Protons in High Density Neutron Matter

We discuss the possible implication of the recent predictions of two new properties of high momentum distribution of nucleons in asymmetric nuclei for neutron star dynamics. The first property is about the approximate scaling relation between proton and neutron high momentum distributions weighted by their relative fractions ($x_p$ and $x_n$) in the nucleus. The second is the existence of inverse proportionality of the high momentum distribution strength of protons and neutrons to $x_{p/n}$. Based on these predictions we model the high momentum distribution functions for asymmetric nuclei and demonstrate that it describes reasonably well the high momentum characteristics of light nuclei. We also extrapolate our results to heavy nuclei as well as infinite nuclear matter and calculate the relative fractions of protons and neutrons with momenta above $k_{F}$. Our results indicate that for neutron stars starting at {\em three} nuclear saturation densities the protons with $x_p = {1\over 9}$ will populate mostly the high momentum tail of the momentum distribution while only $2\%$ of the neutrons will do so. Such a situation may have many implications for different observations of neutron stars which we discuss.Comment: 6 pages, 2 eps figures, For the proceedings of International Conference on "The Modern Physics of Compact Stars and Relativistic Gravity", 18-21 September 2013, Yerevan, Armeni

Final-state interactions in deep-inelastic scattering from a tensor polarized deuteron target

Deep-inelastic scattering (DIS) from a tensor polarized deuteron is sensitive to possible non-nucleonic components of the deuteron wave function. To accurately estimate the size of the nucleonic contribution, final-state interactions (FSIs) need to be accounted for in calculations. We outline a model that, based on the diffractive nature of the effective hadron-nucleon interaction, uses the generalized eikonal approximation to model the FSIs in the resonance region, taking into account the proton-neutron component of the deuteron. The calculation uses a factorized model with a basis of three resonances with mass $W<2$ GeV as the relevant set of effective hadron states entering the final-state interaction amplitude for inclusive DIS. We present results for the tensor asymmetry observable $A_{zz}$ for kinematics accessible in experiments at Jefferson Lab and Hermes. For inclusive DIS, sizeable effects are found when including FSIs for Bjorken $x>0.2$, but the overall size of $A_{zz}$ remains small. For tagged spectator DIS, FSIs effects are largest at spectator momenta around 300 MeV and for forward spectator angles.Comment: 7 pages, 3 figures, proceedings of the Tensor Polarized Solid Target Workshop March 10-12, 2014 (Jefferson Lab, Newport News, USA

Final-state interactions in semi-inclusive deep inelastic scattering off the Deuteron

Semi-inclusive deep inelastic scattering off the Deuteron with production of a slow nucleon in recoil kinematics is studied in the virtual nucleon approximation, in which the final state interaction (FSI) is calculated within general eikonal approximation. The cross section is derived in a factorized approach, with a factor describing the virtual photon interaction with the off-shell nucleon and a distorted spectral function accounting for the final-state interactions. One of the main goals of the study is to understand how much the general features of the diffractive high energy soft rescattering accounts for the observed features of FSI in deep inelastic scattering(DIS). Comparison with the Jefferson Lab data shows good agreement in the covered range of kinematics. Most importantly, our calculation correctly reproduces the rise of the FSI in the forward direction of the slow nucleon production angle. By fitting our calculation to the data we extracted the $W$ and $Q^2$ dependences of the total cross section and slope factor of the interaction of DIS products, $X$, off the spectator nucleon. This analysis shows the $XN$ scattering cross section rising with $W$ and decreasing with an increase of $Q^2$. Finally, our analysis points at a largely suppressed off-shell part of the rescattering amplitude.Comment: 27 pages, 8 figures. Corrected typos, section II.E has been expanded a bit. Figures have been updated to conform to the publication guidelines. Results and conclusions haven't changed. Accepted for publication in PR

High Energy Break-Up of Few-Nucleon Systems

We discus recent developments in theory of high energy two-body break-up reactions of few-nucleon systems. The characteristics of these reactions are such that the hard two-body quasielastic subprocess can be clearly separated from the accompanying soft subprocesses. We discuss in details the hard rescattering model (HRM) in which hard photodisintegration develops in two stages. At first, photon knocks-out an energetic quark which rescatters subsequently with a quark of the other nucleon. The latter provides a mechanism of sharing the initial high momentum of the photon by the outgoing two nucleons. Within HRM we discuss hard break-up reactions involving $^2D$ and $^3He$ targets. Another development of HRM is the prediction of new helicity selection mechanism for hard two-body reactions, which was apparently confirmed in the recent JLab experiment.Comment: To appear in the proceedings of Workshop on Exclusive Reactions at High Momentum Transfer, Newport News, Virgina, 21-24 May 200

DIS on a polarized spin-1 target with spectator tagging

We discuss the process of deep-inelastic electron scattering (DIS) on the polarized deuteron with detection of a nucleon in the nuclear fragmentation region (“spectator tagging”). We cover (a) the general structure of the semi-inclusive DIS cross section on a spin-1 target; (b) the tagged structure functions in the impulse approximation, where deuteron structure is described by the NN light-front wave function; (c) the extraction of free neutron structure through on-shell ex-trapolation in the recoil proton momentum. As an application we consider the extraction of the neutron structure function F 2n and spin structure function g 1n through electron scattering on the (un)polarized deuteron with proton tagging and on-shell extrapolation. Such measurements would be possible at an Electron-Ion Collider (EIC) with polarized deuteron beams and forward proton detectors

Inclusive and Exclusive Scatterings from Tensor Polarized Deuteron

The possibility of using a tensor polarized deuteron target in electroproduction reactions creates new opportunities for studying different phenomena related to the short-range hadronic and nuclear physics. The use of tensor polarized deuteron allows to isolate smaller than average inter-nucleon distances for the bound two-nucleon system. In this report we consider several of high $Q^2$ reactions which are particularly sensitive to the short-range two-nucleon configurations in the deuteron. The one is the relativistic dynamics of electron-bound-nucleon scattering which can be studied in both inclusive and exclusive reactions, other is the strong final state interaction in close proximity of two nucleons that can be used as a sensitive probe for color-transparency phenomena.Comment: 8 pages and 6 figures, proceedings of the Tensor Polarized Solid Target Workshop March 10-12, 2014 (Jefferson Lab, Newport News, USA