Nuclear Theory·nucl-th
15 papers—7 primary·8 cross-listed
[Submitted on 1 Jul 2020]
Sebastian Kubis · Włodzimierz Wójcik · Noemi Zabari
It is shown that recently proposed RMF model with and meson interaction agrees with the observational data and presents an interesting structure with phase transition in the outer part of neutron star core.
[Submitted on 1 Jul 2020]
Patrick Carzon🇺🇸 · Skandaprasad Rao🇺🇸 · Matthew Luzum🇧🇷 · Matthew Sievert🇺🇸 · Jacquelyn Noronha-Hostler🇺🇸
Recent measurements have established the sensitivity of ultracentral heavy-ion collisions to the deformation parameters of non-spherical nuclei. In the case of Xe collisions, a quadrupole deformation of the nuclear profile led to an enhancement of elliptic flow in the most central collisions. In Pb collisions a discrepancy exists in similar centralities, where either elliptic flow is over-predicted or triangular flow is under-predicted by hydrodynamic models; this is known as the -to- puzzle in ultracentral collisions. Motivated by low-energy nuclear structure calculations, we consider the possibility that Pb nuclei could have a pear shape deformation (octupole), which has the effect of increasing triangular flow in central PbPb collisions. Using the recent data from ALICE and ATLAS, we revisit the -to- puzzle in ultracentral collisions, including new constraints from recent measurements of the triangular cumulant ratio and comparing two different hydrodynamic models. We find that, while an octupole deformation would slightly improve the ratio between and , it is at the expense of a significantly worse triangular flow cumulant ratio. In fact, the latter observable prefers no octupole deformation, with for Pb, and is therefore consistent with the expectation for a doubly-magic nucleus even at top collider energies. The -to- puzzle remains a challenge for hydrodynamic models.
[Submitted on 2 Jul 2020]
Eun Jin In · Youngman Kim · Panagiota Papakonstantinou · Seung-Woo Hong
The location of the neutron drip line, currently known for only the lightest elements, remains a fundamental question in nuclear physics. Its description is a challenge for microscopic nuclear energy density functionals, as it must take into account in a realistic way not only the nuclear potential, but also pairing correlations, deformation effects and coupling to the continuum. The recently developed deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) aims to provide a unified description of even-even nuclei throughout the nuclear chart. Here, the DRHBc with the successful density functional PC-PK1 is used to investigate whether and how deformation influences the prediction for the neutron drip-line location for even-even nuclei with 8<=Z<=20, where many isotopes are predicted deformed. The results are compared with those based on the spherical relativistic continuum Hartree-Bogoliubov (RCHB) theory and discussed in terms of shape evolution and the variational principle. It is found that the Ne and Ar drip-line nuclei are different after the deformation effect is included. The direction of the change is not necessarily towards an extended drip line, but rather depends on the evolution of the degree of deformation towards the drip line. Deformation effects as well as pairing and continuum effects treated in a consistent way can affect critically the theoretical description of the neutron drip-line location.
[Submitted on 2 Jul 2020]
Using the idea of the instanton approach to quantum tunneling we try to obtain a method of calculating spontaneous fission rates for nuclei with the odd number of neutrons or protons. This problem has its origin in the failure of the adiabatic cranking approximation which serves as the basis in calculations of fission probabilities. Selfconsistent instanton equations, with and without pairing, are reviewed and then simplified to non-selfconsistent versions with phenomenological single-particle potential and seniority pairing interaction. Solutions of instanton-like equations without pairing and actions they produce are studied for the Woods-Saxon potential along realistic fission trajectories. Actions for unpaired particles are combined with cranking actions for even-even cores and fission hindrance for odd-A nuclei is studied in such a hybrid model. With the assumed equal mass parameters for neighbouring odd-A and even-even nuclei, the model shows that freezing the K {\pi} configuration leads to a large overestimate of the fission hindrance factors. Actions with adiabatic configurations mostly show not enough hindrance; instanton-like actions for blocked nucleons correct this, but not sufficiently.
[Submitted on 1 Jul 2020]
Fatema. H. Obeed · Ali. K. Hasan
In this work the excited energy levels, reduced transition probabilities, , intrinsic quadrupole moments and deformation parameters have been calculated for Zn isotopes with neutrons (N=32,34,36 and 38 ). Nushellx code has been applied for all energy states of (fp-shell) nuclei. Shell-model calculations for the zinc isotopes have been carried out with active particles distributed in the lp, 0f and lp orbits outside doubly-magic closed "56Ni"core nucleus. By using (f5p) model space and (f5pvh) interaction, the theoretical results have been obtained and compared with the available experimental results. The excited energies values, electric transition probability B(E2), intrinsic quadrupole moment (Q) and deformation parameters () have been appeared at complete agreement with the experimental values. As well as, the energy levels have been confirmed and determined for the angular momentum and parity of experimental values which have not been well established and determined experimentally. On the other hand, it has been predicted some of the new energy levels and electric transition probabilities for the Zn isotopes under this study which were previously unknown in experimental information.
[Submitted on 1 Jul 2020]
We study the meson photoproduction on protons and nuclei at the near-threshold center-of-mass energies below 11.4 GeV (or at the corresponding photon laboratory energies below 68.8 GeV). We calculate the absolute excitation functions for the non-resonant and resonant photoproduction of mesons off protons at incident photon laboratory energies of 63--68 GeV by accounting for direct () and two-step () production channels within different scenarios for the non-resonant total cross section of elementary reaction and for branching ratios of the decays . We also calculate an analogous functions for photoproduction of mesons on C and Pb target nuclei in the near-threshold center-of-mass beam energy region of 9.0--11.4 GeV by considering respective incoherent direct () and two-step (, ) production processes within a nuclear spectral function approach. We show that a detailed scan of the total photoproduction cross section on a proton and nuclear targets in the near-threshold energy region in future high-precision experiments at the proposed high-luminosity electron-ion colliders EIC and EicC in the U.S. and China should give a definite result for or against the existence of the non-strange hidden-bottom pentaquark states and (1, 2, 3) as well as clarify their decay rates.
[Submitted on 1 Jul 2020]
We calculate the -matrices of elastic pion-nucleon () scattering up to fourth order in SU(3) heavy baryon chiral perturbation theory. The pertinent low-energy constants are determined by fitting to phase shifts below 200 MeV pion laboratory momentum in the physical region. The scattering lengths and scattering volumes are extracted from the chiral amplitudes, and turn out to be in good agreement with those of other approaches and the available experimental values. We also discuss the subthreshold parameters and the related issues. On the basis of the various phase shifts, the threshold parameters and the subthreshold parameters, the convergence of the chiral expansion is analyzed in detail. The calculation provides the possibility to consider explicitly more complex processes involving strangeness.
[Submitted on 1 Jul 2020] (cross-list from hep-ph)
Liping Gan🇺🇸 · Bastian Kubis🇩🇪 · Emilie Passemar🇺🇸 · Sean Tulin🇨🇦
Decays of the neutral and long-lived and mesons provide a unique, flavor-conserving laboratory to test low-energy Quantum Chromodynamics and search for new physics beyond the Standard Model. They have drawn world-wide attention in recent years and have inspired broad experimental programs in different high-intensity-frontier centers. New experimental data will offer critical inputs to precisely determine the light quark mass ratios, - mixing parameters, and hadronic contributions to the anomalous magnetic moment of the muon. At the same time, it will provide a sensitive probe to test potential new physics. This includes searches for hidden photons, light Higgs scalars, and axion-like particles that are complementary to worldwide efforts to detect new light particles below the GeV mass scale, as well as tests of discrete symmetry violation. In this review, we give an update on theoretical developments, discuss the experimental opportunities, and identify future research needed in this field.
[Submitted on 1 Jul 2020] (cross-list from nucl-ex)
A summary of the QM19 conference is given by highlighting a few selected results. These are discussed as examples to illustrate the exciting future of heavy-ion collisions and the need for further instrumentation. (The arXiv version is significantly longer than the printed proceedings, with more figures.)
[Submitted on 1 Jul 2020] (cross-list from hep-ph)
T. Lappi🇫🇮 · H. Mäntysaari🇫🇮 · A. Ramnath🇫🇮
We calculate finite- corrections to the next-to-leading order (NLO) Balitsky-Kovchegov (BK) equation. We find analytical expressions for the necessary correlators of six Wilson lines in terms of the two-point function using the Gaussian approximation. In a suitable basis, the problem reduces from the diagonalization of a six-by-six matrix to the diagonalization of a three-by-three matrix, which can easily be done analytically. We study numerically the effects of these finite- corrections on the NLO BK equation. In general, we find that the finite- corrections are smaller than the expected . The corrections may be large for individual correlators, but have less of an influence on the shape of the amplitude as a function of the dipole size. They have an even smaller effect on the evolution speed as a function of rapidity.
[Submitted on 2 Jul 2020] (cross-list from hep-ph)
Muhammad Waqas🇨🇳 · Fu-Hu Liu🇨🇳 · Rui-Qin Wang🇨🇳 · Irfan Siddique🇨🇳
The transverse momentum (mass) spectra of the multi-strange and non-multi-strange (i.e. other identified) particles in central gold-gold (Au-Au), lead-lead (Pb-Pb), argon-muriate (Ar-KCl) and nickel-nickel (Ni-Ni) collisions over a wide energy range have been studied in this work. The experimental data measured by various collaborations have been analyzed. The blast-wave fit with Tsallis statistics is used to extract the kinetic freeze-out temperature and transverse flow velocity from the experimental data of transverse momentum (mass) spectra. The extracted parameters increase with the increase of collision energy and appear with the trend of saturation at the Beam Energy Scan (BES) energies at the Relativistic Heavy Ion Collider (RHIC). This saturation implies that the onset energy of phase transition of partial deconfinement is 7.7 GeV and that of whole deconfinement is 39 GeV. Furthermore, the energy scan/dependence of kinetic freeze-out scenarios are observed for the multi-strange and other identified particles, though the multiple freeze-out scenarios are also observed for various particles.
[Submitted on 2 Jul 2020] (cross-list from hep-ph)
Mamiya Kawaguchi🇨🇳 · Shinya Matsuzaki🇨🇳 · Xu-Guang Huang🇨🇳
We discuss phenomenological implications of the anomalous transport induced by the scale anomaly in QCD coupled to an electromagnetic (EM) field, based on a dilaton effective theory. The scale anomalous current emerges in a way perfectly analogous to the conformal transport current induced in a curved spacetime background, or the Nernst current in Dirac and Weyl semimetals -- both current forms are equivalent by a "Weyl transformation". We focus on a spatially homogeneous system of QCD hadron phase, which is expected to be created after the QCD phase transition and thermalization. We find that the EM field can induce a dynamic oscillatory dilaton field which in turn induces the scale anomalous current. As the phenomenological applications, we evaluate the dilepton and diphoton productions induced from the dynamic scale anomalous current, and find that those productions include a characteristic peak structure related to the dynamic oscillatory dilaton, which could be tested in heavy ion collisions. We also briefly discuss the out-of-equilibrium particle production created by a nonadiabatic dilaton oscillation, which happens in a way of the so-called tachyonic preheating mechanism.
[Submitted on 2 Jul 2020] (cross-list from physics.atom-ph)
Yongliang Hao🇳🇱 · Petr Navrátil🇨🇦 · Eric B. Norrgard🇺🇸 · Miroslav Iliaš🇸🇰 · Ephraim Eliav🇮🇱 · Rob G. E. Timmermans🇳🇱 · Victor V. Flambaum🇦🇺 · Anastasia Borschevsky🇳🇱
Measurements of nuclear spin-dependent parity-violating (NSD-PV) effects provide an excellent opportunity to test nuclear models and to search for physics beyond the Standard Model. Molecules possess closely-spaced states with opposite parity which may be easily tuned to degeneracy to greatly enhance the observed parity-violating effects. A high-sensitivity measurement of NSD-PV effects using light triatomic molecules is in preparation [E. B. Norrgard, et al., Commun. Phys. 2, 77 (2019)]. Importantly, by comparing these measurements in light nuclei with prior and ongoing measurements in heavier systems, the contribution to NSD-PV from -boson exchange between the electrons and the nuclei may be separated from the contribution of the nuclear anapole moment. Furthermore, light triatomic molecules offer the possibility to search for new particles, such as the postulated boson. In this work, we detail a sensitive measurement scheme and present high-accuracy molecular and nuclear calculations needed for interpretation of NSD-PV experiments on triatomic molecules composed of light elements Be, Mg, N, and C. The ab initio nuclear structure calculations, performed within the No-Core Shell Model (NCSM) provide a reliable prediction of the magnitude of different contributions to the NSD-PV effects in the four nuclei. These results differ significantly from the predictions of the standard single-particle model and highlight the importance of including many-body effects in such calculations. In order to extract the NSD-PV contributions from measurements, a parity-violating interaction parameter , which depends on molecular structure, needs to be known with high accuracy. We have calculated these parameters for the triatomic molecules of interest using the relativistic coupled-cluster approach.
[Submitted on 30 Jun 2020] (cross-list from astro-ph.HE)
János Takátsy🇭🇺 · Péter Kovács🇭🇺
We comment on the paper of S. Postnikov et al. in Phys. Rev. D 82, 024016 (2010) and give a modified formula that needs to be taken into account when calculating the tidal Love number of neutron stars in case a first order phase-transition occurs at non-zero pressure. We show that the error made when using the original formula tends to zero as and we estimate the maximum relative error to be if the density discontinuity is at larger densities.
[Submitted on 2 Jul 2020] (cross-list from hep-ph)
Fang-Zheng Peng🇨🇳 · Jun-Xu Lu🇨🇳 · Mario Sánchez Sánchez🇫🇷 · Mao-Jun Yan🇨🇳 · Manuel Pavon Valderrama🇨🇳
The LHCb pentaquarks -- the , and -- have been theorized to be and S-wave molecules. Here we explore the possibility that two of these pentaquarks -- the and -- contain in addition a component in P-wave. We will analyze the effects of this extra channel within two effective field theories: the first one will be a standard contact-range effective field theory and the second one will include the non-diagonal pion dynamics connecting the and channels, which happens to be unusually long-ranged. The impact of the coupled-channel dynamics between the and components is modest at best for the and , which will remain to be predominantly molecules. However, if the quantum numbers of the are , the coupled-channel dynamics is likely to induce the binding of a S-wave molecule (coupled to in P-wave) with and a mass similar to the . If this is the case, the could actually be a double peak containing two different pentaquark states.
first authorsco-authorsvia INSPIRE