1. 2.7.2003 MK @Montpellier Proton Structure Functions and at HERA Max Klein (H1, DESY Zeuthen) QCD Montpellier 2003 -Introduction -F2 and FL - and xg -High Q2 -Parton Distributions -Outlook klein@ifh.de

2. 2.7.2003 MK @Montpellier ZEUS H1 positrons protons HERA -tunnel protons: 920 GeV positrons: 27.6 GeV circumference: 6.3 km HERA the world‘s best microscope quarks are pointlike down to

3. 2.7.2003 MK @Montpellier Deep Inelastic Scattering at low x and Q2 /ZEUS DIS npert. regime low x

4. 2.7.2003 MK @Montpellier 1992 data 1997 data luminosity 0.2  20 pb-1 detector upgrades uncertainty 20%  2-3% Low x Physics – the ‚rise‘ of F2(x) Strong interaction dynamics at high parton densities and small coupling constant

5. 2.7.2003 MK @Montpellier Most accurate data on F2(x,Q2) from HERA published so far in DIS region (2-3%) Low x important for QCD and LHC parton Luminosity at Super high energy neutrino physics

6. 2.7.2003 MK @Montpellier Low Q2 data from near beam detector (ZEUS) and shifted vertex (H1) How does F2 behave in transition region to soft physics?

7. 2.7.2003 MK @Montpellier rise towards x  0 Derivative: independent of x for x<0.01 to within exp uncertainty PhysLett B520(01)183 H1 preliminary, DIS02, svx data 2000

8. 2.7.2003 MK @Montpellier low x Independence of ln F2 derivative of x justifies simple ansatz for x dependence at given Q2 change of behaviour at Q2 near 1 GeV2 rich phenomenology and search for new theoretical concept higher precision to observe ln 1/x terms!

9. 2.7.2003 MK @Montpellier interaction dynamics changes at low x for Q2 ~ 1 GeV2 at larger Q2 (in DIS region) xg determines the rise of F2(x) below the gluon distribution vanishes and becomes valence like distribution conventional pQCD analyses become unstable  needs further constraint, from FL at low x conventional QCD is bound to fail. new hadronic state „Colour Glass Condensate“ LMcL et al

10. 2.7.2003 MK @Montpellier exploring perturbative QCD H1 EPJ C21(01)33

11. 2.7.2003 MK @Montpellier H1-DIS measurement of alphas with H1 and BCDMS data  chi2+1 well defined two consistent exp data sets x space: C.Pascaud, F.Zomer, DESY 96-266 joint determination of alphas, xg, V,A no interest in quarks  two pdfs only 9 F2 = 3 xV +11xA = 4xU+xD

12. 2.7.2003 MK @Montpellier HERA results on the strong coupling constant from F2 hep-ex/0208023 PR D67(03)012007 EPJ C21(01)33 R.Wallny Thesis 01-058 H1 0.1150 +- 0.0017(exp) + 0.0009 - 0.0007(model) proton data and only H1+BCDMS Q2(H1)>3, Q2(BCDMS)>7GeV2,W2>10GeV2 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) 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, RT-VFNS fit alphas, xg, uv, dv, sea, dbar-ubar (MRST) if fixed flavour scheme is used: +0.0010 M.Botje programme

13. MK DESY Forum, 25. 03. 2003 NNLO corrections to pQCD NLO folklore: vary renorm. scale (¼.. 4) Q2  determines thy error observation: H1/ZEUS: too large chi2 variations H1: quote uncertainty of +-0.005 ZEUS: use (1/2.. 2) : mention uncertainty of +- 0.004 moment analyses: compare NLO with NNLO: -0.001 (Santiago & Yndurain) NP, hep-ph/0102247 full calculations to 3 loop anomalous dimension progressing NNLO has to include charm treatment in NNLO (mc +-100MeV is +-.0005) higher experimental precision of HERA F2: challenge is less than 1 per cent with efficient tracking + high resolution calorimetry + accurate/lots of lumi

14. MK DESY Forum, 25. 03. 2003 alphas (BCDMS) very low and strongly y dependent („electron method“) low y – large x region in conflict with SLAC F2 shifts imposed by QCD fit to BCDMS data systematic errors of BCDMS data the problem of the BCDMS data

15. MK DESY Forum, 25. 03. 2003 cf also A.Vogt DIS96 Roma  remeasure at HERA with Ep/2 the medium Q2 - larger x region with large luminosity. Systematics superior over fixed target exps. NMC drives fit to high alphas unbound fit requires 1/Q2 terms W cut not enough for Q2>5GeV2: small impact left but then smaller alphas preferred the problems of the NMC data

16. MK DESY Forum, 25. 03. 2003 gluon momentum density xg depends on c treatment! xg is not an observable

17. 2.7.2003 MK @Montpellier 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!

18. MK DESY Forum, 25. 03. 2003 Correlation of alphas and xg is resolvable in DIS fits  determination of alphas and of the gluon distribution inclusive DIS fits yield very small gluon density at large x – jets?

19. 2.7.2003 MK @Montpellier reduced cross section y=1-E‘/Ee E‘ > 3 GeV e ID with Si

20. 2.7.2003 MK @Montpellier longitudinal structure function at low Q2

21. 2.7.2003 MK @Montpellier the longitudinal structure function provides a further constraint to the gluon density  testing QCD to h.o. FL H1 EPJ C21(01)33

22. 2.7.2003 MK @Montpellier determination of the longitudinal structure function H1: EPJ C21(01)33, hep-ex/0304003 EPJ 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

23. 2.7.2003 MK @Montpellier  FL known to 20% in analyses with F2 calculated as x-l or in pQCD  need to vary Ep to measure FL(x,Q2) more accurately and direct

24. 2.7.2003 MK @Montpellier access to FL using radiative events ~36pb -1 ISR reduces E e  variation of y=Q2/sx ZEUS preliminary

25. 2.7.2003 MK @Montpellier electroweak unification in DIS full data 1994-2000 H1 94-00, hep-ex/0304003 EPJ

26. 2.7.2003 MK @Montpellier ZEUS 96-97, DESY 02-105, Phys.Rev. D67(2003)012007H1 94-00, DESY 03-038, hep-ex/0304003 EPJ  Lumi upgrade

27. 2.7.2003 MK @Montpellier neutral currents at high x,Q2: effects of Z exchange HERA 2 high Q2 simulation NC uncertainty ~2% CC uncertainty ~3% A.Mehta DIS01 HERA2: 10 times the luminosity of HERA1

28. 2.7.2003 MK @Montpellier exploratory measurements of xF3 H1: EPJ C19(2001)269 and hep-ex/0304003; ZEUS: hep-ex/0208040, EPJ direct access to valence quarks parity conserving e+ 100 pb-1 e- 15 pb-1 requires maximum possible luminosity

29. 2.7.2003 MK @Montpellier hep-ex/0304003 Sensitive to different Parton flavours e+ to down quarks e- to up quarks still statistics limited x maximum 0.4 best u/d separation with ep/en at HERA important for pdf‘s

30. 2.7.2003 MK @Montpellier hep-ex/0208023. CC data not fitted

31. 2.7.2003 MK @Montpellier parton distribution functions from NLO QCD fits (H1) CC and NC cross sections are sensitive only to U, antiU, D,antiD  new H1 NLO QCD fit in which uv,dv,sea are replaced by these observables No ad hoc pdf parameter Parameterisations from Chi2 saturation  light flavours (xg consistent) First pdf determination with H1 data alone, requires assumption on sea symmetry until eD data at low x exist

32. 2.7.2003 MK @Montpellier F2 charm ICHEP02 beauty to follow Silicon detectors vital

33. 2.7.2003 MK @Montpellier ZEUS upgrades STTMVD new beam pipe

34. 2.7.2003 MK @Montpellier H1 upgrades

35. 2.7.2003 MK @Montpellier parity violation in F2 (gamma-Z) MK DIS01 Bologna singlet

36. 2.7.2003 MK @Montpellier A.Mehta DIS01. helicity dependence of charged current cross section search for r.h. currents classic measurement, possible with modest luminosity but maximum polarisation

37. 2.7.2003 MK @Montpellier summary +Low x discovered the rise of F2 and thus a field of rich theoretical developments, including the final state +pQCD for structure function data tested over 4 orders of magnitude in momentum transfer squared, yet + 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 HERA I HERA II Currently HERA‘s lifetime is limited to 2006/07. Many more years are necessary to employ its scientific potential. There wasn‘t a DIS programme limited to protons at fixed energy, and HERA is a much richer laboratory than any fixed target experiment before. + 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??, F2b + high accuracy, low Ep runs to determine strong coupling constant with 1% accuracy and to measure FL(x)