1. AOD Analysis of the DC2 Coannihilation Model Sample Davide Costanzo Nov 5 th 2004 V. 3.0

2. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 2 Introduction SUSY point in the coannihilation region for DC2 –m0=70GeV, m1/2=350GeV, A0=0, tan β=10, sgn(  )=+ –point in a region favored if SUSY is to explain dark matter –LSP almost degenerate with sleptons. Expect soft leptons in the final state Goals of this exercise –Test and develop AOD-based Susy analysis –Start to explore coannihilation point pPhysics Events generated for this study –400K events simulated with DC2 –Show the case without noise in the calorimeters –Reconstruction and AOD production for ~ 200K events

3. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 3 Physics Process Slow Leptons expected in this case Fast simulation used to give a first preliminary indication Full Simulation needed

4. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 4 Events Selection and Analysis Use packages in cvs: –PhysicsAnalysis/SUSYPhys/SUSYPhysAlgs, SUSYPhysUtils, SUSYPhysUser First step, select objects to be used for analysis (SusyxxxCreator) Remove overlaps in ( ,  ) space

5. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 5 Event Selection and Analysis (2) Set of tools to create histograms –General tools provided in the Utils package –User to implement tools to make histograms –Examples are provided More information in the README file of the User package (and on Frank’s talk at Oct 13 Physics Validation) Develop a strategy which scales with complex analysis –Not necessarily the best model –Quick enough to get started –Clean-up needed…

6. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 6 Jet Reconstruction

7. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 7 Effective Mass M eff (GeV) M eff =p T1 +p T2 +p T3 +p T4 +E t mis s where p Ti are for 4 hardest jets in the event. E T >100 GeV 4 hard jets (p T1,2 >100 GeV; p T3,4 >50 GeV) No isolated electrons or muons (p T >20 GeV)

8. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 8 e and  P T Distribution P T (GeV)

9. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 9

10. 10 opposite sign same sign DiLepton Mass M ll (GeV) Electrons Muons opposite sign same sign Found problem with electrons. Most of the electrons in the low mass peak are reconstructed with softe

11. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 11 Dilepton End Points M ll (GeV) Events with invariant mass < 5GeV are eliminated to remove electrons with low invariant mass Two endpoints are expected. One from l L at 67GeV and one from l R at 100GeV

12. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 12 Dilep + Jet Inv mass Combine two leptons and a jet to form invariant mass of a squark –Four jets with P T1 >100GeV, P T2,3,4 >50GeV –E T > max(100GeV, 0.2M eff ) –Two opposite sign leptons with M ll >10GeV Plot the smallest of the (llj) invariant mass and the largest (llj) invariant mass

13. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 13 Dilep + Jet Inv mass Smaller of the two l + l - q masses.Large of the two l + l - q masses. M llj (GeV) OF/OS leptons subtracted. It is not clear that the endpoint is at 609 GeV.

14. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 14 Tau-Tau invariant mass M ll (GeV) opposite sign same sign

15. Davide Costanzo Nov 5 th Coannihilation Point. AOD Analysis 15 Conclusions Analysis of the Coannihilation point started –We have the tools to analyze Susy events and make plots efficiently –Endpoints are visible, we need to improve the analysis, fit them, … –This is preliminary, but it is a starting point –Reconstruct events with subsequent Atlas releases and hopefully see an improvement