Multijets in e+e- annihilations Hasko Stenzel. 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 2...

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Transcript of Multijets in e+e- annihilations Hasko Stenzel. 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 2...

  • Slide 1
  • Multijets in e+e- annihilations Hasko Stenzel
  • Slide 2
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 2 Outline Jet rates and algorithms energy evolution measurements of s 4-jet analyses color factors measurements of s quark mass effects Multijet event shapes NP-analysis out-of-plane momentum non-global variables beyond 4-jets mostly perturbative QCD !
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  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 3 Jet algorithms Jet definition based on a pair-wise track metric JADE algorithm Durham/k t algorithm Cambridge ordering parameter
  • Slide 4
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 4 Jet rates Corrections applied for: background subtraction (LEPII) ISR/FSR QED corrections acceptance/efficiency detector resolution Corrected distributions represent the hadron level. Hadronisation corrections are applied to perturbative predictions (e.g. for fits). Hadr. corrections Exp. uncertainties Detector corrections Hadronisation uncertainty claimed ~2% at LEPI < 1 % at LEPII
  • Slide 5
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 5 Energy dependence of jet observables As in the case of event-shape Variables, jet rates, mean jet multiplicities and differential jet rates are evolving with energy through the running of s. 3-jet fraction mean jet multiplicity
  • Slide 6
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 6 Measurements of s from jet observables Observables derived from jet rates: differential two jet rate mean jet multiplicity mean jet multiplicity differential 2-jet rate Fits to the data with perturbative prediction O( s 2 )+ NNLA, LogR matching (mostly in the 3-jet region)
  • Slide 7
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 7 Results from an OPAL analysis Observables derived from jet rates: differential two jet rate mean jet multiplicity Cambridge and Durham Measurements at LEPI and LEPII Observable s (91.2) stat exp pert had tot D2CD2C 0.11470.00040.00170.00300.00260.0043 D2DD2D 0.11990.00040.00250.00370.00170.0048 0.12540.00050.00130.00370.00330.0051 0.12720.00040.00060.00340.00390.0052
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  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 8 4-jet observables 4-jet observables have been used extensively to determine QCD color factors s (fixing color factors to QCD) using NLO calculations O( s 3 )+ NNLA L3
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  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 9 QCD color factors in parton splitting 2 2 2 CFCF CACA nfTRnfTR QCD : SU(3) C F =4/3, C A =3, T R =1/2
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  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 10 Color factors from 4-jets Leading order diagrams for 4-jet production
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  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 11 Observables in 4-jet system Bengtsson-Zerwas-Angle: angle between (p 1 x p 2 ) and (p 3 x p 4 ), ie. angle between planes P1 and P2 spanned by the two high and the two low energetic jets P2 P1 p1p1 p2p2 p3p3 p4p4 Angles between the 4 jets, e.g. Complete set of observables: + R 4 (y cut ) + y 23
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  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 12 NLO fits to angular variables and jet rates Including NLLA resummation
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  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 13 Results of simultaneous fit to s and color factors s (M Z )CACA CFCF ALEPH0.1190.0060.0262.930.140.581.350.070.26 OPAL0.1200.0110.0203.020.250.491.340.130.22 QCD34/3
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  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 14 Determination of s from 4-jet observables (fixing color factors to QCD) OPAL recently analysed 4-jet rate D-parameter T minor at LEPI and LEPII
  • Slide 15
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 15 OPAL results on s from 4-jet observables OPAL results s (M Z ) stat. exp. had. scale. mass R 4 (Durham)0.1182 0.00030.00150.00110.00120.0013NLO+NLLA D-parameter0.1047 0.00140.00370.00610.0052-NLO x =1 T minor 0.1318 0.00160.00560.00230.0111-NLO x =1 The uncertainty for s from 4-jet observables is reduced wrt 3-jet case:
  • Slide 16
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 16 ALEPH/DELPHI results on s from R 4 s (M Z ) stat. sys.Data set OPAL0.1182 0.00030.002691-209NLO+NLLA ALEPH0.1170 0.00010.002291NLO+NLLA DELPHI0.1175 0.00050.0030LEPINLO x opt DELPHILogarithmic slope = 1.14 0.3689-209QCD: 1.27 0.10 DELPHI tested the energy dependence of s from 4-jets at E=150 GeV:
  • Slide 17
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 17 Testing b-quark mass effects in the 4-jet rate Cambridge y cut =0.0085 sys. R 4 bl 0.898 0.0140.014 m b (MZ)3.56 0.330.43 MbMb 4.61 0.410.54 DELPHI analysed flavour tagged 4-jet ratios: in order to extract the b-quark mass: preliminary result:
  • Slide 18
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 18 non-perturbative analysis of 4-jet observables L3 s (M z ) 0 (2 GeV) D-parameter 0.1046 0.0078 0.0096 0.682 0.094 0.018 all combined 0.1126 0.0045 0.0039 0.478 0.054 0.024 L3 analysis of mean value of D-parameter Results:
  • Slide 19
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 19 other 4-jet observables BnBn narrow jet broadening MlMl light jet mass T minor Thrust Minor, AKA K out OOblateness, T M -T m y 34 4-jet resolution parameter measured at LEPI & LEPII but not analysed in the scope of power corrections
  • Slide 20
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 20 out-of-plane momentum for near-to-planar configurations with different y cuts
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  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 21 non-global variables sensitive to local radiation in restricted phase space regions: single jet mass and single jet broadening
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  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 22 beyond 4-jets 5- and more jet rates, y ij multijet resolution parameters
  • Slide 23
  • 13.01.2006 FRIF workshop e+e- multi-jets H.Stenzel 23 Conclusion Multijet observables (mostly 4-jets) have given access to precision measurements of s color factors test of quark mass effects many variables have been measured D-parameter, T minor, Oblateness, y 34 out-of-plane momenta non-global variables few of them have been analysed for power corrections D-parameter The potential of 5-jet configurations is to be explored.