Abstract
We present a first global determination of spin-dependent parton distribution functions (PDFs) and their uncertainties using the NNPDF methodology: NNPDFpol1.1. Longitudinally polarized deep-inelastic scattering data, already used for the previous NNPDFpol1.0 PDF set, are supplemented with the most recent polarized hadron collider data for inclusive jet and W boson production from the STAR and PHENIX experiments at RHIC, and with open-charm production data from the COMPASS experiment, thereby allowing for a separate determination of the polarized quark and antiquark PDFs, and an improved determination of the medium- and large-x polarized gluon PDF. We study the phenomenological implications of the NNPDFpol1.1 set, and we provide predictions for the longitudinal double-spin asymmetry for semi-inclusive pion production at RHIC.
Highlights
We presented the NNPDFpol1.0 parton set [1], a first unbiased determination of polarized parton distribution functions (PDFs) of the proton and their associated uncertainties based on the NNPDF methodology [2,3,4,5]
This methodology differs from that used in other recent next-to-leading order (NLO) analyses [6,7,8,9,10], in that it relies on a Monte Carlo sampling and representation of PDFs, and it uses a parametrization of PDFs based on neural networks with a very large number of free parameters
We have presented a first global polarized PDF determination based on NNPDF methodology, which includes, on top of the deep-inelastic scattering data already used in our previous NNPDFpol1.0 polarized PDF set, COMPASS charm production data and all relevant inclusive hadronic data from polarized collisions at RHIC, i.e. essentially all available data which do not require knowledge of light-quark fragmentation functions
Summary
We presented the NNPDFpol1.0 parton set [1], a first unbiased determination of polarized parton distribution functions (PDFs) of the proton and their associated uncertainties based on the NNPDF methodology [2,3,4,5]. The set of experimental data which may be used for the determination of longitudinally polarized PDFs has been extended impressively They include semi-inclusive DIS (SIDIS) in fixed-target experiments [11,12,13,14,15], one- or two-hadron and open-charm production in lepton–nucleon scattering [16,17,18,19,20], and semi-inclusive particle production [21,22,23,24,25,26,27], high-pT jet production [28,29,30] and parity-violating W ± boson production [31,32,33] in polarized proton– proton collisions. We will discuss the phenomenological implications of NNPDFpol1.1 compared to NNPDFpol1.0: we will reassess the spin content of the proton by computing PDF first moments, and give an illustrative example of the predictive power of our new PDF set for the case of longitudinal double-spin asymmetry for single-inclusive particle production in proton–proton collisions recently measured at RHIC
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