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Sparticle reconstruction methods in the CMS detector Massimiliano Chiorboli Universita and INFN Catania.

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Presentation on theme: "Sparticle reconstruction methods in the CMS detector Massimiliano Chiorboli Universita and INFN Catania."— Presentation transcript:

1 Sparticle reconstruction methods in the CMS detector Massimiliano Chiorboli Universita and INFN Catania

2 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting OutlineOutline Past studies on SUSY in CMS Recent studies: sparticle recontruction Decay chain 2 0 l + l Sparticles reconstruction: 2 0 l + l dilepton edge Sbottom recontstruction Gluino reconstruction measurement Conclusions

3 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Sparticle searches in CMS Up to now… Inclusive studies: Excess over the SM Now… Sparticle reconstruction

4 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting The CMS detector

5 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting = LSP ± 145.8lRlR ± 211.4lLlL qRqR qLqL bRbR 600.5tRtR 522.5bLbL 412.5tLtL 643.3g Proposed Post-LEP Benchmarks for Supersymmetry (hep-ph/ ) PYTHIA 6.152

6 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Decay chain p p b b (15% b L, 10% b R ) (35 % b L, 22% b R ) (0.2 %) (60 %) Event final state: 2 high p t isolated leptons OS 2 high p t b jets missing E t

7 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Event production 2 isolated leptons, p T >15 GeV, | |<2.4 2 b-jets, p T >20 GeV, | |<2 PYTHIA CMSJET 4.801: fast simulation, parametrization of the detector SM bkg: tt, Z+jet, W+jet, ZZ, WW, ZW

8 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting First step: 2 0 l + l p p b b SUSY SUSY + SM 10 fb -1 Z+jet tt

9 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting E t miss > 50 GeV 10 fb -1

10 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Dilepton Edge Fit result:

11 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Sbottom reconstruction p p b b Assuming M( 1 0 ) known!

12 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Sbottom reconstruction E t miss > 50 GeVE t miss > 100 GeVE t miss > 150 GeV I choose the most energetic b-jet MC true

13 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Sbottom mass Result of fit: Generated masses: 10 fb -1

14 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Gluino reconstruction p p b b E t miss > 150 GeV

15 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Gluino mass Result of fit: Generated mass: 10 fb -1

16 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Combinatorial suppression (8%) b-jets from sbottoms of real decay chain have a harder spectrum

17 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Combinatorial suppression E b-jet 1 > 250 GeV SbottomGluino 10 fb -1

18 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Combinatorial suppression Sbottom Gluino 10 fb -1 E b-jet 1 > 250 GeV

19 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Sbottom mass Result of fit: Generated masses: 10 fb -1

20 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Gluino mass Generated mass: Result of fit: 10 fb -1

21 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Dependence on M( ) M( 1 0 ) true M( 1 0 ) = M(ll) M( 1 0 ) = M edge I assumed M( 1 0 ) known: we cannot detect the neutralinos! Sbottom Gluino

22 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Realistic situation Sbottom Gluino 5% 3%

23 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting estimation estimation doesnt depend on M( 1 0 ) !

24 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting estimation estimation Result of fit: Generated values: 10 fb -1

25 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Dependence on M(ll) Sbottom Gluino

26 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting With 60 fb -1 SbottomGluino

27 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Sbottoms separation 10 6 Detector resolution prevents the two sbottom separation

28 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting = LSP ± 193.4lRlR ± 299.6lLlL qRqR qLqL bRbR 800.8tRtR 723.0bLbL 589.4tLtL 919.8g Point G

29 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting (16%) (8 %) Decay chain (16% b L, 10% b R ) (15 % b L, 28% b R ) (8 %) (60 %) Less good events More fake events

30 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Dilepton Edge 60 fb -1 SUSY only l slepton l E(ll) > 160 GeV

31 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Dilepton Edge E t miss > 100 GeVE t miss > 50 GeVE t miss > 150 GeV E(ll) > 160 GeV

32 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Dilepton Edge E(ll) > 160 GeVE t miss > 250 GeV

33 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Peaks reconstruction E t miss > 250 GeV Sbottom Gluino M(g)-M(b)

34 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Peaks reconstruction E t miss > 250 GeVE b-jet 1 > 300 GeV SbottomGluinoM(g)-M(b)

35 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Point G with 500 fb -1 No Pile Up! Fit result: E t miss > 250 GeV

36 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Sbottom at point G Result of fit: Generated masses: 500 fb -1

37 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting Gluino at point G Result of fit: Generated mass: 500 fb -1

38 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting at point G at point G Result of fit: Generated values: 500 fb -1

39 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting ConclusionsConclusions estimation of M(l + l - ) max sbottom reconstruction with Resol. ~ 13 %, but 2 sbottoms not resolved gluino reconstruction with Resol. 6 % M(g) - M(b) estimation, independent of M( 1 0 ), with Err ~ 4 % Point B (tan =10, low masses), with 10 fb -1 In some mSUGRA regions CMS will be able to obtain information about the mass spectrum of sparticles from dilepton edges and to reconstruct some sparticles mass peaks:

40 Massimiliano Chiorboli Apr 2002 Euro-GDR Meeting ConclusionsConclusions Point G (tan =20, higher masses), with 500 fb -1 estimation of M(l + l - ) max sbottom reconstruction with Resol. ~ 7% gluino reconstruction with Resol. 6 % M(g) - M(b) estimation, independent of M( 1 0 ), with Err ~ 4 %


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