Nuclear Theory·nucl-th

Tuesday·March 26, 2019

15 papers—10 primary·5 cross-listed

01
A systematic study of the ground state properties of W, Os and Pt isotopes using HFB theory
Nithu Ashok · Antony Joseph
A systematic study of the ground state properties of transitional nuclei W, Os and Pt is conducted with the help of Skyrme Hartree-Fock-Bogoliubov theory. Different Skyrme interactions are employed in the study. Two different bases, harmonic oscillator and transformed harmonic oscillator, are used in our investigation. 2n-separation energy, charge radii, neutron and proton rms radii, neutron skin thickness and deformation parameter have been estimated. The results obtained are in good agreement with the available experimental values.
nucl-thIJMPE(2020)·4 citations
02
Chiral-Imbalance Density Wave in Baryonic Matters
Mamiya Kawaguchi🇯🇵 · Shinya Matsuzaki🇨🇳
We propose a new chirality-imbalance phenomenon arising in baryonic/high dense matters under a magnetic field. A locally chiral-imbalanced (parity-odd) domain can be created due to the electromagnetically induced $U (1)_{A}$ anomaly in high-dense matters. The proposed local-chiral imbalance generically possesses a close relationship to a spacial distribution of an inhomogeneous chiral (pion)-vector current coupled to the magnetic field. To demonstrate such a nontrivial correlation, we take the skyrmion crystal approach to model baryonic/high dense matters. Remarkably enough, we find the chirality-imbalance distribution takes a wave form in a high density region (dobbed ``chiral-imbalance density wave''), when the inhomogeneous chiral condensate develops to form a chiral density wave. This implies the emergence of a nontrivial density wave for the explicitly broken $U (1)_{A}$ current simultaneously with the chiral density wave for the spontaneously broken chiral-flavor current. We further find that the topological phase transition in the skyrmion crystal model (between skyrmion and half-skyrmion phases) undergoes the deformation of the chiral-imbalance density wave in shape and periodicity. The emergence of this chiral-imbalance density wave could give a crucial contribution to studies on the chiral phase transition, as well as the nuclear matter structure, in compact stars under a magnetic field.
nucl-thhep-phJ.Phys.G(2020)·1 citation
03
Principal Component Analysis of collective flow in Relativistic Heavy-Ion Collisions
Ziming Liu🇨🇳 · Wenbin Zhao🇨🇳 · Huichao Song (Peking U.)🇨🇳
In this paper, we implement Principal Component Analysis (PCA) to study the single particle distributions generated from thousands of {\tt VISH2+1} hydrodynamic simulations with an aim to explore if a machine could directly discover flow from the huge amount of data without explicit instructions from human-beings. We found that the obtained PCA eigenvectors are similar to but not identical with the traditional Fourier bases. Correspondingly, the PCA defined flow harmonics $v_{n}^{'}$ are also similar to the traditional $v_{n}$ for $n = 2$ and 3, but largely deviated from the Fourier ones for $n \geq 4$ . A further study on the symmetric cumulants and the Pearson coefficients indicates that mode-coupling effects are reduced for these flow harmonics defined by PCA.
nucl-thcond-mat.dis-nnhep-phnucl-exEPJC(2019)·36 citations
04
A Solution to the Quenched $g_{A}$ Problem in Nuclei and Dense Baryonic Matter
Mannque Rho🇫🇷
When scale symmetry is combined with chiral symmetry in a scale-chiral Lagrangian, it can be shown in Fermi-liquid fixed point theory that $g_{A}^{eff} \approx 1$ in finite nuclei {\it as well as} in dense baryonic matter. This is suggested as a signal for emergence of hidden symmetries of QCD in baryonic matter from low to very high density. This calculation throws doubt on the "first principles" explanation of the quenching of $g_{A}$ in nuclei with two-body meson-exchange currents. It also has relevance to Gamow-Teller matrix elements in neutrinoless double $β$ decay.
nucl-th2 citations
05
On resonance contribution to balance functions
Igor Altsybeev🇷🇺
It is known that resonance decays influence the shape of the charge-balance functions measured in hadronic collisions. That is reflected in their rapidity and azimuthal widths and the integral, and therefore has consequences for different model interpretations. In this paper, we show that the contribution from neutral resonance decays can be removed from the balance function in an analytical way, and test the performance of the removal procedure with PYTHIA events. Prospects for applications of the procedure to real data analysis of balance functions are also discussed.
nucl-thnucl-exActa Phys.Polon.B(2019)·3 citations
06
$α$ scattering cross sections on $^{12}$ C with microscopic coupled-channel calculation
Yoshiko Kanada-En'yo · Kazuyuki Ogata
$α$ elastic and inelastic scattering on $^{12}$ C is investigated with the coupled-channel calculation using microscopic $α$ - $^{12}$ C potentials, which are derived by folding the Melbourne $g$ -matrix $N N$ interaction with the matter and transition densities of $^{12}$ C. These densities are obtained by a microscopic structure model of the antisymmetrized molecular dynamics combined with and without the $3 α$ generator coordinate method. The calculation reproduces satisfactorily well the observed elastic and inelastic cross sections at incident energies of $E_{α} = 130$ ~MeV, 172.5~MeV, 240~MeV, and 386~MeV with no adjustable parameter. Isoscalar monopole and dipole excitations to the $0_{2}^{+}$ , $0_{3}^{+}$ , and $1_{1}^{-}$ states in the $α$ scattering are discussed.
nucl-thPRC(2019)·23 citations
07
Exploring the partonic phase at finite chemical potential within an extended off-shell transport approach
Pierre Moreau🇩🇪 · Olga Soloveva🇩🇪 · Lucia Oliva🇩🇪 · Taesoo Song🇩🇪 · Wolfgang Cassing🇩🇪 · Elena Bratkovskaya🇩🇪
We extend the Parton-Hadron-String Dynamics (PHSD) transport approach in the partonic sector by explicitly calculating the total and differential partonic scattering cross sections as a function of temperature $T$ and baryon chemical potential $μ_{B}$ on the basis of the effective propagators and couplings from the Dynamical QuasiParticle Model (DQPM) that is matched to reproduce the equation of state of the partonic system above the deconfinement temperature $T_{c}$ from lattice QCD. The ratio of shear viscosity $η$ over entropy density $s$ , i.e. $η / s$ , is evaluated using the collisional widths and compared to lQCD calculations for $μ_{B}$ = 0 as well. We find only a very modest change of $η / s$ with the baryon chemical $μ_{B}$ . This also holds for a variety of hadronic observables from central A+A and C+Au collisions in the energy range 5 GeV $\leq s_{N N} \leq$ 200 GeV when implementing the differential cross sections into the PHSD approach. We only observe small differences in the strangeness and antibaryon sector with practically no sensitivity of rapidity and $p_{T}$ distributions to the $μ_{B}$ dependence of the partonic cross sections. Since we find only small traces of a $μ_{B}$ -dependence in heavy-ion observables - although the effective partonic masses and widths as well as their partonic cross sections clearly depend on $μ_{B}$ - this implies that one needs a sizable partonic density and large space-time QGP volume to explore the dynamics in the partonic phase. These conditions are only fulfilled at high bombarding energies where $μ_{B}$ is, however, rather low. On the other hand, when decreasing the bombarding energy and thus increasing $μ_{B}$ , the hadronic phase becomes dominant and accordingly, it will be difficult to extract signals from the partonic dynamics based on "bulk" observables.
nucl-thhep-phPRC(2019)·100 citations
08
Bound State Solutions of the Dirac-Shifted Tietz-Wei Potential Plus a Generalized Ring-Shaped Potential with Spin and Pseudospin symmetry
K. O. Suleman · K. J. Oyewumi · L. A. Sunmonu · D. A. Ajadi
In this study, approximate bound state solutions of the Dirac equation with the newly proposed shifted Tietz-Wei (sTW) potential were obtained for any arbitrary quantum number. Using Generalized Parametric Nikiforov Methods, the eigenenergy equations as well as the upper and lower spinors of the wave function corresponding to spin and pseudospin symmetric solutions were obtained by solving the radial equation. The Pekeris approximation scheme in terms of the parameters of the shifted Tietz-Wei potential was used to deal with the spin-orbit coupling potential term k(k+1)/r^2. The solutions obtained for the radial and polar angular parts of the wave functions were written in terms of the well-known Jacobi polynomial.
nucl-thcond-mat.other0 citations
09
Coupled channels approach to $η N$ and $η^{'} N$ interactions
Ales Cieply🇨🇿 · Peter C. Bruns🇨🇿
We present a coupled channels separable potential approach to $η N$ and $η^{'} N$ interactions using a chiral-symmetric interaction kernel. The s-wave $π N$ amplitudes and $π^{-} p$ induced total cross sections are reproduced satisfactorily in a broad interval of energies despite limiting the channel space to two-body interactions of pseudoscalar mesons with the baryon ground-state octet. It is demonstrated that an explicit inclusion of the $η_{0}$ meson singlet field leads to a more attractive $η N$ interaction, with the real part of the scattering length exceeding 1 fm. The $η^{'} N$ diagonal coupling appears sufficient to generate an $η^{'} N$ bound state but the inter-channel dynamics moves the respective pole far from physical region making the $η^{'} N$ interaction repulsive at energies around the channel threshold. The $N^{*} (1535)$ and $N^{*} (1650)$ resonances are generated dynamically and the origin and properties of the $S$ -matrix poles assigned to them are studied in detail. We also hint at a chance that the $N^{*} (1895)$ state might also be formed provided a suitably varied model setting is found.
nucl-thhep-phNPA(2019)·16 citations
10
Relativistic self-energy decomposition of nuclear symmetry energy and equation of state of neutron matter within QCD sum rules
Bao-Jun Cai🇨🇳 · Lie-Wen Chen🇨🇳
Abstract (abridged edition): Properties of the relativistic nucleon self-energy decomposition of the symmetry energy as well as the equation of state (EOS) of pure neutron matter (PNM) are explored systematically within the QCD sum rules (QCDSR). Our results in the present work have demonstrated that the QCDSR approach can be used to explore the properties of asymmetric nuclear matter (ANM) in a quantitative manner, at least in lower density region. The QCDSR approach establishes a bridge connecting the EOS of ANM and the non-perturbative QCD vacuum, and thus provides a useful way to understand the properties of dense nucleonic matter from non-perturbative QCD vacuum. These studies are helpful to investigate the QCD origins about the uncertainties of nucleonic matter properties, e.g., the uncertainties of the symmetry energy. On the other hand, the exact knowledge on the EOS of ANM extracted from experiments, observations and model-independent calculations is also very useful for understanding the quark/gluon condensates in nuclear medium, which can provide important information on the chiral symmetry restoration phase transition in nuclear matter as well as the in-medium effects of hadron properties.
nucl-thhep-phnucl-exPRC(2019)·12 citations
11
Simple non-perturbative resummation schemes beyond mean-field II: thermodynamics of scalar $ϕ^{4}$ theory in 1+1 dimensions at arbitrary coupling
Paul Romatschke🇺🇸
Recently, non-perturbative approximate solutions were presented that go beyond the well-known mean-field resummation. In this work, these non-perturbative approximations are used to calculate finite temperature equilibrium properties for scalar $ϕ^{4}$ theory in two dimensions such as the pressure, entropy density and speed of sound. Unlike traditional approaches, it is found that results are well-behaved for arbitrary temperature/coupling strength, are independent of the choice of the renormalization scale $μ ˉ^{2}$ , and are apparently converging as the resummation level is increased. Results also suggest the presence of a possible analytic cross-over from the high-temperature to the low-temperature regime based on the change in the thermal entropy density.
↳ hep-thcond-mat.str-elhep-latnucl-thMod.Phys.Lett.A(2020)·12 citations
12
Non-quadratic improved Hessian PDF reweighting and application to CMS dijet measurements at 5.02 TeV
Kari J. Eskola🇫🇮 · Petja Paakkinen🇫🇮 · Hannu Paukkunen🇫🇮
Hessian PDF reweighting, or "profiling", has become a widely used way to study the impact of a new data set on parton distribution functions (PDFs) with Hessian error sets. The available implementations of this method have resorted to a perfectly quadratic approximation of the initial $χ^{2}$ function before inclusion of the new data. We demonstrate how one can take into account the first non-quadratic components of the original fit in the reweighting, provided that the necessary information is available. We then apply this method to the CMS measurement of dijet pseudorapidity spectra in proton-proton (pp) and proton-lead (pPb) collisions at 5.02 TeV. The measured pp dijet spectra disagree with next-to-leading order (NLO) theory calculations using the CT14 NLO PDFs, but upon reweighting the CT14 PDFs, these can be brought to a much better agreement. We show that the needed proton-PDF modifications also have a significant impact on the predictions for the pPb dijet distributions. Taking the ratio of the individual spectra, the proton-PDF uncertainties effectively cancel, giving a clean probe of the PDF nuclear modifications. We show that these data can be used to further constrain the EPPS16 nuclear PDFs and strongly support gluon nuclear shadowing at small $x$ and antishadowing at around $x \approx 0.1$ .
↳ hep-phnucl-thEPJC(2019)·52 citations
13
Nucleosynthesis in heavy-ion collisions at the LHC via the Saha equation
Volodymyr Vovchenko🇩🇪 · Kai Gallmeister🇩🇪 · Jürgen Schaffner-Bielich🇩🇪 · Carsten Greiner🇩🇪
The production of light (anti-)(hyper-)nuclei in heavy-ion collisions at the LHC is considered in the framework of the Saha equation, making use of the analogy between the evolution of the early universe after the Big Bang and that of "Little Bangs" created in the lab. Assuming that disintegration and regeneration reactions involving light nuclei proceed in relative chemical equilibrium after the chemical freeze-out of hadrons, their abundances are determined through the famous cosmological Saha equation of primordial nucleosynthesis and show no exponential dependence on the temperature typical for the thermal model. A quantitative analysis, performed using the hadron resonance gas model in partial chemical equilibrium, shows agreement with experimental data of the ALICE collaboration on d, $^{3}$ He, $_{Λ}^{3}$ H, and $^{4}$ He yields for a very broad range of temperatures at $T ≲ 155$ MeV. The presented picture is supported by the observed suppression of resonance yields in central Pb-Pb collisions at the LHC.
↳ hep-phnucl-exnucl-thPLB(2020)·50 citations
14
Excited-state quantum phase transitions in systems with two degrees of freedom: III. Interacting boson systems
Michal Macek · Pavel Stránský · Amiram Leviatan · Pavel Cejnar
The series of articles [Ann. Phys. 345, 73 (2014) and 356, 57 (2015)] devoted to excited-state quantum phase transitions (ESQPTs) in systems with $f = 2$ degrees of freedom is continued by studying the interacting boson model of nuclear collective dynamics as an example of a truly many-body system. The intrinsic Hamiltonian formalism with angular momentum fixed to $L = 0$ is used to produce a generic first-order ground-state quantum phase transition with an adjustable energy barrier between the competing equilibrium configurations. The associated ESQPTs are shown to result from various classical stationary points of the model Hamiltonian, whose analysis is more complex than in previous cases because of (i) a non-trivial decomposition to kinetic and potential energy terms and (ii) the boundedness of the associated classical phase space. Finite-size effects resulting from a partial separability of both degrees of freedom are analyzed. The features studied here are inherent in a great majority of interacting boson systems.
↳ quant-phnucl-thPRC(2019)·34 citations
15
Interwoven limit cycles in the spectra of mass imbalanced many-boson system
W. De Paula · A. Delfino · T. Frederico · Lauro Tomio
The independence between few-body scales beyond the van der Waals universality is demonstrated for the extreme mass-imbalanced case of a specific many-boson system. This finding generalizes the scaling properties of universal tetramers to a broader class of heterogeneous few-boson systems. We assume two heavy atoms interacting with $(N - 2) -$ lighter ones at the unitary limit, using a particular case where no interactions are active between identical particles, by investigating the interwoven spectra of this many-body system for an arbitrary number of light bosons. A large mass-ratio between the particles allows us to treat this $N -$ body system analytically, by solving an effective inverse-squared long-range interaction which is stablished for the two heavy bosons. For a cluster with $N - 2$ light bosons ( $N \geq 4$ ), we discuss the implications of the corresponding long-range potentials associated with different subsystem thresholds, implying in independent interwoven limit cycles for the correlation between the energies of excited $N -$ body system. Our study with extreme mass-imbalanced few-boson bound states provides a fundamental understanding of the scaling behavior of their interwoven spectra. The novel insights enlarge the well-known Efimov physics paradigm and show the existence of different limit cycles, which could be probed by new experiments.
↳ quant-phnucl-thJ.Phys.B(2020)·8 citations

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first authorsco-authorsvia INSPIRE