Sparticle reconstruction in final states with di-leptons

Sparticle Sparticle reconstruction in final reconstruction in final states with di-leptonsstates with di-leptons

M. Chiorboli, M. Chiorboli, M. GalantiM. Galanti, A. Tricomi, A. TricomiUniversity and INFN, CataniaUniversity and INFN, Catania

Credits: Luc PapeCredits: Luc Pape

Mario GalantiMario GalantiUniversity & INFN - University & INFN - CataniaCatania

PRS session, CPT WeekPRS session, CPT WeekNovember ‘04November ‘04

OutlineOutline

Aim: measurement of sparticle Aim: measurement of sparticle masses from kinematical end-masses from kinematical end-point analyses in events point analyses in events containing containing 22

00→→1100ll (l=e,ll (l=e,))

Feasibility study:Feasibility study:– first step: parton levelfirst step: parton level– preliminary attempts with FAMOSpreliminary attempts with FAMOS



End-point analysisEnd-point analysis

q~q

01

02

~

In sequential decays, all the sparticle masses involved can be extracted from the measurement of edges and thresholds in the effective mass distributions

Maxima and minima of effective masses correspond to collinear configurations

Only squark chains considered at this stage

Squark coming from gluino decays or directly produced



Event selection: parton Event selection: parton levellevel

50k events @ LM150k events @ LM1– MM½½=250, sign(=250, sign(μμ)=+, M)=+, M00=60, A=60, A00=0, tan(=0, tan(ββ)=10)=10– total SUSY cross section 41.6 pbtotal SUSY cross section 41.6 pb– M(M(~g~g)>M()>M(~q~q))– BR(BR(~~22

00→→ ~ll →~ll → ~~1100llll ) = 11.2%) = 11.2%

– BR(BR(~~2200→ → ~~11

00ll) negligiblell) negligible Generated processes: Generated processes: ~q~g, ~g~g, ~~q~g, ~g~g, ~~g~g Forced decays: ~gForced decays: ~g→ → ~qq, ~q ~qq, ~q → → ~~22

00q, q, ~~22

0 0 → → ~ll, ~l ~ll, ~l → → ~~1100ll

Pythia 6.224 + Isajet 7.69Pythia 6.224 + Isajet 7.69



Dilepton end pointDilepton end point

q~q

01

02

~

Use dilepton signature to tag presence of 0

2 in event, then work back up decay chain constructing invariant mass distributions of combinations of leptons and jets



max2

2max,2 ql

X

Rql M

M

MM

(l2q)max,2 (2nd lepton, l1 flipped)

(l1q) and (l2q) edges(l1q) and (l2q) edges

q~q

1

2

01

02

~

Upper endpoint of Upper endpoint of m(l1q) is reached for m(l1q) is reached for all values of m(ll)all values of m(ll)

Max of m(l2q) varies Max of m(l2q) varies as a function of m(ll)as a function of m(ll)– Two endpoints, for Two endpoints, for

high and low m(ll) high and low m(ll) valuesvalues

m(l1q) and m(l2q)

m(l

l)



No Mll cut

(l1q) and (l2q) edges(l1q) and (l2q) edges

The two end points can be The two end points can be separated by cutting on M(ll)separated by cutting on M(ll)

q~q

01

02

~

Mll > 70 GeV/c2Mll < 20 GeV/c2

q2q1

22max,

21max,

2max

GeV/c 210)2(

GeV/c 317)2(

GeV/c 395)1(

qlM

qlM

qlM

expected values:

M(lq) M(lq) M(lq)



m(ll) vs. m(l1q) and m(l2q)

GeV

/c2

Parameter dependenceParameter dependence

LM1

GeV/c2

B

GeV

/c2

GeV/c2

Mll > 70 GeV/c2

Mll < 20 GeV/c2

No Mll cut



(llq) edges(llq) edges Two upper end points for high and low m(ll)Two upper end points for high and low m(ll) Lower threshold depending on M(ll) Lower threshold depending on M(ll)

(parametrization known)(parametrization known)

2

20

2

21max, 11

XQ

XQllq M

M

M

MMM

2

20

2

22max, 11

RQ

RQllq M

M

M

MMM

2

20

2

23max,

)(

)(11

RQ

X

X

RQllq MM

MM

M

MMM

M(llq)max,1

M(llq)max,2 or M(llq)max,3

m(l

l)

m(llq)



llq edgesllq edges

No Mll cut Mll < 30 GeV/c2Mll > 75 GeV/c2

M(llq) M(llq) M(llq)

23max,

21max,

GeV/c 404)(

GeV/c 448)(

llqM

llqM

expected values:



(llq) edges(llq) edges

M(llq)

M(l

2q

)

Identification of l1 Identification of l1 and l2 mandatory and l2 mandatory to observe the true to observe the true maxima in llq maxima in llq distributiondistribution

Distinction Distinction between the two between the two leptons: under leptons: under investigationinvestigation

M(llq)

M(l

1q

)



First attempt with First attempt with FAMOSFAMOS

10k events produced @ LM110k events produced @ LM1– FAMOS_0_9_0_pre4, CMKIN _3_1_0FAMOS_0_9_0_pre4, CMKIN _3_1_0– Only Only ~q ~~q ~

process, process, forced decaysforced decays Created rootfiles with information on:Created rootfiles with information on:

– muons:muons: FastMuonLvl3FinderFastMuonLvl3Finder – jets:jets: FamosPersistentJetFinderFamosPersistentJetFinder– missing Et:missing Et: FamosMETfromCaloTowerFamosMETfromCaloTower– No electrons yetNo electrons yet– No mu isolation yetNo mu isolation yet– No b-taggingNo b-tagging



Dilepton edge with Dilepton edge with FAMOSFAMOS

Event selection:Event selection:– 2 muons (P2 muons (Ptt>15 GeV/c)>15 GeV/c)

– ≥≥1 jet 1 jet – missing Et > 100 GeVmissing Et > 100 GeV

Dilepton mass Dilepton mass distribution with muons distribution with muons onlyonly

M(ll)



m(l

l)

m(llq)

M(lq)M(lq)

m(llq)

m(l

l)Mll < 30 GeV/c2

FA

MO

S:

PA

RTO

N L

EV

EL:



Open questionsOpen questions

How to treat combinatorial in real How to treat combinatorial in real analysisanalysis– High jet multiplicity in eventsHigh jet multiplicity in events

l1 vs. l2 separationl1 vs. l2 separation– Under studyUnder study

Dependence on parametersDependence on parameters



Conclusions and Conclusions and near future plansnear future plans

From parton level studies, the end From parton level studies, the end point analysis looks promisingpoint analysis looks promising

FAMOS:FAMOS:– Test release 1_0_0Test release 1_0_0– Electron reconstructionElectron reconstruction– b-taggingb-tagging– Muon isolationMuon isolation

More realistic analyses:More realistic analyses:– All SUSY samplesAll SUSY samples– SM backgroundSM background

Documents

Sparticle reconstruction in final states with di-leptons