First look into sbottom and gluino reconstruction
Massimiliano Chiorboli
University and INFN Catania
Catania CMS Week 20/06/2001Massimiliano Chiorboli
SUGRA parameters
m0 200 GeV
m1/2 100 GeV
tan 2
A0 0
sign -
44.5> 300
95.0309.3
94.5275.0
273.4299.2
m (GeV)m (GeV)g~
Lb~
Rb~
q~
2~
1~
02
~LSP ~0
1
nb 1 nb 3.1 q~,g~SUSYtot
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Decay chainand event topology
bb~
g~ q~ pp
b~02
01
~
p
p
g~
b~
b
b
01
~
02
~
Event final state:
• 2 high pt isolated leptons OS
• 2 high pt b jets
• missing Et
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Events production
SPYTHIA (PYTHIA 6.136) CMSJET 4.703
3 fb-1
51’000
28’000
531’000
2’005’000
1’088’000
Signal
g~g~
g~q~
q~q~
g~~
q~~
72’000
65’000
SUSY bkg~~
t~t~
1’860’000
SM bkgtt
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Events selection
at least 2 isolated leptons with pt>15 GeV and ||<2.4
at least 2 b-jets with pt>15 GeV and ||<2 0.5
%
<10-4
10-4
0.6
<0.1
0.7
5.0
1.4
Events
1’302
40010
165
48
3’765
54’216
27’228
g~g~
g~q~
q~q~
g~~
q~~
~~
t~t~
tt
Catania CMS Week 20/06/2001Massimiliano Chiorboli
invariant mass of e+e- and +
due to kinematics, the distribution shows an edge
Reconstruction of 0
102
~~
is forbidden 01
02
~~~
02
~01
~
SUSY
tt
Catania CMS Week 20/06/2001Massimiliano Chiorboli
85929
SUSY
tt
Subtracting invariant mass of OSOF pairs eliminate SM and combinatorial bkg
Reconstruction of 0
102
~~
Catania CMS Week 20/06/2001Massimiliano Chiorboli
estimation)~M()~M( 0
102
GeV) (50.5 GeV 39.090.50)~M()~M( 01
02
)~M()~M(M 01
02
max
Catania CMS Week 20/06/2001Massimiliano Chiorboli
signal
bkg
Sbottom reconstruction
GeV 52M GeV 45
pp
M
M1
01
02
~
~
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Sbottom reconstruction (II)
reconstructed neutralino combined with the most energetic b-jet, assuming Mknown
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Sbottom reconstruction (III)
(275.0)
GeV 0.370.265)b~
M( rec
Assuming M(10) = 44.5 GeV
At the moment, no jet energy correction
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Gluino reconstruction
combination of the reconstructed sbottom and a b-jet
~ 10 % of the selected events have >2 b-jets
the b-jet closest to the reconstructed sbottom is chosen
b)b~
( angle
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Gluino reconstruction (II)
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Gluino reconstruction (III)
jet)-b b~
( angle rec
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Gluino reconstruction (IV)
Cut on this angle to select the b-jet coming from the gluino
0.4 cos
0.8 cos
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Gluino reconstruction (V)
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Sbottom and gluino after cuts (cos > 0.8)
(299.2) GeV 8.392.295)g~M( rec
(275.0) GeV 7.311.263)b~
M( rec
Catania CMS Week 20/06/2001Massimiliano Chiorboli
evaluation)b
~M(-)g~M(
0.4 cos 0.8 cos cut no
Catania CMS Week 20/06/2001Massimiliano Chiorboli
evaluation (II))b
~M(-)g~M(
(24.2) GeV 5.45.21)b~
M()g~M( recrec
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Dependence from
10 mass assumed to be known
) ~ M(01
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Results within 3 fb-1
GeV 39.090.50)~M()~M( 01
02
true01assumed
01truerec )~M()~M( 6.1)b
~M()b
~M(
GeV 7.311.263)b~
M( rec true01 )~M(for
GeV 8. 39 2. 295 ) g~ M(rec
true01assumed
01truerec )~M()~M( 6.1)g~M()g~M(
true01 )~M(for
GeV 5.45.21)b~
M()g~M( recrec )~M( fromt indipenden 01
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Future plans
Scanning the mSUGRA parameters plane
Including the jet energy correction
Improving the cuts
Studying this decay chain as a benchmark channel for the b-tagging
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Gluino reconstruction
(299.2)
GeV 8.39
2.295)g~M( rec
Catania CMS Week 20/06/2001Massimiliano Chiorboli
Sbottom reconstruction
(275.0)
GeV 0.37
0.265)b~
M( rec
Assuming M(10) = 44.5 GeV
At the moment, no jet energy correction