We have calculated the in-medium magnetic moments of octet baryons in the presence of hot and dense symmetric nuclear matter. Effective magnetic moments of baryons have been derived from medium modified quark masses within chiral SU(3) quark mean field model.
Further, for better insight of medium modification of baryonic magnetic moments, we have considered the explicit contributions from the valence quarks, sea quarks as well as sea orbital angular momentum of sea quarks. These effects have been successful in giving the description of baryonic magnetic moments in vacuum.
The magnetic moments of baryons are found to vary significantly as a function of density of nuclear medium.
We describe a constraint analysis for the interaction of the vector-meson octet with the baryon octet. Applying Dirac's Hamiltonian method, we verify that the standard interaction in terms of two independent SU(3) structures is consistent at the classical level. We argue how the requirement of self consistency with respect to perturbative renormalizability may lead to relations among the renormalized coupling constants of the system.
A complete and minimal relativistic Lagrangian is constructed at next-to-leading order for SU(3) chiral perturbation theory in the presence of baryon octet and baryon decuplet states. The Lagrangian has 13 terms for the pure decuplet sector, 6 terms for the transition sector from baryon octet to decuplet and (as already known from the literature) 16 terms for the pure octet sector. The minimal field content of 25 of these terms is meson-baryon four-point interactions. 3 terms give rise to the mass splitting for baryon octet and decuplet states, respectively. 2 terms give rise to overall mass s…
We study the interaction of vector mesons with the octet of stable baryons in the framework of the local hidden gauge formalism using a coupled channels unitary approach. We examine the scattering amplitudes and their poles, which can be associated to known J^P=1/2^-,3/2^- baryon resonances, in some cases, or give predictions in other ones. The formalism employed produces doublets of degenerate J^P=1/2^-,3/2^- states, a pattern which is observed experimentally in several cases. The findings of this work should also be useful to guide present experimental programs searching for new resonances, …
We analyze the constraint structure of the interaction of vector mesons with baryons using the classical Dirac constraint analysis. We show that the standard interaction in terms of two independent SU(3) structures is consistent at the classical level. We then require the self-consistency condition of the interacting system in terms of perturbative renormalizability to obtain relations for the renormalized coupling constants at the one-loop level. As a result we find a universal interaction with one coupling constant which is the same as in the massive Yang-Mills Lagrangian of the vector-meson…
The electromagnetic properties of baryon octet are studied in the perturbative chiral quark model (PCQM). The relativistic quark wave function is extracted by fitting the theoretical results of the proton charge form factor to experimental data and the predetermined quark wave function is applied to study the electromagnetic form factors of other octet baryons as well as magnetic moments, charge and magnetic radii. The PCQM results are found, based on the predetermined quark wave function, in good agreement with experimental data.
We present a study of axial charges of baryon ground and resonant states with relativistic constituent quark models. In particular, the axial charges of octet and decuplet $N$, $Σ$, $Ξ$, $Δ$, $Σ^*$, and $Ξ^*$ baryons are considered. The theoretical predictions are compared to existing experimental data and results from other approaches, notably from lattice quantum chromodynamics and chiral perturbation theory. The relevance of axial charges with regard to $π$-dressing and spontaneous chiral-symmetry breaking is discussed.
The self-energies of the full set of flavor SU(3) octet and decuplet baryons are computed within a relativistic chiral effective theory framework. The leading nonanalytic chiral behavior is derived for the octet and decuplet masses, and a finite-range regularization consistent with Lorentz and gauge invariance is applied to account for the finite size of the baryons. Using a four-dimensional dipole form factor, the relative importance of various meson-baryon loop contributions to the self-energies is studied numerically as a function of the dipole range parameter and meson mass, and comparison…
Medium modification of the magnetic moments of octet baryons in the isospin asymmetric nuclear medium at finite temperature has been calculated using medium modified quark and baryon masses derived in chiral SU(3) quark mean field model. The magnetic moments of baryons are found to vary significantly as a function of density of nuclear medium as well as with the increase in isospin asymmetry of the medium. The rise of temperature is found to decrease the effect of isospin asymmetry on masses and magnetic moments of baryons. The results of present investigation may be helpful to understand the …
Using SU(3) symmetry to constrain the pion BB' couplings, assuming SU(3) breaking comes only from one-loop pion cloud contributions, and using the the covariant spectator theory to describe the photon coupling to the quark core, we show how the experimental masses and magnetic moments of the baryon octet can be used to set a model independent constraint on the strength of the pion cloud contributions to the octet, and hence the nucleon, form factors at Q2=0.
The recently proposed $N^*(890)$ $1/2^-$ baryon is studied in a flavor $SU(3)$ scheme with $K$ matrix unitarization, by fitting to low energy cross section and phase shift data. It is found that $N^*(890)$ co-exists with low lying poles in other channels, which have been extensively discussed in the literature, though they belong to different octets, in the $SU(3)$ limit. Hence the existence of $N^*(890)$ is further verified.
The lightest baryon octet is studied within a covariant and confining Nambu--Jona-Lasinio model. By solving the relativistic Faddeev equations including scalar and axialvector diquarks, we determine the masses and axial charges for ΔS = 0 transitions. For the latter the degree of violation of SU(3) symmetry arising because of the strange spectator quark(s) is found to be up to 10%.
Partial decay widths of the nucleon resonances $S_{11}(1535)$, $S_{11}(1650)$, $D_{13}(1520)$ and $D_{13}(1700)$ to the pseudoscalar mesons and octet baryons are studied within a chiral constituent quark model. The effects of the configurations mixing between the states $|N^{2}_{8}P_{M}>$ and $|N^{4}_{8}P_{M}>$ are considered, taking into account the breakdown of the $SU(6)\otimes O(3)$ symmetry. In addition, possible contributions of the strangeness components in the $S_{11}$ resonances are investigated. Experimental data for the partial decay widths of the $S_{11}$ and $D_{13}$ resonances ar…
We explore the electromagnetic contribution to the charge symmetry breaking in the octet baryon masses using a subtracted dispersion relation based on the Cottingham formula. For the proton-neutron mass splitting we report a minor revision of the recent analysis of Walker-Loud, Carlson and Miller. For the electromagnetic structure of the hyperons we constrain our analysis, where possible, by a combination of lattice QCD and SU(3) symmetry breaking estimates. The results for the baryon mass splittings are found to be compatible with recent lattice QCD+QED determinations. The uncertainties in th…
The SU(3) octet states with baryon number B = 2, hexaquark dibaryons, are considered. Decay coupling constants sum rules for dibaryon octet into two ordinary baryon octets with ?$λ_8$ first order SU(3) symmetry breaking are given. An SU(4) extension of the analysis is commented upon. Possibilities for the experimental observation of multibaryon and anti-multibaryon states are pointed out.
Transverse densities describe the distribution of charge and current at fixed light-front time and provide a frame-independent spatial representation of hadrons as relativistic systems. We calculate the transverse densities of the octet baryons at peripheral distances b = O(M_pi^{-1}) in an approach combining chiral effective field theory (ChEFT) and dispersion analysis. The densities are represented as dispersive integrals of the imaginary parts of the baryon electromagnetic form factors in the timelike region (spectral functions). The spectral functions on the two-pion cut at t > 4 M_pi^2 ar…
We report on a recent study of finite-volume effects on the lowest-lying octet baryon masses using the covariant baryon chiral perturbation theory up to next-to-leading order by analysing the latest $n_f = 2 + 1$ lattice QCD results from the NPLQCD Collaboration.
Octet Baryons at Finite Temperature: QCD Sum Rules vs. Chiral Symmetry
在QCD求和规则的框架下研究了热π气体中八重态重子的相关子。出现在超导体OPE侧的凝聚体通过与热π介子的相互作用而变得依赖于T。我们提出了一个明确的证明，$O(T^2)$的凝聚体的依赖性是完全补偿的极残基和$π+ B \rightarrow B'$散射效应的光谱函数的变化。因此重子质量在这个数量级上是恒定的，尽管$\langle\bar{u}u\rangle_T\simeq\langle\bar{u}u\rangle_0(1-T^2/8f_π^2)$，这与Leutwyler和Smilga的手征对称性约束是一致的。
Magnetic properties of octet baryons are investigated within the framework of chiral perturbation theory. Utilizing a power counting for large magnetic fields, the Landau levels of charged mesons are treated exactly giving rise to baryon energies that depend non-analytically on the strength of the magnetic field. In the small-field limit, baryon magnetic moments and polarizabilities emerge from the calculated energies. We argue that the magnetic polarizabilities of hyperons provide a testing ground for potentially large contributions from decuplet pole diagrams. In external magnetic fields, su…
Using the QCD sum rules method, we estimate the mass and residues of the first radial excitations of octet baryons. The contributions coming from the ground state baryons are eliminated by constructing the linear combinations of the sum rules corresponding to different Lorentz structures. Our predictions of the masses of the first radial excitations of octet baryons are in good agreement with the data.
We study higher twist distribution amplitudes for the SU_F(3) baryon octet. We identify independent functions for all baryons in the isospin symmetry limit and calculate the Wandzura-Wilczek contributions to the twist-4 and 5 distributions amplitudes.
In light of the developments of the chiral constituent quark model ($χ$CQM) in studying low energy hadronic matrix elements of the ground-state baryons, we have extended this model to investigate their transition properties. The magnetic moments of transitions from the $J^P=\frac{3}{2}^+$ decuplet to $J^P=\frac{1}{2}^+$ octet baryons have been calculated with explicit valence quark spin, sea quark spin and sea quark orbital angular momentum contributions. Since the experimental data is available for only a few transitions, we have compared our results with the results of other available models…
在$e^+ e ^-$湮灭过程中，随着产生的强子质量的增加，八重态重子的产生截面有明显的抑制。我们提出了一个简单的参数化的碎裂函数到八重态重子的两个输入模型的指导下：SU（3）味对称性的一部分是由夸克-双夸克模型，重子质量抑制的一部分是由弦模型的启发。我们只需要八个自由参数来描述所有八重态重子的碎裂函数。这些自由参数是通过拟合$e^+ e ^-$湮灭过程中八重态重子产生的实验数据确定的。然后利用所得的碎裂函数预测了带电轻子DIS中八重态重子产生的截面，并与已有的实验数据进行了比较。此外，$pp$碰撞中的重子产生被认为是检验预测的质量抑制的理想领域。
The electromagnetic form factors of octet baryons are estimated within light cone QCD sum rules method, using the most general form of the interpolating current for baryons. A comparison of our predictions on the magnetic dipole and electric form factors with the results of other approaches is performed.
We study the radiative decay into $γ$ and a baryon of the SU(3) octet and decuplet of nine and ten resonances that are dynamically generated from the interaction of vector mesons with baryons of the octet and the decuplet respectively. We obtain quite different partial decay widths for the various resonances, and for different charge states of the same resonance, suggesting that the experimental investigation of these radiative decays should bring much information on the nature of these resonances. For the case of baryons of the octet we determine the helicity amplitudes and compare them with …
We extend a previous analysis of the lowest-lying octet baryon masses in covariant baryon chiral perturbation theory (ChPT) by explicitly taking into account the contribution of the virtual decuplet baryons. Up to next-to-next-to-next-to-leading order (N$^3$LO), the effects of these heavier degrees of freedom are systematically studied. Their effects on the light-quark mass dependence of the octet baryon masses are shown to be relatively small and can be absorbed by the available low-energy constants up to N$^3$LO. Nevertheless, a better description of the finite-volume corrections of the latt…
We report an analysis of the octet baryon masses using the covariant baryon chiral perturbation theory up to next-to-next-to-next-to-leading order with and without the virtual decuplet contributions. Particular attention is paid to the finite-volume corrections and the finite lattice spacing effects on the baryon masses. A reasonable description of all the publicly available $n_f=2+1$ lattice QCD data is achieved.Utilyzing the Feynman-Hellmann theorem, we determine the nucleon sigma terms as $σ_{πN}=55(1)(4)$ MeV and $σ_{sN}=27(27)(4)$ MeV.
Ground state $1/2^+$ octet baryon sum rules predicting a chain of inequalities for hadron photoproduction total cross-sections on corresponding baryons
We report on a recent study of the ground-state octet baryon masses using the covariant baryon chiral perturbation theory with the extended-on-mass-shell renormalization scheme up to next-to-next-to-next-to-leading order. By adjusting the available 19 low-energy constants, a good fit of the $n_f=2+1$ lattice quantum chromodynamics results from the PACS-CS, LHPC, HSC, QCDSF-UKQCD and NPLQCD collaborations is achieved.
We present a 2+1--flavor lattice QCD calculation of the electromagnetic Dirac and Pauli form factors of the octet baryons. The magnetic Sachs form factor is extrapolated at six fixed values of $Q^2$ to the physical pseudoscalar masses and infinite volume using a formulation based on heavy baryon chiral perturbation theory with finite-range regularization. We properly account for omitted disconnected quark contractions using a partially-quenched effective field theory formalism. The results compare well with the experimental form factors of the nucleon and the magnetic moments of the octet bary…
Dubnicka-Dubnickova-Kuraev (DDK) sum rules are considered. It is shown that integrals over differences of the total photoproduction cross-sections on octet baryons could be understood in terms of unitary symmetry approach. All the DDK sum rules for these quantities are expressed in terms of only three parameters.
By adopting the nonlinear realization of chiral symmetry, a holographic model for the baryon octet is proposed. The mass spectra of the baryon octet and their low-lying excited states are calculated, which show good consistency with experiments. The couplings of pion to nucleons are derived in two gauges and are shown to be equivalent with each other. It also shows that only derivative couplings of pion to nucleons appear in this holographic model. The coupling constant is then calculated.
The electromagnetic form factors of octet baryons are investigated with the nonlocal chiral effective theory. The nonlocal interaction generates both the regulator which makes the loop integral convergent and the $Q^2$ dependence of form factors at tree level. Both octet and decuplet intermediate states are included in the one loop calculation. The momentum dependence of baryon form factors are studied up to 1 GeV$^2$ with the same number of parameters as for the nucleon form factors. The obtained magnetic moments of all the baryon octets as well as the radii are in good agreement with the exp…
Sea quark contents of the octet baryons are investigated by employing an extended chiral constituent quark approach, which embodies higher Fock five-quark components in the baryons wave-functions. The well-known flavor asymmetry of the nucleon sea $\bar{d}-\bar{u}$, is used as input to predict the probabilities of $\bar{u}$, $\bar{d}$ and $\bar{s}$ in the nucleon, $Λ$, $Σ$ and $Ξ$ baryons, due to the intrinsic five-quark components in the baryons wave functions.
We report on a recent study of the ground-state octet baryon masses and sigma terms in covariant baryon chiral perturbation theory with the extended-on-mass-shell scheme up to next-to-next-to-next-to-leading order. To take into account lattice QCD artifacts, the finite-volume corrections and finite lattice spacing discretization effects are carefully examined. We performed a simultaneous fit of all the $n_f = 2+1$ lattice octet baryon masses and found that the various lattice simulations are consistent with each other. Although the finite lattice spacing discretization effects up to $\mathcal{…
Axial-vector transitions of decuplet to octet baryons are parametrized at low energies guided by a complete and minimal chiral Lagrangian up to next-to-leading order. It is pointed out that beyond the well-known leading-order term, there is only one contribution at next-to-leading order. This contribution is flavor symmetric. Therefore the corresponding low-energy constant can be determined in any strangeness sector. As functions of this low-energy constant, we calculate the decay widths and Dalitz distributions for the decays of decuplet baryons to octet baryons, pions, and photons and for th…
We have calculated the axial-vector form factors of the low lying octet baryons ($N$, $Σ$, $Ξ$ and $Λ$) in the chiral constituent quark model ($χ$CQM). In particular, we have studied the implications of chiral symmetry breaking and SU(3) symmetry breaking for the singlet ($g^0_{A}$) and non-singlet ($g^3_{A}$ and $g^8_{A}$) axial-vector coupling constants expressed as combinations of the spin polarizations at zero momentum transfer. The conventional dipole form of parametrization has been used to analyse the $Q^2$ dependence of the axial-vector form factors ($G^0_{A}(Q^2)$, $G^3_{A}(Q^2)$ and …
