Carlo vertex X y 25  m 1 cm ρ z             E (GeV) p T (GeV)  (deg) u6660-0.45-129 d4944-0.49127 b 1169130-0.75-93 b 279 -0.11-109  98192.3554  2015-0.83127

3. 3 B tagging X-Y pT > 2 GeV X-Y (j1,j2) pT > 5 GeV Detector center j2 j1   Bjets with large IP   But hard reconstruction because of activity … u jet 20 mm Rec. vertex Monte Carlo vertex j1 j2 Detector center Reconstructed tracks Monte Carlo tracks 4 mm SV1+IP3D b-jet 11.97 b-jet 25.8 d jet  jet 15 mm Monte Carlo vertex E (GeV) p T (GeV)  (deg) u6660-0.45-129 d4944-0.49127 b 1169130-0.75-93 b 279 -0.11-109  98192.3554  2015-0.83127

4. 4 Jets in calorimeters   tt  Wb Wb  udb   b (Evt #7 in first file of #5200 with 11.0.41) b1 b2 E rec (GeV)  rec  rec (deg) b-jet 1153-0.77-93 d-jet52-0.48139 b-jet 2+u151-0.32-116 E (GeV) p T (GeV)  (deg) u6660-0.45-129 d4944-0.49127 b 1169130-0.75-93 b 279 -0.11-109  98192.3554  2015-0.83127 u  d    A lot of jets in this event !   u-jet and b-jet2 are to close to be distinguished, even with cone 0.4 Jet circle  R=0.4