Abstract
A precise knowledge of nuclear parton distribution functions (nPDFs) is---among other things---important for the unambiguous interpretation of hard process data taken in $pA$ and $AA$ collisions at the Relativistic Heavy Ion Collider (RHIC) and the LHC. The available fixed target data for deep inelastic scattering (DIS) and Drell-Yan (DY) lepton pair production mainly constrain the light quark distributions. It is hence crucial to include more and more collider data in global analyses of nPDFs in order to better pin down the different parton flavors, in particular the gluon distribution at small $x$. To help constrain the nuclear gluon PDF, we extend the nCTEQ15 analysis by including single inclusive hadron (SIH) production data from RHIC (PHENIX and STAR) and LHC (ALICE). In addition to the DIS, DY, and SIH datasets, we will also include LHC $W/Z$ production data. As the SIH calculation is dependent on hadronic fragmentation functions (FFs), we use a variety of FFs available in the literature to properly estimate this source of uncertainty. We study the impact of these data on the PDFs and compare with both the nCTEQ15 and nCTEQ15WZ sets. The calculations are performed using a new implementation of the nCTEQ code (ncteq++) including a modified version of incnlo, which allows faster calculations using precomputed grids. The extension of the nCTEQ15 analysis to include the SIH data represents an important step toward the next generation of PDFs.
Highlights
Parton distribution functions (PDFs) are fundamental quantities required to calculate predictions for any process involving hadrons in the initial state
To help constrain the nuclear gluon PDF, we extend the nCTEQ15SIH fit and its baseline (nCTEQ15) analysis by including single inclusive hadron (SIH) production data from Relativistic Heavy Ion Collider (RHIC) (PHENIX and STAR) and LHC (ALICE)
As the SIH calculation is dependent on hadronic fragmentation functions (FFs), we use a variety of FFs available in the literature to properly estimate this source of uncertainty
Summary
Parton distribution functions (PDFs) are fundamental quantities required to calculate predictions for any process involving hadrons in the initial state. On the other hand, unbiased fits to the experimental data provide important global constraints on these theoretical ideas and are an indispensable ingredient for many current and future experimental (i.e., at the LHC, and RHIC and EIC) and theoretical analyses (e.g., for the very successful Statistical Hadronization Model describing the freeze-out of the quark gluon plasma [36]). This is the approach we take in the following. We will demonstrate that our results are largely independent of the final-state hadron fragmentation and that our interpretation of the nuclear effects as modifications of a cold initial state is currently totally consistent with the available experimental data
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