Sparticle reconstruction methods in the CMS detector Massimiliano Chiorboli Universita and INFN...

Sparticle reconstruction methods Sparticle reconstruction methods in the CMS detectorin the CMS detector

Sparticle reconstruction methods Sparticle reconstruction methods in the CMS detectorin the CMS detector

Massimiliano Chiorboli

Universita’ and INFN Catania

18-20 Apr 2002Euro-GDR Meeting Massimiliano Chiorboli

OutlineOutlineOutlineOutline

Past studies on SUSY in CMS

Recent studies: sparticle recontruction

Decay chain

Sparticles reconstruction: 2200 l l++ll- - 11

0 0 dilepton edge

Sbottom recontstruction

Gluino reconstruction

measurement

Conclusions

)bM(-)gM(~~ )bM(-)gM(~~


Sparticle searches in CMSSparticle searches in CMSSparticle searches in CMSSparticle searches in CMS

Up to now…

Inclusive studies:

Excess over the SM

Now…

Sparticle reconstruction


The CMS detectorThe CMS detectorThe CMS detectorThe CMS detector


99.610 = LSP

186.01±145.8lR

379.72±211.4lL

186.820549qR

358.830570qL

379.140549.7bR

600.5tR522.5bL

412.5tL643.3g

Proposed Post-LEP Benchmarks for Supersymmetry Proposed Post-LEP Benchmarks for Supersymmetry (hep-ph/0106204)(hep-ph/0106204)Proposed Post-LEP Benchmarks for Supersymmetry Proposed Post-LEP Benchmarks for Supersymmetry (hep-ph/0106204)(hep-ph/0106204)

pb 41.41TOTSUSY

PYTHIA 6.152


Decay chainDecay chainDecay chainDecay chain

p

p

g~

b~

b

b

01

~

02

~ ~

0A

)( sign

10β tan

100m

250m

0

0

21

bb~

g~ pp

b~02

01

~

(15% bL, 10% bR)

(35 % bL, 22% bR)

(0.2 %)

01

~ ~

(60 %)

Event final state:

• 2 high pt isolated leptons OS

• 2 high pt b jets

• missing Et


Event productionEvent productionEvent productionEvent production

2 isolated leptons, pT>15 GeV, ||<2.4

2 b-jets, pT>20 GeV, ||<2

• PYTHIA 6.152• CMSJET 4.801: fast simulation, parametrization of

the detector

SM bkg: tt, Z+jet, W+jet, ZZ, WW, ZW


First step: First step: 2200 l l++ll- - 11

00First step: First step: 2200 l l++ll- - 11

00

02

~ 01

~

~p

p

g~

b~

b

b

01

~

02

~ ~

SUSY SUSY + SM

10 fb-1

)μM(μ )eM(e -

Z+jet

tt

~

2

χ~2~

2~

2

χ~max

M

)M)(MM(MM

01

02


)μM(μ )eM(e -

Etmiss > 50 GeV

10 fb-1

)μM(e -)μM(e - )μM(μ )eM(e --


Dilepton EdgeDilepton EdgeDilepton EdgeDilepton Edge

GeV 85.32 M

)M)(MM(MM

2

χ

222

χmax01

02

~

~~~~

GeV 0.91 85.48 Mmax

Fit result:


Sbottom reconstructionSbottom reconstructionSbottom reconstructionSbottom reconstruction

p

p

g~

b~

b

b

01

~

02

~ ~

Assuming M(10)

known!

p

M

M1p

01

02

~

~

GeV 92 M GeV 75


Sbottom reconstructionSbottom reconstructionSbottom reconstructionSbottom reconstruction

Etmiss > 50 GeV Et

miss > 100 GeV Etmiss > 150 GeV

I choose the most energetic b-jet

p

M

M1p

01

02

~

~MC true


Sbottom massSbottom massSbottom massSbottom mass

55.8

GeV 8.1516.4b)~M( 02

Result of fit:

GeV 7.549)b~

M(

GeV 5.522)b~

M(

R

L

Generated masses:

10 fb-1


Gluino reconstructionGluino reconstructionGluino reconstructionGluino reconstruction

p

p

g~

b~

b

b

01

~

02

~ ~

b)b~

( angle

Etmiss > 150 GeV


Gluino massGluino massGluino massGluino mass

9.54σ

GeV 7.2631.8bb)χ~M( 02

Result of fit:

GeV 643.3)gM( ~Generated mass:

10 fb-1


Combinatorial suppressionCombinatorial suppressionCombinatorial suppressionCombinatorial suppression

tt~ g~ 1

t~ b,~ (2.7%), b~ 0221

(8%)

%) (3.5t ~ b~ 11

%) (1W t~ b~ 11

t~ b,~ (2.7%), b~ 0221

%) (1.6t ~ b~ 12

%) (1.2W t~ b~ 12

t~ b,~ (2.7%), b~ 0221

GeV 60 t)t~M(-)g~M(

GeV 200 b)~M(-)t~M(

GeV 170 t)~M(-)b~

M(

GeV 20 W)t~M(-)b~

M( GeV 330 b)~M(-)b

~M( 0

2

b-jets from sbottoms of real decay chain have a harder spectrum



Eb-jet 1 > 250 GeV

Sbottom Gluino

10 fb-1



Sbottom Gluino

10 fb-1Eb-jet 1 > 250 GeV


Sbottom massSbottom massSbottom massSbottom mass

68.8

GeV 7.7515.9b)~M( 02

Result of fit:

GeV 7.549)b~

M(

GeV 5.522)b~

M(

R

L

Generated masses:

10 fb-1


Gluino massGluino massGluino massGluino mass

GeV 643.3)gM( ~Generated mass:

9.04σ

GeV 8.3639.3bb)χ~M( 02

Result of fit:10 fb-1


Dependence on M(Dependence on M())Dependence on M(Dependence on M())

M(10) true

M(10) = M(ll)

M(10) = M edge

p2p

M

M1p

01

02

~

~

I assumed M(10) known: we cannot detect the neutralinos!

Sbottom

Gluino


Realistic situationRealistic situationRealistic situationRealistic situation

Sbottom

Gluino

GeV 9.489)b~

(M M)~(M

GeV 9.515)b~

(M )true~(M)~(Mmax0

1

01

01

5%

GeV 7.619)g~(M M)~(M

GeV 3.639)g~(M )true~(M)~(Mmax0

1

01

01

3%


estimationestimation estimationestimation

doesn’t depend on M(10) !

)b~

M(-)g~M(

GeV 30)~M( 01

)bM(-)gM(~~ )bM(-)gM(~~


estimationestimation estimationestimation

6.32σ

GeV 6.387.5b)χ~M(bb)χ~M( 02

02

Result of fit:

)bM(-)gM(~~ )bM(-)gM(~~

GeV 6.93)b~

M(-)g~M(

GeV 8.120)b~

M(-)g~M(

R

L

Generated values:

10 fb-1


Dependence on M(ll)Dependence on M(ll)Dependence on M(ll)Dependence on M(ll)

GeV 92 M GeV 75 GeV 92 M GeV 60

GeV 92 M GeV 80

Sbottom

Gluino


With 60 fbWith 60 fb-1-1With 60 fbWith 60 fb-1-1

Sbottom

7.45

GeV 9.39.521b)~M( 02

GeV 88 M GeV 82

1.41σ

GeV 4.38.296bb)χ~M( 02

Gluino


Sbottoms separationSbottoms separationSbottoms separationSbottoms separation

1b~

2b~

38

36bb~bb~bb~

g~ ,g~q~ 01

021

bb~bb~bb~

g~ ,g~q~ 01

022

106

106

Detector resolution prevents the two sbottom separation


152.510 = LSP

294.51±193.4lR

546.12±299.6lL

294.820780qR

532.430814qL

545.340771.3bR

800.8tR723.0bL

589.4tL919.8g

Point GPoint GPoint GPoint G

pb 6.00TOTSUSY


tt~ g~ 1

t~ b,~ %), (2.7 %) (8.5 b~ 0221

(16%) (8 %)

Decay chainDecay chainDecay chainDecay chain

bb~

g~ pp

b~02

(16% bL, 10% bR)

(15 % bL, 28% bR)

01

~ ~

(8 %) (60 %)

%) (3.5 %) (7t ~ b~ 11

(1%) %) (3W t~ b~ 11

%) (1.6 %) (2.6t ~ b~ 12

%) (1.2 %) (3.2W t~ b~ 12

Less good events

More “fake” events



60 fb-1

)μM(μ )eM(e -

SUSY only l

slepton l

E(ll) > 160 GeV



Etmiss > 100 GeVEt

miss > 50 GeV Etmiss > 150 GeV

E(ll) > 160 GeV



)μM(μ )eM(e - )μM(e -)μM(e - )μM(μ )eM(e --

E(ll) > 160 GeV Etmiss > 250 GeV

GeV 140 M GeV 105


Peaks reconstructionPeaks reconstructionPeaks reconstructionPeaks reconstruction

Etmiss > 250 GeV

Sbottom Gluino M(g)-M(b)


Peaks reconstructionPeaks reconstructionPeaks reconstructionPeaks reconstruction

Etmiss > 250 GeV Eb-jet 1 > 300 GeV

Sbottom Gluino M(g)-M(b)


Point G with 500 fbPoint G with 500 fb-1-1Point G with 500 fbPoint G with 500 fb-1-1

No Pile Up!

GeV 136.84 M

)M)(MM(MM

~

2

χ~2~

2~

2

χ~max01

02

GeV 2.9 138.6 Mmax

Fit result:

)μM(μ )eM(e -

)μM(e -)μM(e - )μM(μ )eM(e --

Etmiss > 250 GeV


Sbottom at point GSbottom at point GSbottom at point GSbottom at point G

1.51

GeV 13.5 5.738b)~M( 02

Result of fit:

GeV 3.771)b~

M(

GeV 0.723)b~

M(

R

L

Generated masses:

500 fb-1


Gluino at point GGluino at point GGluino at point GGluino at point G

9.54σ

GeV 10.1 2.913bb)χ~M( 02

Result of fit:

GeV 8.199)g~M(

Generated mass:

500 fb-1


at point Gat point G at point Gat point G

2.30σ

GeV 6.6175.2b)χ~M(bb)χ~M( 02

02

Result of fit:

GeV 5.148)b~

M(-)g~M(

GeV 8.196)b~

M(-)g~M(

R

L

Generated values:

)bM(-)gM(~~ )bM(-)gM(~~

500 fb-1


ConclusionsConclusionsConclusionsConclusions

• estimation of M(l+l-)max

• sbottom reconstruction with Resol. ~ 13 %, but 2 sbottoms not resolved

• gluino reconstruction with Resol. 6 %

• M(g) - M(b) estimation, independent of M(10), with Err ~ 4 %

Point B (tan =10, low masses), with 10 fb-1

~2~

2~

2~

2~ M)MM)(MM( 0

102

In some mSUGRA regions CMS will be able to obtain information about the mass spectrum of sparticles from dilepton edges and to reconstruct some sparticles mass peaks:


ConclusionsConclusionsConclusionsConclusions

Point G (tan =20, higher masses), with 500 fb-1

• estimation of M(l+l-)max

• sbottom reconstruction with Resol. ~ 7%

• gluino reconstruction with Resol. 6 %

• M(g) - M(b) estimation, independent of M(10), with Err ~ 4 %

~2~

2~

2~

2~ M)MM)(MM( 0

102

Sparticle reconstruction methods in the CMS detector Massimiliano Chiorboli Universita and INFN...

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Transcript of Sparticle reconstruction methods in the CMS detector Massimiliano Chiorboli Universita and INFN...