ttbar events with Atlantis

1
ttbar events with Atlantis

• Ex tt?Wb Wb ?udb tntb (Evt 7 in first file of
  5200 with 11.0.41)

E (GeV) pT (GeV) h f (deg)
u 66 60 -0.45 -129
d 49 44 -0.49 127
b 1 169 130 -0.75 -93
b 2 79 79 -0.11 -109
? 98 19 2.35 54
n? 20 15 -0.83 127
f
d jet
j1
?
pTmiss
j2
u
d
u jet
j2
j1
t
pTmiss
m from j1

• 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 r-z view

d jet
u jet
?
j2
j1
m from j1
m from j1
2
Primary vertex
Reconstructed tracks Monte Carlo tracks
E (GeV) pT (GeV) h f (deg)
u 66 60 -0.45 -129
d 49 44 -0.49 127
b 1 169 130 -0.75 -93
b 2 79 79 -0.11 -109
? 98 19 2.35 54
n? 20 15 -0.83 127
X-Y plane pT gt 5 GeV
p
p
p
p
p
y
p
p
p
Detector center
Rec. vertex
X
p
p
p
p
Monte Carlo vertex
p
p
K
K
25 mm
r-Z plane pT gt 5 GeV

• Transverse plane Primary vertex displaced by
  20mm, precision 15 mm
• z Primary vertex displaced by 9cm, precision
  100 mm
• Pb 8 particles (6p, 1K, 1Proton) originated from
  the MC vertex. FSR from jets?

?
z
Detector center
Monte Carlo vertex
Rec. vertex
1 cm
3
B tagging
Reconstructed tracks Monte Carlo tracks
Rec. vertex
E (GeV) pT (GeV) h f (deg)
u 66 60 -0.45 -129
d 49 44 -0.49 127
b 1 169 130 -0.75 -93
b 2 79 79 -0.11 -109
? 98 19 2.35 54
n? 20 15 -0.83 127
X-Y (j1,j2) pT gt 5 GeV
Detector center
d jet
t jet
X-Y pT gt 2 GeV
Detector center
Monte Carlo vertex
j2
Monte Carlo vertex
15 mm
20 mm
u jet
j2
j1
4 mm
4 mm
j1

SV1IP3D
b-jet 1 1.97
b-jet 2 5.8

• Bjets with large IP
• But hard reconstruction because of activity

4
Jets in calorimeters

• tt?Wb Wb ?udb tntb (Evt 7 in first file of 5200
  with 11.0.41)

E (GeV) pT (GeV) h f (deg)
u 66 60 -0.45 -129
d 49 44 -0.49 127
b 1 169 130 -0.75 -93
b 2 79 79 -0.11 -109
? 98 19 2.35 54
n? 20 15 -0.83 127
E rec (GeV) h rec f rec (deg)
b-jet 1 153 -0.77 -93
d-jet 52 -0.48 139
b-jet 2u 151 -0.32 -116
b1
Jet circle DR0.4
b2
d
u
t

• A lot of jets in this event !
• u-jet and b-jet2 are to close to be
  distinguished, even with cone 0.4

f