Sparticle reconstruction in final states with di-leptons

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

2. 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 PRS session, CPT Week November ‘04

3. End-point analysis q 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 PRS session, CPT Week November ‘04

4. 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 PRS session, CPT Week November ‘04

5. Dilepton end point q 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 PRS session, CPT Week November ‘04

6. (l1q) and (l2q) edges m(ll) q (l2q)max,2 (2nd lepton, l1 flipped) m(l1q) and m(l2q) • 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 PRS session, CPT Week November ‘04

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

8. Parameter dependence No Mll cut Mll > 70 GeV/c2 Mll < 20 GeV/c2 m(ll) vs. m(l1q) and m(l2q) LM1 B GeV/c2 GeV/c2 GeV/c2 GeV/c2 PRS session, CPT Week November ‘04

9. (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 PRS session, CPT Week November ‘04 m(llq)

10. llq edges expected values: No Mll cut Mll > 75 GeV/c2 Mll < 30 GeV/c2 PRS session, CPT Week November ‘04 M(llq) M(llq) M(llq)

11. (llq) edges Identification of l1 and l2 mandatory to observe the true maxima in llq distribution Distinction between the two leptons: under investigation M(l2q) M(llq) M(l1q) PRS session, CPT Week November ‘04 M(llq)

12. First attempt with FAMOS • 10k events produced @ LM1 • FAMOS_0_9_0_pre4, CMKIN _3_1_0 • Only ~q ~c10process, forced decays • Created rootfiles with information on: • muons:FastMuonLvl3Finder • jets:FamosPersistentJetFinder • missing Et:FamosMETfromCaloTower • No electrons yet • No mu isolation yet • No b-tagging PRS session, CPT Week November ‘04

13. 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) PRS session, CPT Week November ‘04

14. M(lq) Mll < 30 GeV/c2 FAMOS: M(lq) PARTON LEVEL: m(ll) m(ll) PRS session, CPT Week November ‘04 m(llq) m(llq)

15. Open questions • How to treat combinatorial in real analysis • High jet multiplicity in events • l1 vs. l2 separation • Under study • Dependence on parameters PRS session, CPT Week November ‘04

16. 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 PRS session, CPT Week November ‘04