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Register a new userSingle heavy baryons with chiral partner structure in a three-flavor chiral model
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We construct an effective hadronic model including single heavy baryons (SHBs) belonging to the $(mathbf{3},mathbf{3})$ representation under $mbox{SU}(3)_L times mbox{SU}(3)_R$ symmetry, respecting the chiral symmetry and heavy-qaurk spin-flavor symmetry. When the chiral symmetry is spontaneously broken, the SHBs are divided into the baryons with negative parity of $bar{mathbf 3}$ representation under $mbox{SU}(3)$ flavor symmetry which is the chiral partners to the ones with positive parity of ${mathbf 6}$ representation. We determine the model parameters from the available experimental data for the masses and strong decay widths of $Sigma_c^{(ast)}$, $Lambda_c (2595)$, $Xi_c (2790)$, and $Xi_c (2815)$. Then, we predict the masses and strong decay widths of other baryons including $Xi_b$ with negative parity. We also study radiative decays of SHBs including $Omega_c^ast$ and $Omega_b^ast$ with positive parity.
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In $XQM$, a quark can emit Goldstone bosons. The flavor symmetry breaking in the Goldstone boson emission process is used to intepret the nucleon flavor-spin structure. In this paper, we study the inner structure of constituent quarks implied in $XQM
$ caused by the Goldstone boson emission process in nucleon. From a simplified model Hamiltonian derived from $XQM$, the intrinsic wave functions of constituent quarks are determined. Then the obtained transition probabilities of the emission of Goldstone boson from a quark can give a reasonable interpretation to the flavor symmetry breaking in nucleon flavor-spin structure.
The relevance of chiral symmetry in baryons is highlighted in three examples in the nucleon spectroscopy and structure. The first one is the importance of chiral dynamics in understanding the Roper resonance. The second one is the role of chiral symmetry in the lattice calculation of $pi N sigma$ term and strangeness. The third one is the role of chiral $U(1)$ anomaly in the anomalous Ward identity in evaluating the quark spin and the quark orbital angular momentum. Finally, the chiral effective theory for baryons is discussed.
The mass spectra of singly charmed and bottom baryons, $Lambda_{c/b}(1/2^pm,3/2^-)$ and $Xi_{c/b}(1/2^pm,3/2^-)$, are investigated using a nonrelativistic potential model with a heavy quark and a light diquark. The masses of the scalar and pseudoscalar diquarks are taken from a chiral effective theory. The effect of $U_A(1)$ anomaly induces an inverse hierarchy between the masses of strange and non-strange pseudoscalar diquarks, which leads to a similar inverse mass ordering in $rho$-mode excitations of singly heavy baryons.
We calculate the magnetic moments of heavy baryons with a single heavy quark in the bound-state approach. In this approach the heavy baryons is considered as a heavy meson bound in the field of a light baryon. The light baryon field is represented as a soliton excitation of the light pseudoscalar and vector meson fields. For these calculations we adopt a model that is both chirally invariant and consistent with the heavy quark spin symmetry. We gauge the model action with respect to photon field in order to extract the electromagnetic current operator and obtain the magnetic moments by computing pertinent matrix elements of this operator between the bound state wavefunctions. We compare our predictions for the magnetic moments with results of alternative approaches for the description of heavy baryon properties.
The chiral $SU(3)$ Lagrangian with charmed baryons of spin $J^P=1/2^+$ and $J^P=3/2^+$ is analyzed. We consider all counter terms that are relevant at next-to-next-to-next-to-leading order (N$^3$LO) in a chiral extrapolation of the charmed baryon masses. At N$^2$LO we find 16 low-energy parameters. There are 3 mass parameters for the anti-triplet and the two sextet baryons, 6 parameters describing the meson-baryon vertices and 7 symmetry breaking parameters. The heavy-quark spin symmetry predicts four sum rules for the meson-baryon vertices and degenerate masses for the two baryon sextet fields. Here a large-$N_c$ operator analysis at NLO suggests the relevance of one further spin-symmetry breaking parameter. Going from N$^2$LO to N$^3$LO adds 17 chiral symmetry breaking parameters and 24 symmetry preserving parameters. For the leading symmetry conserving two-body counter terms involving two baryon fields and two Goldstone boson fields we find 36 terms. While the heavy-quark spin symmetry leads to $36-16=20$ sum rules, an expansion in $1/N_c$ at next-to-leading order (NLO) generates $36-7= 29$ parameter relations. A combined expansion leaves 3 unknown parameters only. For the symmetry breaking counter terms we find 17 terms, for which there are $17-9=8$ sum rules from the heavy-quark spin symmetry and $17-5=12 $ sum rules from a $1/N_c$ expansion at NLO.
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