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 FK: Mini-Symposium: Short Range Correlations III |
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Chair: Axel Schmidt, GWU |
Friday, October 30, 2020 2:00PM - 2:12PM |
FK.00001: The Transparent Nucleus: Unperturbed inverse kinematics nucleon knockout measurements with a 48 GeV/c carbon beam Julian Kahlbow Measuring ground-state distributions of nucleons in atomic nuclei is a formidable challenge in nuclear physics, often met by particle knockout reactions. In this talk I present results from a new fully exclusive proton-knockout measurement in inverse kinematics at high energy that overcomes limitations posed by initial and final state interactions (ISI/FSI). The experiment was carried out at the JINR (Russia), where a $^{12}$C beam at 48~GeV/c impinged on a liquid hydrogen target, the reaction products were measured with the BM$@$N detector setup, using in particular a proton spectrometer and charged particle tracking system. By missing momentum reconstruction, quasielastic $pp$ scattering at large angles is identified, while the selection of the heavy fragment suppresses FSI. It is shown that this kind of $^{12}$C($p,2p$)$^{11}$B reaction probes single nucleon properties in a single-step knockout reaction, being in agreement with theoretical calculations. We probe Short-Range Correlations (SRC) in the same way by the break up of SRC pairs in $^{12}$C($p,2pN$)$^{10}$B/$^{10}$Be reactions. We not only identify SRCs in such kinematical conditions for the first time but also deduce factorization and other pair properties from direct measurements. [Preview Abstract] |
Friday, October 30, 2020 2:12PM - 2:24PM |
FK.00002: 48 GeV/c ${}^{12}$C beam induced reaction with multiple fragments emission Goran Johansson An inverse kinematics exclusive measurement of the ${}^{12}$C(p, 2p)X reaction was performed at JINR, Dubna, Russia at 4 (GeV/c)/A. Multiple nuclear (e.g. ${}^{4}$He) fragments were detected in coincidence with the two protons knocked out in the reaction. We report here the study of the fragmentation of the residual X system after the quasi elastic (QE) knockout of a single nucleon or of a nucleon in a short range correlated (SRC) pair. This analysis is complementary to the study of a single heavy fragment (B or Be) reported by Julian Khalbow to this meeting. The multiple light fragment production is related to the stability of the residual system after the knockout. It can teach us about the energy deposit in the process, and the nuclear ground state prior to the single nucleon or SRC pair removal. [Preview Abstract] |
Friday, October 30, 2020 2:24PM - 2:36PM |
FK.00003: Probing few-body nuclear dynamics via $^3$H and $^3$He $(e,e’p)$pn cross-section mesurements Dien Nguyen We will report the first measurement of the (e,e’p) three-body breakup reaction cross sections in helium-3 ($^3$He) and tritium ($^3$3H) at large momentum transfer ($Q^2$~1.9 (GeV/c)$^2$) and ($x_B > 1$) kinematics, where the cross-section should be sensitive to quasielastic (QE) scattering from single nucleons. The data cover missing momenta $40 < p_{miss} < 500$ MeV/c that, in the QE limit with no rescattering, equals the initial momentum of the probed nucleon. The measured cross-sections are compared with state-of-the-art ab-initio calculations. Overall good agreement, within 20\%, is observed between data and calculations for the full pmiss range for $^3$H and for $100 < p_{miss} < 350$ MeV/c for $^3$He. Including the effects of rescattering of the outgoing nucleon improves agreement with the data at $p_{miss} > 250$ MeV/c and suggests contributions from charge-exchange (SCX) rescattering. The isoscalar sum of $^3$He plus $^3$H, which is largely insensitive to SCX, is described by calculations to within the accuracy of the data over the entire $p_{miss}$ range. This validates current models of the ground state of the three-nucleon system up to very high initial nucleon momenta of 500 MeV/c. [Preview Abstract] |
Friday, October 30, 2020 2:36PM - 2:48PM |
FK.00004: Exploring short-range correlation effects with quantum Monte Carlo Diego Lonardoni Quantum Monte Carlo (QMC) techniques provide a versatile and systematic approach to nuclear systems. Recent advances allow one 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 one to properly asses the short-distance and high-momentum behavior of calculated nuclear properties. In this talk, I will present recent QMC results for nuclei from 2H to 40Ca, that enable one to explore short-range correlation (SRC) effects, such as the many-body factorization of the nuclear wave function and the position-momentum equivalence of SRCs, and to connect to the experimental information extracted from electron scattering. [Preview Abstract] |
Friday, October 30, 2020 2:48PM - 3:00PM |
FK.00005: Mean-field properties of short-ranged correlations abundance Or Hen While mean-field approximations, such as the nuclear shell model, provide a good description of many bulk nuclear properties, they fail to capture the short-distance and high-momentum components of the nuclear many-body wave function. In this talk I will discuss recent analysis of ab-initio Quantum Monte Carlo (QMC) calculations of nuclei from deuteron to Ca using the Generalized Contact Formalism. Our analysis shows a universal factorization of the many-body nuclear wave function at short-distance into a strongly-interacting pair and a weakly-interacting residual system. The residual system distribution is consistent with that of an un-correlated system, showing that short-distance correlation effects are predominantly embedded in two-body correlations. The nuclear scaling of our extracted spin- and isospin-dependent nuclear contact terms is shown to be scale and scheme independent and the same for short-distance and high-momentum pairs. These findings therefore allow extending the application of mean-field approximations to SRC pair formation by showing that the relative abundance of short-range pairs in the nucleus is a long-range (i.e., mean-field) quantity that is insensitive to the short-distance nature of the nuclear force. [Preview Abstract] |
Friday, October 30, 2020 3:00PM - 3:12PM |
FK.00006: Tagged DIS with BAND: Experimental overview Caleb Fogler The Backward Angle Neutron Detector (BAND) was designed to detect backward-recoiling spectator neutrons from the deep inelastic scattering (DIS) of electrons off of protons bound in deuterium. This technique of spectator-tagged DIS allows the determination of the proton’s nuclear modification as a function of virtuality or proton initial momentum. BAND was installed upstream of the CLAS12 spectrometer in Hall B at Jefferson Lab, and took production data in January 2020. In this talk, I will present the physics background and motivations for our experiment. I will give an overview about the design and construction of BAND and how it works with CLAS12 to detect spectator neutrons. Lastly, I will talk about the development of GEANT4 simulations to provide critical input to the BAND analysis. [Preview Abstract] |
Friday, October 30, 2020 3:12PM - 3:24PM |
FK.00007: Tagged DIS with BAND: Analysis status Tyler Kutz The Backward Angle Neutron Detector (BAND) was designed to detect backward-recoiling spectator neutrons from the deep inelastic scattering (DIS) of electrons off of protons bound in deuterium. The technique of spectator-tagged DIS allows the determination of the proton’s nuclear modification as a function of virtuality or initial momentum. BAND was installed upstream of the CLAS12 spectrometer in Hall B at Jefferson Lab, and took production data in early 2020. \\ Recoiling spectator neutrons are identified by their time of flight, requiring precise timing calibration of BAND. Further, the spectator neutrons must be separated from a constant background of random neutron coincidences. The background-subtracted data can then be used to form a ratio of bound to free proton structure as a function of virtuality. This talk will discuss the calibration and analysis of BAND data and present preliminary results based on the available data. [Preview Abstract] |
Friday, October 30, 2020 3:24PM - 3:36PM |
FK.00008: Testing the EMC-SRC Hypothesis with the LAD Experiment Sara Ratliff The EMC effect, the observation that Deep Inelastic Scattering (DIS) from nuclei differs significantly from that on free nucleons, has puzzled nuclear physicists for nearly forty years. A potential cause for this phenomenon is short-range correlations between nucleons within a nucleus, which can be directly tested using the technique of recoil tagging. The upcoming LAD experiment in Jefferson Lab Hall C will measure backwards recoiling spectator protons in coincidence with DIS electrons from a deuterium target, and will serve as a complement to the BAND experiment. The eponymous Large Acceptance Detector consists of three walls of plastic scintillator, which will determine proton momenta through a combination of timing and energy loss measurements. High-resolution GEM detectors will help provide crucial background suppression.I will present the current status of the preparations for LAD and showcase how BAND and LAD can definitively test the SRC-EMC hypothesis. [Preview Abstract] |
Friday, October 30, 2020 3:36PM - 3:48PM |
FK.00009: Quest for $\Delta$ isobars in nuclei Mark Strikman Light cone structure of configurations in nuclei containing $\Delta$ - isobars is discussed. Optimal strategies for observing such configurations in hard nuclear processes is presented. [Preview Abstract] |
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