Calculation of baryon spectra based on an improved quark potential
TL;DR: In this article, an improved QCD-inspired quark potential is introduced and employed to calculate baryon spectra, which has some novel features: (i) the one-gluon exchange potential in it is derived from the exact three-dimensional relativistic equation and contains a retardation term which is logarithmic; (ii) the confining part of the potential is generated from a linear potential Bethe-Salpeter (BS) kernel and a general Lorentz structure of the confinement and includes therefore various spindependent terms added to the linear potential
Abstract: An improved QCD-inspired quark potential is introduced and employed to calculate baryon spectra. This potential has some novel features: (i) the one-gluon exchange potential in it is derived from the exact three-dimensional relativistic equation and contains a retardation term which is logarithmic; (ii) the confining part of the potential is generated from a linear potential Bethe-Salpeter (BS) kernel and a general Lorentz structure of the confinement and includes therefore various spin-dependent terms added to the linear potential; (iii) the off-shell correction part of the potential which is related to the negative energy component of the BS amplitude automatically gives rise to a harmonic oscillator term. We analyse the contributions of all parts of the potential to the baryon spectrum and find that the potential we use makes some improvements to theoretical baryon masses, especially for the Roper resonance.
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TL;DR: In this paper, the application of non-relativistic constituent quark models to study one, two and three non-strange baryon systems was reviewed, and the binding energies of three NN*(1440) systems were analyzed.
Abstract: We review the application of non-relativistic constituent quark models to study one, two and three non-strange baryon systems. We present results for the baryon spectra, potentials and observables of the nucleon?nucleon (NN), N?, ?? and NN*(1440) systems, and binding energies of three non-strange baryon systems. We emphasize the observable effects related to quark antisymmetry and its interplay with quark dynamics.
169 citations
TL;DR: In this article, the electromagnetic transitions of the Roper N (1440) resonance were studied and it was shown that within a non-relativistic constituent quark model scheme, a comprehensible understanding of Roper phenomenology can be achieved.
47 citations
TL;DR: In this paper, a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer (Q(2)=0.27-1.3 (GeV/c)(2) and final hadronic state mass in the nucleon resonance region (W=1.08-2.0 GeV).
Abstract: We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer [Q(2)=0.27-1.3 (GeV/c)(2)] and final hadronic state mass in the nucleon resonance region (W=1.08-2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target ((ND3)-N-15) and detected the scattered electrons with the CEBAF large acceptance spectrometer. From our data, we extract the longitudinal double spin asymmetry A(parallel toparallel to) and the spin structure function g(1)(d). Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function g(1)(d) and study its approach to both the deep inelastic limit at large Q(2) and to the Gerasimov-Drell-Hearn sum rule at the real photon limit (Q(2)-->0). We find that the first moment varies rapidly in the Q(2) range of our experiment and crosses zero at Q(2) between 0.5 and 0.8 (GeV/c)(2), indicating the importance of the Delta resonance at these momentum transfers.
13 citations
TL;DR: In this paper, the spectra of heavy quark effective theory and the radii of several baryons have also been estimated based on the statistical model as an input to calculate the lifetime τ of Λc+ and Λb0.
Abstract: Based on heavy quark effective theory, in conjunction with the statistical model as an input, the spectra of heavy flavor baryons (Qqq) have been studied along with the radii of several baryons which have also been estimated. The relation of the size parameter (ro) of the baryons with their corresponding masses (M) has also been explored. Our estimates of ro, the radii of Λc+ and Λb0 when used as inputs to compute the lifetime τ of Λc+, and the branching fraction ΓSL/Γ of Λb0(Λb0 → Λc+ ν) exhibit an exact agreement with the corresponding experimental findings.
6 citations
TL;DR: In this paper, it is shown that the potential model constructed by the one-gluon exchange interaction plus the scalar linear potential cannot explain the splittings of P states of heavy quarkonium in this note.
Abstract: It is shown that the potential model constructed by the one-gluon exchange interaction plus the scalar linear potential cannot well explain the splittings of P states of heavy quarkonium in this note. However, if the model is modified by the hypothesis that the Lorentz structure of confinement is expressed by a combination of five independent Lorentz invariants, such as scalar, pseudoscalar, vector, axial-vector and tensor-type couplings, we find that the model is able to reproduce almost all the features of the P-state splittings for the cc system.
2 citations
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TL;DR: In this article, the relativistic $S$-matrix formalism of Feynman is applied to the bound-state problem for two interacting Fermi-Dirac particles.
Abstract: The relativistic $S$-matrix formalism of Feynman is applied to the bound-state problem for two interacting Fermi-Dirac particles. The bound state is described by a wave function depending on separate times for each of the two particles. Two alternative integral equations for this wave function are derived with kernels in the form of an expansion in powers of ${g}^{2}$, the dimensionless coupling constant for the interaction. Each term in these expansions gives Lorentz-invariant equations. The validity and physical significance of these equations is discussed. In extreme nonrelativistic approximation and to lowest order in ${g}^{2}$ they reduce to the appropriate Schr\"odinger equation.One of these integral equations is applied to the deuteron ground state using scalar mesons of mass $\ensuremath{\mu}$ with scalar coupling. For neutral mesons the Lorentz-invariant interaction is transformed into the sum of the instantaneous Yukawa interaction and a retarded correction term. The value obtained for ${g}^{2}$ differs only by a fraction proportional to ${(\frac{\ensuremath{\mu}}{M})}^{2}$ from that obtained by using a phenomenological Yukawa potential. For a purely charged meson theory a correction term is obtained by a direct solution of the relativistic integral equation using only the first term in the expansion of the kernel. This correction is due to the fact that a nucleon can emit, or absorb, positive and negative mesons only alternately. The constant ${g}^{2}$ is increased by a fraction of $1.1(\frac{\ensuremath{\mu}}{M})$ or 15 percent.
1,962 citations
TL;DR: In this article, the spectrum and mixing angles of negative-parity baryons in a quark-model framework inspired by quantum chromodynamics were discussed, and good agreement with experiment in the $S = 0$ and $S=\ensuremath{-}1$ sectors were obtained.
Abstract: We discuss the spectrum and mixing angles of negative-parity baryons in a quark-model framework inspired by quantum chromodynamics. We take into account in zero order the removal of the degeneracy between the two $P$-wave states of the three-quark system in the $S=\ensuremath{-}1$ sector, as well as the hyperfine interaction between quarks, but neglect spin-orbit coupling. We find good agreement with experiment in the $S=0$ and $S=\ensuremath{-}1$ sectors where there are data and predict the $S=\ensuremath{-}2, \ensuremath{-}3$ sectors.
722 citations
TL;DR: The theory of the Bethe-Salpeter equation is reviewed extensively in this paper, with the main effort devoted to describing systematically the theoretical results rather than numerical calculations and applications of the BSE.
Abstract: The theory of the Bethe-Salpeter equation is reviewed extensively. The main effort is devoted to describing systematically the theoretical results rather than numerical calculations and applications of the Bethe-Salpeter equation. An almost complete bibliography of the Bethe-Salpeter equation also is presented.
388 citations
TL;DR: In this article, the effect of atomic ordering on the superconducting transition temperature of the Nb-Nb-15$ compound was studied and the Bragg-Williams long-range order parameter was determined by least-squares analysis of neutron-diffraction data from powdered samples both before and after irradiation.
Abstract: We have utilized the technique of neutron-induced disorder to study the effect of atomic ordering on the superconducting transition temperature ${T}_{c}$ of the $A\ensuremath{-}15$ compound ${\mathrm{Nb}}_{3}$Al. Large depressions in ${T}_{c}$ are observed when ${\mathrm{Nb}}_{3}$Al is irradiated with high-energy neutrons ($Eg1$ MeV) at 140 \ifmmode^\circ\else\textdegree\fi{}C. For samples whose value of ${T}_{c}$ before irradiation was 18.7 K no superconductivity was oberved to 1.4 K after irradiation to a fluence of $1.4\ifmmode\times\else\texttimes\fi{}{10}^{19} \frac{n}{{\mathrm{cm}}^{2}}$. The widths of the transition temperatures remain constant as ${T}_{c}$ is depressed and ${T}_{c}$ is recovered by annealing at 750 \ifmmode^\circ\else\textdegree\fi{}C after irradiation. The Bragg-Williams long-range-order parameter $S$ was determined by least-squares analysis of neutron-diffraction data from powdered samples both before and after irradiation. A reduction in $S$ of 18% is observed for samples irradiated to a fluence of $1.2\ifmmode\times\else\texttimes\fi{}{10}^{19} \frac{n}{{\mathrm{cm}}^{2}}$. For the same fluence ${T}_{c}$ is depressed to 52% of its value before irradiation. The lattice parameter ${a}_{0}$ of the $A\ensuremath{-}15$ phase expands upon irradiation, increasing from 5.183 \AA{} for unirradiated samples to 5.200 \AA{} for samples irradiated to $5.0\ifmmode\times\else\texttimes\fi{}{10}^{19} \frac{n}{{\mathrm{cm}}^{2}}$. The results are discussed in terms of $A$-site occuptation in the ${A}_{3}B A\ensuremath{-}15$ structure and extrapolations of ${T}_{c}$ for complete order are considered.
213 citations
TL;DR: In this paper, the phase transition behavior of isostructural lanthanide orthoaluminates and pentaphosphates has been investigated in the presence of specific heat and their associated entropies.
Abstract: From the specific-heat (${\mathit{C}}_{\mathit{p}}$) measurements on the isostructural ${\mathrm{NH}}_{4}$L(${\mathrm{SO}}_{4}$${)}_{2}$\ensuremath{\cdot}${4\mathrm{H}}_{2}$O (L=La, Ce, Pr, Nd, Sm, Eu, Gd, and Tb) Tb) crystals at 100 K T300 K, it is shown that these crystals undergo two structural phase transitions, ${\mathit{T}}_{1}$ and ${\mathit{T}}_{2}$, in the aforesaid temperature range. The observed shapes of the anomalies in the specific heat and their associated entropies are such that ${\mathrm{NH}}_{4}$La(${\mathrm{SO}}_{4}$${)}_{2}$\ensuremath{\cdot}${4\mathrm{H}}_{2}$O crystals have a low-temperature phase-transition behavior that is different from that observed in ${\mathrm{NH}}_{4}$L(${\mathrm{SO}}_{4}$${)}_{2}$\ensuremath{\cdot}${4\mathrm{H}}_{2}$O (L=Ce, Pr, Nd, Sm, Eu, Gd, and Tb). Also, our room-temperature infrared results and unit-cell parameters of ${\mathrm{NH}}_{4}$Dy(${\mathrm{SO}}_{4}$${)}_{2}$\ensuremath{\cdot}${4\mathrm{H}}_{2}$O crystals indicate that the lattice is isostructural with the rest of the series but no transitions occur at 100 K T300 K. Unlike other isostructural lanthanide series, the phase-transition temperatures for ${\mathrm{NH}}_{4}$L(${\mathrm{SO}}_{4}$${)}_{2}$\ensuremath{\cdot}${4\mathrm{H}}_{2}$O show no straightforward correlation either with the unit-cell parameters or with the host-lanthanide-ion's ionic radius. Further, the lattice-stability model, which successfully maps the trend of phase-transition temperatures for isostructural lanthanide orthoaluminates or pentaphosphates, is inadequate for predicting the observed behavior of ${\mathrm{NH}}_{4}$L(${\mathrm{SO}}_{4}$${)}_{2}$\ensuremath{\cdot}${4\mathrm{H}}_{2}$O lattices.
144 citations