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Resolving Strangeness Asymmetries in NuTeV and CTEQ Dimuon Global Analysis

The analysis of strangeness in parton distribution functions (PDFs) reveals several unresolved issues within the NuTeV and CTEQ collaborations. Key points include non-conservation of strangeness at low-x, the need for global fits to adjust d-quark distributions, and potential inconsistencies in dimuon acceptance and Monte Carlo simulations. The current status indicates a weakly negative net momentum difference and a possible 30% excess of strange momentum. Ongoing investigations aim to clarify these findings and their implications on the NuTeV sin²θ_W measurement.

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Resolving Strangeness Asymmetries in NuTeV and CTEQ Dimuon Global Analysis

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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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