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Structure Functions at HERA Max Klein (H1, DESY Zeuthen) Status and Future RADCOR 02 Kloster Banz Introduction -F2 at Low x -Measurement of alphas and xg -High Q2 -Quark Distributions -FL now and then -Summary no jets, spin

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HERA ZEUS H1 positrons protons HERA -tunnel protons: 920 GeV positrons: 27.5 GeV circumference: 6.3 km

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introduction 1997 luminosity 0.2 20 pb-1 detector upgrades uncertainty 20% 2-3%

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deep inelastic scattering at low x and Q2 most recent, 0.6pb-1 H1 DIS 02 Cracow low x

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kinematic reconstruction BST SPACAL low x preliminary (H1) small photoproduction bgd: E-pz, BST track

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low x

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reduced cross section y<0.8 low x

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Fractal Proton Structure – Self Similarity log dependence of (unintegrated parton) density fit to H197 low Q2 data and to ZEUS 97 BPT T.Lastovicka hep-ph/ EPJ in print for 172 points, D2=1 low x

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low x

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QCD below its applicability low x ZEUS hep-ex/

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rise towards x 0 should have lowered Ee low x derivative independent of x for x<0.01 to within exp uncertainty PhysLett B520(01)183 H1 preliminary, DIS02, svx data 2000

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PhysLett B520(01)183 derivative ~ lnQ2 still higher accuracy desirable low x

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low x

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exploring perturbative QCD alphas H1 EPJ C21(01)33

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determination of the gluon momentum density to NLO H1 EPJ C21(01)33 fixed flavour nr scheme Laenen, Riemersma, Smith, vanNeerven need precision data at low Q2, all x! alphas

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DIS measurement of alphas with H1 and BCDMS data alphas y(BCDMS) > 0.3 Q2(BCDMS) >7 GeV2 no NMC, E665 chi2+1 well defined is BCDMS correct? low Ep run H1 EPJ C21(01)33 joint determination of alphas, xg, V,A F2 =xV/3 +11xA/9 = 4xU/9+xD/9 xg ~x bg

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Results on the strong coupling constant hep-ex/ alphas EPJ C21(01)33 H (exp) (model) if: systematíc errors are not fitted: NMC replaces BCDMS (exp) 4 light flavours: BCDMS deuteron data added: (exp) large chi2 variations if Q2 (¼.. 4) Q2 renormalisation scale: (H1) (1/2.. 2) : (ZEUS) not included in error ZEUS (unc) (corr) (norm) (model) p:BCDMS,NMC,E665 d:NMC,E665 d/p: NMC xF3: CCFR systematíc errors are not allowed to vary in chi2 minimisation Q2>2.5 GeV2, W2>20GeV2, RTvfns, b(uv)=1/2, b(dv)=1/2 fit alphas, xg, uv, dv, sea, dbar-ubar (MRST) if fixed flavour scheme is used:

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electroweak unification in DIS K.Long ICHEP02 high Q2 full data

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ICHEP02 H1 preliminaryhigh Q2

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ICHEP02 H1 preliminaryhigh Q2

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neutral currents at high x,Q2 high Q2 HERA 2 high Q2 simulation NC uncertainty ~2% CC uncertainty ~3% A.Mehta DIS01 HERA2: 10 times the luminosity of HERA1

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exploratory measurements of xF3 H1: EPJ C19(2001)269; ZEUS: hep-ex/ high Q2 direct access to valence quarks parity conserving e+ 100 pb-1 e- 15 pb-1 requires maximum possible luminosity

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hep-ex/ high Q2 CC data (ZEUS) high Q2 CC data not fitted

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ICHEP02 prel. high Q2 CC data (H1) high Q2

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MK high x Philadelphia 00 pdf e+, 250pb-1 e-, 250pb-1 simulation HERA2

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A.Mehta DIS01. CC polarisation dependence high Q2 search for r.h. currents classic measurement, possible with modest luminosity but maximum polarisation

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parity violation in F2 (gamma-Z) MK DIS01 Bologna high Q2

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parton distribution functions from NLO QCD fits ZEUS hep-ex/ ; H1 ICHEP02 pdf

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parton distribution functions from NLO QCD fits (H1) H1 ICHEP02 pdf CC and NC cross sections are sensitive only to U, antiU, D,antiD (F2N has c-s admixture) new H1 NLO QCD fit in which uv,dv,sea are replaced by the observables light flavours (xg consistent) possible with H1 data alone with assumption on sea symmetry

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sea symmetry (simulation of ed) MK, DIS 02 pdf 40pb-1 ep 20pb-1 ed note (s-c)/3 =5/18 W2(cc)-F2N

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up and down quarks at high Q2 ZEUS hep-ex/ ; H1 ICHEP02 pdf

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access to the longitudinal structure function FL H1 EPJ C21(01)33

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determination of the longitudinal structure function FL H1: EPJ C21(01)33, DIS01 and ICHEP02 y<0.9 (this is E‘~2..3 GeV!) assumption on F2 more accurate data at large Q2 to come consistent with NLO QCD i.e. scaling violations of F2 limited to smallest x

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FL simulation with lowered Ep FL MK Ringberg H1 internal 02: bins and Ep choices may be optimised 3..4 beam energies L ~ Ep systematics challenge smallest E‘ (BST: E/p) ultimate accuracy of ~5% Q2~1 GeV2: redo i.a.region

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F2 charm FL ICHEP02 beauty to follow Silicon detectors vital

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diffractive partons FL H1, DIS02

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summary +Low x physics discovered as a new field of theoretical development and experimental fun + so far pQCD is consistent with structure function data but the ultimate precision of data and thy (N3LO) is still to be / is being approached (F2 1%, FL 5%, hiQ2 2% NC, 3% CC, about!) + F2c and F2D evolve towards precision testing grounds HERA1 HERA2 HERA3 + high luminosity, Silicon detectors, improved calibrations large x, high Q2 (competetive searches) + NC,CC unfold pdf‘s, employ polarisation and charge dependence of cross sections, xg at high x?? + high accuracy, low Ep runs determine strong coupling constant with 1% accuracy and measure FL(x) + explore flavour decomposition at low x (eD) + discover saturation (eA) + understand confinement (better) + spin structure of the proton at low x and high Q2

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ZEUS upgrades ZEUS expected to be operational in 2006 (U.Schneekloth at Durham) STTMVD new beam pipe

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H1 upgrades major upgrades. H1 expected to be operational for years to come and follow – design 1986!

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Workshops its time to conclude DESY directorate asks for proposals by end of 2003 Physics Ressources TESLA synch.radiation

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