Overview of Parton Distribution Functions (with a decided high-x BJ bias)

1. Overview of Parton Distribution Functions(with a decided high-xBJ bias) Jorge G. Morfín Fermilab DNP04 - Chicago, IL

2. Outline • Quick review of everything but valence quarks • The valence quarks • Look at high-x: • Recent indications of more and less quarks at high-x? • d/u • How to cleanly measure valence quarks at high-x (and individual sea-quark distributions at all x)

3. Who? Alekhin, CTEQ, MRST, Botje, H1, ZEUS, GRV, …. http://durpdg.dur.ac.uk/hepdata/pdf.html PDFs from Global Fits Formalism LO, NLO, NNLO DGLAP MSbar factorization Q02 functional form @ Q02 sea quark (a)symmetry etc. fi (x,Q2) fi (x,Q2) Data DIS (SLAC, BCDMS, NMC, E665, CCFR, H1, ZEUS, … ) Drell-Yan (E605, E772, E866, …) High ET jets (CDF, D0) W rapidity asymmetry (CDF) N dimuon (CCFR, NuTeV) etc. J. Stirling - Hix2004

4. MRST Parton Distributions in the Proton Martin, Roberts, Stirling, Thorne

5. Comparison of three modern PDF global fits Djouadi & Ferrag, hep-ph/0310209 • small MRST and CTEQ differences largely understood, see hep-ph/0211080 - J. Stirling; Hix2004

6. How has our picture of the PDF’s evolved over the years.With thanks to Wu-Ki Tung - MSU Gluon

7. Does the gluon go negative at small x and low Q? (MRST) Gluon

8. Uncertainty in the Gluon DistributionNormalized to CTEQ6M Dashed - CTEQ5HJ Dotted - MRST01 Solid - CTEQ5M

9. The non-strange sea quarks DY Asymmetry exerts its Influence - NA51 and E866

10. Experimental input: (low statistics) data on Dimuon (charm) production in Neutrino-Nucleus scattering.

11. A better determination of kshould emerge from current full NLO analyses of the CCFR-NuTeV dimuon data. k =

12. Is the strangeness sector charge symmetric? Still no experimental data to decide, one way or the other.

13. New CCFR-NuTeV dimuon data that can, in principle, determine s(x) and sbar(x) separately!

14. The Valence u Quark: progression of improvements

15. NLO fits to more fixed-target DIS data sets

16. HERA exerts its influence

17. All in the details now, at least for lower x

18. It looks like we know the d and u quark fairly well…right?

19. OOPS! Indication that the valence quarks not quite right at high-x??E866 Preliminary Results (R. Towell - Hix2004) xbeam xtarget • xbeam distribution measures 4u + d as x--> 1. • Both MRST and CTEQ overestimate valence distributions as x --> 1 by 15-20%. • Possibly related to d/u ratio as x --> 1, but requires full PDF-style fit. • Radiative corrections have recently been calculated. (Not yet fully applied)

20. Relative Concentration of Valence Quarks in the Nucleon d/u

22. Latest look at d/u… What’s going on at high-x?

23. CTEQ uncertainties in u and d quark fitsTheory uncertainties NOT included

24. CTEQ High-x Working Group With C. Keppel - Jefferson Lab

25. Extraction of d/u using deuterium targets involves nuclear D2 corrections

26. What happens when we include (preliminary) E866? PRELIMINARY

27. Compare 6.1 with E866 to CTEQ5 with deuteron correction (F-S) - time to revisit deuteron corrections… PRELIMINARY

28. Range of Deuteron Corrections in the Literature (a few somewhat dated) This line is what CTEQ used for “Large-x paper” Wally Melnitchouk:

29. Implement full FS instead of approximate line and compare with MST correction PRELIMINARY

30. PRELIMINARY PRELIMINARY

31. Preliminary Impressions of CTEQ High-x Study E866 discrepancy can be reduced/removed with deuteron corrections, change in d/u ratio looks similar to CTEQ6.1 + E866 fit. Extracting d/u will continue to be a problem as long as we must invoke deuteron corrections Need final data with radiative corrections, but feeling a bit better about E866…

32. OOPS! NuTeV Compared to CCFR (currently in PDF fits)at High-x Indicates Effect Opposite to E866 nuclear effects? V. Radescu - DIS04

33. How do we Resolve the High-x Quark Dilemma? The cleanest, most straightforward way to study high x quarks, including the d/u ratio is with n / n - proton scattering

34. Neutrino - Proton ScatteringNo messy nuclear corrections! At high x F2np - xF3np = 4xu F2np - xF3np = 4xd F2np + xF3np = 4xu

35. Similar Expressions for Neutrino-Nucleon Scattering - What Can We Learn With All Six Neutrino Structure Functions? Using Leading order expressions (for isoscalar target): Combining measured values in a given x-Q2 bin, for example

36. n How do we measure Neutrino-Proton Scattering?The MINERnA Experiment in the NuMI Beam at FermilabApproved in April C, Fe and Pb Nuclear targets Main Physics Topics with Expected Produced Statistics • Quasi-elastic 300 K events off 3 tons CH • Resonance Production 600 K total, 450 K 1p • Coherent Pion Production 25 K CC / 12.5 K NC • Nuclear Effects C:0.6M, Fe: 1M and Pb: 1 M • Pert/nonPert and Structure Functions 2.8 M total /1.2 M DIS event • Strange and Charm Particle Production > 60 K fully reconstructed events • Generalized Parton Distributions(few K events?)

37. Both HEP and NP collaborators D. Drakoulakos, P. Stamoulis, G. Tzanakos, M. Zois University of Athens, Athens, Greece D. Casper University of California, Irvine, California E. Paschos University of Dortmund, Dortmund, Germany D. Boehnlein, D. A. Harris, M. Kostin, J.G. Morfin, P. Shanahan, P. Spentzouris Fermi National Accelerator Laboratory, Batavia, Illinois M.E. Christy, W. Hinton, C.E .Keppel Hampton University, Hampton, Virginia R. Burnstein, A. Chakravorty, O. Kamaev, N. Solomey Illinois Institute of Technology, Chicago, Illinois S.Kulagin Institute for Nuclear Research, Moscow, Russia I. Niculescu. G. .Niculescu James Madison University, Harrisonburg, Virginia G. Blazey, M.A.C. Cummings, V. Rykalin Northern Illinois University, DeKalb, Illinois W.K. Brooks, A. Bruell, R. Ent, D. Gaskell,, W. Melnitchouk, S. Wood Jefferson Lab, Newport News, Virginia S. Boyd, D. Naples, V. Paolone University of Pittsburgh, Pittsburgh, Pennsylvania A. Bodek, H. Budd, J. Chvojka, P. de Babaro, S. Manly, K. McFarland, I.C. Park, W. Sakumoto, R. Teng University of Rochester, Rochester, New York R. Gilman, C. Glasshausser, X. Jiang, G. Kumbartzki, K. McCormick, R. Ransome Rutgers University, New Brunswick, New Jersey H. Gallagher, T. Kafka, W.A. Mann, W. Oliver Tufts University, Medford, Massachusetts J. Nelson William and Mary College, Williamsburg, Virginia Red = HEP, Blue = NP, Green = Theorist

38. After initial (parasitic to MINOS) run -would add a Liquid H2/D2(/O/Ar) TargetNOT YET APPROVED FOR THIS Technically easy/inexpensive to build and operate. Meeting safety specifications the major effort. Fid. vol: r = 80 cm. l = 150 cm. 350 K CC events in LH2 800 K CC events in LD2 2.5x1020 POT he-n beam. H_2/D_2 MINOS Near ≈ Statistical Errors for .7 / 2 year of he-n / n xBj CH LH2 LD2 .6 - .65 0.6% 2.2% 1.5% .65 - .7 0.7 2.6 1.7 .7 - .75 1.0 3.7 2.5 .75 - .8 1.3 5 3 .8 - .85 2 7 5 .85 - .9 3 11 7 .9 - 1.0 4 14 10 Planes of C, Fe, Pb For part of run

39. Summary • Aside from low x gluon, PDFs fairly well established for x < 0.3-0.4. • For x > 0.3, uncertainty of the gluon grows dramatically. • (d - u) / (d+u) reasonably constrained by E866 out to x ≈ 0.4. • k = (s + s) / (u + d) seems to be increasing with x (NuTeV input). • (s - s) / (s + s) and heavy quarks need further clarification (NuTeV). • The valence u-quark is reasonable out to x = 0.5, while the d-quark uncertainty blows up around x = 0.3. Whoops…E866 & NuTeV!! • d/u at high-x still uncertain due to spread in deuteron correction. • BoNuS experiment at Jlab, particularly with upgrade, will help • THE CLEANEST WAY TO MEASURE d/u: n + p SCATTERING • The MINERnA Experiment at Fermilab, an NP + HEP collaboration, could make a high-statistics measurement of n + p scattering.