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Nuclear Theory·nucl-th

Tuesday·January 7, 2020

9 papers—4 primary·5 cross-listed

All9Primary4Cross-lists5
  1. 01

    Proposals for the test of the isospin invariance in the pion-nucleon interaction at low energy

    Evangelos Matsinos · Günther Rasche

    This work elaborates on former remarks of ours regarding two sets of predictions for the observables of the charge-exchange reaction at low energy (pion laboratory kinetic energy MeV). The first prediction is obtained via the triangle identity from the results of fits to low-energy elastic-scattering data, whereas the second is based on the same analysis of the combined low-energy and charge-exchange databases. Assuming the integrity of the data used in our fits (i.e., the absence of significant systematic effects in the determination of the absolute normalisation of the datasets) and the insignificance of residual effects in the electromagnetic corrections, a significant difference between these two sets of predictions may be interpreted as departure from the isospin invariance in the low-energy interaction. We examine the sensitivity of the standard low-energy observables to the effect, and identify the kinematical regions which are promising for experimental survey. Accurate experiments under the suggested conditions will differentiate between the predictions, and thus provide an independent test of the isospin invariance in the low-energy interaction.

    nucl-thhep-ph0 citations
  2. 02

    Vorticity in low-energy heavy-ion collisions

    Xian-Gai Deng🇨🇳 · Xu-Guang Huang🇨🇳 · Yu-Gang Ma🇨🇳 · Song Zhang🇨🇳

    We study the kinematic and thermal vorticities in low-energy heavy-ion collisions by using the Ultra-relativistic Quantum Molecular Dynamics (UrQMD) model. We explore their time evolution and spatial distribution. We find that the initial vorticities have a non-monotonic dependence on the collision energy : as grows the vorticities first increase steeply and then decrease with the turning point around GeV depending on the centrality.

    nucl-thhep-phnucl-exPRC(2020)·103 citations
  3. 03

    Atomic nuclei from quantum Monte Carlo calculations with chiral EFT interactions

    Stefano Gandolfi🇺🇸 · Diego Lonardoni🇺🇸 · Alessandro Lovato🇺🇸 · Maria Piarulli🇺🇸

    Quantum Monte Carlo methods are powerful numerical tools to accurately solve the Schrödinger equation for nuclear systems, a necessary step to describe the structure and reactions of nuclei and nucleonic matter starting from realistic interactions and currents. These ab-initio methods have been used to accurately compute properties of light nuclei -- including their spectra, moments, and transitions -- and the equation of state of neutron and nuclear matter. In this work we review selected results obtained by combining quantum Monte Carlo methods and recent Hamiltonians constructed within chiral effective field theory.

    nucl-thFront.Phys.(2020)·83 citations
  5. 05

    Structure of collective modes in transitional and deformed nuclei

    M. A. Caprio🇺🇸

    The collective structure of atomic nuclei intermediate between spherical and quadrupole deformed structure presents challenges to theoretical understanding. However, models have recently been proposed in terms of potentials which are soft with respect to the quadrupole deformation variable beta. To test these models, information is needed on low-spin states of transitional nuclei. The present work involves measurement of electromagnetic decay properties of low-spin states for nuclei in the A=100 (gamma-soft) and N=90 (axially symmetric) transition regions. Population in beta-decay and thermal neutron capture are used, and measurements are carried out using gamma-ray coincidence spectroscopy, fast electronic scintillation timing, and gamma-ray induced Doppler broadening techniques, in experiments at Yale, TRIUMF ISAC, and the ILL. To facilitate interpretation of these nuclei, a new approach is developed that simplifies the application of the geometric collective model by use of scaling properties. Solutions are also obtained for the E(5) Hamiltonian for finite well depth.

    ↳ nucl-exnucl-th6 citations
  6. 06

    Theoretical and practical progresses in the HAL QCD method

    Sinya Aoki🇯🇵

    In this report, we discuss some theoretical and practical progresses in the HAL QCD potential method. We first clarify the issue of the derivative expansion for the non-local potential in the HAL QCD method. As the non-local potential in the original literature is not uniquely defined, we propose a procedure to define a non-local potential from NBS wave functions in terms of the derivative expansion. We then demonstrate how this definition works by using quantum mechanics with a separable potential. Secondly we discuss an issue of Hermiticity of the HAL QCD potential. Since the NBS wav functions are not orthogonal to each other in general, the HAL QCD potential is necessary to be non-Hermitian. We consider the next-to-leading order potential, which can be made Hermitian exactly by the change of variables. In general we can also make the higher order HAL QCD potential Hermitian order by order in the derivative expansion. An explicit example on how the procedure works is given for lattice QCD calculations. Finally we discuss how we can extract the HAL QCD potential from the NBS wave function in the boosted system. An explicit formula for this is derived.

    ↳ hep-latnucl-thPoS(2019)·5 citations
  7. 07

    Possible Formation of a Perfect Fluid in , -Pb, Xe-Xe and Pb-Pb Collisions at the Large Hadron Collider Energies: A Color String Percolation Approach

    Dushmanta Sahu🇮🇳 · Sushanta Tripathy🇮🇳 · Raghunath Sahoo🇮🇳 · Swatantra Kumar Tiwari🇮🇳

    Isothermal compressibility () is an important thermodynamic observable which gives information about the deviation of a system from perfect fluid behavior. In this work, for the first time we have estimated the isothermal compressibility of QCD matter formed in high energy hadronic and nuclear collisions using color string percolation model (CSPM), where we investigate the change in as a function of final state charged particle multiplicity and initial percolation temperature across various collision species. The estimated initial percolation temperature for different collision systems at different collision energies helps us to have a better understanding of the system at the initial phase of evolution. The comparison of the CSPM results for isothermal compressibility with that for the well known fluids, indicates that the matter formed in heavy-ion collisions might be the {\it closest perfect fluid} found in nature. This estimation complements the well-known observation of minimum shear viscosity to entropy density ratio for a possible QGP medium created in heavy-ion collision experiments. A threshold of pseudorapidity density of charged particles, in the final state event multiplicity is observed, after which one may look for a possible QGP formation at the LHC energies.

    ↳ hep-phhep-exnucl-exnucl-thEPJA(2022)·17 citations
  8. 08

    Applying Noether's theorem to matter in the Milky Way: evidence for external perturbations and non-steady-state effects from Gaia Data Release 2

    Susan Gardner🇺🇸 · Austin Hinkel🇺🇸 · Brian Yanny🇺🇸

    We apply Noether's theorem to observations of main-sequence stars from the Gaia Data Release 2 archive to probe the matter distribution function of the Galaxy. That is, we examine the axial symmetry of stars at vertical heights , kpc, to probe the quality of the angular momentum as an integral of motion. The failure of this symmetry test would speak to a Milky Way, in both its visible and dark matter, that is not isolated and/or not in steady state. The left-right symmetry-breaking pattern we have observed, north and south, reveals both effects, with a measured deviation from symmetry of typically 0.5%. We show that a prolate form of the gravitational distortion of the Milky Way by the Large Magellanic Cloud, determined from fits to the Orphan stream by Erkal et al., 2019, is compatible with the size and sign of the axial-symmetry-breaking effects we have discovered in our sample of up to 14.4 million main-sequence stars, speaking to a distortion of an emergent, rather than static, nature.

    ↳ astro-ph.GAhep-phnucl-thApJ(2020)·9 citations
  9. 09

    Stringy excited baryons in holographic QCD

    Yasuhiro Hayashi🇯🇵 · Takahiro Ogino🇯🇵 · Tadakatsu Sakai🇯🇵 · Shigeki Sugimoto🇯🇵

    We analyze excited baryon states using a holographic dual of QCD that is defined on the basis of an intersecting D4/D8-brane system. Studies of baryons in this model have been made by regarding them as a topological soliton of a gauge theory on a five-dimensional curved spacetime. However, this allows one to obtain only a certain class of baryons. We attempt to present a framework such that a whole set of excited baryons can be treated in a systematic way. This is achieved by employing the original idea of Witten, which states that a baryon is described by a system composed of open strings emanating from a baryon vertex. We argue that this system can be formulated by an ADHM-type matrix model of Hashimoto-Iizuka-Yi together with an infinite tower of the open string massive modes. Using this setup, we work out the spectra of excited baryons and compare them with the experimental data. In particular, we derive a formula of the nucleon Regge trajectory assuming that the excited nucleons lying the trajectory are characterized by the excitation of a single open string attached on the baryon vertex.

    ↳ hep-thhep-lathep-phnucl-thPTEP(2020)·6 citations

Affiliations

first authorsco-authorsvia INSPIRE