sparticle reconstruction in dilepton final state

Sparticle reconstruction Sparticle reconstruction in dilepton final statein dilepton final state

M. Chiorboli, M. Galanti & A. M. Chiorboli, M. Galanti & A. TricomiTricomi

University & INFN CataniaUniversity & INFN Catania

CMS Physics Review I. SUSY/BSMCERN, 20-21 September 2004

PRS Physics Review I: SUSY/BPRS Physics Review I: SUSY/BSMSM

Alessia TricomiUniversity & INFN Catania

TopologyTopology

2 high pt isolated leptons OS

(leptons = e,)

2 high pt (b) jets

missing EtSM bkg: tt, Z+jet, W+jet, ZZ, WW, ZW, QCD jets

g~ pp

b(q)02

~

Reconstruction of sbottoms, squarks and Reconstruction of sbottoms, squarks and gluinosgluinos

p

p

g~

b~

b(q)

b(q)

01

02

~)~(

~qqbb

01



Mass reconstruction: what can be doneMass reconstruction: what can be done

End-point analysis: from global End-point analysis: from global fitfit Sparticle massesSparticle masses 1 1 mass determinationmass determination

Mass peak reconstructionsMass peak reconstructions

p

p

g~

b~

b(q)

b(q)

01

02

~



Mass reconstruction: what existsMass reconstruction: what exists

p

p

g~

b~

b

b

01

02

~

p

M

M1p

01

02

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

Model dependence:

assumed to be known

Jet association

01

M

10 fb-1

sbottomsbottom

10 fb-1

sbottom sbottom chainchain

Kinematical Kinematical peculiarities can be peculiarities can be

exploitedexploited



Edge analysisEdge analysis

In sequential decays many In sequential decays many other edges and thresholds can other edges and thresholds can be extractedbe extracted

This was first pioneered by This was first pioneered by ATLASATLAS

Several interesting Several interesting development by Luc (see his development by Luc (see his talktalk))

Combining all these Combining all these informationinformation

sparticle masses sparticle masses

p

p

g~

b~

b(q)

b(q)

01

02

~



Plan for the new analysisPlan for the new analysisTO DO LISTTO DO LIST StatusStatusParton level studies to exploit the Parton level studies to exploit the feasibility of the methods feasibility of the methods (Pythia+Isajet) (Pythia+Isajet)

work in progresswork in progress

Fast simulation study to understand Fast simulation study to understand the CMS capability to reconstruct the CMS capability to reconstruct sparticles in the dilepton channelsparticles in the dilepton channel (FAMOS) (FAMOS)

playing and familiarizing playing and familiarizing with FAMOSwith FAMOS

Full simulation & reconstructionFull simulation & reconstruction

detailed study @ mSUGRA point LM1 detailed study @ mSUGRA point LM1

background study: tt, Z+jet, W+jet… background study: tt, Z+jet, W+jet…

tool optimization:tool optimization:

jet calibrationjet calibration

b taggingb tagging

mass fitmass fit

All to be doneAll to be done



Present work: parton level studiesPresent work: parton level studies

Generator: Generator: 100K events with 100K events with

Pythia 6.224 + Isajet Pythia 6.224 + Isajet 7.69 7.69

No particular problem No particular problem encounteredencountered

Luc’s suggestion Luc’s suggestion seems promisingseems promising i.e. Mi.e. Mllll vs M vs Mllqllq

MMlqlq for different M for different Mllll cuts cuts

Mll vs. Mllq



What is neededWhat is needed

SignalSignal ~ ~ 600k events for 10 fb600k events for 10 fb-1 -1 @LM1@LM1 to be producedto be produced

Bkg: tt, Z+jet, W+jet, qcdBkg: tt, Z+jet, W+jet, qcd most important ttmost important tt from past fast simulation studies Z+jet, from past fast simulation studies Z+jet,

W+jet, qcd… seem negligibleW+jet, qcd… seem negligible something already in production (something already in production (~ ~

600k tt events)600k tt events)

10tan

0

)(

60

250

00

21

A

sign

m

m



Main systematicsMain systematics

End-point analysisEnd-point analysis jet resolutionjet resolution knowledge of theoretical shapesknowledge of theoretical shapes

Sparticle peak reconstructionSparticle peak reconstruction uncertainty on the uncertainty on the 11 mass from end- mass from end-

point analysispoint analysis dilepton windowdilepton window jet association (how to be model jet association (how to be model

independent?)independent?)



ManpowerManpower

InstitutionInstitution CataniaCatania

People involvedPeople involved Massimiliano Chiorboli (Post-Doc)Massimiliano Chiorboli (Post-Doc) Mario Galanti (PhD student)Mario Galanti (PhD student) Alessia Tricomi (Researcher)Alessia Tricomi (Researcher)

Is enough?Is enough? it should be if no delay from HW it should be if no delay from HW

productionproduction



Summary & PlansSummary & Plans

Topology:Topology: Generators: Pythia 6.224+Isajet 7.69 Generators: Pythia 6.224+Isajet 7.69 Analysis @ point LM1:Analysis @ point LM1:

Parton level studies: feasibility of edge determinationsParton level studies: feasibility of edge determinations Fast simulation: first studies with FAMOS (just started) Fast simulation: first studies with FAMOS (just started) Full simulation: OSCAR+ORCAFull simulation: OSCAR+ORCA Second stage: study CMS capability to reconstruct sparticles Second stage: study CMS capability to reconstruct sparticles

in dilepton channel with FAMOS in other benchmark pointsin dilepton channel with FAMOS in other benchmark points Important tools:Important tools:

b tagging (already involved in algo studies)b tagging (already involved in algo studies) jet calibration jet calibration

Main bkg: ttMain bkg: tt

01

02

02

~ ;b(q))q~(b~

);~(~~ qqbbg

backupbackup



How to distinguish the two leptonsHow to distinguish the two leptons

Luc suggestion

sparticle reconstruction in dilepton final state

Documents

jet associationprs physics

ttprs physics

mllqprs physics

gluinosppbqbqprs physics

doneprs physics

susybsmbackupprs physics

tt eventsprs physics

jet calibration b