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Experimental tests of the SM (1): the strong force FK8022, Lecture 5 Core texts: Review of Particle Physics : QCD minireview Further reading: Quarks and Leptons, an Introductory Course in Modern Physics, Halzen and Martin.
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Free parameters of the Standard Model 19 free parameters (massless neutrino version). SM tests require both collider and non-colliders Masses ParameterValueMethod mumu 1.9 MeVLattice mdmd 4.4 MeVLattice msms 87 MeVLattice mcmc 1.3 MeVCollider mbmb 4.24 MeVCollider mtmt 173 GeVCollider meme 511 keVNon-collider mm 106 MeVNon-collider mm 1.78 GeVCollider mzmz 91.2 GeVCollider mHmH 125 GeVCollider Couplings ParameterValueMethod 0.0073non-collider + collider GFGF 1.17x10 -5 Non-collider ss 0.12Lattice + collider ParameterValueMethod (CKM) 13.1 o Collider (CKM) 2.4 o Collider (CKM) 0.2 o Collider (CKM-CPV) 0.995Collider (strong CP) ~0Non-collider Flavour and CP violation
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Free parameters of the Standard Model Masses ParameterValueMethod mumu 1.9 MeVLattice mdmd 4.4 MeVLattice msms 87 MeVLattice mcmc 1.3 MeVCollider mbmb 4.24 MeVCollider mtmt 173 GeVCollider meme 511 keVNon-collider mm 106 MeVNon-collider mm 1.78 GeVCollider mzmz 91.2 GeVCollider mHmH 125 GeVCollider Couplings ParameterValueMethod 0.0073non-collider + collider GFGF 1.17x10 -5 Non-collider ss 0.12Lattice + collider ParameterValueMethod (CKM) 13.1 o Collider (CKM) 2.4 o Collider (CKM) 0.2 o Collider (CKM-CPV) 0.995Collider (strong CP) ~0Non-collider Flavour and CP violation Collider tests of the strong and electroweak sectors (this lecture). CKM, CPV (lecture 6), Higgs (lectures 8,9)
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AcceleratorColliding particles Beam energy (GeV) LabRunning period Physics topics LHC pp 4000, 7000(2015) CERN2008-Higgs, general purpose Tevatron pp 1000Tevatron1986-2011Top quark, general purpose HERA ep 30( e ), 920 (p)DESY1992-2005QCD, general purpose CEBAF ep 6( e - )+fixed target JLAB1994-QCD, flavour LEP1,2 e+e-e+e- 45-105CERN1989-2000EW,general purpose SLC e+e-e+e- 45SLAC1989-1998EW, general purpose DAFNE e+e-e+e- 0.5Frescati1999-QCD, flavour PEP-II/Babar e+e-e+e- 9( e - ),3( e + )SLAC1999-2008Flavour KEKB/Belle e+e-e+e- 8( e - ),4( e + )KEK1999-2010Flavour BEPC e+e-e+e- 3.7Beijing2008-QCD, flavour Recent and current colliders Diverse and complementary collider program
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Strategy for QCD tests
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Collider environments to study QCD
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Lepton-nucleon deep-inelastic scattering P e e.- ’ P p p P P
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= data point x Q2Q2 e - P e e-e- p P p parton xP p parton selected data
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DIS cross section
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10 F 2 for different scenarios of proton structure x F2F2 H1 experiment at HERA
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Quasi-free quarks and Bjorken scaling
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Bjorken scaling and the quark parton model Quasi-free quarks Strongly bound quarks
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The final part of the story: perturbative QCD processes + + +
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Scaling violations HERA Low energy DIS Standard Model
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Extraction of s
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Testing QCD at e + e - colliders
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Event shapes in e + e -
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Event shapes
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Event shape measurements at LEP Rates over several orders of magnitude. Excellent description of QCD-based models.
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Extraction of s e+e+ e-e-
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More measurements of s Lecture 9
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QCD at hadron-hadron colliders p p hadrons
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Jet production at the LHC jet
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Summary of QCD tests CollisionObservableDescribed by pQCD s (M z ) HERA (ep) Structure function 0.114±0.002 LEP/SLC (e + e - ) Event shapes 0.119 ± 0.004 LHC/Tevatron (hh) Jets 0.115+0.009 World average Combination of many measurements/techniques 0.1185 ± 0.0006 2
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Measuring the hadronic contribution to e-e- e-e- e +,e - e-e- e-e- e-e- e-e- ++
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Summary Range of active and recent colliders – Large general purpose experiments – Small experiments tackling specific problems – Coherent program Each collision environment and collider energy makes a unique contribution to the study of the strong force pQCD remains to be falsified despite increasing precision and energy scale – s (M z ) 0.1185 ± 0.0006 2
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