First look into sbottom and gluino reconstruction

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


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


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


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


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


85929

SUSY

tt

Subtracting invariant mass of OSOF pairs eliminate SM and combinatorial bkg

Reconstruction of 0

102

~~


estimation)~M()~M( 0

102

GeV) (50.5 GeV 39.090.50)~M()~M( 01

02

)~M()~M(M 01

02

max


signal

bkg

Sbottom reconstruction

GeV 52M GeV 45

pp

M

M1

01

02

~

~


Sbottom reconstruction (II)

reconstructed neutralino combined with the most energetic b-jet, assuming Mknown


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


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


Gluino reconstruction (II)


Gluino reconstruction (III)

jet)-b b~

( angle rec


Gluino reconstruction (IV)

Cut on this angle to select the b-jet coming from the gluino

0.4 cos

0.8 cos


Gluino reconstruction (V)


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


evaluation)b

~M(-)g~M(

0.4 cos 0.8 cos cut no


evaluation (II))b

~M(-)g~M(

(24.2) GeV 5.45.21)b~

M()g~M( recrec


Dependence from

10 mass assumed to be known

) ~ M(01


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


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


Gluino reconstruction

(299.2)

GeV 8.39

2.295)g~M( rec


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

First look into sbottom and gluino reconstruction

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