Very preliminary look at Very preliminary look at sparticle mass measurements sparticle mass measurements

through end-pointsthrough end-points

Massimiliano ChiorboliMassimiliano ChiorboliAlessia TricomiAlessia Tricomi

Università and INFN CataniaUniversità and INFN Catania

Sparticle mass peaksSparticle mass peaks

Last CPT week we showed that it is possible to Last CPT week we showed that it is possible to reconstruct sparticle mass peaks combining reconstruct sparticle mass peaks combining jets and leptons arising from their decaysjets and leptons arising from their decays

p

p

g~

b~

b

b

01

~02

~~

Sbottom reconstructionSbottom reconstruction

p

p

g~

b~

b

b

01

~

02

~ ~

10 fb-1

sbottomsbottom

p

M

M1p

01

02

~

~

At the end-point:At the end-point:

Gluino ReconstructionGluino Reconstruction

p

p

g~

b~

b

b

01

~

02

~ ~

10 fb-1

sbottom sbottom chainchain

Sbottom ChainSbottom Chain Squark ChainSquark Chain

10 fb-1 60 fb-1 300 fb-1 10 fb-1 60 fb-1 300 fb-1

M(sbottom)M(sbottom) 500±7 502±4 497±2 M(squark) 536±10 532±2 536±1

(sbottom)(sbottom) 42±5 41±4 36±3 (squark) 60±9 36±1 31±1

M(gluino)M(gluino) 594±7 592±4 591±3 M(gluino) 592±7 595±2 590±2

(gluino)(gluino) 42±7 46±3 39±3 (gluino) 75±5 59±2 59±2

Fundamental questionFundamental question

How can we do that without depending How can we do that without depending on M(on M(11

00)?)?

These peaks are built assuming M(These peaks are built assuming M(1100) known) known

Kinematical peculiarities Kinematical peculiarities can be exploited can be exploited

p

p

g~

b~

b

b

01

~02

~~

Signal selectionSignal selection

SUSY events generated with ISAJET 7.51 + PYTHIA SUSY events generated with ISAJET 7.51 + PYTHIA 6.1586.158

Detector simulated with CMSJET 4.801Detector simulated with CMSJET 4.801

Point B: mPoint B: m0 0 = 100, m= 100, m1/21/2=250, tan=250, tan=10, A=10, A00=0, =0, >0>0

Integrated luminosity 30 fbIntegrated luminosity 30 fb-1-1

2 isolated leptons, pT>10 GeV, ||<2.5

2 jets, pT1>150 GeV, pT2>100 GeV, pT3,4>50 GeV

ETmiss > 150 GeV

SM bkg not yet considered

1st edge: dilepton1st edge: dilepton

Dilepton edgeDilepton edge

GeV 0.9 77.8Mmax

GeV 22.77M

)M)(MM(MM

~

2

χ~2~

2~

2

χ~max01

02

Result of the fit:Result of the fit:

llq edgellq edge

4 jet4 jet

2 jet2 jet

llq edgellq edge

GeV 3 434Mmax

jet

GeV 71.410M

)M)(MM(MM

02

01

02

02L

~

2

χ~2~

2~

2q~max

jet

Result of the fit:Result of the fit:

lq edgeslq edges

We cannot distinguish the two leptonsWe cannot distinguish the two leptons

lq edge separationlq edge separationhep-ph/0007009hep-ph/0007009

lqlqminmin edge edge

GeV 2 033Mmax

GeV 37.300M

)M)(MM(MM

02

R02

02L

~

2~

2~

2~

2q~min

jet

Result of the fit:Result of the fit:

lqlqmaxmax edge edge

GeV 2 163Mmaxjet

GeV 22.354M

)M)(MM(MM

02

R02

02L

~

2~

2~

2~

2q~max

jet

Result of the fit:Result of the fit:

How to distinguish the How to distinguish the two leptons?two leptons?

We tried the solution We tried the solution proposed by Luc, but proposed by Luc, but the scatter plot doesn’t the scatter plot doesn’t seem to show particular seem to show particular structures.structures.

However, a deep study However, a deep study has to be performed to has to be performed to optimize cutsoptimize cuts

Mass determinationMass determination

We solved the system analitically and get We solved the system analitically and get M(M(11

00), M(), M(2200), M(slepton)), M(slepton)

Sizeable difference from nominal values to Sizeable difference from nominal values to be understood.be understood.

The solutions are very sensitive to small The solutions are very sensitive to small variations of the input parameters.variations of the input parameters.

We would need theoretical shapes of the We would need theoretical shapes of the end-points in order to perform reasonable end-points in order to perform reasonable fits.fits.

Conclusions & Future PlansConclusions & Future Plans

Use of edges looks promising but still a Use of edges looks promising but still a lot of work neededlot of work needed Optimization of cutsOptimization of cuts Theoretical shape of the edgesTheoretical shape of the edges SM bkgSM bkg Better estimate of errorsBetter estimate of errors