Session LE: Mini-Symposium: Short Range Correlations and Bound Nucleon Structure Across Scales III

Exploring short-range correlation effects with quantum Monte Carlo

Quantum Monte Carlo (QMC) techniques provide a versatile and systematic approach to nuclear systems. Recent advances allow to perform calculations from light to medium-mass nuclei for a variety of nuclear Hamiltonians, including those constructed using phenomenological potentials and local interactions derived from chiral effective field theory. The fully correlated nature of the many-body wave functions employed in QMC methods allows us to properly asses the short-distance and high-momentum behavior of calculated nuclear properties. In this talk, I will present QMC results for nuclei from $^3$H to $^{40}$Ca, enabling us to explore short-range correlation effects and connect to the experimental information extracted from electron scattering.   

Bound and Free Nucleon Structure

Understanding the partonic structure of the nucleon in the valence region (high xB) is a long standing question. Constraining the neutron-to-proton structure function ratio (F2n/F2p) at high xB has been a goal of many experiments. Many approaches have been made since the 90's towards this, such as neutron structure extractions from proton and deuterium deep inelastic scattering (DIS) measurements. However, how one treats nucleon smearing, off-shell effects, and more, lead to different extractions in the valence region. We present a new model approach to extract the nucleon structure at high xB using all world nuclear DIS data on the proton and on nuclei from deuterium to lead. By consistently accounting for nuclear modification effects, we obtain reduced uncertainty and find a F2n/F2p consistent with predictions such as those of perturbative QCD, but in disagreement with predictions such as the scalar di-quark dominance model. Predictions are also made for F3He/F3H, recently measured by the MARATHON collaboration, the nuclear correction function needed to extract F2n/F2p from F3He/F3H, and the systematic uncertainty associated with this extraction.   

Investigating the EMC effect in highly-virtual nucleons at Jefferson Lab's Hall B

We are measuring how the quark-structure of the bound proton varies with its initial momentum to directly determine how and why the structure of bound protons differs from free ones. We will do this using Deep Inelastic Electron Scattering (DIS) from a bound proton in deuterium, detecting the backward spectator neutron to "tag" the initial momentum of the struck proton. This will help resolve the 35-year-old enigma of the EMC effect. We constructed and installed a Backward Angle Neutron Detector (BAND) just upstream of the existing CLAS12 spectrometer at Jefferson Lab to detect the backward spectator neutrons at scattering angles between 160 and 170 degrees. We detect the scattered electron with CLAS12 and the recoiling neutron with CLAS12 at intermediate angles or by BAND at backward angles, thereby ``tagging'' the DIS scattering off the proton in the deuteron. I will present the BAND detector and preliminary results from the Spring 2019 experimental runs.   

EMC Effect in Lighter Nuclei

As part of the 12 gev commissioning experiments in hall c at Jefferson Lab, e12-10-008 made measurements of the emc effect in selected light nuclei. This experiment is a measurement of inclusive electron scattering which aims to extract the ratio of nuclear structure function of several nuclei to those from deuterium. This is the first measurement of the Emc ratio for targets 10b and 11b, which was included to expand the set of lighter nuclei to test the idea that the local nuclear density plays an important role in quark modification. In this talk, I will be showing some preliminary results and our current analysis status.   

Searching for the Onset of Color Transparency in Quasielastic 12C(e,e'p)

Color Transparency (CT) is a prediction of QCD that at high momentum transfer $Q^2$, a system of quarks which would normally interact strongly with nuclear matter could form a small color-neutral object whose compact transverse size would be maintained for some distance, passing through the nucleus undisturbed. A clear signature of CT would be a dramatic rise in nuclear transparency $T$ with increasing $Q^2$. The existence of CT would contradict traditional Glauber multiple scattering theory, which predicts constant $T$. CT is a prerequisite to the validity of QCD factorization theorems, which provide access to the generalized parton distributions that contain information about the transverse and angular momenta carried by quarks in nucleons. The E12-06-107 experiment at JLab measured $T$ in quasielastic electron-proton scattering with carbon-12 and liquid hydrogen targets, for $Q^2$ between 8 and 14.3 $GeV^2$, a range over which $T$ should differ appreciably from Glauber calculations. Supported in part by US DOE grant DE-FG02-03ER41240.   

A new comparison of the $F_{2}^{A}/F_{2}^{p}$ and $F_{2}^{A}/F_{2}^{n}$ structure function ratios $\backslash $\textbf{f1}

h $-abstract-$\backslash $pardUsing electron scattering data from SLAC E139 and muon scattering data from NMC in the DIS region, we determine the $F_{2}^{A}/F_{2}^{p}$ and $F_{2}^{A}/F_{2}^{n}^{\mathrm{\thinspace }}$structure function ratios, spanning 0.07 le $x_{B}$ le 0.7 and 1 le $Q^{2}$ le 200 GeV/c$^{\mathrm{2}}$ and 0.006 le $x_{B}$ le 0.6 and 1 le $Q^{2}$ le 55 GeV/c$^{\mathrm{2}}$, respectively. This region is of particular relevance to studies of EMC Effect. Assuming no $Q^{2}$ dependence, we compare the structure function ratios for isoscalar nuclei and study non-isoscalar nuclei with the possibility to look for flavor dependence. This talk will present the results of the mentioned ratios for isoscalar nuclei using the new $F_{2}^{n}$ global data from the CTEQ-JLab Collaboration.$\backslash $pard-/abstract-$\backslash $\tex   

First Cross Section Results of D(e,e'p)n at Very High Recoil Momenta

Preliminary D(e,e'p)n electro-disintegration cross sections at $Q^{2} = 4.25$ GeV$^{2}$ with recoil momenta up to 900 MeV/c will be presented. The experiment ran for a total of 6 days of beam time in April 2018 at Jefferson Lab in Hall C and it seeks to study the short range structure of the deuteron by probing its high momentum components beyond 500 MeV/c, where currently no data exists. The experiment was part of a group of Hall C experiemnts that commissioned the new Hall C Super High Momentum Spectrometer (SHMS). At the selected kinematics, Meson Exchange Currents (MEC) and Isobar Configurations (IC) are suppressed. Final State Interactions (FSI) have also been suppressed by choosing a kinematic region where the neutron recoil angle is between 35 and 45 degrees with respect to the momentum transfer. This suppression was seen in a previous D(e,e'p)n experiment (Boeglin et al. Phys Rev Lett. 2011) and is also predicted in modern theoretical calculations (W. Boeglin \& M. Sargsian Int.J.Mod.Phys. 2015). In this region, the Plane Wave Impulse Approximation (PWIA) dominates and comparisons between measured and predicted cross sections are sensitive to the deuteron momentum distributions. Comparisons between data and calculations with different NN potentials will be shown.   

Probe nucleon mass inside nuclei

Nucleon masses in the nucleus are believed less than those in free space due to the binding in nuclear medium, particularly in the Short-Range Correlation (SRC). Extraction of nucleon mass inside nucleus, especially depending on its initial momentum, is a long-standing problem for both nuclear experimental and theoretical fundamental studies. High-energy electron quasi-elastic scattering associated with a knock-out proton by the virtual photon in (e,e'p) reaction is an appropriate way to probe the mass of the partner neutron in a SRC pair from missing mass spectra. The results of mass decrease with momentum will be shown not only in mean-field but also in SRC region, which are analyzed from light nucleus and heavier ones. The intrinsic features reflected are the modifications of quark dynamical characteristics when the confinement space of nucleon located inside nucleus, especially in high local density environment of SRC.