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Park, Kijun

Publications and source records attributed to Park, Kijun.

At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Pion and kaon structure at the electron-ion collider

Understanding the origin and dynamics of hadron structure and in turn that of atomic nuclei is a central goal of nuclear physics. Here, this challenge entails the questions of how does the roughly 1 GeV mass-scale that characterizes atomic nuclei appear; why does it have the observed value; and, enigmatically, why are the composite Nambu-Goldstone (NG) bosons in quantum chromodynamics (QCD) abnormally light in comparison? In this perspective, we provide an analysis of the mass budget of the pion and proton in QCD; discuss the special role of the kaon, which lies near the boundary between dominance of strong and Higgs mass-generation mechanisms; and explain the need for a coherent effort in QCD phenomenology and continuum calculations, in exa-scale computing as provided by lattice QCD, and in experiments to make progress in understanding the origins of hadron masses and the distribution of that mass within them. We compare the unique capabilities foreseen at the electron-ion collider (EIC) with those at the hadron-electron ring accelerator (HERA), the only previous electron-proton collider; and describe five key experimental measurements, enabled by the EIC and aimed at delivering fundamental insights that will generate concrete answers to the questions of how mass and structure arise in the pion and kaon, the Standard Model's NG modes, whose surprisingly low mass is critical to the evolution of our Universe.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2016

Exclusive single pion electroproduction off the proton: Results from CLAS

Exclusive meson electroproduction off protons is a powerful tool to probe the effective degrees of freedom in excited nucleon states at the varying distance scale where the transition from the contributions of both quark core and meson-baryon cloud to the quark core dominance. During the past decade, the CLAS collaboration has executed a broad experimental program to study the excited states of the proton using polarized electron beam and both polarized and unpolarized proton targets. The measurements covered a broad kinematic range in the invariant mass $W$ and photon virtuality $Q^2$ with nearly full coverage in polar and azimuthal angles in the hadronic CM system. As results, several low-lying nucleon resonance states in particular from pion threshold to $W < 1.6$ GeV have been explored. These include $\Delta$(1232)$\frac{3}{2}^+$, $N(1440)\frac{1}{2}^+$, $N(1520)\frac{3}{2}^-$, and $N(1535)\frac{1}{2}^-$ states. In addition, we recently published the differential cross sections and helicity amplitudes of the reaction $\gamma^*p\to n\pi^+$ at higher $W$ (1.6 to 2.0 GeV) which are the $N(1675)\frac{5}{2}^-$, $N(1680)\frac{5}{2}^+$, and $N(1710)\frac{1}{2}^+$ states. These excited states with isospin $1/2$ and with masses near 1.7 GeV can be accessed in single $n\pi^+$ production as there are no isospin $3/2$ states present in this mass range with the same spin-parity assignments. As a result, I will briefly discuss these states from CLAS results of the single charged pion electroproduction data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Tagged spectator deep-inelastic scattering as a tool to study neutron structure

The poster summarizes results from the FY14/15 JLab LDRD project "Physics potential of polarized light ions with EIC@JLab" regarding possible measurements of neutron structure functions (unpolarized and polarized) in deep-inelastic scattering with spectator nucleon tagging at a future Electron-Ion Collider. Also included are some results by Cosyn et al. regarding the theoretical description of the JLab 6 GeV BONuS data. Presented by W. Cosyn at 11th European Research Conference "Electromagneitc Interactions with Nucleons and Nuclei," Paphos, Cyprus, 1-7 November, 2015

Cosyn, Wim↗
DOE OSTI2015

Exclusive Single Pion off the Proton: Results from CLAS

Exclusive meson electroproduction off protons is a powerful tool to probe the effective degrees of freedom in excited nucleon states at the varying distance scale where the transition from the contributions of both quark core and meson-baryon cloud to the quark core dominance. During the past decade, the CLAS collaboration has executed a broad experimental program to study the excited states of the proton using polarized electron beam and both polarized and unpolarized proton targets. The measurements covered a broad kinematic range in the invariant mass $W$ and photon virtuality $Q^2$ with nearly full coverage in polar and azimuthal angles in the hadronic CM system. As results, several low-lying nucleon resonance states in particular from pion threshold to $W < 1.6$ GeV have been explored. These include $\Delta$(1232)$\frac{3}{2}^+$, $N(1440)\frac{1}{2}^+$, $N(1520)\frac{3}{2}^-$, and $N(1535)\frac{1}{2}^-$ states. In addition, we recently published the differential cross sections and helicity amplitudes of the reaction $\gamma^*p\to n\pi^+$ at higher $W$ (1.6 to 2.0 GeV) which are the $N(1675)\frac{5}{2}^-$, $N(1680)\frac{5}{2}^+$, and $N(1710)\frac{1}{2}^+$ states. These excited states with isospin $1/2$ and with masses near 1.7 GeV can be accessed in single $n\pi^+$ production as there are no isospin $3/2$ states present in this mass range with the same spin-parity assignments. As a result, I will briefly discuss these states from CLAS results of the single charged pion electroproduction data.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Measurements of $ep \to e^\prime π^+n$ at W = 1.6 - 2.0 GeV and extraction of nucleon resonance electrocouplings at CLAS

Differential cross sections of the exclusive process $e p \to e^\prime \pi^+ n$ were measured with good precision in the range of the photon virtuality $Q^2 = 1.8 - 4.5$ GeV$^2$, and the invariant mass range of the $\pi^+ n$ final state W = 1.6 - 2.0 GeV using the CEBAF Large Acceptance Spectrometer. Data were collected with nearly complete coverage in the azimuthal and polar angles of the $n\pi^+$ center-of-mass system. More than 37,000 cross section points were measured. The contributions of the isospin $I = {1\over 2}$ resonances $N(1675){5\over 2}^-$, $N(1680){5\over 2}^+$ and $N(1710){1\over 2}^+$ were extracted at different values of $Q^2$ using a single-channel, energy-dependent resonance amplitude analysis. Two different approaches, the unitary isobar model and the fixed-$t$ dispersion relations, were employed in the analysis. We observe significant strength of the $N(1675){5\over 2}^-$ in the $A_{1/2}$ amplitude, which is in strong disagreement with quark models that predict both transverse amplitudes to be strongly suppressed. For the $N(1680){5\over 2}^+$ we observe a slow changeover from the dominance of the $A_{3/2}$ amplitude at the real photon point ($Q^2=0$) to a $Q^2$ where $A_{1/2}$ begins to dominate. The scalar amplitude $S_{1/2}$ drops rapidly with $Q^2$ consistent with quark model prediction. For the $N(1710){1\over 2}^+$ resonance our analysis shows significant strength for the $A_{1/2}$ amplitude at $Q^2 < 2.5$ GeV$^2$.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2015

Neutron structure with (un)polarized deuterons and forward spectator tagging at the Electron-Ion Collider

An Electron-Ion Collider (EIC) would enable novel measurements of neutron structure through deep-inelastic electron-deuteron scattering with coincidence tagging of the forward-moving spectator proton. The free neutron structure functions can be obtained by extrapolating the measured recoil momentum distributions to the on-shell point. Such measurements provide essential information for the flavor separation of the nucleon parton densities, the nucleon spin decomposition, and precision studies of QCD evolution in the flavor-singlet and nonsinglet sectors. The EMC effect in light nuclei can be elucidated by measuring the recoil momentum dependence of the nuclear modification. A Jefferson Lab LDRD project has supported a study of neutron structure measurements with spectator tagging at an EIC, with Monte Carlo simulation of the physical processes and the accelerator and detector requirements. We present results of a model-independent extraction of the free neutron structure function $F_2^n$, as well as the spin structure function $g_1^n$, through on-shell extrapolation in the spectator momentum.

Park, Kijun↗
DOE OSTI2014

Polarized light ions and spectator nucleon tagging at EIC

The neutron's deep-inelastic structure functions provide essential information for the flavor separation of the nucleon parton densities, the nucleon spin decomposition, and precision studies of QCD phenomena in the flavor-singlet and nonsinglet sectors. Traditional inclusive measurements on nuclear targets are limited by dilution from scattering on protons, Fermi motion and binding effects, final-state interactions, and nuclear shadowing at x ll 0.1. An Electron-Ion Collider (EIC) would enable next-generation measurements of neutron structure with polarized deuteron beams and detection of forward-moving spectator protons over a wide range of recoil momenta (0 < p(R) < several 100MeV in the nucleus rest frame). The free neutron structure functions could be obtained by extrapolating the measured recoil momentum distributions to the on-shell point. The method eliminates nuclear modifications and can be applied to polarized scattering, as well as to semi-inclusive and exclusive final states. We review the prospects for neutron structure measurements with spectator tagging at EIC, the status of R&D efforts, and the accelerator and detector requirements.

Guzey, Vadim↗
DOE OSTI2014

Exclusive single pion electroproduction off the proton in the invariant mass range up to 2 GeV and at Q2$<$5GeV2 with CLAS.

Exclusive meson electroproduction off protons is a powerful tool to probe the effective degrees of freedom in excited nucleon states at the varying distance scale where the transition from the contributions of both quark core and meson-baryon cloud to the quark core dominance. During the past decade, the CLAS collaboration has executed a broad experimental program to study the excited states of the proton using polarized electron beam and (un)polarized proton targets. The measurements covered a broad kinematic range in the invariant mass W and photon virtuality Q2 with nearly full coverage in solid angles in the hadronic CMSystem. As results, several low-lying nucleon resonance states have been explored, such as ?(1230)3/2+, N(1440)1/2+, N(1520)3/2-, and N(1535)1/2- in particular for W<1.6 GeV. In this talk, we present preliminary cross-sections and helicity amplitudes of the reaction g*p?npi+ at higher W (1.6 to 2.0 GeV). Some of the excited states with isospin 1/2 and with masses near 1.7 GeV can be accessed in single npi+ production as there are no isospin 3/2 states present in this mass range with the same spin-parity assignments. These are the N(1675)5/2-, N(1680)5/2+, and N(1710)1/2+ states. We will briefly discuss preliminary results for these states.

Burkert, Volker↗
DOE OSTI2014

Exclusive single pion electroproduction off the proton in the high-lying resonances at Q2 < 5 GeV2 from CLAS

The differential cross sections and structure functions for the exclusive electroproduction process ep --> e'n pi+ were measured in the range of the invariantmass for the np+ system 1.6 GeV lte W lte 2.0 GeV, and the photon virtuality 1.8 GeV2 lte Q2 lte 4.0 GeV2 using CLAS at Jefferson Lab. For the first time, these kinematics are probed in the exclusive p+ production from the protons with nearly full coverage in the azimuthal and polar angles of the np+ center-of-mass system. In this analysis, approximately 39,000 differential cross-section data points in terms of W, Q2, cosq theta* _ pi, and phi*_p-, were obtained. The preliminary differential cross section and structure function analyses are carried out, which allow us to extract the helicity amplitudes in high-lying resonances.

Park, Kijun↗
DOE OSTI2014

PROGRESS ON THE INTERACTION REGION DESIGN AND DETECTOR INTEGRATION AT JLAB'S MEIC

One of the unique features of JLab's Medium-energy Electron-Ion Collider (MEIC) is a full-acceptance detector with a dedicated, small-angle, high-resolution detection system, capable of covering a wide range of momenta (and charge-to-mass ratios) with respect to the original ion beam to enable access to new physics. We present an interaction region design developed with close integration of the detection and beam dynamical aspects. The dynamical aspect of the design rests on a symmetry-based concept for compensation of non-linear effects. The optics and geometry have been optimized to accommodate the detection requirements and to ensure the interaction region's modularity for ease of integration into the collider ring lattices. As a result, the design offers an excellent detector performance combined with the necessary provisions for non-linear dynamical optimization.

Morozov, Vasiliy↗
DOE OSTI2014

Neutron structure via forward tagging of the $eD\to e^{\prime}NX$ reaction at the Electron-Ion Collider

I report about the status of a Jefferson Lab 2014 LDRD project exploring the physics potential of deep-inelastic scattering on polarized light ions with forward spectator nucleon tagging with the proposed Electron-Ion Collider (EIC). Such measurements offer unique capabilities for precision studies of neutron spin structure, nuclear modifications of partonic structure, and multiple scattering effects at high energies. We simulate the tagged processes on the $D$ as a function of the $Q^2$, $x_{\rm Bj}$, and the spectator momenta. We quantify the effects of the intrinsic motion of beam particles, as well as the EIC detector acceptance and resolution, on the projected observables. We present results of a model-independent extraction of the free neutron structure function $F_2^n$ through on-shell extrapolation in the spectator momentum~\cite{MSargsian}. Comparison of the bound proton structure function $F_2^p$ with the free proton result provides a crucial test of the method and allows for an unambiguous identification of nuclear binding effects. Future work will extend these studies to polarized deuterons (spin structure functions $g_1^n$ and $g_1^p$) and hard exclusive processes (GPDs), and model the final-state detection through a full GEANT4-based simulation.

Park, Kijun↗
DOE OSTI2014

Measurement Of Differential Cross Sections Of p(e,e'{pi}{sup +})n For High-Lying Resonances At Q{sup 2} < 5 GeV{sup 2}

The exclusive electro-production process ep -> e'n{pi}{sup +} was measured in the range of the invariant mass for n{pi}{sup +} system 1.6 GeV <= W <= 2.0 GeV, and the photon virtuality 1.8 GeV{sup 2} <= Q{sup 2} <= 4.0 GeV{sup 2} using CLAS. For the first time, these kinematics are probed in exclusive {pi}{sup +} production from the protons with nearly full coverage in the azimuthal and polar angles of the n{pi}{sup +} center-of-mass system. In this experiment, approximately 39,000 differential cross-section data points were measured. In this proceeding, preliminary results of our latest analysis work are presented on differential cross sections and structure functions as well as Legendre Moments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Cross section measurement of the exclusive single pion electroproduction for Q2<5 GeV2 from CLAS

The study of nucleon excitations is the key to our understanding of the effective degrees of freedom at different distance scales where the transition from the contributions of both quark core and meson-baryon cloud to the quark core dominance takes place. The exclusive meson electroproduction off protons is a powerful tool to probe these effective degrees of freedom in excited nucleon states. During the last decade, a broad experimental program has been executed with the CLAS detector in Hall B at Jefferson Lab, to study the excited states of the proton using polarized electron beams and (un)polarized proton targets. In this talk, results of our latest analysis work will be presented for the reaction of ep?e?n?+ at W=1.6-2.0GeV, and Q2=1.8-4.0GeV2. A preliminary extraction of the helicity amplitudes, A(1/2), A(3/2), and S(1/2) will be also presented for the N(1680)5/2+ and the N(1720)3/2+ states, in particular. Result of this new analysis as well as ongoing work on the p?0 and p?+?? channels in similar kinematics, will allow for the determination of electro-couplings of several high-lying excited proton states (W>1.6GeV) at distances where quark degrees of freedom become increasingly important and eventually dominant as photon virtuality increase.

Park, Kijun↗