We investigate chiral properties of local (non-derivative) fields of baryons consisting of three quarks with flavor SU(3) symmetry. We construct explicitly independent local three-quark fields belonging to definite Lorentz and flavor representations. Chiral symmetry is spontaneously broken and therefore the baryon fields can have different chiral representations. It turns out that the allowed chiral representations are strongly correlated with the Lorentz group representations due to the color and spatial structure of the local three-quark fields. We discuss some implications of the allowed chiral symmetry representations on phenomenological Lagrangians with chiral U(3)_L \otimes U(3)_R symmetry.
In this talk, we give a short review of our recent works on studying the singly heavy baryon, doubly heavy baryon, and triply heavy baryon spectra from QCD sum rules.
For a large set of flavor symmetries, the lowest-dimensional baryon- or lepton-number violating operators in the Standard Model effective field theory (SMEFT) with flavor symmetry are of mass dimension 9. As a consequence, baryon- and lepton-number violating processes are further suppressed with the introduction of flavor symmetries, e.g., the allowed scale associated with proton decay is typically lowered to $10^5$ GeV, which is significantly lower than the GUT scale. To illustrate these features, we discuss Minimal Flavor Violation for the Standard Model augmented by sterile neutrinos.
In this paper we study lepton flavor violating semileptonic decays of heavy baryons in a framework of a model with large extra dimensions and a single generation . Resulting branching ratios for these decays mediated by Kaluza-Klein modes of photon and Z-boson are presented in a model-independent form.
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.
This is a contribution to the review "50 Years of Quantum Chromdynamics" edited by F. Gross and E. Klempt [arXiv:2212.11107], to be published in EPJC. The contribution reviews the properties of baryons with one heavy flavor: the lifetimes of ground states and the spectrum of excited states. The importance of symmetries to understand the excitation spectrum is underlined. An overview of searches for pentaquarks is given.
We investigate the gravitational form factors of the baryon octet within the framework of the SU(3) chiral quark-soliton model, considering the effects of flavor SU(3) symmetry breaking, and the corresponding energy-momentum tensor distributions. We examine the effects of flavor SU(3) symmetry breaking to the mass, angular momentum, pressure, and shear force distributions of the baryon octet. We first find that a heavier baryon is energetically more compact than a lighter one. For the spin distributions of the baryon octet, they are properly normalized to their spins and are decomposed into th…
We consider charmless weak decays of beauty-baryons into decuplet baryons and pseudoscalar mesons in a general framework based on $SU(3)$-flavor decomposition of the decay amplitudes. The dynamical assumption independent $SU(3)$ analysis accounts for the effects of an arbitrarily broken $SU(3)$ symmetry in these decays. An alternative approach in terms of quark diagrams is also provided and compared with the $SU(3)$ decomposition in the limit of exact $SU(3)$-flavor symmetry. Furthermore, the symmetries of the effective Hamiltonian is used to relate or neglect reduced $SU(3)$ amplitudes to der…
The quantum group $SU_q(3)=U_q(su(3))$ is taken as a baryon flavor symmetry. Accounting for electromagnetic contributions to baryons masses to zeroth order, new charge specific $q$-deformed octet and decuplet baryon mass formulas are obtained. These new mass relations have errors of only 0.02\% and 0.08\% respectively; a factor of 20 reduction compared to the standard Gell-Mann-Okubo mass formulas. A new relation between the octet and decuplet baryon masses that is accurate to 1.2\% is derived. An explicit formula for the Cabibbo angle, taken to be $\fracπ{14}$, in terms of the deformation par…
The quark flavor distribution functions of the octet baryons ($N$, $Σ$, $Ξ$ and $Λ$) have been calculated in the chiral constituent quark model ($χ$CQM). In particular, the valence and sea quark flavor distribution functions of the scalar density matrix elements of octet baryons have been computed explicitly. The implications of chiral symmetry breaking and SU(3) symmetry breaking have been discussed in detail for the sea quark asymmetries, fraction of a particular quark (antiquark) present in a baryon, flavor structure functions and the Gottfried integral. The meson-baryon sigma terms $σ_{πB}…
The magnetic and transition magnetic moments of the ground-state baryons are computed in heavy baryon chiral perturbation theory in the large-$N_c$ limit, where N_c is the number of colors. SU(3) symmetry breaking is systematically studied twofold: On the one hand, one-loop nonanalytic corrections of orders m_q^{1/2} and m_q ln m_q are included, with contributions of baryon intermediate states from both flavor octet and flavor decuplet multiplets, assuming degeneracy between baryon states within a given flavor multiplet but nondegeneracy between baryons of different multiplets. On the other ha…
We study the spectrum of light flavor baryons in a quark-model framework by taking into account the order $\mathrm{O}(α_s^2)$ hyperfine interactions due to two-gluon exchange between quarks. The calculated spectrum agree better with the experimental data than the results from hyperfine interactions with only one-gluon exchange. It is also shown that two-gluon exchange hyperfine interactions bring a significantly improved correction to the Gell-Mann--Okubo mass formula. Two-gluon exchange corrections on baryon excitations (including negative parity baryons) are also briefly discussed.
High order cumulants of the baryon number distribution are calculated in a 2+1 flavor low energy effective model. Quantum fluctuations are encoded through the functional renormalization group approach. The chiral and deconfinement phase transitions are investigated at finite temperature and baryon chemical potential. The equation of state for the QCD matter, fluctuations of the baryon number and the strangeness up to sixth order are calculated, and one finds the results are consistent with those from lattice QCD.
Baryon number fluctuations are believed to be good signatures of the QCD phase transition and its CP. Since the fluctuations are proportional to the various order baryon-number susceptibilities and the quark-number density is related to the dressed quark propagator, then by the two flavor NJL model we can calculate the moments of the up and down quarks. By comparing the two flavor NJL model results with the experimental data of $Sσ$ and $κσ^2$ for the net-proton distributions of Au+Au collisions by STAR, we found that the NJL results fit the experiments better at large collision energies and s…
The baryon axial vector current is computed at one-loop order in large-N_c baryon chiral perturbation theory, where N_c is the number of colors. Loop graphs with octet and decuplet intermediate states are systematically incorporated into the analysis and the effects of the decuplet-octet mass difference and SU(3) flavor symmetry breaking are accounted for. As expected, large-N_c cancellations between different one-loop graphs are observed as a consequence of the large-N_c spin-flavor symmetry of QCD baryons. Fitting our analytical formulas against experimental data on baryon semileptonic decay…
The Chiral String-Soliton Model is a joining of the two notions about the light chiral baryons: the chiral soliton models (like the Skyrme model) and the Quark-Gluon String models. The ChSS model is based on the Effective Chiral Lagrangian which was proposed in [arXiv:hep-ph/0306216]. We have studied the physical properties of the light chiral baryon within the framework of this ChSS model.
Baryon triality (B3) is a Z3 discrete symmetry that can protect the proton from decay. Although its realization does not require supersymmetry, it is particularly appealing in the supersymmetry as an alternative to the popular R-parity. We discuss the issues in gauging B3, and present the minimal supersymmetric model with B3 as the remnant discrete symmetry of a TeV scale U(1) gauge symmetry. A flavor-dependent U(1) charge is necessary to achieve this, and it results in very distinguishable and flavorful predictions for the LHC experiments. We find a complementarity between a 2-lepton sneutrin…
We study baryon resonances with heavy flavor in a molecular approach, thus as dynamically generated by baryon-meson scattering. This is accomplished by using a unitary coupled-channel model taking, as bare interaction, the extension of the Weinberg-Tomozawa SU(3) Lagrangian. A special attention is payed to the inclusion of heavy-quark spin symmetry and to the study of the generated baryon resonances that complete the heavy-quark spin multiplets. Our model reproduces the Λ_b(5912) and Λ_b(5920) baryons, which were recently observed by the LHCb collaboration. According to our analysis, these two…
In this article, we study the masses and pole residues of the ${1\over 2}^\pm$ flavor antitriplet heavy baryon states ($Λ_c^+$, $Ξ_c^+,Ξ_c^0)$ and ($Λ_b^0$, $Ξ_b^0,Ξ_b^-)$ by subtracting the contributions from the corresponding ${1\over 2}^\mp$ heavy baryon states with the QCD sum rules, and observe the masses are in good agreement with the experimental data and make reasonable predictions for the unobserved ${1\over 2}^-$ bottom baryon states. Once reasonable values of the pole residues $λ_Λ$ and $λ_Ξ$ are obtained, we can take them as basic parameters to study the revelent hadronic processes…
We study the phase diagram of a chiral random matrix model with three quark flavors at finite temperature and chemical potential, taking the chiral and diquark condensates as independent order parameters. Fixing the ratio of the coupling strengths in the quark-antiquark and quark-quark channels applying the Fierz transformation, we find that the color-flavor locked (CFL) phase is realized at large chemical potential, while the ordinary chirally-broken phase appears in the region with small chemical potential. We investigate responses of the phases by changing small quark masses in the cases wi…
We present an effective model, which is an extension of the usual linear sigma model, that contains a low energy multiplet for every hadronic particle type. These multiplets are a scalar nonet, a pseudoscalar nonet, a vector nonet, an axialvector nonet, a baryon octet and a baryon decuplet. Tree level baryon masses and possible two body decuplet decays are calculated. The baryon masses are generated through spontaneous symmetry breaking. The calculated quantities are used to determine the model parameters through a multiparametric minimalization process, which compares the calculated physical …
In this paper, to be closer to the realities of the relativistic heavy ion collisions than the thermal equilibrium assumption often used in the calculations of baryon number susceptibilities, the creatures of the collisions are treated as isotropic systems with temperature gradient. In addition, the quarks are thought as the quasi-particles with thermal masses. By doing these and according to Boltzmann transport equation, we get our results of the experimental observables $Sσ$ and $κσ^2$. We found that the results show a gap in value and a centrality dependence, which might indicate the relati…
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 experimen…
This paper studies the leading chiral corrections to heavy quark-diquark symmetry predictions for doubly heavy baryon semileptonic decay form factors. We derive the coupling between heavy diquarks and weak current in the limit of heavy quark-diquark symmetry, and construct the chiral Lagrangian for doubly heavy baryons coupled to weak current. We evaluate chiral corrections to doubly heavy baryon zero-recoil semileptonic decay for both unquenched and partially quenched QCD. This theory is used to derive chiral extrapolation expressions for measurements of form factors of doubly heavy baryon ze…
The anomalous dimension of spin-1/2 baryon operators in QCD is derived at leading 1/Nf order using the minimal subtraction scheme. A residual ambiguity, originating from the presence of evanescent operators in dimensional regularization, is parametrized by a function of the renormalized coupling. Our result is shown to agree with previous 2 and 3 loop calculations performed in two different renormalization schemes.
Flavor-Dependent Dynamical Spin-Orbit Coupling in Light-Front Holographic QCD: A New Approach to Baryon Spectroscopy
Department of Physics and Astronomy, University of California, Los Angeles（加州大学洛杉矶分校物理与天文学系）；Department of Physics and Astronomy University of California Los Angeles（加州大学洛杉矶分校物理与天文学系）
We have investigated the axial charges of the ground octet baryons within the extended chiral constituent quark model, where all the possible compact five-quark Fock components $qqq(q\bar{q}) (q=u, d, s)$ in the baryons are considered. The transition couplings between the three- and five-quark components in the baryons are assumed to be via the $^{3}P_{0}$ mechanism, which could reproduce the sea asymmetry in proton very well. The numerical results for the flavor-dependent axial charges of the octet baryons are comparable to those predicted by other theoretical approaches. It is shown that the…
