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Progress report on sbottom and gluino reconstruction Massimiliano Chiorboli Universita and INFN Catania.

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Presentation on theme: "Progress report on sbottom and gluino reconstruction Massimiliano Chiorboli Universita and INFN Catania."— Presentation transcript:

1 Progress report on sbottom and gluino reconstruction Massimiliano Chiorboli Universita and INFN Catania

2 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Proposed Post-LEP Benchmarks for Supersymmetry (hep-ph/ ) I chose points B and G I ran my events using PYTHIA, fixing the 5 mSUGRA parameters …but (as Filip suggested) PYTHIA doesnt reproduce well these benchmarks

3 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Benchmark points Benchmark points are defined at low scale, according to the outputs (BRs, spectra…) given by ISAJET 7.58 The true point B is less favourable than the one I studied in my previous analysis I cannot call that point point B, but I can say it is a favourable SUSY situation (15% b L, 10% b R ) (35 % b L, 22% b R ) (0.2 %) (60%) (38%) (17% b L, 10% b R ) (37 % b L, 25% b R ) (0.04 %) (16.4%) (83.2%) PYTHIAISAJET Main dependency ISASUSY vs PYTHIA

4 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting CMSJET and ISAJET I ran my events using the CMSJET version interfaced to ISAJET, but… ISAJET doesnt provide vertex info … so FATSIM (or any other package to perform b-tagging with impact parameter) doesnt work with ISAJET. I used PYHTIA, putting by hand low scale parameters (thanks to Filip). ISAJET spectrum and BRs are reproduced within 1%

5 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Point B spectra = LSP ± 145.8lRlR ± 211.4lLlL qRqR qLqL bRbR 600.5tRtR 522.5bLbL 412.5tLtL 643.3g = LSP ± 136.2lRlR ± 196.5lLlL qRqR qLqL bRbR 575.9tRtR 496.0bLbL 392.9tLtL 595.1g Point B Favourable Point

6 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Decay Chain p p b b Event final state: 2 high p t isolated leptons OS 2 high p t b jets missing E t 2 isolated leptons, p T >15 GeV, | |<2.4 2 b-jets, p T >20 GeV, | |<2.4 SM bkg: tt, Z+jet, W+jet, ZZ, WW, ZW

7 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting First step: 2 0 l + l p p b b SUSY SUSY + SM 10 fb -1 Z+jet tt Favourable Point

8 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Dilepton edge at Point B E t miss > 50 GeV 10 fb -1 Favourable PointPoint B SM

9 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Dilepton edge at Point B SUSY only E(ll) > 100 GeV W l Favourable Point Point B

10 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Dilepton edge at Point B E(ll) > 100 GeV E t miss > 50 GeVE t miss > 100 GeVE t miss > 150 GeV

11 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Dilepton edge fit Favourable Point Point B 10 fb -1

12 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Sbottom reconstruction p p b b Assuming M( 1 0 ) known! Combining the 2 0 obtained from the two leptons with one of the b-jets of the event we can reconstruct the sbottom Selecting events with dileptons in edge

13 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting The ATLAS method ATLAS Note Phys-109 (Hinchliffe, Paige…) Combination of the dilepton pair with all the b-jets in the event Selecting the most energetic b-jet

14 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Sbottom reconstruction Highest p t b-jet smallest largest Most energetic b-jet Comparing the reconstruction: E of the jet P t of the jet Angle b-jet/ll

15 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Sbottom reconstruction E t miss > 50 GeV E t miss > 100 GeVE t miss > 150 GeV Favourable Point Point B E t miss cut effects

16 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Combinatorial suppression (8%) Favourable Point We want to select b-jets coming from sbottoms: In the same decay chains there are also other b-jet and dilepton sources:

17 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Combinatorial suppression (8%) Point B We want to select b-jets coming from sbottoms: In the same decay chains there are also other b-jet and dilepton sources:

18 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Combinatorial suppression E b-jet 1 > 250 GeV Favourable Point Point B b-jet energy cut effect:

19 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Sbottom mass Result of fit Generated masses: E t miss > 150 GeV 10 fb -1 E b-jet 1 > 250 GeV Favourable Point Point B

20 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Gluino reconstruction p p b b E t miss > 150 GeV ATLAS method b-jet closest in angle to the reconstructed sbottom

21 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Gluino mass Result of fit Generated masses: Favourable Point Point B E t miss > 150 GeV 10 fb -1 E b-jet 1 > 250 GeV

22 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting estimation estimation doesnt depend on M( 1 0 ) ! Stability of the results:

23 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting estimation estimation Result of fit Generated values: Favourable Point Point B E t miss > 150 GeV 10 fb -1 E b-jet 1 > 250 GeV Independent from the mass of the neutralino 1:

24 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting B-taggingB-tagging The sbottom and gluino reconstruction depends strongly on the b-tagging capability of the detector In CMSJET the b-tagging is performed by the FATSIM package A jet is a b-jet if it contains at least two tracks with a significance ip > bcut b c uds - g Susy events Point B

25 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting b-tagging perfomance b c udsg c + udsg ip cont >269%42% >361%30% >454%25% >547%22%

26 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Sbottom and b selection E t miss > 150 GeV10 fb -1 E b-jet 1 > 250 GeVNo E b-jet 1 cut Point B

27 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Gluino and b selection E t miss > 150 GeV10 fb -1 E b-jet 1 > 250 GeVNo E b-jet 1 cut Point B

28 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting We need a full simulation to understand how much the b-tagging perfomance can affect the sparticle reconstruction Im starting to produce CMSIM events and I will redo this analysis applying the b-tagging packages in ORCA.

29 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Results with 10 fb -1 Result of fit Generated masses: b-tag: >3 Point B E t miss > 150 GeV 10 fb -1 E b-jet 1 > 250 GeV E(ll) > 100 GeV

30 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Dependence on M( ) M( 1 0 ) true M( 1 0 ) = M(ll) M( 1 0 ) = M edge Sbottom Gluino Favourable Point

31 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Realistic situation Sbottom Gluino 5% 3% Favourable Point

32 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Realistic situation Sbottom Gluino 6% 5% Point B

33 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Dependence on M(ll) Sbottom Gluino Favourable Point

34 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting With 60 fb -1 SbottomGluino Favourable Point

35 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Point B With 60 fb -1

36 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Sbottoms separation 10 6 Detector resolution prevents the two sbottoms separation Favourable Point

37 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting with 60 fb -1 with 60 fb fb -1 Result of fit: Generated values: Favourable Point

38 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting with 60 fb -1 with 60 fb -1 Result of fit: Generated values: 60 fb -1 Point B

39 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Point B We can reconstruct sbottoms and gluinos even at low integrated luminosity (10 fb -1 ). Resolution <10%, Errors on mass determination of 1-2%, but we have to consider that we dont know M( 1 ) error 5-6% if we approximate M( 1 ) M(ll) max. This approximation is valid only in a mSUGRA scenario for which M( 2 ) 2M( 1 ), if we want a model independent analysis, we have to find other solutions At 60 fb -1 no sbottom separation, and I think neither at higher integrated luminosity due to detector resolution Extrapolating at 300 fb -1, and considering the possible contribution form a LC, which gives us M( 1 ), we can have errors of 0.5%

40 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Point G = LSP ± 193.4lRlR ± 299.6lLlL qRqR qLqL bRbR 800.8tRtR 723.0bLbL 589.4tLtL 919.8g PYTHIA 6.152

41 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting (8 %) (60 %) (16%) (16%) (8 %) Decay chain (16% b L, 10% b R ) (15 % b L, 28% b R ) Less good events More fake events

42 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Dilepton Edge 60 fb -1 SUSY only

43 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting E(ll) > 200 GeV l slepton l l + l - SUSY only W l 60 fb -1

44 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Dilepton Edge E t miss > 100 GeVE t miss > 50 GeVE t miss > 150 GeV E(ll) > 200 GeV60 fb -1

45 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting E(ll) > 200 GeVE t miss > 250 GeV 60 fb -1

46 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Sbottom and gluino E t miss > 250 GeV SbottomGluino

47 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Sbottom and gluino E t miss > 250 GeV E b-jet 1 > 280 GeV

48 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Point G with 300 fb -1 No Pile Up! E t miss > 250 GeV Fit result:

49 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Sbottom at point G Result of fit: Generated masses: 300 fb -1 E t miss > 250 GeV E b-jet 1 > 280 GeV E(ll) > 180 GeV

50 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Gluino at point G Result of fit: Generated mass: 300 fb -1 E t miss > 250 GeV E b-jet 1 > 280 GeV E(ll) > 180 GeV

51 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting at point G at point G Result of fit: Generated values: 300 fb -1 E t miss > 250 GeV E b-jet 1 > 280 GeV E(ll) > 180 GeV

52 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting

53 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Squark reconstruction (5.2% d L, 5.6% u L, 5.2% s L, 5.6% c L ) (32%) (16.4%) (22.4%) 2 isolated leptons, p T >15 GeV, | |<2.4 2 jets (not b), p T >20 GeV, | |<2.4 b-jet veto No SM bkg: 2 leptons + high E t miss cut

54 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Squark recontruction This would need a better understanding of the BKGs

55 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting Point G We need high statistics to see reasonably good peaks At 300 fb -1 we can reconstruct sbottoms and gluino with resolution 7%, errors 1-2%, assuming M( 1 ) known from a LC Even in this case we cannot separate the two sbottoms Maybe we can reconstruct also the light squarks

56 Massimiliano Chiorboli 7 Jun 2002 CMS Week - Physics Meeting E b-jet 1 P T b-jet 1 b-jet 1 E b-jet 2 P T b-jet 2 b-jet 2


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