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Nuclear Theory·nucl-th

Thursday·June 4, 2015

10 papers—5 primary·5 cross-listed

All10Primary5Cross-lists5
  1. 01

    Dibaryons in a constituent quark model

    Woosung Park🇰🇷 · Aaron Park🇰🇷 · Su Houng Lee🇰🇷

    We investigate the properties of dibaryons containing u and d quarks in the constituent quark model. In constructing the ground state wave function, we choose the spatial part to be fully symmetric and the remaining color, isospin and spin part to be antisymmetric so as to satisfy the the Pauli principle. By adapting the IS coupling scheme that combine the isospin basis function with the spin basis function, and subsequently coupling this to the color singlet basis function, we construct the color isospin spin states compatible with the physical states of the dibaryon. By using the variational method, we then calculate the mass of the dibaryon in a nonrelativistic potential model, involving Coulomb, color confinement and color-spin hyperfine interaction. In particular, to asses the stability for different types of the confinement potential, we introduce one that is linearly proportional to the interquark distance and another to its square root. For all cases considered, we find that there are no compact bound states against the strong decay.

    nucl-thhep-phPRD(2015)·65 citations
  2. 02

    Comment on "Lattice determination of - mixing"

    Avraham Gal🇮🇱

    A recent lattice QCD (LQCD) calculation of - mixing by the QCDSF-UKQCD Collaboration [Phys. Rev. D 91, 074512 (2015)] finds a mixing angle about half of that found from the Dalitz-von Hippel (DvH) flavor SU(3) mass formula which relates the - mixing matrix element to known octet baryon mass differences and which has been used widely to evaluate charge symmetry breaking effects in hypernuclei. We show that the LQCD-calculated - mixing matrix element and octet baryon masses satisfy the DvH mass formula, concluding thereby that a good LQCD evaluation of - mixing requires an equally good reproduction of octet baryon mass differences which is yet to be demonstrated.

    nucl-thhep-lathep-phnucl-exPRD(2015)·13 citations
  3. 03

    A systematic study of longitudinal and transverse helicity amplidutes in the hypercentral Constituent Quark Model

    E. Santopinto🇮🇹 · M.M. Giannini🇮🇹

    We report in a systematic way the predictions of the non-relativistic hypercentral Constituent Quark model for the electromagnetic excitations of baryon resonances. The longitudinal and transverse helicity amplitudes are calculated with no free parameters for fourteen resonances, both for proton and neutron. The calculations lead to an overall fair description of data, specially in the medium range, where quark degrees of freedom are expected to dominate.

    nucl-thhep-phPRC(2012)·86 citations
  4. 04

    Cancellation of the sigma meson in thermal models

    Wojciech Broniowski🇵🇱 · Francesco Giacosa🇵🇱 · Viktor Begun🇵🇱

    The by now well-established scalar-isoscalar resonance (the meson) seems potentially relevant in the evaluation of thermodynamic quantities of a hadronic gas, since its mass is low. However, we recall that its contribution to isospin-averaged observables is, to a surprising accuracy, canceled by the repulsion from the pion-pion scalar-isotensor channel. As a result, in practice one should not incorporate in standard hadronic resonance-gas models for studies of isospin averaged quantities. In our analysis we use the formalism of the virial expansion, which allows one to calculate the thermal properties of an interacting hadron gas in terms of derivatives of the scattering phase shifts, hence in a model-independent way directly from experimentally accessible quantities. A similar cancellation mechanism occurs for the scalar kaonic interactions between the channel (containing the alleged or the meson) and the channel.

    nucl-thhep-phnucl-exPRC(2015)·85 citations
  5. 05

    Quantifying truncation errors in effective field theory

    R. J. Furnstahl🇺🇸 · N. Klco🇺🇸 · D. R. Phillips🇺🇸 · S. Wesolowski🇺🇸

    Bayesian procedures designed to quantify truncation errors in perturbative calculations of quantum chromodynamics observables are adapted to expansions in effective field theory (EFT). In the Bayesian approach, such truncation errors are derived from degree-of-belief (DOB) intervals for EFT predictions. Computation of these intervals requires specification of prior probability distributions ("priors") for the expansion coefficients. By encoding expectations about the naturalness of these coefficients, this framework provides a statistical interpretation of the standard EFT procedure where truncation errors are estimated using the order-by-order convergence of the expansion. It also permits exploration of the ways in which such error bars are, and are not, sensitive to assumptions about EFT-coefficient naturalness. We first demonstrate the calculation of Bayesian probability distributions for the EFT truncation error in some representative examples, and then focus on the application of chiral EFT to neutron-proton scattering. Epelbaum, Krebs, and Meißner recently articulated explicit rules for estimating truncation errors in such EFT calculations of few-nucleon-system properties. We find that their basic procedure emerges generically from one class of naturalness priors considered, and that all such priors result in consistent quantitative predictions for 68% DOB intervals. We then explore several methods by which the convergence properties of the EFT for a set of observables may be used to check the statistical consistency of the EFT expansion parameter.

    nucl-thhep-phnucl-exphysics.data-anPRC(2015)·319 citations

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first authorsco-authorsvia INSPIRE