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
Mario Galanti
University & INFN - Catania
PRS session, CPT Week
November ‘04

3. 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

4. Event selection: parton level
50k 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 Isajet 7.69
Mario Galanti
University & INFN - Catania
PRS session, CPT Week
November ‘04

5. 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

6. (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

7. (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)

8. 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

9. 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)

10. 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)

11. (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)

12. First attempt with FAMOS
10k events 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

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)
Mario Galanti
University & INFN - Catania
PRS session, CPT Week
November ‘04

14. 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)

15. 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

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
Mario Galanti
University & INFN - Catania
PRS session, CPT Week
November ‘04