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W . de Boer

Measurements of the strong coupling constant: History and Prospects for Grand Unified Theories. W . de Boer. Outline Measurements of  s Prospects for GUTs. Incomplete History of the SM (1972-2012). -. . QCD Asymptotic Freedom. Higgs Mechanism. THE PARTICLE PHYSICS TRIUMF.

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W . de Boer

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  1. Measurements of the strong coupling constant: History and Prospects for Grand Unified Theories W. de Boer Outline Measurements of s Prospects for GUTs

  2. IncompleteHistoryofthe SM (1972-2012) - . QCD Asymptotic Freedom Higgs Mechanism THE PARTICLE PHYSICS TRIUMF pp top quark W,Z bosons Tevatron SPS e+e- (+fixedtarget) c,b,tau,gluon 3 neutrinos SUSY unification PEP, PETRA, TRISTAN SLC, LEP pp QCD atTeVscale Higgsat 126 GeV LHC ep PDF HERA Electro- Weak Unification Lattice non-pert. QCD

  3. Historyofsmeasurements From PDB 1992 From PDB 2012 Phys. Rev. D86, 010001 (2012) 0.113  0.003 (170+45 ) -30 Factor 4 improvement in serror in last 20 yrs

  4. HERA

  5. Alpha_sfrom DIS DIS Fractionalenergyofparton in proton canbedeterminedfromelectronenergy: DIS withmeasurementofonly leptonisinclusivemeasurement. sinceintegratedover all jet multiplicities. Exclusivemeasurementofjetmultiplicities also dependeon alpha-s. Combining incl. and excl. meas. decorrelategluon PDF andalpha_s(ZEUS). Cross sectiononlydependent on x in parton model, ifpartonprobabilitydistribution (PDF) independent of Q2(Bjorkenscaling). However, at larger Q2moregluonsresolved, thusenhancingx-sectionatsmall x anddecreasing itat large x (scalingviolation). Scalingviolation dependenton alpha-s, but stronglycorrelatedwith gluon PDF

  6. Legacy measurementsfrom HERA Larger x-range, equal Q2 Non-pertpropt2/Q2 Calc. In NLO only T. Schorner-Sadenius, arXiv1111.7290, forHERA combinationgroup Scaledependence(4%) dominant in NLO

  7. e+e- fragmentation

  8. Alpha_sfromscalingviolation in e+e- annihilation crossing e+e- DIS Pro: no PDF ofprotoninvolved same rangeof Q2 (LEP=104 GeV2) Con: muchsmallerrangeof x (CM=LAB, so lowenergyparticlesinside beam pipe) b-quarkprod. higherat Z0) (havetoparametrize heavy quarkfragm., lightquarkfragm. andgluonfragm.) Results: usinglundstringfragm. fct. as parametrizationoffragm. fctsand integrating O(s2) ME: s(MZ)=0.118  0.005 (DELPHI,1993) polynomialparam. offragm. fct. and DGLAP eqns: s(MZ)=0.126  0.009 (ALEPH,1994) s(MZ)=0.124  0.0060.009 (DELPHI,1997) (errordominatedbyscaledep. In NLO, as in DIS)

  9. e+e- eventshapes

  10. Event shapes in e+e- annihilation (PDG 2012) PRD, arXiv:1006.3080,World data on Thrustreanalysed in NNLO. Systematics? QCD atpartonlevelis NOTexperimentathadronlevel!

  11. LHC

  12. LHC electroweakproduction x-sections in NNLO QCD excl. n-jets

  13. LHC electroweakproduction x-sections in NLO QCD

  14. QCD atHadronColliders Inclusive is one of the most elementary measurements at hadron colliders. – Inclusive jet cross sections at Tevatron/LHC test pQCD over 8-9 orders of magnitude up to 2 TeV – Primary and powerful source of PDF constraint! – LHC experiments are covering larger phase space in jet pT and |y| than Tevatron (probe down to x0.5x10-3, well studied earlier by DIS) but still have less sensitivity at high x.m

  15. Di-jetmassesat 7 TeV CMS: CMS PAS QCD-11-004 Atlas: arXiv:1112.6297 CMS: CMS PAS QCD-11-004 Atlas: arXiv:1112.6297 With ~5/fb per experiment of 2011 data, jet physics extended to the TeV range Dijet mass leads the way in highest energy reach, with highest masses 4 TeV Excellent confirmation of perturbative QCD up to the very highest scales!

  16. Errors at LHC dominatedbyhigherorders Correlated uncertainties look better: typical veto, NNLO ~ 15%.Stewart, Tackmann Alphas measurementsathadroncolliders: D0 frompTdependenceofinclusivejetcrosssection: αs(M2Z) = 0.1161+0.0041−0.0048 (NLO) arXiv:0911.2710 CMS fromttbar x-section (NLO): aS(mZ) = 0.1178+0.0048-0.0042,

  17. LATTICE QCD

  18. Lattice QCD (Wilson 1974) • Discretise space time on lattice with V=L3xt • Lattice spacing a small compared with nucleon size • Quarks exist on lattice points, • Gauge fieldson links • Path Integrals solved on supercomputers. • QCD Scale fixed by masses and mass splittings

  19. Quenched Approximation • In the quenched approximation vacuum polarization effects of quark loops are turned off. • Popular approximation in past (reduces computation time by about 103-105) • Nowadays 2+1 approximation, i.e. 2 light quarks + s-quark in loop • What are remaining errors? R. Gupta, “Introduction to Lattice QCD”, arXiv:hep-lat/9807028

  20. Alphas valuesfromlattice QCD From Kronberg in Alphas Workshop, arXiv:1110.0016v3 Variation: 0.117-0.121s(MZ)=0.1190.002?

  21. Tau decaysand e+e- hadronic x-sections

  22. 5-loop calculations in QCD (20.000 diagrams) Baikov, Chetyrkin, Kühn, 0801.1821 C Errors dominatedbyexperiment. . O(s4) term =+0.005 at MZ. Errors reduced by evolution Theor. errorsfrom non-pert. contr. atM dominate. O(s5)=0.005 atMtau. Errors reducedbyevolution.

  23. Alpha_sfrom tau decays PDG 2012 Calculationupto NNNLO Non-perturbativeregime (Q2=M=1.7 GeV) Different approaches for treatment of the perturbative expansion (fixed-order or “contour-improved”) SM review rescales errors to get 2/dof=1 Extrapolation to MZreduces relative error: s(MZ)=0.1200.002

  24. e+e- hadronic x-sections

  25. R ratio in e+e- G.~D'Agostini, W.~de Boer andG.~Grindhammer, %``Determination Of Alpha-s And The Z0 MassFromMeasurementsOf The Total Hadronic Cross-section In E+ E- Annihilation,''  Phys.\ Lett.\ B {\bf 229} (1989) 160. Simultaneous fit ofs, MZ and sin2W: MZ=89.41.3 GeV, s=0.

  26. Electroweakfitsfrom different programs ZFITTER, Bardin et al. , usedbyelectroweakworkinggroup GAPS, J. Erler, , used in PDB GFITTER, . 0811.0009, usedby GFITTER Group: All consistentwith: Why experimental error so large? Very simple exp.: numbercountingwith highstatistics in 4 independent LEP experiments! Answer: 2 hardlycompatiblealphasmeasurementsat LEP!!! alphasfromhadronic x-section: alphas=errordominatedbyluminosityerrr

  27. Global electroweakfitsandgaugecouplingunification. Wim de Boer, Christian Sander Phys.Lett. B585 (2004) 276-286 hep-ph/0307049

  28. Theoreticaluncertainties in LEP luminosity (BHLUMI) Jadach, hep-ph/0306083

  29. SummaryofalphasatMz NNNLO, theor. errordominates NNLO, theor. error? NNNLO, theor. errornegligible Averagecompletelydominated bylatticegaugetheory, ifone believeserrorand NNNLO negl. Myestimate: 0.1200.001

  30. Heavy Higgsmassesnear GUT scale strong functionofs s=0.118 s=0.116 .Minimal Supersymmetric SU(5) and Gauge CouplingUnificationatThree Loops, W. Martens, L. Mihaila, J. Salomon, M. Steinhauser. Phys.Rev. D82 (2010) 095013 , arXiv:1008.3070 [

  31. ProspectsfromGigaZ linear collider Gfitter Group, 0811.0009 Hope tohaveenoughstatisticstomeasurealphasfromRl INDEPENDENT ofLumi andsettlehadronicvacuumpolarizationat 10-4level! (Input forlattice QCD, g-2 andgaugecouplingunification !)

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