Nuclear Theory·nucl-th

Tuesday·December 17, 2019

14 papers—6 primary·8 cross-listed

01
Calculation Binding energy for 223,225,227Ra isotopes in relativistic heavy cluster model
Keivan Darooyi Divshali · Mohammad Reza Shojaei
14C is a stable isotope and emitted from medium and heavy mass nuclei. The 14C result is in excellent agreement with a favored ground-state-to-ground-state transition according to the cluster model of Blendowske et al. We study Ra isotopes in relativistic core-cluster model, solve the Dirac equation with the new phenomenological potential by parametric Nikiforov-Uvarov method, and obtain wave function and binding energy.
nucl-th0 citations
02
Extrapolating Lattice QCD Results using Effective Field Theory
Moti Eliyahu🇮🇱 · Betzalel Bazak🇮🇱 · Nir Barnea🇮🇱
Lattice simulations are the only viable way to obtain ab-initio Quantum Chromodynamics (QCD) predictions for low energy nuclear physics. These calculations are done, however, in a finite box and therefore extrapolation is needed to get the free space results. Here we use nuclear Effective Field Theory (EFT), designed to provide a low energy description of QCD using baryonic degrees of freedom, to extrapolate the lattice results from finite to infinite volumes. To this end, we fit the EFT to the results calculated with nonphysical high quark masses and solve it with the stochastic variational method in both finite and infinite volumes. Moreover, we perform similar EFT calculations of the physical point and predict the finite-volume effects to be found in future Lattice QCD calculations for atomic nuclei with mass number $A \leq 4$ .
nucl-thhep-latPRC(2020)·27 citations
03
Comparing Sinc and Harmonic Oscillator Basis for Bound States of a Gaussian Interaction
Mamoon Sharaf · Ryan McCarty · Robert A. M. Basili · James P. Vary
We investigate the use of the sinc collocation and harmonic oscillator bases for solving a two-particle system bound by a Gaussian potential described by the radial Schrödinger equation. We analyze the properties of the bound state wave functions by investigating where the basis-state wave functions break down and relate the breakdowns to the infrared and ultraviolet scales for both bases. We propose a correction for the asymptotic infrared region, the long range tails of the wave functions. We compare the calculated bound state eigenvalues and mean square radii obtained within the two bases. From the trends in the numerical results, we identify the advantages and disadvantages of the two bases. We find that the sinc basis performs better in our implementation for accurately computing both the deeply- and weakly-bound states whereas the harmonic oscillator basis is more convenient since the basis-state wave functions are orthogonal and maintain the same mathematical structure in both position and momentum space. These mathematical properties of the harmonic oscillator basis are especially advantageous in problems where one employs both position and momentum space. The main disadvantage of the harmonic oscillator basis as illustrated in this work is the large basis space size required to obtain accurate results simultaneously for deeply- and weakly-bound states. The main disadvantage of the sinc basis could be the numerical challenges for its implementation in a many-body application.
nucl-th1 citation
04
Combining phase-space and time-dependent reduced density matrix approach to describe the dynamics of interacting fermions
Thomas Czuba🇫🇷 · Denis Lacroix🇫🇷 · David Regnier🇫🇷 · Ibrahim Ulgen🇹🇷 · Bulent Yilmaz🇹🇷
The possibility to apply phase-space methods to many-body interacting systems might provide accurate descriptions of correlations with a reduced numerical cost. For instance, the so--called stochastic mean-field phase-space approach, where the complex dynamics of interacting fermions is replaced by a statistical average of mean-field like trajectories is able to grasp some correlations beyond the mean-field. We explore the possibility to use alternative equations of motion in the phase-space approach. Guided by the BBGKY hierarchy, equations of motion that already incorporate part of the correlations beyond mean-field are employed along each trajectory. The method is called Hybrid Phase-Space (HPS) because it mixes phase-space techniques and the time-dependent reduced density matrix approach. The novel approach is applied to the one-dimensional Fermi-Hubbard model. We show that the predictive power is improved compared to the original stochastic mean-field method. In particular, in the weak-coupling regime, the results of the HPS theory can hardly be distinguished from the exact solution even for long time.
nucl-thcond-mat.str-elEPJA(2020)·10 citations
05
Alpha-particle condensation: a nuclear quantum phase transition
J.-P. Ebran🇫🇷 · M. Girod🇫🇷 · E. Khan🇫🇷 · R.D. Lasseri🇫🇷 · P. Schuck🇫🇷
When the density of a nuclear system is decreased, homogeneous states undergo the so-called Mott transition towards clusterised states, e.g. alpha clustering, both in nuclei and in nuclear matter. Here we investigate such a quantum phase transition (QPT) by using microscopic energy density functional (EDF) calculations both with the relativistic and the Gogny approaches on the diluted $^{16}$ O nucleus. The evolution of the corresponding single-particle spectrum under dilution is studied, and a Mott-like transition is predicted at about 1/3 of the saturation density. Complementary approaches are used in order to understand this QPT. A study of spatial localisation properties as a function of the density allows to derive a value of the Mott density in agreement with the one obtained by fully microscopic calculations in $^{16}$ O and in nuclear matter. Moreover a study of the spontaneous symmetry breaking of the rotational group in $^{16}$ O, down to the discrete tetrahedral one, provides further insight on the features displayed by the single-particle spectrum obtained within the EDF approach.The content of the tetrahedrally deformed A-nucleon product state in terms of spherical particle-hole configurations is investigated. Finally a study of quartet condensation and the corresponding macroscopic QPT is undertaken in infinite matter.
nucl-thPRC(2020)·18 citations
06
Antiproton physics
Jean-Marc Richard🇫🇷
We review the physics of low-energy antiprotons, and its link with the nuclear forces. This includes: antinucleon scattering on nucleons and nuclei, antiprotonic atoms and antinucleon-nucleon annihilation into mesons.
nucl-thhep-phFront.in Phys.(2020)·25 citations
07
A new approach to search for free neutron-antineutron oscillations using coherent neutron propagation in gas
V. Gudkov🇺🇸 · V. V. Nesvizhevsky🇫🇷 · K. V. Protasov🇫🇷 · W. M. Snow🇺🇸 · A. Yu. Voronin🇷🇺
Coherent forward neutron propagation in gas is discussed as a new approach to search for neutron-antineutron oscillations ( $n - n ˉ$ ), which violate both $B$ and $B - L$ conservation. We show that one can increase the probability of neutron - antineutron transitions to essentially the free neutron oscillation rate in the presence of a nonzero external magnetic field by tuning the density of an appropriate mixture of gases so that the neutron optical potential of the gas cancels that from an external magnetic field.
↳ hep-phnucl-thPLB(2020)·21 citations
08
Compton scattering from $^{4}$ He at the TUNL HI $γ$ S facility
X. Li🇺🇸 · M.W. Ahmed🇺🇸 · A. Banu🇺🇸 · C. Bartram🇺🇸 · B. Crowe🇺🇸 · E.J. Downie🇺🇸 · M. Emamian🇺🇸 · G. Feldman🇺🇸 · H. Gao🇺🇸 · D. Godagama🇺🇸 · H.W. Grießhammer🇺🇸 · C.R. Howell🇺🇸 and 17 other authors
Differential cross sections for elastic Compton scattering from $^{4}$ He have been measured with high statistical precision at the High Intensity $γ$ -ray Source at laboratory scattering angles of $5 5^{\circ}$ , $9 0^{\circ}$ , and $12 5^{\circ}$ using a quasi-monoenergetic photon beam with a weighted mean energy value of $81.3$ MeV. The results are compared to previous measurements and similar fore-aft asymmetry in the angular distribution of the differential cross sections is observed. This experimental work is expected to strongly motivate the development of effective-field-theory calculations of Compton scattering from $^{4}$ He to fully interpret the data.
↳ nucl-exhep-exhep-phnucl-thPRC(2020)·9 citations
09
Threshold cusps and triangle singularities in hadronic reactions
Feng-Kun Guo🇨🇳 · Xiao-Hai Liu · Shuntaro Sakai🇨🇳
The spectrum of hadrons is the manifestation of color confinement of quantum chromodynamics. Hadronic resonances correspond to poles of the S-matrix. Since 2003, lots of new hadron resonant structures were discovered in the mass regions from light mesons to hadrons containing a pair of a heavy quark and an antiquark. Many of them are candidates of exotic hadrons, and they are usually observed as peaks in invariant mass distributions. However, the S-matrix also has kinematical singularities due to the on-shellness of intermediate particles for a process, such as two-body thresholds and triangle singularities, and they can produce peaks as well. On the one hand, such singularities may be misidentified as resonances; on the other hand, they can be used as tools for precision measurements. In this paper, we review the threshold cusps and various triangle singularities in hadronic reactions, paying attention to their manifestations in phenomena related to exotic hadron candidates.
↳ hep-phhep-exnucl-thPPNP(2020)·381 citations
10
Systematic study on production of hidden-bottom pentaquark via $γ p$ and $π^{-} p$ scatterings
Xiao-Yun Wang🇨🇳 · Jun He🇨🇳 · Xurong Chen🇨🇳
The production of hidden-bottom pentaquark $P_{b}$ states via $γ p$ and $π^{-} p$ scatterings is studied within an effective Lagrangian approach and the vector-meson-dominance mechnism. For the $P_{b}$ production in the process $γ p \to Υ p$ , the dipole Pomeron model is employed to calculate the background contribution, and the experimental data can be well described. For the process $π^{-} p \to Υ n$ , the Reggeized $t$ -channel with $π$ exchange is considered as the main background for the $P_{b}$ production. Near the threshold, two-peak structure from the states $P_{b (11080)$ and $P_{b} (11125)$ can be observed if energy bin width is chosen as 0.01 GeV, and the same result is obtained in the $π^{-} p$ scattering. Moreover, by taking the branching ratio of Br $[P_{b} \to π N] ≃ 0.05%$ , the numerical result shows that the average value of cross section from the $P_{b} (11080)$ state produced in the $γ p$ or $π^{-} p$ scattering reaches at least 0.1 nb with a bin of 0.1 GeV. Even if we reduce the branching ratio of the $P_{b}$ state into $π N$ channel by one order, the theoretical average of the cross section from $P_{b} (11080)$ production in $π^{-} p$ scattering can reach the order of 0.01 nb with a bin of 0.1 GeV, which means that the signal can still be clearly distinguished from the background. The experimental measurements and studies on the hidden-bottom pentaquark $P_{b}$ state production in the $γ p$ or $π^{-} p$ scattering near-threshold energy region around $W ≃ 11$ GeV are strongly suggested, which are accessible at COMPASS and JPARC. Particularly, the result of the photoproduction suggests that it is very promising to observe the hidden-bottom pentaquark at proposed EicC facility in China.
↳ hep-phhep-exnucl-exnucl-thPRD(2020)·21 citations
11
Two-particle azimuthal correlations as a probe of collective behaviour in deep inelastic $ep$ scattering at HERA
ZEUS Collaboration
Two-particle azimuthal correlations have been measured in neutral current deep $\mbox in e l a s t i c$ $ep$ scattering with virtuality $Q^{2} > 5$ GeV $^{2}$ at a centre-of-mass energy $s = 318$ GeV recorded with the ZEUS detector at HERA. The correlations of charged particles have been measured in the range of laboratory pseudorapidity $- 1.5 < η < 2.0$ and transverse momentum $0.1 < p_{T} < 5.0$ GeV and event multiplicities $N_{ch}$ up to six times larger than the average $⟨ N_{ch} ⟩ \approx 5$ . The two-particle correlations have been measured in terms of the angular observables $c_{n} {2} = ⟨ ⟨ cos n Δ φ ⟩ ⟩$ , where $n$ is between 1 and 4 and $Δ φ$ is the relative azimuthal angle between the two particles. Comparisons with available models of deep inelastic scattering, which are tuned to reproduce inclusive particle production, suggest that the measured two-particle correlations are dominated by contributions from multijet production. The correlations observed here do not indicate the kind of collective behaviour recently observed at the highest RHIC and LHC energies in high-multiplicity hadronic collisions.
↳ hep-exhep-phnucl-exnucl-thJHEP(2020)·56 citations
12
Dirac spectrum and the BEC-BCS crossover in QCD at nonzero isospin asymmetry
B. B. Brandt🇩🇪 · F. Cuteri🇩🇪 · G. Endrődi🇩🇪 · S. Schmalzbauer🇩🇪
For large isospin asymmetries, perturbation theory predicts the QCD ground state to be a superfluid phase of $u$ and $d ˉ$ Cooper pairs. This phase, which is denoted as the BCS phase, is expected to be smoothly connected to the standard phase with Bose-Einstein condensation (BEC) of charged pions at $μ_{I} \geq m_{π} /2$ by an analytic crossover. A first hint for the existence of the BCS phase, which is likely characterised by the presence of both, deconfinement and charged pion condensation, is coming from the lattice observation that the deconfinement crossover smoothly penetrates into the BEC phase. To further scrutinize the existence of the BCS phase, in this proceedings article we investigate the complex spectrum of the massive Dirac operator in 2+1-flavor QCD at nonzero temperature and isospin chemical potential. The spectral density near the origin is related to the BCS gap via a generalization of the Banks-Casher relation to the case of complex Dirac eigenvalues (derived for the zero-temperature, high-density limits of QCD at nonzero isospin chemical potential).
↳ hep-lathep-phnucl-thParticles(2020)·23 citations
13
Pion observables with the Minkowski Space Pion Model
J. P. B. C. de Melo (Laboratório de Física Teórica e Computacional, LFTC/Universidade Cruzeiro do Sul/Universidade Cidade de São Paulo)🇧🇷 · Rômulo M. Moita🇧🇷 · Tobias Frederico (Instituto Tecnológico de Aeronáutica, DCTA 12.228-900 São José dos Campos, SP, Brazil)🇧🇷
The pion structure in Minkowski space is described in terms of an analytic model of the Bethe-Salpeter amplitude combined with Euclidean Lattice QCD results for the running quark mass. In the present work, a pion model previously proposed, which allows for a Nakanishi integral representation, is studied in order to verify the sensitivity of the pion electromagnetic form factor to small variations of the quark self-energy. In addition, we extend the previous work, providing the Nakanishi integral representation for the invariants associated with a decomposition of the pion Bethe-Salpeter amplitude.
↳ hep-phnucl-thPoS(2019)·2 citations
14
Drawing insights from pion parton distributions
Minghui Ding🇨🇳 · Khépani Raya🇲🇽 · Daniele Binosi🇮🇹 · Lei Chang🇨🇳 · Craig D. Roberts🇺🇸 · Sebastian M. Schmidt🇩🇪
A symmetry-preserving continuum approach to the two valence-body bound-state problem is used to calculate the valence, glue and sea distributions within the pion; unifying them with, inter alia, electromagnetic pion elastic and transition form factors. The analysis reveals the following momentum fractions at the scale $ζ_{2} := 2$ GeV: $⟨ x_{valence} ⟩ = 0.48 (3)$ , $⟨ x_{glue} ⟩ = 0.41 (2)$ , $⟨ x_{sea} ⟩ = 0.11 (2)$ ; and despite hardening induced by the emergent phenomenon of dynamical chiral symmetry breaking, the valence-quark distribution function, $q^{π} (x)$ , exhibits the $x ≃ 1$ behaviour predicted by quantum chromodynamics (QCD). After evolution to $ζ = 5.2$ GeV, the prediction for $q^{π} (x)$ matches that obtained using lattice-regularised QCD. This confluence should both stimulate improved analyses of existing data and aid in planning efforts to obtain new data on the pion distribution functions.
↳ hep-phhep-exhep-latnucl-ex+1CPC(2020)·55 citations

Affiliations

first authorsco-authorsvia INSPIRE