How to measure the Charm Density in the Proton at EIC

We study two experimental ways to measure the heavy-quark content of the proton: using the Callan-Gross ratio $R(x,Q^2)=F_L/F_T$ and/or the azimuthal $\cos(2\phi)$ asymmetry in deep inelastic lepton-nucleon scattering. Our approach is based on the following observations. First, unlike the production cross sections, the ratio $R(x,Q^2)=F_L/F_T$ and the azimuthal $\cos(2\phi)$ asymmetry in heavy-quark leptoproduction are sufficiently stable, both parametricallly and perturbatively, in a wide region of variables $x$ and $Q^2$ within the fixed-flavor-number scheme of QCD. Second, both these quantities, $R(x,Q^2)=F_L/F_T$ and $\cos(2\phi)$ asymmetry, are sensitive to resummation of the mass logarithms of the type $\alpha_{s}\ln\left(Q^{2}/m^{2}\right)$ within the variable-flavor-number schemes. These two facts together imply that the heavy-quark densities in the nucleon can, in principle, be determined from high-$Q^2$ data on the Callan-Gross ratio and/or the azimuthal asymmetry in heavy-quark leptoproduction. In particular, the charm content of the proton can be measured in future studies at the proposed Large Hadron-Electron (LHeC) and Electron-Ion (EIC) Colliders.Comment: 9 pages, 4 figures, LaTeX. Talk given at the Workshop on Exclusive Reactions at High Momentum Transfer (IV), May 18-21, 2010, TJNAF, Newport News, VA and Electron-Ion Collider Collaboration Meeting, July 29-31, 2010, Catholic University of America, Washington, D

On the reactions p + p -> p + Lambda + K^+ and p + p -> p + Sigma^0 + K^+ near thresholds

The cross sections for the reactions of the strange production p + p -> p + Lambda + K^+ and p + p -> p + Sigma^0 + K^+ near thresholds of the final states p Lambda K^+ and p Sigma^0 K^+ are calculated in the effective Lagrangian approach. Our approach is based on the dominant contribution of the one-pion exchange and strong interaction of the colliding protons in the initial state. The theoretical values of the cross sections agree reasonably well with the experimental data. The polarization properties of the Lambda and Sigma^0 hyperons are discussed.Comment: 15 pages, 1 Postscript figure, Latex, to appear in Eur. Phys. J