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Structure Functions at HERA

Structure Functions at HERA. Status and Future. Max Klein (H1, DESY Zeuthen). -Introduction -F2 at Low x -Measurement of alphas and xg -High Q2 -Quark Distributions -FL now and then -Summary. no jets, spin. RADCOR 02 Kloster Banz 10.9.2002. klein@ifh.de. HERA.

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Structure Functions at HERA

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  1. Structure Functions at HERA Status and Future Max Klein (H1, DESY Zeuthen) -Introduction -F2 at Low x -Measurement of alphas and xg -High Q2 -Quark Distributions -FL now and then -Summary no jets, spin RADCOR 02 Kloster Banz 10.9.2002 10.9.2002 MK @RADCOR02 klein@ifh.de

  2. HERA • protons: 920 GeV • positrons: 27.5 GeV • circumference: 6.3 km • HERA -tunnel • H1 • protons • positrons • ZEUS • positrons • protons 10.9.2002 MK @RADCOR02

  3. 1992 1997 luminosity 0.2  20 pb-1 detector upgrades uncertainty 20%  2-3% 10.9.2002 MK @RADCOR02 introduction

  4. deep inelastic scattering at low x and Q2 most recent, 0.6pb-1 H1 DIS 02 Cracow 10.9.2002 MK @RADCOR02 low x

  5. kinematic reconstruction BST SPACAL BST preliminary (H1) small photoproduction bgd: E-pz, BST track 10.9.2002 MK @RADCOR02 low x

  6. 10.9.2002 MK @RADCOR02 low x

  7. reduced cross section y<0.8 10.9.2002 MK @RADCOR02 low x

  8. Fractal Proton Structure – Self Similarity log dependence of (unintegrated parton) density fit to H197 low Q2 data and to ZEUS 97 BPT for 172 points, D2=1 T.Lastovicka hep-ph/0203260 EPJ in print 10.9.2002 MK @RADCOR02 low x

  9. 10.9.2002 MK @RADCOR02 low x

  10. QCD below its applicability ZEUS hep-ex/0208023 10.9.2002 MK @RADCOR02 low x

  11. rise towards x0 derivative independent of x for x<0.01 to within exp uncertainty H1 preliminary, DIS02, svx data 2000 PhysLett B520(01)183 should have lowered Ee 10.9.2002 MK @RADCOR02 low x

  12. derivative ~ lnQ2 still higher accuracy desirable PhysLett B520(01)183 10.9.2002 MK @RADCOR02 low x

  13. 10.9.2002 MK @RADCOR02 low x

  14. exploring perturbative QCD H1 EPJ C21(01)33 10.9.2002 MK @RADCOR02 alphas

  15. determination of the gluon momentum density to NLO fixed flavour nr scheme Laenen, Riemersma, Smith, vanNeerven need precision data at low Q2, all x! H1 EPJ C21(01)33 10.9.2002 MK @RADCOR02 alphas

  16. DIS measurement of alphas with H1 and BCDMS data joint determination of alphas, xg, V,A F2 =xV/3 +11xA/9 = 4xU/9+xD/9 y(BCDMS) > 0.3 Q2(BCDMS) >7 GeV2 • no NMC, E665 • chi2+1 well defined bg xg ~x is BCDMS correct?  low Ep run H1 EPJ C21(01)33 10.9.2002 MK @RADCOR02 alphas

  17. Results on the strong coupling constant H1 0.1150 +-0.0017(exp)+0.0009-0.0007(model) if: systematíc errors are not fitted: +0.0005 NMC replaces BCDMS 0.116+-0.003 (exp) 4 light flavours: +0.0003 BCDMS deuteron data added: 0.1158 +- 0.0016 (exp) EPJ C21(01)33 ZEUS 0.1166 +-0.0008(unc)+-0.0032(corr)+-0.0036(norm)+-0.0018(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: +0.0010 hep-ex/0208023 large chi2 variations if Q2  (¼ .. 4) Q2 renormalisation scale:+-0.005 (H1)  (1/2.. 2) : +- 0.004 (ZEUS) not included in error 10.9.2002 MK @RADCOR02 alphas

  18. electroweak unification in DIS full data 1994-2000 K.Long ICHEP02 10.9.2002 MK @RADCOR02 high Q2

  19. 10.9.2002 MK @RADCOR02 ICHEP02 H1 preliminary high Q2

  20. 10.9.2002 MK @RADCOR02 ICHEP02 H1 preliminary high Q2

  21. neutral currents at high x,Q2 HERA 2 high Q2 simulation NC uncertainty ~2% CC uncertainty ~3% HERA2: 10 times the luminosity of HERA1 A.Mehta DIS01 10.9.2002 MK @RADCOR02 high Q2

  22. exploratory measurements of xF3 e+ 100 pb-1 e- 15 pb-1 requires maximum possible luminosity direct access to valence quarks parity conserving H1: EPJ C19(2001)269; ZEUS: hep-ex/0208040 10.9.2002 MK @RADCOR02 high Q2

  23. high Q2 CC data (ZEUS) CC data not fitted hep-ex/0208023. 10.9.2002 MK @RADCOR02 high Q2

  24. high Q2 CC data (H1) ICHEP02 prel. 10.9.2002 MK @RADCOR02 high Q2

  25. e+, 250pb-1 e-, 250pb-1 simulation HERA2 MK high x Philadelphia 00 10.9.2002 MK @RADCOR02 pdf

  26. CC polarisation dependence search for r.h. currents classic measurement, possible with modest luminosity but maximum polarisation A.Mehta DIS01. 10.9.2002 MK @RADCOR02 high Q2

  27. parity violation in F2 (gamma-Z) MK DIS01 Bologna 10.9.2002 MK @RADCOR02 high Q2

  28. parton distribution functions from NLO QCD fits ZEUS hep-ex/0208023; H1 ICHEP02 10.9.2002 MK @RADCOR02 pdf

  29. parton distribution functions from NLO QCD fits (H1) 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 H1 ICHEP02 10.9.2002 MK @RADCOR02 pdf

  30. sea symmetry (simulation of ed) 40pb-1 ep 20pb-1 ed note (s-c)/3 =5/18 W2(cc)-F2N MK, DIS 02 10.9.2002 MK @RADCOR02 pdf

  31. up and down quarks at high Q2 ZEUS hep-ex/0208023; H1 ICHEP02 10.9.2002 MK @RADCOR02 pdf

  32. access to the longitudinal structure function H1 EPJ C21(01)33 10.9.2002 MK @RADCOR02 FL

  33. determination of the longitudinal structure function 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 H1: EPJ C21(01)33, DIS01 and ICHEP02 10.9.2002 MK @RADCOR02 FL

  34. 3..4 beam energies L ~ Ep systematics challenge smallest E‘ (BST: E/p) ultimate accuracy of ~5% Q2~1 GeV2: redo i.a.region FL simulation with lowered Ep MK Ringberg H1 internal 02: bins and Ep choices may be optimised 10.9.2002 MK @RADCOR02 FL

  35. F2 charm beauty to follow Silicon detectors vital ICHEP02 10.9.2002 MK @RADCOR02 FL

  36. diffractive partons H1, DIS02 10.9.2002 MK @RADCOR02 FL

  37. 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 + 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 HERA3 10.9.2002 MK @RADCOR02

  38. ZEUS upgrades STT MVD new beam pipe ZEUS expected to be operational in 2006 (U.Schneekloth at Durham) 10.9.2002 MK @RADCOR02

  39. H1 upgrades major upgrades. H1 expected to be operational for years to come and follow – design 1986! 10.9.2002 MK @RADCOR02

  40. Workshops its time to conclude • DESY directorate asks for proposals by end of 2003 • Physics • Ressources • TESLA • synch.radiation 10.9.2002 MK @RADCOR02

  41. 10.9.2002 MK @RADCOR02

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