The main goal of this workshop is to address theoretical calculation and interpretation issues associated with the flavor structure of the nucleon’s light sea, including its number or momentum distributions (PDFs), helicity distributions, transverse-momentum-dependent parton distributions (TMDs) such as the Sivers distribution, and the flavor asymmetry of these distributions. New data from ongoing experiments will become available from jet, hadron, direct photon, and W+/-boson measurements at the RHIC STAR and PHENIX experiments, from Fermilab E906 Drell-Yan measurements, and from semi-inclusive deep-inelastic scattering (SIDIS) measurements at COMPASS. In addition, several new experiments are in the preparation stage and aim to collect data over the next few years, including the polarized target Drell-Yan experiment at Fermilab (E1039), RHIC’s run with transversely polarized protons at 510 GeV in Run-2017, and a new generation of SIDIS experiments with the JLab-12GeV upgrade.

We plan to start the workshop with 2 days of coordinated and focused presentations to summarize the progress made in understanding the flavor structure of the nucleon's sea over the last decade with reviews of existing knowledge, present puzzles and interpretation of data from existing measurements; to discuss and define the state of the theory; and to identify the focused work to be carried out during the rest of the workshop. We will explore what is needed for better understanding the flavor structure of the nucleon's light sea from both theory and experiment, and to provide predictions and guidance for upcoming measurements. More specifically, the workshop will focus on the following:

1. Review the current status and future prospects of experimental measurements:

1. Investigate the strengths and weaknesses, as well as the complementarities, of various measurements, such as inclusive and semi-inclusive DIS, Drell-Yan, electro-weak, jet/multi-jet, and hadron and/or photon production in high-energy p+p collisions, in probing the nucleon's sea structure and its dynamics.

2. Identify observables involving transverse degrees of freedom of partons inside the nucleon, both in momentum and position space, to help in understanding the spin-orbit correlations and orbital angular momentum of the confined quarks and gluons.


2. Critically assess the current theoretical tools and uncertainties of global fit analyses:

1. Review the status of perturbative QCD factorization and its breaking, and understand the QCD evolution and universality properties for various PDFs and TMDs, as well as the state-of-the-art of the QCD global fitting methods used for extracting these distributions, e.g., those used to extract NNPDF, CTEQ, DSSV parton distributions, various sets of TMDs, and related endeavors.

2. Compare the various techniques for extracting TMDs from data, and develop much-needed improvements, making use of experience gained for extracting the ordinary collinear PDFs.


3. Explore new theoretical tools for studying the nucleon's sea:

1. Review the current status and recent progress of lattice QCD calculations, and other non-perturbative methods for the structure of the nucleon's sea, and investigate new lattice QCD approaches, as well as other non-perturbative methods, for studying sea distributions, in particular, as a function of x.

2. Review and extend higher-order perturbative calculations for processes relevant for the extraction of the nucleon's sea distributions, in terms of fixed-order perturbative studies as well as all-order QCD resummation.