PaperPanorama
FAQ

Nuclear Theory·nucl-th

Thursday·December 1, 2016

13 papers—8 primary·5 cross-listed

All13Primary8Cross-lists5
  1. 01

    Emergent phenomena and partonic structure in hadrons

    Craig D. Roberts🇺🇸 · Cedric Mezrag🇺🇸

    Modern facilities are poised to tackle fundamental questions within the Standard Model, aiming to reveal the nature of confinement, its relationship to dynamical chiral symmetry breaking (DCSB) - the origin of visible mass - and the connection between these two, key emergent phenomena. There is strong evidence to suggest that they are intimately connected with the appearance of momentum-dependent masses for gluons and quarks in QCD, which are large in the infrared: MeV and MeV. DCSB, expressed in the dynamical generation of a dressed-quark mass, has an enormous variety of verifiable consequences, including an enigmatic result that the properties of the (almost) massless pion are the cleanest expression of the mechanism which is responsible for almost all the visible mass in the Universe. This contribution explains that these emergent phenomena are expressed with particular force in the partonic structure of hadrons, e.g. in valence-quark parton distribution amplitudes and functions, and, consequently, in numerous hadronic observables, so that we are now in a position to exhibit the consequences of confinement and DCSB in a wide range of hadron observables, opening the way to empirical verification of their expression in the Standard Model.

    nucl-thhep-lathep-phnucl-exEPJ Web Conf.(2017)·7 citations
  2. 02

    Scale-Chiral Symmetry, Proton Mass and Sound Velocity in Compact-Star Matter

    Won-Gi Paeng🇰🇷 · Mannque Rho🇫🇷

    With a light dilaton and the light-quark vector mesons incorporated into an effective scale-invariant hidden local symmetric Lagrangian, scale-chiral symmetry -- hidden in QCD -- arises at a high density, , as an "emergent" symmetry, a phenomenon absent in standard chiral perturbative approaches but highly relevant for massive compact stars. What takes place as the density increases beyond in compressed baryonic matter is (1) a topology change from skyrmions to half-skyrmions, (2) parity doubling in the nucleon structure, (3) the maximum neutron star mass and the radius km and (4) the sound velocity due to the "vector manifestation (VM)" fixed point of and a "walking" dilaton condensate, which is intricately connected to the source of the proton mass.

    nucl-thhep-ph6 citations
  3. 03

    Tritium -decay in pionless effective field theory

    Hilla De-Leon🇮🇱 · Lucas Platter🇺🇸 · Doron Gazit🇮🇱

    We calculate the -decay of tritium at next-to-leading order in pionless effective field theory. At this order, a low-energy parameter enters the calculation that is also relevant for a high-accuracy prediction of the solar proton-proton fusion rate. We use the tritium half-life to determine this parameter and provide uncertainty estimates. We show proper renormalization of our calculation analyzing the residual cutoff dependence of observables. We find that next-to-leading order corrections contribute about to the triton decay Gamow-Teller strength. We show that these conclusions are insensitive to different arrangements of the effective range expansion.

    nucl-thPRC(2019)·32 citations
  4. 04

    Production of proton-rich nuclei around Z=84-90 in fusion-evaporation reactions

    Peng-Hui Chen · Zhao-Qing Feng · Fei Niu · Ya-Fei Guo · Hong-Fei Zhang · Jun-Qing Li · Gen-Ming Jin

    Within the framework of the dinuclear system model, production cross sections of proton-rich nuclei with charged numbers of Z=84-90 are investigated systematically. Possible combinations with the Si, S, Ar bombarding the target nuclides Ho, Tm, Yb, Lu, Hf and Ta are analyzed thoroughly. The optimal excitation energies and evaporation channels are proposed to produce the proton-rich nuclei. The systems are feasible to be constructed in experiments. It is found that the neutron shell closure of N=126 is of importance during the evaporation of neutrons. The experimental excitation functions in the Ar induced reactions can be nicely reproduced. The charged particle evaporation is comparable with neutrons in cooling the excited proton-rich nuclei, in particular for the channels with and proton evaporation. The production cross section increases with the mass asymmetry of colliding systems because of the decrease of the inner fusion barrier. The channels with pure neutron evaporation depend on the isotopic targets. But it is different for the channels with charged particles and more sensitive to the odd-even effect.

    nucl-thEPJA(2017)·14 citations
  5. 05

    Higher-order baryon number susceptibilities: interplay between the chiral and the nuclear liquid-gas transitions

    A. Mukherjee🇩🇪 · S. Schramm🇩🇪 · J. Steinheimer🇩🇪

    We use an improved version of the SU(3) flavour parity-doublet quark-hadron model to investigate the higher order baryon number susceptibilities near the chiral and the nuclear liquid-gas transitions. The parity-doublet model has been improved by adding higher-order interaction terms of the scalar fields in the effective mean field Lagrangian, resulting in a much-improved description of nuclear ground-state properties, in particular the nuclear compressibility. The resulting phase diagram of the model agrees qualitatively with expectations from lattice QCD, i.e., it shows a crossover at zero net baryo-chemical potential and a critical point at finite density. Using this model, we investigate the dependence of the higher-order baryon number susceptibilities as function of temperature and chemical potential. We observe a strong interplay between the chiral and liquid-gas transition at intermediate baryo chemical potentials. Due to this interplay between the chiral and the nuclear liquid-gas transitions, the experimentally measured cumulants of the net baryon number may show very different beam energy dependence, subject to the actual freeze-out temperature.

    nucl-thhep-phPRC(2017)·71 citations
  6. 06

    Power Counting in Peripheral Partial Waves: The Singlet Channels

    M. Pavón Valderrama🇨🇳 · M. Sánchez Sánchez🇫🇷 · C.-J. Yang🇫🇷 · Bingwei Long🇨🇳 · Jaume Carbonell🇫🇷 · U. van Kolck🇫🇷

    We analyze the power counting of the peripheral singlet partial waves in nucleon-nucleon scattering. In agreement with conventional wisdom, we find that pion exchanges are perturbative in the peripheral singlets. We quantify from the effective field theory perspective the well-known suppression induced by the centrifugal barrier in the pion-exchange interactions. By exploring perturbation theory up to fourth order, we find that the one-pion-exchange potential in these channels is demoted from leading to subleading order by a given power of the expansion parameter that grows with the orbital angular momentum. We discuss the implications of these demotions for few-body calculations: though higher partial waves have been known for a long time to be irrelevant in these calculations (and are hence ignored), here we explain how to systematize the procedure in a way that is compatible with the effective field theory expansion.

    nucl-thPRC(2017)·42 citations
  7. 07

    Quasifission dynamics and stability of superheavy systems

    Kazuyuki Sekizawa · Sophia Heinz

    Recent experiments revealed intriguing similarities in the Ni+Pb, Xe+Pb, and U+U reactions at energies around the Coulomb barrier. The experimental data indicate that for all systems substantial energy dissipation takes place, in the first stage of the reaction, although the number of transferred nucleons is small. On the other hand, in the second stage, a large number of nucleons are transferred with small friction and small consumption of time. To understand the observed behavior, various reactions were analyzed based on the microscopic time-dependent Hartree-Fock (TDHF) theory. From a systematic analysis for Ca+Sn, Ca+Pb, Ar+Pb, Ni+Pb, Ni+U, Xe+ Pt, and U+U reactions, we find that TDHF reproduces well the measured trends. In addition, the Balian-Vénéroni variational principle is applied to head-on collisions of U+U, and the variance of the fragment masses is compared with the experimental data, showing significant improvement. The underlying reaction mechanisms and possible future studies are discussed.

    nucl-thnucl-exActa Phys.Polon.Supp.(2017)·8 citations
  8. 08

    Novel Role of Superfluidity in Low-Energy Nuclear Reactions

    Piotr Magierski · Kazuyuki Sekizawa · Gabriel Wlazłowski

    We demonstrate, within symmetry unrestricted time-dependent density functional theory, the existence of new effects in low-energy nuclear reactions which originate from superfluidity. The dynamics of the pairing field induces solitonic excitations in the colliding nuclear systems, leading to qualitative changes in the reaction dynamics. The solitonic excitation prevents collective energy dissipation and effectively suppresses fusion cross section. We demonstrate how the variations of the total kinetic energy of the fragments can be traced back to the energy stored in the superfluid junction of colliding nuclei. Both contact time and scattering angle in non-central collisions are significantly affected. The modification of the fusion cross section and possibilities for its experimental detection are discussed.

    nucl-thnucl-exPRL(2017)·79 citations

Affiliations

first authorsco-authorsvia INSPIRE