Bulletin of the American Physical Society
2020 Fall Meeting of the APS Division of Nuclear Physics
Volume 65, Number 12
Thursday–Sunday, October 29–November 1 2020; Time Zone: Central Time, USA
Session EK: Mini-Symposium: Short Range Correlations II |
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Chair: Julian Kahlbow, MIT |
Friday, October 30, 2020 10:30AM - 11:06AM |
EK.00001: Recent insight into the structure of short-range correlations and the EMC effect. Invited Speaker: John Arrington Jefferson Lab has had great success using high-energy probes to significantly advance our understanding of energetic, high-density components of nuclear structure. Studies of high-momentum nucleons associated with short-range correlations (SRCs) have mapped out the strength and isospin dependence of these energetic components in nuclei, providing new insight into their connection to nuclear structure and the N-N interaction. Studies of nuclear parton distributions and the EMC effect have also shown unexpected behavior in light nuclei, and raised questions about a correlation or common origin for the EMC effect and short-range correlations. It also suggests a mechanism for a flavor dependence in the EMC effect for non-isoscalar nuclei, which could have significant impact on a range of other experiments at Jefferson Lab and in high-energy scattering and collider experiments around the world. ~ I will highlight key insights gained from the 6 GeV program at Jefferson Lab, discuss the potential impact on measurements of neutrino and electron scattering from nuclei and A-A, and briefly present future experiments aimed at further illuminating these exotic components of nuclear structure. [Preview Abstract] |
Friday, October 30, 2020 11:06AM - 11:18AM |
EK.00002: Recent Analyses of Flavor Dependence of the EMC effect Nadia Fomin, John Arrington The modification of nuclear quark distributions, known as the EMC effect, first observed 40 years ago, has been under study for several decades and has recently become been an area of active theoretical interest and work as well. Electron scattering data on light nuclei from the 6GeV era at Jefferson lab yielded some suggestive results, ruling out previously favored simple density or A dependent pictures. Additionally, a correlation was observed between the size of the EMC effect and the nuclear dependence of short-range N-N correlations, which are measured in a very different kinematic regime. This correlation has been an object of intense interest and many analysis efforts, looking for clues of isospin dependence in the EMC effect as well as using it to inform upcoming experiments. Existing measurements and results will be reviewed and goals for upcoming measurements presented. [Preview Abstract] |
Friday, October 30, 2020 11:18AM - 11:30AM |
EK.00003: New Analysis of EMC Data in Heavy Nuclei Jason Bane, John Arrington, Nadia Fomin, Dave Gaskell The modification of nuclear quark distributions, known as the EMC effect, has been under study for several decades. Over a thousand theory papers have been published on the subject, but the underlying physics is not yet understood. Electron scattering data on light nuclei from the 6 GeV era at Jefferson lab yielded some suggestive results, negating simple density or A dependent pictures. Additionally, a correlation was observed with the nuclear dependence of short-range N-N correlations (SRCs), which are measured in a very different kinematic regime. This talk will include new results on the EMC effect from heavier targets that can be directly combined with already published SRC data to provide additional information on the EMC-SRC connection. Also, the role of Coulomb Corrections will be discussed and, in particular, their relevance in the observation of a possible nuclear dependence of R=\sigma_L/\sigma_T. [Preview Abstract] |
Friday, October 30, 2020 11:30AM - 11:42AM |
EK.00004: Mapping the tensor-to-scalar transition in the short-range nucleon-nucleon interaction Axel Schmidt, Igor Korover The predominance of proton-neutron short-range correlated pairing for nucleons with $\approx$300--600~MeV$/c$ of relative momentum is now well-understood as a consequence of the tensor force in the nucleon-nucleon ($NN$) interaction. The isospin structure of pairs with even higher relative momenta can reveal new information about the interactions between nucleons at extremely short distance scales. I will present the results of new measurements of the $(e,e'p)$, $(e,e'pp)$, and $(e,e'pn)$ reactions in high-$Q^2$, $x_B>1$ kinematics in the missing momentum range of 300--1000~MeV$/c$. The data are well reproduced by theoretical calculations using Generalized Contact Formalism with both chiral and phenomenological $NN$ interaction models. This agreement between the theory and data suggests that all of the measured high missing-momentum protons belong to SRC pairs. Furthermore, the results show clear evidence of a transition from an isospin-dependent tensor-$NN$ interaction at $\approx 400$~MeV$/c$ to an isospin-independent scalar interaction at high-momentum around $\approx 800$~MeV$/c$. [Preview Abstract] |
Friday, October 30, 2020 11:42AM - 11:54AM |
EK.00005: Probing for high momentum protons in~$^{\mathrm{4}}$He via the~$^{\mathrm{4}}$He(e,e$\prime $p)X~reaction Konrad Aniol, Fatiha Benmokhtar Experimental cross sections for the $^{\mathrm{4}}$He(e; e'p)X reaction up to a missing momentum of 0.632 GeV/$c$ at x$_{\mathrm{B}}=$1.24 and Q$^{\mathrm{2}}=$2 (GeV/$c)^{\mathrm{2}}$ are reported.The data are compared to Relativistic Distorted Wave Impulse Approximation (RDWIA) calculations for the $^{\mathrm{4}}$He(e; e'p)$^{\mathrm{3}}$H channel. Significantly more events in the narrow triton missing mass region that we used, 0.017 GeV $\le $ Emiss $\le $ 0.022 GeV, are measured for missing momenta pm $\ge $ 0:45 GeV/$c$ than are predicted by the theoretical model. This narrow missing mass region was chosen to minimize (pnn) and (p,d) background bleeding into the (p,t) state in the theoretical model. These excess events suggest that the effects of initial-state multi-nucleon correlations are stronger than expected by the RDWIA model. The ratio of the experimental cross sections to the theory cross sections shows a smooth dependence with missing momentum except in the region where the proton's predicted momentum distribution has a deep minimum. [Preview Abstract] |
Friday, October 30, 2020 11:54AM - 12:06PM |
EK.00006: GCF Analysis of SRC Measurements via the (e,e’N) and (e,e’NN) Reactions Jackson Pybus The Generalized Contact Formalism (GCF) is a new effective theory that allows to consistently describe the short-distance and high-momentum part of the nuclear wave function, as well as hard nucleon knockout reaction cross-sections. In this talk I will present the application of the GCF for modeling recent measurements of short-range correlated nucleon pairs in nuclei using the $(e,e’NN)$ reaction. The calculations allow discriminating between different nucleon-nucleon interaction models while utilizing both instant form and relativistic light-front SRCs and using input from many-body ab-initio calculations. Special emphasis will be given to proper model uncertainty estimation and presentation of predictions for upcoming experiments where the GCF allows optimizing their sensitivity to observables of interest. [Preview Abstract] |
Friday, October 30, 2020 12:06PM - 12:18PM |
EK.00007: GCF Analysis of High-x Scaling in Inclusive Electron Scattering Andrew Denniston The relative abundances of short-range correlated (SRC) pairs in nuclei are typically extracted from measurements of inclusive electron scattering cross-section ratios of nucleus A to d (a2) at large-Q2 and high-x. While vast amounts of data exist, there are few rigorous theoretical calculations of a2 which incorporate the isospin dependence of the nucleon-nucleon (NN) potential and the impact of low-energy nuclear structure of the measured nuclei. In this talk I will present a theoretical study of a2 by using the generalized contact formalism (GCF) which was recently shown to reproduce SRC studies via nucleon-knockout reactions and accounts for the isospin dependence of the NN potential at high momenta. The calculation shows that the measured value of a2 is sensitive not only to the number of SRC pairs in the measured nuclei, but also to the pair motion and to nuclear structure effects. Therefore, independently of the accuracy of the data, the relative pair abundances of SRC pairs in the nucleus can only be extracted with accuracy of about 20{\%}. Focusing on recent measurements of Ca isotopes, we find that the constraint placed on the isospin dependence of SRCs has large uncertainty driven by low-energy nuclear structure. [Preview Abstract] |
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