Sparticle reconstruction in final states with di-leptons M. Chiorboli, M. Galanti, A. Tricomi University and INFN, Catania Credits: Luc Pape

Outline Aim: measurement of sparticle masses from kinematical end-point analyses in events containing c20→c10ll (l=e,m) Feasibility study: first step: parton level preliminary attempts with FAMOS Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04

End-point analysis 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 q Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04

Event selection: parton level 50k events @ LM1 M½=250, sign(μ)=+, M0=60, A0=0, tan(β)=10 total SUSY cross section 41.6 pb M(~g)>M(~q) BR(~c20→ ~ll → ~c10ll ) = 11.2% BR(~c20→ ~c10ll) negligible Generated processes: ~q~g, ~g~g, ~c~g Forced decays: ~g→ ~qq, ~q → ~c20q, ~c20 → ~ll, ~l → ~c10l Pythia 6.224 + Isajet 7.69 Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04

Dilepton end point Use dilepton signature to tag presence of c02 in event, then work back up decay chain constructing invariant mass distributions of combinations of leptons and jets q Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04

(l1q) and (l2q) edges (l2q)max,2 (2nd lepton, l1 flipped) q m(l1q) and m(l2q) m(ll) Upper endpoint of m(l1q) is reached for all values of m(ll) Max of m(l2q) varies as a function of m(ll) Two endpoints, for high and low m(ll) values Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04

(l1q) and (l2q) edges expected values: q The two end points can be separated by cutting on M(ll) No Mll cut Mll > 70 GeV/c2 Mll < 20 GeV/c2 Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04 M(lq) M(lq) M(lq)

m(ll) vs. m(l1q) and m(l2q) Parameter dependence m(ll) vs. m(l1q) and m(l2q) LM1 B GeV/c2 GeV/c2 GeV/c2 GeV/c2 No Mll cut Mll < 20 GeV/c2 Mll > 70 GeV/c2 Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04

M(llq)max,2 or M(llq)max,3 (llq) edges Two upper end points for high and low m(ll) Lower threshold depending on M(ll) (parametrization known) M(llq)max,2 or M(llq)max,3 m(ll) M(llq)max,1 Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04 m(llq)

llq edges expected values: No Mll cut Mll > 75 GeV/c2 Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04 M(llq) M(llq) M(llq)

(llq) edges M(l2q) Identification of l1 and l2 mandatory to observe the true maxima in llq distribution Distinction between the two leptons: under investigation M(llq) M(l1q) Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04 M(llq)

First attempt with FAMOS 10k events produced @ LM1 FAMOS_0_9_0_pre4, CMKIN _3_1_0 Only ~q ~c10 process, forced decays Created rootfiles with information on: muons: FastMuonLvl3Finder jets: FamosPersistentJetFinder missing Et: FamosMETfromCaloTower No electrons yet No mu isolation yet No b-tagging Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04

Dilepton edge with FAMOS Event selection: 2 muons (Pt>15 GeV/c) ≥1 jet missing Et > 100 GeV Dilepton mass distribution with muons only M(ll) Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04

Mll < 30 GeV/c2 FAMOS: PARTON LEVEL: M(lq) Mll < 30 GeV/c2 FAMOS: M(lq) PARTON LEVEL: m(ll) m(ll) Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04 m(llq) m(llq)

Open questions How to treat combinatorial in real analysis High jet multiplicity in events l1 vs. l2 separation Under study Dependence on parameters Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04

Conclusions and near future plans From parton level studies, the end point analysis looks promising FAMOS: Test release 1_0_0 Electron reconstruction b-tagging Muon isolation More realistic analyses: All SUSY samples SM background Mario Galanti University & INFN - Catania PRS session, CPT Week November ‘04