3,968 research outputs found

    Fixed target Drell-Yan data and NNLO QCD fits of parton distribution functions

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    We discuss the influence of fixed target Drell-Yan data on the extraction of parton distribution functions at next-to-next-to-leading order (NNLO) in QCD. When used in a parton distribution fit, the Drell-Yan (DY) data constrain sea quark distributions at large values of Bjorken x. We find that not all available DY data are useful for improving the precision of parton distribution functions (PDFs) obtained from a fit to the deep inelastic scattering (DIS) data. In particular, some inconsistencies between DIS-based parton distribution functions and DY data for large values of dilepton rapidity are found. However, by selecting a sample of the DY data that is both representative and consistent with the DIS data, we are able to perform a combined PDF fit that significantly improves the precision of non-strange quark distributions at large values of x. The NNLO QCD corrections to the DY process are crucial for improving the precision. They reduce the uncertainty of the theoretical prediction, making it comparable to the experimental uncertainty in DY cross-sections over a broad range of x.Comment: 12 pages, revte

    Quark fragmentation functions in a diquark model for proton and Λ\Lambda hyperon production

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    A simple quark-diquark model for nucleon and Λ\Lambda structure is used to calculate leading twist light-cone fragmentation functions for a quark to inclusively decay into P or Λ\Lambda. The parameters of the model are determined by fitting to the known deep-inelastic structure functions of the nucleon. When evolved from the initial to the final Q2Q^2 scale, the calculated fragmentation functions are in remarkable agreement (for z>0.4z>0.4 ) with those extracted from partially inclusive epep and e+e−e^+ e^- experiments at high energies. Predictions are made, using no additional parameters, for longitudinally and transversely polarized quarks to fragment into p or Λ\Lambda.Comment: 15 pages, latex, figures may be obtained by writing to hafsa%png-qau%[email protected]

    Nuclear PDFs from neutrino deep inelastic scattering

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    We study nuclear effects in charged current deep inelastic neutrino-iron scattering in the frame-work of a chi^2 analysis of parton distribution functions. We extract a set of iron PDFs and show that under reasonable assumptions it is possible to constrain the valence, light sea and strange quark distributions. Our iron PDFs are used to compute x_{Bj}-dependent and Q^2-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. We compare our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for charged lepton-iron scattering. We find that, except for very high x_{Bj}, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering.Comment: 25 pages, 10 figures; minor updates to match published versio