W . de Boer

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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. - PowerPoint PPT Presentation
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W. de Boer

Measurements of the strong coupling constant:History and Prospects for Grand Unified TheoriesOutline

Measurements of s

Prospects for GUTs

KIT Universitt des Landes Baden-Wrttemberg undnationales Forschungszentrum in der Helmholtz-GemeinschaftInstitut fr Experimentelle Kernphysikwww.kit.eduNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 20121Incomplete History of the SM (1972-2012)pp

QCD at TeV scaleHiggs at 126 GeV

LHCep

PDF

HERAe+e-(+fixed target)c,b,tau,gluon3 neutrinosSUSY unification

PEP, PETRA, TRISTANSLC, LEPTHEPARTICLEPHYSICSTRIUMFpp

top quarkW,Z bosons

TevatronSPS

-Lattice non-pert.QCDElectro-WeakUnificationHiggsMechanism.QCDAsymptoticFreedomNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 20122

History of s measurements From PDB 1992

From PDB 2012

0.113 0.003 (170+45 ) -30 Factor 4 improvement in s error in last 20 yrs Phys. Rev. D86, 010001 (2012)Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 20123HERANr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 20124

Alpha_s from DISDIS

Fractional energy of parton in protoncan be determined from electron energy:Cross section only dependent on x in parton model,if parton probability distribution (PDF) independentof Q2 (Bjorken scaling).However, at larger Q2 more gluons resolved,thus enhancing x-section at small x and decreasingit at large x (scaling violation). Scaling violationdependent on alpha-s, but strongly correlated withgluon PDF

DIS with measurement of onlylepton is inclusive measurement.since integrated over all jetmultiplicities. Exclusive measurement of jet multiplicities also depende on alpha-s. Combining incl. and excl. meas. decorrelate gluon PDF and alpha_s (ZEUS).Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 20125Legacy measurements from HERA

Larger x-range, equal Q2Non-pert propt 2/Q2Calc. In NLO only

T. Schorner-Sadenius, arXiv1111.7290, for HERA combination group

Scale dependence (4%) dominant in NLO Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 20126e+e-fragmentationNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 20127Alpha_s from scaling violation in e+e- annihilationDISe+e-

Pro: no PDF of proton involved same range of Q2 (LEP=104 GeV2)Con: much smaller range of x (CM=LAB, so low energy particles inside beam pipe) b-quark prod. higher at Z0) (have to parametrize heavy quark fragm., light quark fragm. and gluon fragm.) Results: using lund string fragm. fct. as parametrization of fragm. fcts and integrating O(s2) ME: s(MZ)=0.118 0.005 (DELPHI,1993) polynomial param. of fragm. fct. and DGLAP eqns: s(MZ)=0.126 0.009 (ALEPH,1994) s(MZ)=0.124 0.0060.009 (DELPHI,1997) (error dominated by scale dep. In NLO, as in DIS)crossingNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 20128e+e-event shapesNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 20129

PRD, arXiv:1006.3080, World data on Thrust reanalysed in NNLO.Systematics? QCD at parton level is NOT experiment at hadron level!Event shapes in e+e- annihilation (PDG 2012)Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201210LHCNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201211LHC electroweak production x-sections in NNLO QCD

excl. n-jetsNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201212

LHC electroweak production x-sections in NLO QCDNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201213

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 (probedown to x0.5x10-3, well studied earlier by DIS) but still have less sensitivity at high x.mQCD at Hadron CollidersNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 2012Bandurin ichep

14

With ~5/fb per experiment of 2011 data, jet physics extended to the TeV rangeDijet mass leads the way in highest energy reach, with highest masses 4 TeVExcellent confirmation of perturbative QCD up to the very highest scales!CMS: CMS PAS QCD-11-004 Atlas: arXiv:1112.6297Di-jet masses at 7 TeVCMS: CMS PAS QCD-11-004 Atlas: arXiv:1112.6297Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201215

Correlated uncertainties look better: typical veto, NNLO ~ 15%.Stewart, TackmannErrors at LHC dominated by higher ordersAlphas measurements at hadron colliders:D0 from pT dependence of inclusive jet cross section :s(M2Z) = 0.1161+0.00410.0048 (NLO) arXiv:0911.2710CMS from ttbar x-section (NLO): aS(mZ) = 0.1178+0.0048-0.0042,Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 2012pQCD Ichep16LATTICEQCDNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201217Lattice 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 fields on links Path Integrals solved on supercomputers.QCD Scale fixed by masses and mass splittings

Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201218Quenched ApproximationIn 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 loopWhat are remaining errors?

R. Gupta, Introduction to Lattice QCD, arXiv:hep-lat/9807028Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201219

Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201220

From Kronberg in Alphas Workshop, arXiv:1110.0016v3Alphas values from lattice QCDVariation: 0.117-0.121s(MZ)=0.1190.002?Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201221Tau decays and e+e- hadronicx-sectionsNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201222

Baikov, Chetyrkin, Khn, 0801.18215-loop calculations in QCD (20.000 diagrams)

C

Theor. errors from non-pert. contr. at M dominate. O(s5)=0.005 at Mtau.Errors reduced by evolution.Errors dominated by experiment.. O(s4) term =+0.005 at MZ.Errors reduced by evolution

Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 2012These terms may become of relevance for the International Linear Collider (ILC) running in theGIGA-Z mode with an anticipated precision ofs = 0.0005 0.0007 [29], and already today for theanalysis of -decays.23

Calculation up to NNNLO

Non-perturbative regime(Q2=M=1.7 GeV)

Different approaches fortreatment of the perturbative expansion (fixed-order or contour-improved)

SM review rescales errorsto get 2/dof=1

Extrapolation to MZ reducesrelative error:

s(MZ)=0.1200.002

Alpha_s from tau decaysPDG 2012Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201224e+e-hadronic x-sectionsNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201225

G.~D'Agostini, W.~de Boer and G.~Grindhammer, %``Determination Of Alpha-s And The Z0 Mass From Measurements Of The Total Hadronic Cross-section In E+ E- Annihilation,''Phys.\ Lett.\ B {\bf 229} (1989) 160. R ratio in e+e- Simultaneous fit of s, MZ and sin2W: MZ=89.41.3 GeV, s=0. Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201226Electroweak fits from different programsZFITTER, Bardin et al. , used by electroweak working groupGAPS, J. Erler, , used in PDBGFITTER, . 0811.0009, used by GFITTER Group:

All consistent with:Why experimental error so large? Very simple exp.: number counting withhigh statistics in 4 independent LEP experiments!Answer: 2 hardly compatible alphas measurements at LEP!!! alphas from hadronic x-section: alphas=error dominated byluminosity errrNr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201227

Global electroweak fits and gauge coupling unification. Wim de Boer, Christian Sander Phys.Lett. B585 (2004) 276-286 hep-ph/0307049Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 2012The luminosity influences the hadronic cross section sighad. If the luminosity is larger than measured than value of sighad decreases. This causes a increase in as and the number of neutrino families N. Note that a 2 deviation in Nn corresponds to a 3sig deviation in sighad.28

Jadach, hep-ph/0306083

Theoretical uncertainties in LEP luminosity (BHLUMI)Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201229Summary of alphas at Mz

NNNLO, theor. error dominatesNNLO, theor. error?NNNLO, theor. error negligibleAverage completely dominatedby lattice gauge theory, if onebelieves error and NNNLO negl.My estimate: 0.1200.001Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201230

Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 2012Summary of measurements of s as a function of the respective energyscale Q. The respective degree of QCD perturbation theory used in the extractionof s is indicated in brackets (NLO: next-to-leading order; NNLO: next-to-next-toleading order; res. NNLO: NNLO matched with resummed next-to-leading logs;N3LO: next-to-NNLO).31

Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 2012The lines are combinations of as(MZ) and sin2 W, which yield gauge unification. Unification with the world average for sin2 W requires as > 0.123, if SUSY mass scales are required to be below 1 TeV. The value is close to as = 0.122(2), which is the average from Rl and R , the only measured ratios calculated up to order O(as3) in QCD.Note that this value is high compared with the measurement from the Z0 hadronic peak cross section s = 0.115(4), but the latter is dominated by the common luminosity errors from LEP. The too low number of neutrino species, as measured at LEP, suggests that the luminosity is off by 3. If true, perfect gauge unification can be obtained for SUSY mass scales below 1 TeV.32

Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 2012Here the running of the couplings in the SM (left) and MSSM (right) is shown. In the MSSM unificationis possible due to threshold corrections of supersymmetric particles.33

s=0.118s=0.116Heavy Higgs masses near GUT scale strong function of s.Minimal Supersymmetric SU(5) and Gauge Coupling Unification at Three Loops, W. Martens, L. Mihaila, J. Salomon, M. Steinhauser. Phys.Rev. D82 (2010) 095013 , arXiv:1008.3070 [Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 201234Prospects from GigaZ linear collider

Gfitter Group, 0811.0009Hope to have enough statistics to measure alphas from Rl INDEPENDENT of Lumiand settle hadronic vacuum polarization at 10-4 level! (Input for lattice QCD, g-2 and gauge coupling unification !)Nr.Wim de Boer, Quantum Chromodynamics: History and Prospects, Oberwlz, Sep. 3-8., 2012Table 4: Measurement prospects at future accelerators for key observables used in the electroweak fit, andtheir impact on the electroweak fit. The columns give, from the left to the right: present errors, the expecteduncertainties for the LHC with 10 fb.1 integrated luminosity, the ILC without and with the option to runat the Z resonance and along the W-pair production threshold (GigaZ) for one year of nominal running.The estimated improvement for (5)had(M2Z ) (given in parenthesis of the corresponding line) over the currentuncertainty is unrelated to these accelerators, and must come from new low-energy hadronic cross sectionmeasurements and a more accurate theory (see text). The lower rows give the results obtained for MH andS(M2Z ). For MH are also given the results with improved (5)had(M2Z ) precision (parentheses this has noimpact on S(M2Z )), and when in addition ignoring the theoretical uncertainties [brackets]. Note that allerrors obtained on MH are strongly central value dependent (see text).systematics are needed. High-statistics ISR analyses performed at the35

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