Nuclear Theory·nucl-th

Tuesday·January 5, 2021

13 papers—8 primary·5 cross-listed

01
Passage of heavy quarks through the fluctuating hot QCD medium
Mohammad Yousuf Jamal🇮🇳 · Bedangadas Mohanty🇮🇳
The change in the energy of the moving heavy (charm and bottom) quarks due to field fluctuations present in the hot QCD medium has been studied. A finite quark chemical potential has been considered while modeling the hot QCD medium counting the fact that the upcoming experimental facilities such as Anti-proton and Ion Research (FAIR) and Nuclotron-based Ion Collider fAcility (NICA) are expected to operate at finite baryon density and moderate temperature. The effective kinetic theory approach has been adopted where the collisions have been incorporated using the well defined collisional kernel, known as Bhatnagar-Gross-Krook (BGK). To incorporate the non-ideal equations of state (EoSs) effects/ medium interaction effects, an extended effective fugacity model has been adopted. The momentum dependence of the energy change due to fluctuation for the charm and bottom quark has been investigated at different values of collision frequency and chemical potential. The results are exciting as the heavy quarks are found to gain energy due to fluctuations while moving through the produced medium at finite chemical potential and collision frequency.
nucl-thEPJC(2021)·11 citations
02
A matter of shape: seeing the deformation of atomic nuclei at high-energy colliders
Giuliano Giacalone🇫🇷
This work establishes a deep connection between two seemingly distant branches of nuclear physics: nuclear structure and relativistic heavy-ion collisions. At the heart of this connection is the recent discovery made at particle colliders that the elliptic flow of outgoing hadrons in central nucleus-nucleus collisions is strongly impacted by the quadrupole deformation of the colliding nuclear species. I review the physics of the soft sector of relativistic heavy-ion collisions, and I explain that the interpretation of elliptic flow data in central $^{197}$ Au+ $^{197}$ Au, $^{238}$ U+ $^{238}$ U, and $^{129}$ Xe+ $^{129}$ Xe collisions requires a deep understanding the structure of these ions. Subsequently, I introduce a technique that permits one to isolate collision configurations in which the deformed shapes of the colliding nuclei maximally break rotational (azimuthal) symmetry in the interaction region. This allows me to construct observables that possess an unparalleled sensitivity to the quadrupole deformation of the colliding ions, and thus to conclude that nuclear experiments at high energy can be used to place new quantitative constraints on the deformation of atomic nuclei. I emphasize the great opportunities offered by potential collider experiments aimed at the systematic study of nuclear deformation across the valley of stability.
nucl-thhep-exhep-phnucl-ex24 citations
03
Chaos in QCD? Gap equations and their fractal properties
T. Klaehn🇺🇸 · L.C. Loveridge🇺🇸 · M. Cierniak🇵🇱
We discuss how iterative solutions of QCD inspired gap-equations at finite chemical potential show domains of chaotic behavior as well as non-chaotic domains which represent one or the other of the only two -- usually distinct -- positive mass gap solutions with broken or restored chiral symmetry, respectively. In the iterative approach gap solutions exist which exhibit restored chiral symmetry beyond a certain dynamical cut-off energy. A chirally broken, non-chaotic domain with no emergent mass poles and hence with no quasi-particle excitations exists below this energy cutoff. The transition domain between these two energy separated domains is chaotic. As a result, the dispersion relation is that of quarks with restored chiral symmetry, cut at a dynamical energy scale, determined by fractal structures. We argue that the chaotic origin of the infrared cut-off could hint at a chaotic nature of confinement and the deconfinement phase transition.
nucl-thhep-thParticles(2023)·1 citation
04
Bound-to-continuum potential model for the $(p, γ)$ reactions of the CNO cycle
Le-Anh Nguyen🇻🇳 · Minh-Loc Bui🇻🇳
The study of CNO cycle involves the examination of the proton radiative capture, or the $(p, γ)$ reactions below 2 MeV. The astrophysical $S$ factor characterizing the $(p, γ)$ reaction is usually reduced to the electric dipole transition $E 1$ from the scattering state to the bound state. In this work, the partial scattering and the single-particle bound wave functions in the reduced matrix element of the transition are obtained from the single self-consistent mean-field potential deduced from the Skyrme Hartree-Fock calculation. The astrophysical $S$ factors of the $(p, γ)$ reactions in the CNO cycle were successfully reproduced. The self-consistent Hartree-Fock calculation from the discrete to the continuum is a promising approach for the microscopic analysis of the nucleon-induced reactions in nuclear astrophysics.
nucl-thPRC(2021)·12 citations
05
Nuclear charge densities in spherical and deformed nuclei: towards precise calculations of charge radii
Paul-Gerhard Reinhard🇩🇪 · Witold Nazarewicz🇺🇸
Background: Precise measurements of atomic transitions affected by electron-nucleus hyperfine interactions offer sensitivity to explore basic properties of the atomic nucleus and study fundamental symmetries, including the search for new physics beyond the Standard Model of particle physics. Such measurements impose higher precision requirements on a theoretical description. Purpose: The nuclear charge density is composed of the proton point distribution folded with the nucleonic charge distributions. The latter induce subtle relativistic corrections due to the coupling of nucleon magnetic moments with the nuclear spin-orbit density. We assess the precision of nuclear charge density calculations by studying the behavior of relativistic corrections. Methods: The calculations are performed using Skyrme energy density functionals and density-dependent pairing force. We used the general expression for the spin-orbit form factor that is valid for spherical and deformed nuclei. Results: We studied the impact of various correction terms on the charge radii, fourth radial moments, diffraction radii, and surface thickness of spherical and deformed nuclei. The spin-orbit corrections to charge radial moments and surface thickness show strong shell fluctuations which impact high-precision predictions of isotopic shifts. Conclusions: To establish reliable constraints on the existence of new forces from isotope shift measurements,precise calculations of nuclear charge densities of deformed nuclei are needed. The proper inclusion of the spin-orbit charge density and other correction terms is essential when aiming at extraction of subtle effects which become particularly visible in isotopic trends.
nucl-thPRC(2021)·64 citations
06
$Ξ$ -nucleus potential for $Ξ^{-}$ quasifree production in the $^{9}$ Be( $K^{-}$ , $K^{+}$ ) reaction
Toru Harada🇯🇵 · Yoshiharu Hirabayashi🇯🇵
We study phenomenologically a $Ξ^{-}$ production spectrum of the $^{9}$ Be( $K^{-}$ , $K^{+}$ ) reaction at 1.8 GeV/ $c$ within the distorted-wave impulse approximation using the optimal Fermi-averaged $K^{-} p \to K^{+} Ξ^{-}$ amplitude. We attempt to clarify properties of a $Ξ$ -nucleus potential for $Ξ^{-}$ - $^{8}$ Li, comparing the calculated spectrum with the data of the BNL-E906 experiment. The results show a weak attraction in the $Ξ$ -nucleus potential for $Ξ^{-}$ - $^{8}$ Li, which can sufficiently explain the data in the $Ξ^{-}$ quasifree region. The strength of $V_{0}^{Ξ} =$ $- 17 \pm 6$ MeV is favored within the Woods-Saxon potential, accompanied by the reasonable absorption of $W_{0}^{Ξ} =$ $- 5$ MeV for $Ξ^{-} p \to Ξ^{0} n$ , $ΛΛ$ transitions in nuclear medium. It is difficult to determine the value of $W_{0}^{Ξ}$ from the data due to the insufficient resolution of 14.7 MeV FWHM. The energy dependence of the Fermi-averaged $K^{-} p \to K^{+} Ξ^{-}$ amplitude is also confirmed by this analysis, and its importance in the nuclear ( $K^{-}$ , $K^{+}$ ) reaction is emphasized.
nucl-thPRC(2021)·15 citations
07
Pseudospin and spin symmetry in the relativistic generalized Woods-Saxon potential including Coulomb-like tensor potential
J. Akbar🇮🇩 · A. Suparmi🇮🇩 · C. Cari🇮🇩
The Dirac Equation is solved approximately for relativistic generalized Woods-Saxon potential including Coulomb-like tensor potential in exact pseudospin and spin symmetry limits. The bound states energy eigenvalues are found by using wavefunction boundary conditions, and corresponding radial wavefunctions are obtained in terms of hypergeometric function. Some numerical examples are given for the dependence of bound states energy eigenvalues on quantum numbers and potential parameters.
nucl-thNPA(2021)·3 citations
08
Resonances in $^{12}$ C and $^{24}$ Mg: what do we learn from a microscopic cluster theory?
P. Descouvemont🇧🇪
We discuss resonance properties in three-body systems, with examples on $^{12} C$ and $^{24} Mg$ . We use a microscopic cluster model, where the generator coordinate is defined in the hyperspherical formalism. The $^{12} C$ nucleus is described by an $α + α + α$ structure, whereas $^{24} Mg$ is considered as an $^{16} O + α + α$ system. We essentially pay attention to resonances. We review various techniques which may extend variational methods to resonances. We consider $0^{+}$ and $2^{+}$ states in $^{12} C$ and $^{24} Mg$ . We show that the r.m.s. radius of a resonance is strongly sensitive to the variational basis. This has consequences for the Hoyle state ( $0_{2}^{+}$ state in $^{12} C$ ) whose radius has been calculated or measured in several works. In $^{24} Mg$ , we identify two $0^{+}$ resonances slightly below the three-body threshold.
nucl-thEPJA(2021)·4 citations
09
The Mystery of Bloom-Gilman Duality: A Light Front Holographic QCD Perspective
Aiden B. Sheckler🇺🇸 · Gerald A. Miller🇺🇸
Light front wave functions motivated by holographic constructions are used to study Bloom-Gilman duality of deep inelastic scattering. Separate expressions for structure functions in terms of quark and hadronic degrees of freedom are presented, with a goal of relating the two expressions. A two-parton model is defined and resonance transition form factors are computed using previously derived light front wave functions. A new form of global duality is derived from the valence quark-number sum rule. Using a complete set of hadronic states is necessary for this new global duality to be achieved. Previous original work does not provide such a set. This is remedied by amending the model to include a longitudinal confining potential, and the resulting complete set is sufficient to carry out the study of Bloom-Gilman duality. Expressions for transition form factors are obtained and all are shown to fall asymptotically as 1/Q2. The Feynman mechanism dominates the asymptotic behavior of the model. These transition form factors are used to assess the validity of the global and local duality sum rules, with the result that both neither are satisfied. Evaluations of the hadronic expression for q(x,Q2) provide more details about this lack. This result shows that the observed validity of both global and local forms of duality for deep inelastic scattering must be related to a feature of QCD that is deeper than completeness. Our simple present model suggests a prediction that Bloom-Gilman duality would not be observed if deep inelastic scattering experiments were to be made on the pion. The underlying origin of the duality phenomenon in deep inelastic scattering is deeply buried within the confinement aspects of QCD, and remains a mystery.
↳ hep-phnucl-exnucl-thPRD(2021)·7 citations
10
P-wave nucleon-pion scattering amplitude in the $Δ (1232)$ channel from lattice QCD
Giorgio Silvi🇩🇪 · Srijit Paul🇩🇪 · Constantia Alexandrou🇨🇾 · Stefan Krieg🇩🇪 · Luka Leskovec🇺🇸 · Stefan Meinel🇺🇸 · John Negele🇺🇸 · Marcus Petschlies🇩🇪 · Andrew Pochinsky🇺🇸 · Gumaro Rendon🇺🇸 · Sergey Syritsyn🇺🇸 · Antonino Todaro🇩🇪
We determine the $Δ (1232)$ resonance parameters using lattice QCD and the Lüscher method. The resonance occurs in elastic pion-nucleon scattering with $J^{P} = 3/ 2^{+}$ in the isospin $I = 3/2$ , $P$ -wave channel. Our calculation is performed with $N_{f} = 2 + 1$ flavors of clover fermions on a lattice with $L \approx 2.8$ fm. The pion and nucleon masses are $m_{π} = 255.4 (1.6)$ MeV and $m_{N} = 1073 (5)$ MeV, and the strong decay channel $Δ \to π N$ is found to be above the threshold. To thoroughly map out the energy-dependence of the nucleon-pion scattering amplitude, we compute the spectra in all relevant irreducible representations of the lattice symmetry groups for total momenta up to $P = \frac{2 π}{L} (1, 1, 1)$ , including irreps that mix $S$ and $P$ waves. We perform global fits of the amplitude parameters to up to 21 energy levels, using a Breit-Wigner model for the $P$ -wave phase shift and the effective-range expansion for the $S$ -wave phase shift. From the location of the pole in the $P$ -wave scattering amplitude, we obtain the resonance mass $m_{Δ} = 1378 (7) (9)$ MeV and the coupling $g_{Δ - π N} = 23.8 (2.7) (0.9)$ .
↳ hep-lathep-phnucl-thPRD(2021)·46 citations
11
A survey of heavy-antiheavy hadronic molecules
Xiang-Kun Dong🇨🇳 · Feng-Kun Guo🇨🇳 · Bing-Song Zou🇨🇳
Many efforts have been made to reveal the nature of the overabundant resonant structures observed by the worldwide experiments in the last two decades. Hadronic molecules attract special attention because many of these seemingly unconventional resonances are located close to the threshold of a pair of hadrons. To give an overall feature of the spectrum of hadronic molecules composed of a pair of heavy-antiheavy hadrons, namely, which pairs are possible to form molecular states, we take charmed hadrons for example to investigate the interaction between them and search for poles by solving the Bethe-Salpeter equation. We consider all possible combinations of hadron pairs of the $S$ -wave singly-charmed mesons and baryons as well as the narrow $P$ -wave charmed mesons. The interactions, which are assumed to be meson-exchange saturated, are described by constant contact terms which are resummed to generate poles. It turns out that if a system is attractive near threshold by the light meson exchange, there is a pole close to threshold corresponding to a bound state or a virtual state, depending on the strength of interaction and the cutoff. In total, 229 molecular states are predicted. The observed near-threshold structures with hidden-charm, like the famous $X (3872)$ and $P_{c}$ states, fit into the spectrum we obtain. We also highlight a $Λ_{c} Λ ˉ_{c}$ bound state that has a pole consistent with the cross section of the $e^{+} e^{-} \to Λ_{c} Λ ˉ_{c}$ precisely measured by the BESIII Collaboration.
↳ hep-phhep-exhep-latnucl-thProgr.Phys.(2021)·240 citations
12
Maximum entropy kinetic matching conditions for heavy-ion collisions
Derek Everett🇺🇸 · Chandrodoy Chattopadhyay🇺🇸 · Ulrich Heinz🇺🇸
Coupling hadronic kinetic theory models to fluid dynamics in phenomenological studies of heavy ion collisions requires a prescription for ``particlization''. Existing particlization models are based on implicit or explicit assumptions about the microscopic degrees of freedom that go beyond the information provided by the preceding fluid dynamical history. We propose an alternative prescription which uses only macroscopic information provided by the hydrodynamic output. This method follows directly from the connections between information theory and statistical mechanics.
↳ hep-phnucl-thPRC(2021)·24 citations
13
Effect of nuclear magnetization distribution within the Woods-Saxon model: Hyperfine splitting in neutral Tl
S. D. Prosnyak🇷🇺 · L. V. Skripnikov🇷🇺
Three models of the nuclear magnetization distribution are applied to predict the hyperfine structure of the hydrogenlike heavy ions and neutral thallium atoms: the uniformly magnetized ball model and single-particle models for the valence nucleon with the uniform distribution and the distribution determined by the Woods-Saxon potential. Results for the hydrogenlike ions are in excellent agreement with previous studies. The application of the Woods-Saxon model is now extended to the neutral systems with the explicit treatment of the electron correlation effects within the relativistic coupled cluster theory using the Dirac-Coulomb Hamiltonian. We estimate the uncertainty for the ratio of magnetic anomalies and numerically confirm its near nuclear-model independence. The ratio is used as a theoretical input to predict the nuclear magnetic moments of short-lived thallium isotopes. We also show that the differential magnetic anomalies are strongly model dependent. The accuracy of the single-particle models significantly surpasses the accuracy of the simplest uniformly magnetized ball model for the prediction of this quantity. Skripnikov [Skripnikov, J. Chem. Phys. 153, 114114 (2020)] has shown that the Bohr-Weisskopf contribution to the magnetic dipole hyperfine structure constant for an atom or a molecule induced by a heavy nucleus can be factorized into the electronic part and the universal nuclear magnetization dependent part. We numerically confirm this factorization for the Woods-Saxon single-particle model with an uncertainty less than 1%.
↳ physics.atom-phnucl-thPRC(2021)·14 citations

Affiliations

first authorsco-authorsvia INSPIRE