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Extracting Free Neutron Structure Functions: Insights from Recent Collaborations

This study investigates the free neutron structure function using data from various nuclei, aiming to better understand the evolution parameter related to two-nucleon short-range correlations (2N-SRC). Collaborators include L. B. Weinstein, D. Higinbotham, J. Gomez, O. Hen, R. Shneor, and Eli Piasetzky. We present findings on the free neutron’s cross-section and compare it to theoretical models, highlighting the significance of medium corrections and the EMC effect during extraction processes. Our analysis reveals inconsistencies with standard smearing models, emphasizing nuclear modification effects on nucleon structure.

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Extracting Free Neutron Structure Functions: Insights from Recent Collaborations

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  1. Free neutron structure function • No ‘free’ neutron target (life time ~ 12 minutes) Work done in collaboration with: L. B. Weinstein (ODU) D. Higinbotham, J. Gomez (JLab) O. Hen, R. Shneor (TAU) Eli Piasetzky Tel Aviv University, Israel Newport News, VA, USA, April 2011

  2. The ‘evolution parameter’ is the amount of 2N-SRC in nuclei 4He d 197Au 56Fe 12C 22% 20% 14% 4% The probability to find 2N-SRC in the nucleus

  3. d distribution at large x Uncertainty due to nuclear effects Adapted from J. F. Owens talk in this conference

  4. d distribution at large x Uncertainty due to nuclear effects Adapted from J. F. Owens talk in this conference

  5. 1 1 1 ­ = ­ + ­ - ¯ p u ( ud ) u ( ud ) u ( ud ) = = = 0 1 1 S S S 3 2 18 1 2 - ­ - ¯ d ( uu ) d ( uu ) = = 1 1 S S 3 3 Toy models for large x Proton Wavefunction (Spin and Flavor Symmetric) Adapted from J.P. Chen

  6. See previous talk by Or Hen Phys. Rev. Lett. 106, 052301, 2011 EMC Slopes 0.35 ≤ XB ≤ 0.7 SRC Scaling factors XB ≥ 1.4

  7. Conclusion: One should not neglect the EMC effect using deuteron and proton data to extract free neutron properties Deuteron is not a free np pair EMC The slopes for 0.35 ≤ XB ≤ 0.7 0.079±0.06 bound to free n p pairs (as opposed to bound to deuteron) SRC A Phys. Rev. Lett. 106, 052301, 2011 SRC=0 free nucleons

  8. The free neutron DIS cross section

  9. Where is the ratio of cross sections for absorbing a longitudinal to that for a transverse photon. See talk by Patricia Solvignon Gessman, Saito,Thomas,Annu. Rev. Nucl. Part. Sci. 1995. 45:337

  10. The free neutron structure function For 0.35 ≤ XB ≤ 0.7 SLAC Data, J. Arrington et al. JPG 36(2009)205005. Fermi smearing using relativistic deuteron momentum density Extracted from this work With medium correction Phys. Rev. Lett. 106, 052301, 2011

  11. The free neutron structure function Compared to CT calculations Preliminary calculation by :H. l. Lai, P. Nadolsky, J. Pumplin, .P.Yuan SU6 Fh07b / fh02c are CT10 / CT10W like Chebyshev fits pQCD See talk by J.Pumplin in this conference SLAC Data, Scalar qq See talk by Heidi Schellman in this conference

  12. The d / u ratio Compared to CT calculations SLAC Data, SU6 pQCD Fh07b / fh02c are CT10 / CT10W like Chebyshev fits See talk by J.Pumplin in this conference Scalar qq Preliminary calculation by :H. l. Lai, P. Nadolsky, J. Pumplin, .P.Yuan

  13. Summary We employ a phenomenological procedure to extract the free F2n/F2p structure function ratio from proton and deuteron DIS. At large Bjorken x, we obtain a substantially different F2n/F2pratio compared to using the standard smearing model to account for the Fermi motion of the nucleons in the deuteron. Better agreement with W charge and W lepton asymmetries. Narrow uncertainties in PDFs at large x due to nuclear effects in deuteron structure function. Sharpen theoretical understanding of nuclear modifications of nucleons in nuclei.

  14. arXiv:1003.4497 [hep-ph] Phys. Rev. Lett. 106, 052301, 2011

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