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What Needs to Be Resolved?

What Needs to Be Resolved?. NuTeV. CTEQ. Functional form does not evolve correctly from Q 0 of 12.6 GeV 2 to range of 4-100 GeV 2 Strangeness not conserved (low x) Not global fit with outside PDFs, d-quark distributions not adjusted for changes in s(x).

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What Needs to Be Resolved?

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  1. What Needs to Be Resolved? NuTeV CTEQ • Functional form does not evolve correctly • from Q0 of 12.6 GeV2 to range of 4-100 GeV2 • Strangeness not conserved (low x) • Not global fit • with outside PDFs, d-quark distributions not adjusted for changes in s(x) • Inclusive measurements fit to same PDFs with NLO cross-section that go into LO cross-section for dimuons • Dimuon acceptance mildly inconsistent with data • mc used isn’t best fit to dimuon data • Nuclear corrections for proton PDFs handled consistently in two analyses? K. McFarland, Rochester

  2. CTEQ “Lepton-Photon” Result • Olness, Tung et alia [CTEQ] NLO/LO fitSmall asymmetry, ~+10%(CTEQ NLO d-quark PDFs) • inconsistency with zero not claimed • uses inclusive data and dimuons • Paper speculates about errors in NuTeV analysis • Strangeness not conserved at x below charm production threshold • Evolution not correct for assumed functional form • They are good points; do they matter? K. McFarland, Rochester

  3. Main findings of the CTEQ Dimuon Global Analysis pertaining to the Strangeness Asymmetry of the nucleon parton distributions (so far) ceff2 vs. [S-] for one series of LM fits The dimuon data sets do give the main constraints on s, sbar in the global analysis; The shape (width) of the parabola is a robust feature of all current global fits; The center of the parabola wanders by ~ 0.1 for different series of LM fits; A conservative estimate:-0.1 < [S-]*100 < 0.5 ? The blue curve flops around in different series, hence is not a robust feature of the GA..

  4. Dimuon Data and Asymmetry • x region of CTEQ asymmetry is covered by NuTeV dimuon data • so it’s all a question of interpretation… CTEQ Asymmetry NuTeV Dimuons K. McFarland, Rochester

  5. Comparison of fit-B with data K. McFarland, Rochester

  6. Comparison of fit-B with data K. McFarland, Rochester

  7. Comparison of fit-B with data K. McFarland, Rochester

  8. Comparison of fit-B with data K. McFarland, Rochester

  9. Comparison of fit-B with data Ccfr n K. McFarland, Rochester

  10. Comparison of fit-B with data NuTeV n K. McFarland, Rochester

  11. Comparison of fit-B with data - NuTeV n K. McFarland, Rochester

  12. Comparison of fit-B with data - Ccfr n K. McFarland, Rochester

  13. What Needs to Be Resolved? NuTeV CTEQ • Functional form does not evolve correctly • from Q0 of 12.6 GeV2 to range of 4-100 GeV2 • Strangeness not conserved (low x) • Not global fit • with outside PDFs, d-quark distributions not adjusted for changes in s(x) • Inclusive measurements fit to same PDFs with NLO cross-section that go into LO cross-section for dimuons • Dimuon acceptance mildly inconsistent with data • mc used isn’t best fit to dimuon data • Nuclear corrections for proton PDFs handled consistently in two analyses? K. McFarland, Rochester

  14. Current NuTeV Status • Have refit at NLO with total strangeness constraint of CTEQ • See little change in netmomentum difference • Still precise constraint.Still weakly negative • Panagiotis Spentzouris is hereand can give details if desired • Work is ongoing K. McFarland, Rochester

  15. Summary on Strange Sea • A 30% excess of strange momentum overanti-strange would explain the NuTeV sin2qW • NuTeV analysis is consistent with zero, weakly negative using “all-iron” internal PDFs • uncertainty of 5% with assumed functional forms • CTEQ measurement favors +10% • We need to sort this out, but it won’t “fix” the NuTeV sin2qW K. McFarland, Rochester

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