Nucleon partonic spin structure to be explored by the unpolarized Drell-Yan program of COMPASS experiment at CERN

The observation of the violation of Lam-Tung relation in the $\pi N$ Drell-Yan process triggered many theoretical speculations. The TMD Boer-Mulders functions characterizing the correlation of transverse momentum and transverse spin for partons in unpolarized hadrons could nicely account for the violation. The COMPASS experiment at CERN will measure the angular distributions of dimuons from the unpolarized Drell-Yan process over a wide kinematic region and study the beam particle dependence. Significant statistics is expected from a successful run in 2015 which will bring further understanding of the origin of the violation of Lam-Tung relation and of the partonic transverse spin structure of the nucleon.Comment: Proceedings of the 21st International Symposium on Spin Physics - October 20-24, 2014, Beijing, China; 6 pages, 3 figures, 1 tabl

Extraction of Various Five-Quark Components of the Nucleons

We have generalized the approach of Brodsky {\it et al.} for the intrinsic charm quark distribution in the nucleons to the light-quark sector involving intrinsic $\bar u, \bar d, s$ and $\bar s$ sea quarks. We compare the calculations with the existing $\bar d - \bar u$, $s + \bar s$, and $\bar u + \bar d - s -\bar s$ data. The good agreement between the theory and the data allows the extraction of the probabilities for the $|uudu\bar{u}>$, $|uudd\bar{d}>$, and $|uuds\bar{s}>$ five-quark Fock states in the proton. We also calculate the $x$-dependence of the intrinsic charm after taking into consideration the QCD evolution of the intrinsic quark distribution.Comment: 4 pages, 4 figures; version published; Wrong page number of Ref. [3] is correcte

Flavor Asymmetry of the Nucleon Sea and the Five-Quark Components of the Nucleons

The existence of the five-quark Fock states for the intrinsic charm quark in the nucleons was suggested some time ago, but conclusive evidence is still lacking. We generalize the previous theoretical approach to the light-quark sector and study possible experimental signatures for such five-quark states. In particular, we compare the $\bar d - \bar u$ and $\bar u + \bar d - s -\bar s$ data with the calculations based on the five-quark Fock states. The qualitative agreement between the data and the calculations is interpreted as evidence for the existence of the intrinsic light-quark sea in the nucleons. The probabilities for the $|uudu\bar{u}>$ and $|uudd\bar{d}>$ Fock states are also extracted.Comment: 4 pages, 3 figure