Nuclear Theory·nucl-th

Tuesday·March 13, 2018

15 papers—8 primary·7 cross-listed

01
[Submitted on 9 Mar 2018]
Nucleon Quark Distribution Functions from the Dyson-Schwinger Equations
Kyle D. Bednar🇺🇸 · Ian C. Cloët🇺🇸 · Peter C. Tandy🇺🇸
We present results for the nucleon's leading-twist spin-independent valence parton distribution functions obtained from a theoretical framework based on the Dyson-Schwinger equations (DSEs) of QCD that previously gave an excellent description of nucleon electromagnetic form factors. We employ the rainbow-ladder truncation of the DSEs and utilize nucleon bound state amplitudes from the Poincaré-covariant Faddeev equation, where the dominant scalar and axial-vector quark-quark correlations are included. This DSE framework is used to numerically evaluate the first 20 moments of the valence $u$ and $d$ quark distribution functions, from which the $x$ -dependence of the distributions is found to be well constrained. We find good agreement with empirical parameterizations of experimental data and make the prediction that the $d / u$ ratio in the $x \to 1$ limit, invariant under scale evolution, takes the value $d / u \to 0.087 \pm 0.010$ . We find that this ratio is rather sensitive to the strength of axial-vector diquark correlations. However, contrary to a naive expectation, our result for the $d / u$ ratio in the $x \to 1$ limit does not vanish when only scalar diquark correlations are present, although it is an order of magnitude smaller than our $d / u$ result that also includes axial-vector diquarks. The valence quark distribution results are set in a broader context via a simple pion cloud model estimate of sea-quark light-cone momenta and gluon light-cone momentum.
Comments:
8 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1803.03656 [pdf]
PLB(2018)·21 citations
02
[Submitted on 9 Mar 2018]
Competition between delta isobars and hyperons and properties of compact stars
Jia Jie Li (ITP, Frankfurt)🇩🇪 · Armen Sedrakian (FIAS)🇩🇪 · Fridolin Weber (SDSU)🇺🇸
The $Δ$ -isobar degrees of freedom are included in the covariant density functional (CDF) theory to study the equation of state (EoS) and composition of dense matter in compact stars. In addition to $Δ$ 's we include the full octet of baryons, which allows us to study the interplay between the onset of delta isobars and hyperonic degrees of freedom. Using both the Hartree and Hartree-Fock approximation we find that $Δ$ 's appear already at densities slightly above the saturation density of nuclear matter for a wide range of the meson- $Δ$ coupling constants. This delays the appearance of hyperons and significantly affects the gross properties of compact stars. Specifically, $Δ$ 's soften the EoS at low densities but stiffen it at high densities. This softening reduces the radius of a canonical $1.4 M_{⊙}$ star by up to 2~km for a reasonably attractive $Δ$ potential in matter, while the stiffening results in larger maximum masses of compact stars. We conclude that the hypernuclear CDF parametrizations that satisfy the 2 $M_{⊙}$ maximum mass constraint remain valid when $Δ$ isobars are included, with the important consequence that the resulting stellar radii are shifted toward lower values, which is in agreement with the analysis of neutron star radii.
Comments:
7 pages, 4 figures; v2: minor changes, matches published version
Subjects:
Nuclear Theory (nucl-th); High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR)
arXiv:
1803.03661 [pdf]
PLB(2018)·122 citations
03
[Submitted on 10 Mar 2018]
Extraction of Heavy-Flavor Transport Coefficients in QCD Matter
R. Rapp🇺🇸 · P.B. Gossiaux🇫🇷 · A. Andronic🇩🇪 · R.Averbeck🇩🇪 · S.Masciocchi🇩🇪 · A. Beraudo🇮🇹 · E. Bratkovskaya🇩🇪 · P. Braun-Munzinger🇩🇪 · S. Cao🇺🇸 · A. Dainese🇮🇹 · S.K. Das🇨🇳 · M. Djordjevic🇷🇸 and 19 other authors
We report on broadly based systematic investigations of the modeling components for open heavy-flavor diffusion and energy loss in strongly interacting matter in their application to heavy-flavor observables in high-energy heavy-ion collisions, conducted within an EMMI Rapid Reaction Task Force framework. Initial spectra including cold-nuclear-matter effects, a wide variety of space-time evolution models, heavy-flavor transport coefficients, and hadronization mechanisms are scrutinized in an effort to quantify pertinent uncertainties in the calculations of nuclear modification factors and elliptic flow of open heavy-flavor particles in nuclear collisions. We develop procedures for error assessments and criteria for common model components to improve quantitative estimates for the (low-momentum) heavy-flavor diffusion coefficient as a long-wavelength characteristic of QCD matter as a function of temperature, and for energy loss coefficients of high-momentum heavy-flavor particles.
Comments:
78 pages, 29 figures, report on an EMMI Rapid Reaction Task Force; v2: small revision, accepted for publication in Nucl. Phys. A
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex)
arXiv:
1803.03824 [pdf]
NPA(2018)·311 citations
04
[Submitted on 11 Mar 2018]
Coexisting partial dynamical symmetries and multiple shapes
A Leviatan · N Gavrielov
We present an algebraic procedure for constructing Hamiltonians with several distinct partial dynamical symmetries (PDSs), of relevance to shape-coexistence phenomena. The procedure relies on a spectrum generating algebra encompassing several dynamical symmetry (DS) chains and a coherent state which assigns a particular shape to each chain. The PDS Hamiltonian maintains the DS solvability and quantum numbers in selected bands, associated with each shape, and mixes other states. The procedure is demonstrated for a variety of multiple quadrupole shapes in the framework of the interacting boson model of nuclei.
Comments:
18 pages, 11 figures, talk at Symposium "Symmetries in Science XVII", July 30 - August 4, 2017, Bregenz, Austria
Subjects:
Nuclear Theory (nucl-th); Quantum Physics (quant-ph)
arXiv:
1803.03982 [pdf]
J.Phys.Conf.Ser.(2018)·2 citations
05
[Submitted on 12 Mar 2018]
Energy spectra in $p$ -shell $Λ$ hypernuclei and $_{Λ}^{19} F$ and spin-dependent $Λ N$ interactions
Yoshiko Kanada-En'yo🇯🇵 · Masahiro Isaka🇯🇵 · Toshio Motoba🇯🇵
Energy spectra of $0 s$ -orbit $Λ$ states in $p$ -shell $Λ$ hypernuclei ( $_{Λ}^{A} Z$ ) and those in $_{Λ}^{19} F$ are studied with the microscopic cluster model and antisymmetrized molecular dynamics using the $G$ -matrix effective $Λ N$ ( $Λ N G$ ) interactions. Spin-dependent terms of the ESC08a version of the $Λ N G$ interactions are tested and phenomenologically tuned to reproduce observed energy spectra in $p$ -shell $_{Λ}^{A} Z$ . Spin-dependent contributions of the $Λ N$ interactions to spin-doublet splitting and excitation energies are discussed. Energy spectra for unobserved excited states in $p$ -shell $_{Λ}^{A} Z$ and $_{Λ}^{19} F$ are predicted with the modified $Λ N G$ interactions.
Comments:
27 pages, 4 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.04089 [pdf]
PTEP(2019)·1 citation
06
[Submitted on 12 Mar 2018]
Ab Initio No Core Shell Model with Leadership-Class Supercomputers
James P. Vary🇺🇸 · Robert Basili🇺🇸 · Weijie Du🇺🇸 · Matthew Lockner🇺🇸 · Pieter Maris🇺🇸 · Dossay Oryspayev🇺🇸 · Soham Pal🇺🇸 · Shiplu Sarker🇺🇸 · Hasan Metin Aktulga🇺🇸 · Esmond Ng🇺🇸 · Meiyue Shao🇺🇸 · Chao Yang🇺🇸
Nuclear structure and reaction theory is undergoing a major renaissance with advances in many-body methods, strong interactions with greatly improved links to Quantum Chromodynamics (QCD), the advent of high performance computing, and improved computational algorithms. Predictive power, with well-quantified uncertainty, is emerging from non-perturbative approaches along with the potential for guiding experiments to new discoveries. We present an overview of some of our recent developments and discuss challenges that lie ahead. Our foci include: (1) strong interactions derived from chiral effective field theory; (2) advances in solving the large sparse matrix eigenvalue problem on leadership-class supercomputers; (3) selected observables in light nuclei with the JISP16 interaction; (4) effective electroweak operators consistent with the Hamiltonian; and, (5) discussion of A=48 system as an opportunity for the no-core approach with the reintroduction of the core.
Comments:
23 pages, 7 figures, Conference Proceedings online at http://ntse.khb.ru/files/uploads/2016/proceedings/Vary.pdf
Subjects:
Nuclear Theory (nucl-th)
arXiv:
1803.04101 [pdf]
Proceedings of the International Conferen…·3 citations
07
[Submitted on 12 Mar 2018]
The Tjon Band in Nuclear Lattice Effective Field Theory
Nico Klein🇩🇪 · Serdar Elhatisari🇩🇪 · Timo A. Lähde🇩🇪 · Dean Lee🇺🇸 · Ulf-G. Meißner🇩🇪
We explore the lattice spacing dependence in Nuclear Lattice Effective Field Theory for few-body systems up to next-to-next-to leading order in chiral effective field theory including all isospin breaking and electromagnetic effects, the complete two-pion-exchange potential and the three-nucleon forces. We calculate phase shifts in the neutron-proton system and proton-proton systems as well as the scattering length in the neutron-neutron system. We then perform a full next-to-next-to-leading order calculation with two-nucleon and three-nucleon forces for the triton and helium-4 and analyse their binding energy correlation. We show how the Tjon band is reached by decreasing the lattice spacing and confirm the continuum observation that a four-body force is not necessary to describe light nuclei.
Comments:
15 pages, 9 figures
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1803.04231 [pdf]
EPJA(2018)·23 citations
08
[Submitted on 12 Mar 2018]
Charmonium states in strong magnetic fields
Amal Jahan CS🇮🇳 · Nikhil Dhale🇮🇳 · Sushruth Reddy P🇮🇳 · Shivam Kesarwani🇮🇳 · Amruta Mishra🇮🇳
The medium modifications of the masses of the charmonium states (J/ $ψ$ , $ψ$ (3686) and $ψ$ (3770)) in asymmetric nuclear matter in the presence of strong magnetic fields are studied using an effective chiral model. The mass modifications arise due to medium modifications of the scalar dilaton field, which simulates the gluon condensates of QCD within the effective hadronic model. The effects due to the magnetic field as well as isospin asymmetry are observed to be appreciable at high densities for the charmonium states, which can have consequences, e,g, in the production of the open charm mesons and the charmonium states, in the asymmetric heavy ion collisions at the compressed baryonic matter (CBM) experiments at the future facility at GSI. The presence of magnetic field leads to Landau quantization of the energy levels of the proton in the asymmetric nuclear matter. The effects of the anomalous magnetic moments of the proton and neutron on the masses of the charmonium states are studied and are observed to lead to larger masses of the charmonium states, as compared to when these effects are not taken into account.
Comments:
21 pages, 4 figures, accepted in Phys. Rev.C. arXiv admin note: text overlap with arXiv:1003.0077, arXiv:1005.5018, arXiv:1801.06405
Subjects:
Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
arXiv:
1803.04322 [pdf]
PRC(2018)·41 citations
09
[Submitted on 9 Mar 2018] (cross-list from hep-ph)
The groomed and ungroomed jet mass distribution for inclusive jet production at the LHC
Zhong-Bo Kang🇺🇸 · Kyle Lee🇺🇸 · Xiaohui Liu🇨🇳 · Felix Ringer🇺🇸
We study jet mass distributions measured in the single inclusive jet production in proton-proton collisions $pp \to jet + X$ at the LHC. We consider both standard ungroomed jets as well as soft drop groomed jets. Within the Soft Collinear Effective Theory (SCET), we establish QCD factorization theorems for both cases and we study their relation. The developed framework allows for the joint resummation of several classes of logarithmic corrections to all orders in the strong coupling constant. For the ungroomed case, we resum logarithms in the jet radius parameter and in the small jet mass. For the groomed case, we resum in addition the logarithms in the soft threshold parameter $z_{cut}$ which is introduced by the soft drop grooming algorithm. In this way, we are able to reliably determine the absolute normalization of the groomed jet mass distribution in proton-proton collisions. All logarithmic corrections are resummed to the next-to-leading logarithmic accuracy. We present numerical results and compare with the available data from the LHC. For both the groomed and ungroomed jet mass distributions we find very good agreement after including non-perturbative corrections.
Comments:
38 pages, 9 figures, published version
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1803.03645 [pdf]
JHEP(2018)·64 citations
10
[Submitted on 10 Mar 2018] (cross-list from astro-ph.HE)
Nuclear Reactions in the Crusts of Accreting Neutron Stars
R. Lau · M. Beard · S. S. Gupta · H. Schatz · A. V. Afanasjev · E. F. Brown · A. Deibel · L. R. Gasques · G. W. Hitt · W. R. Hix · L. Keek · P. Möller and 4 other authors
X-ray observations of transiently accreting neutron stars during quiescence provide information about the structure of neutron star crusts and the properties of dense matter. Interpretation of the observational data requires an understanding of the nuclear reactions that heat and cool the crust during accretion, and define its nonequilibrium composition. We identify here in detail the typical nuclear reaction sequences down to a depth in the inner crust where the mass density is 2E12 g/cm^3 using a full nuclear reaction network for a range of initial compositions. The reaction sequences differ substantially from previous work. We find a robust reduction of crust impurity at the transition to the inner crust regardless of initial composition, though shell effects can delay the formation of a pure crust somewhat to densities beyond 2E12 g/cm^3. This naturally explains the small inner crust impurity inferred from observations of a broad range of systems. The exception are initial compositions with A >= 102 nuclei, where the inner crust remains impure with an impurity parameter of Qimp~20 due to the N = 82 shell closure. In agreement with previous work we find that nuclear heating is relatively robust and independent of initial composition, while cooling via nuclear Urca cycles in the outer crust depends strongly on initial composition. This work forms a basis for future studies of the sensitivity of crust models to nuclear physics and provides profiles of composition for realistic crust models.
Comments:
25 Pages, accepted for publication in Ap. J
Subjects:
High Energy Astrophysical Phenomena (astro-ph.HE); Solar and Stellar Astrophysics (astro-ph.SR); Nuclear Theory (nucl-th)
arXiv:
1803.03818 [pdf]
ApJ(2018)·73 citations
11
[Submitted on 10 Mar 2018] (cross-list from hep-ph)
Exploring the hadron resonance gas phase on the QCD phase diagram
Subhasis Samanta🇮🇳 · Sandeep Chatterjee🇵🇱 · Bedangadas Mohanty🇮🇳
Lattice computations of strongly interacting matter at finite temperature $T$ and baryon chemical potential $μ_{B}$ suggest that the QCD thermodynamics deep in the hadronic phase can be adequately modeled by an ideal hadron resonance gas (I-HRG). However, it is not clear where on the $(μ_{B}, T)$ plane this description breaks down, making it essential to account for hadronic interactions and change in the nature of the degrees of freedom. We have studied several thermodynamic functions within the I-HRG model and try to identify the region of the QCD phase diagram where it becomes essential to include non-ideal effects into the I-HRG model. We work with only those thermodynamic quantities that show a monotonic rise with $T$ and $μ_{B}$ in I-HRG. Their high temperature limiting values where QCD becomes simply a Stefan-Boltzmann (SB) gas of massless quarks and gluons is known. The rise of these quantities in I-HRG beyond the corresponding SB limit values indicate the need to include interactions into I-HRG to study QCD thermodynamics. This works as a guiding principle on the QCD phase diagram where interacting HRG can take over from I-HRG. For $μ_{B} / T \leq 2$ , $χ_{2}^{Q}$ shoots the SB limit at the smallest $T$ , while for higher values of $μ_{B} / T$ , $C_{B S} = - 3 χ_{11}^{B S} / χ_{2}^{S}$ takes over. We further comment on the relative positions between the freezeout curve obtained by thermal fits to the measured hadron yields and the obtained line where I-HRG overshoots SB limit.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1803.03844 [pdf]
J.Phys.G(2019)·7 citations
12
[Submitted on 11 Mar 2018] (cross-list from hep-ph)
Target-normal single-spin asymmetry in elastic electron-nucleon scattering
Oleksandr Koshchii🇺🇸 · Andrei Afanasev🇺🇸
We estimate the target-normal single-spin asymmetry at nearly forward angles in elastic electron-nucleon scattering. In the leading-order approximation, this asymmetry is proportional to the imaginary part of the two-photon exchange (TPE) amplitude, which can be expressed as an integral over the doubly virtual Compton scattering (VVCS) tensor. We develop a model that parametrizes the VVCS tensor for the case of nearly forward scattering angles. Our parametrization ensures a proper normalization of the imaginary part of the TPE amplitude on the well-known forward limit expression, which is given in terms of nucleon structure functions measurable in inelastic electron-nucleon scattering experiments. We discuss applicability limits of our theory and provide target-normal single-spin asymmetry predictions for both elastic electron-proton and electron-neutron scattering.
Comments:
14 pages, 6 figures; v2: contains extended discussions, results are unchanged; v3: minor changes, matches published version; v4: corrected Fig. 5
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1803.04004 [pdf]
PRD(2018)·16 citations
13
[Submitted on 12 Mar 2018] (cross-list from hep-ph)
Electromagnetic form factors of singly heavy baryons in the self-consistent SU(3) chiral quark-soliton model
June-Young Kim🇰🇷 · Hyun-Chul Kim🇰🇷
The self-consistent chiral quark-soliton model is a relativistic pion mean-field approach in the large $N_{c}$ limit, which describes both light and heavy baryons on an equal footing. In the limit of the infinitely heavy mass of the heavy quark, a heavy baryon can be regarded as $N_{c} - 1$ valence quarks bound by the pion mean fields, leaving the heavy quark as a color static source. The structure of the heavy baryon in this scheme is mainly governed by the light-quark degrees of freedom. Based on this framework, we evaluate the electromagnetic form factors of the lowest-lying heavy baryons. The rotational $1/ N_{c}$ and strange current quark mass corrections in linear order are considered. We discuss the electric charge and magnetic densities of heavy baryons in comparison with those of the nucleons. The results of the electric charge radii of the positive-charged heavy baryons show explicitly that the heavy baryon is a compact object. The electric form factors are presented. The form factor of $Σ_{c}^{++}$ is compared with that from a lattice QCD. We also discuss the results of the magnetic form factors. The magnetic moments of the baryon sextet with spin 1/2 and the magnetic radii are compared with other works and the lattice data.
Comments:
21 pages, 13 figures. The version which will appear in Physical Review D
Subjects:
High Energy Physics — Phenomenology (hep-ph); High Energy Physics — Experiment (hep-ex); High Energy Physics — Lattice (hep-lat); Nuclear Theory (nucl-th)
arXiv:
1803.04069 [pdf]
PRD(2018)·52 citations
14
[Submitted on 12 Mar 2018] (cross-list from hep-ph)
Characterization of quark gluon plasma as seen through the energy loss of heavy quarks
Ashik Ikbal Sheikh🇮🇳 · Zubayer Ahammed🇮🇳
The shear viscosity to entropy density ratio ({\eta}/s) of quark gluon plasma produced in ultra- relativistic heavy-ion collisions has been studied from the energy loss of heavy quarks in QGP medium. We have also studied the bulk viscosity to entropy density ratio ({\zeta}/s) and fluidity measure(F) of the medium using the obtained {\eta}/s values. In addition to that, we have estimated the heavy quark bound state potential (V) inside this medium. Our finding of {\eta}/s agrees well with the results obtained by Lattice QCD (LQCD) and functional renormalization group technique.
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
1803.04123 [pdf]
0 citations
15
[Submitted on 12 Mar 2018] (cross-list from hep-lat)
Lattice Calculation of Parton Distribution Function from LaMET at Physical Pion Mass with Large Nucleon Momentum
Jiunn-Wei Chen🇹🇼 · Luchang Jin🇺🇸 · Huey-Wen Lin🇺🇸 · Yu-Sheng Liu🇨🇳 · Yi-Bo Yang🇺🇸 · Jian-Hui Zhang🇩🇪 · Yong Zhao🇺🇸
We present a lattice-QCD calculation of the unpolarized isovector parton distribution function (PDF) using ensembles at the physical pion mass with large proton boost momenta $P_{z} \in {2.2, 2.6, 3.0}$ ~GeV within the framework of large-momentum effective theory (LaMET). In contrast to our previous physical-pion PDF result, we increase the statistics significantly, double the boost momentum, increase the investment in excited-state contamination systematics, and switch to $γ_{t}$ operator to avoid mixing with scalar matrix elements. We use four source-sink separations in our analysis to control the systematics associated with excited-state contamination. The one-loop LaMET matching corresponding to the new operator is calculated and applied to our lattice data. We detail the systematics that affect PDF calculations, providing guidelines to improve the precision of future lattice PDF calculations. We find our final parton distribution to be in reasonable agreement with the PDF provided by the latest phenomenological analysis.
Comments:
6 pages, 4 figures
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Experiment (nucl-ex); Nuclear Theory (nucl-th)
arXiv:
1803.04393 [pdf]
110 citations

Affiliations

first authorsco-authorsvia INSPIRE