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Nuclear Theory·nucl-th

Tuesday·February 12, 2019

11 papers—7 primary·4 cross-listed

All11Primary7Cross-lists4
  1. 01

    [Submitted on 8 Feb 2019]

    Including off-diagonal anisotropies in anisotropic hydrodynamics

    Mohammad Nopoush🇺🇸 · Michael Strickland🇺🇸

    In this paper we present a method for efficiently including the effects of off-diagonal local rest frame momentum anisotropies in leading-order anisotropic hydrodynamics. The method relies on diagonalization of the space-like block of the anisotropy tensor and allows one to reduce the necessary moments of the distribution function in the off-diagonal case to a linear combination of diagonal-anisotropy integrals. Once reduced to diagonal-anisotropy integrals, the results can be computed efficiently using techniques described previously in the literature. We present a general framework for how to accomplish this and provide examples for off-diagonal anisotropy moments entering into the energy-momentum tensor and viscous update equations which emerge when performing anisotropic pressure matching.

    Comments:
    17 pages; v3 - improvement made to discussion
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Phenomenology (hep-ph)
    arXiv:
    1902.03303 [pdf]
    PRC(2019)·16 citations
  2. 02

    [Submitted on 8 Feb 2019]

    Similarity renormalization group evolution of hypernuclear Hamiltonians

    Roland Wirth · Robert Roth

    Unitary transformations of a Hamiltonian generally induce interaction terms beyond the particle rank present in the untransformed Hamiltonian that have to be captured and included in a many-body calculation. In systems with strangeness such as hypernuclei, the three-body terms induced by the hyperon-nucleon interaction are strong, so their inclusion is crucial. We present in detail a procedure for computing hyperon-nucleon-nucleon interaction terms that are induced during a similarity renormalization group (SRG) flow. The SRG is carried out in a basis spanned by antisymmetric harmonic-oscillator states with respect to three-body Jacobi coordinates. We discuss basis construction, antisymmetrization, numerical evaluation of the flow equations, and separation of the genuine three-body terms. We then use the hypernuclear no-core shell model with SRG-evolved Hamiltonians, addressing the sensitivity of hypernuclear states and hyperon separation energies to changes in the nucleonic Hamiltonian by example of Li, Be, B, C, and the hyper-helium chain. We also present a survey of the hyper-hydrogen chain, exploring the structure of hypernuclei with extreme neutron-proton asymmetries.

    Comments:
    13 pages, 6 figures; accepted version
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1902.03324 [pdf]
    PRC(2019)·27 citations
  3. 03

    [Submitted on 9 Feb 2019]

    Relativistic second order dissipative hydrodynamics from effective fugacity quasi particle model

    Sukanya Mitra🇺🇸

    In this work a second order relativistic viscous hydrodynamic model has been presented based on the effective fugacity quasi-particle model (EQPM). The hydro model has been derived from the effective relativistic second-order transport equation under EQPM for a multi-particle (two component) system and solving it in Grad's 14 moment method. The EQPM model describes the strongly interacting thermal system of QCD interactions through its fugacity parameters extracted from an updated lattice equations of state. The proper time evolution of temperature and pressure anisotropy is observed to be affected significantly due to the inclusion of EQPM model compared to an ideal system.

    Comments:
    Accepted in Physical Review D
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1902.03343 [pdf]
    PRD(2019)·7 citations
  4. 04

    [Submitted on 9 Feb 2019]

    Normalized multi-pion Hanbury Brown and Twiss correlation functions of pion-emitting sources with Bose-Einstein condensation

    Ghulam Bary🇨🇳 · Peng Ru🇨🇳 · Wei-Ning Zhang🇨🇳

    Recently, the ALICE collaboration analyzed the three- and four-pion Hanbury Brown-Twiss (HBT) correlations in Pb-Pb collisions at the Large Hadron Collider (LHC). The measured suppressions of three- and four-pion correlations may originate from a substantial coherence of the particle-emitting sources. In this work we investigate the normalized three- and four-pion HBT correlation functions for evolving pion gas (EPG) sources with Bose-Einstein condensation. We find that the intercepts of the normalized correlation functions at zero relative momentum are sensitive to source condensation and particle momentum. The normalized correlation functions in low average-momentum regions of three and four pions decrease with decreasing temperature and increasing particle number of the source, indicating a dependence of the normalized correlation functions on source condensation. However, this dependence becomes weak in an intermediate average-momentum region because particles with high momenta are likely emitted from excited states incoherently in the EPG model, even if the source has a considerable condensation fraction. For a wide momentum range, the normalized correlation functions for low source temperatures are enhanced at larger relative momenta because of a rapid increase of two-pion chaoticity parameter with increasing particle momentum. We hope the significant enhancement of the normalized four-pion correlation function at high relative momentum will be identified through future analyses of experimental data.

    Comments:
    18 pages, 7 figures
    Subjects:
    Nuclear Theory (nucl-th)
    arXiv:
    1902.03434 [pdf]
    J.Phys.G(2019)·10 citations
  5. 05

    [Submitted on 10 Feb 2019]

    Nuclear Physics without High-Momentum Potentials: Constructing the Nuclear Effective Interaction Directly from Scattering Observables

    K. S. McElvain🇺🇸 · W. C. Haxton🇺🇸

    The traditional approach to nuclear physics encodes phase shift information in a nucleon-nucleon (NN) potential, producing a nucleon-level interaction that captures the sub-GeV consequences of QCD. A further reduction to the nuclear scale is needed to produce an effective interaction for soft Hilbert spaces, such as those employed in the shell model. Here we describe an alternative construction of this effective interaction, from QCD directly to the nuclear scale, that is direct and precise. This eliminates the need for constructing and renormalizing the high-momentum NN potential. Instead, continuum phase shifts and mixing angles are used directly at the nuclear scale. The method exploits the analytic continuity in energy of HOBET (Harmonic-Oscillator-Based Effective Theory) to connect bound states to continuum solutions at specific energies. The procedure is systematic, cutoff independent, and convergent, yielding keV accuracy at NNLO or NLO, depending on the channel. Lepage plots are provided.

    Comments:
    9 pages
    Subjects:
    Nuclear Theory (nucl-th); High Energy Physics — Lattice (hep-lat)
    arXiv:
    1902.03543 [pdf]
    PLB(2019)·8 citations
  6. 06

    [Submitted on 10 Feb 2019]

    The analysing powers in proton-deuteron elastic scattering

    Yu.Uzikov🇷🇺 · C.Wilkin🇬🇧

    It is shown that the ratio of the deuteron and proton analysing powers in proton-deuteron elastic scattering at small angles is sensitive to subtle effects in a theoretical description. These include the transverse spin-spin term in the elementary nucleon-nucleon amplitudes and double-scattering corrections. On the other hand there is far less sensitivity to the spin-orbit amplitude and to binding or other kinematic effects associated with the use of the deuteron, as either target or projectile. The available data are in agreement with the results of a refined Glauber theory model.

    Comments:
    3 pages with 2 figures
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1902.03596 [pdf]
    PLB(2019)·3 citations
  7. 07

    [Submitted on 11 Feb 2019]

    Core-excitation effects in three-body breakup reactions studied using the Faddeev formalism

    A. Deltuva

    Previous studies of reactions in three-body (proton, neutron, nuclear core) systems revealed a nontrivial effect of the core excitation: the transfer cross section cannot be factorized into the spectroscopic factor and the single-particle cross section obtained neglecting the core excitation. This observable, up to a kinematic factor, is the angular distribution of the core nucleus in the reaction. The study of the core excitation effect for the most closely related observable in the three-body breakup, i.e., the core angular distribution, is aimed in the present work. Breakup of the one-neutron halo nucleus in the collision with the proton is described using three-body Faddeev-type equations extended to include the excitation of the nuclear core. The integral equations for transition operators are solved in the momentum-space partial-wave representation. Breakup of 11Be nucleus as well as of model -wave nuclei is studied at beam energies of 30, 60, and 200 MeV per nucleon. Angular and momentum distributions for the 10Be core in ground and excited states is calculated. In sharp contrast to reactions, the differential cross section in most cases factorizes quite well into the spectroscopic factor and the single-particle cross section. Due to different reaction mechanisms the core excitation effect in the breakup is very different from transfer reactions. A commonly accepted approach to evaluate the cross section, i.e., the rescaling of single-particle model results by the corresponding spectroscopic factor, appears to be reliable for breakup though it fails in general for transfer reactions.

    Comments:
    6 pages, 5 figures, to be published in Phys. Rev. C
    Subjects:
    Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
    arXiv:
    1902.03872 [pdf]
    PRC(2019)·9 citations

Affiliations

first authorsco-authorsvia INSPIRE