The heavy baryon system bounded by the strong interaction has a rich internal structure, so its mass spectra can have the fine structure similar to the line spectra of atom bounded by the electromagnetic interaction. We systematically study the internal structure of $P$-wave $Ω_b$ baryons and calculate their $D$-wave decay properties. The present study, together with our previous studies on their mass spectra and $S$-wave decay properties, suggest that all the four excited $Ω_b$ baryons recently discovered by LHCb can be well explained as $P$-wave $Ω_b$ baryons, and their beautiful fine structure is directly related to the rich internal structure of $P$-wave $Ω_b$ baryons.
Stimulated by recent progress made by the LHCb Collaboration in discoveries of new bottom baryons, e.g., the $Ξ_{b}(6227)^{-}$ and the $Σ_{b}(6097)^{\pm}$, we re-examine the orbitally excited spectrum of the charmed and bottom baryons using Regge approach in the heavy quark-diquark picture. The results indicate that the spin-averaged mass spectrum of the orbitally-excited charmed and bottom baryons can be described by a linear Regge relation, which is derived from the rotating QCD string model. By giving further mass-splitting analysis of spin-dependent interactions, we explain the baryons $Ξ_…
Motivated by recent results on charmed baryons from CLEO and FOCUS, we reexamine the couplings of the orbitally excited charmed baryons. Due to its proximity to the [Sigma_c pi] threshold, the strong decays of the Lambda_c(2593) are sensitive to finite width effects. This distorts the shape of the invariant mass spectrum in Lambda_{c1}-> Lambda_c pi^+pi^- from a simple Breit-Wigner resonance, which has implications for the experimental extraction of the Lambda_c(2593) mass and couplings. We perform a fit to unpublished CLEO data which gives M(Lambda_c(2593)) - M(Lambda_c) = 305.6 +- 0.3 MeV an…
We demonstrate in a model independent way that, in the combined heavy quark and large N_c limit, there exists a new contracted U(4) symmetry which connects orbitally excited heavy baryons to the ground states.
In the framework of diquark model for production we discuss the yields and observation prospects for excited states of doubly heavy baryons at LHC kinematic conditions.
In this talk I report on a computation of the spectra of exotic pentaquarks and radial excitations of the low--lying ${1/2}^+$ and ${3/2}^+$ baryons in a chiral soliton model.
The spectrum of excited $Λ_Q$-type heavy baryons is considered in the large $N_c$ limit. The universal form factors for $Λ_b$ semileptonic decay to excited charmed baryons are calculated in the large $N_c$ limit. We find that the Bjorken sum rule (for the slope of the Isgur--Wise function) and Voloshin sum rule (for the mass of the light degrees of freedom) are saturated by the first doublet of excited $Λ_Q$ states.
In this note we collect and summarize the predictions of the Holography Inspired Stringy Hadron (HISH) model. We list the masses and widths of predicted excited states across the spectrum, based on placing the different hadrons on the non-linear Regge trajectories of a string with massive endpoints. Our predicted states include: (i) Light, heavy-light and heavy-heavy mesons. (ii) Baryons, including charmed, doubly charmed and bottom baryons. (iii) Glueballs, together with a method to disentangle them from flavorless mesons. (iv) Genuine tetraquarks, which are not "molecules" of hadrons, and ar…
Selecting the newly observed $Ξ_b(6227)^-$ by LHCb as a study example, we decode its inner structure by giving the mass spectrum analysis and the investigation of its two-body strong decay behaviors. Our result indicates that the $Ξ_b(6227)^-$ is a good candidate of the $P$-wave $Ξ_b^{\prime}$ state with $J^P=3/2^-$ or $5/2^-$. In addition, we further provide the information of the properties of the partners of the $Ξ_b(6227)^-$. These predicted states include three $2S$ states and the remaining $1P$ states in the bottom-strange baryon family. The calculated sizable Okubo-Zweig-Iizuka$-$allowe…
The yield of doubly charmed baryons with excited heavy diquark in $S$ wave and $P$ wave states has been estimated at LHC energies. The observation possibility of such baryons is discussed.
An approach to baryons in the framework of the microscopic Generalized Nambu-Jona-Lasinio chiral potential quark model is considered and quite general arguments are given in favor of effective restoration of chiral symmetry in excited baryons.
L=1 excited heavy baryon masses are analyzed by heavy quark and large N_c expansions. In heavy quark limit, mass is parameterized by Λ-bar and it is expanded further by spin-flavor breaking operators to the zeroth order of 1/N_c. Expanding coefficients will be fixed by more data on the excited baryons in the near future.
We briefly discuss the large Nc picture for excited baryons, present a new method for the calculation of matrix elements and illustrate it by computing the strong decays of heavy exotic states.
Spin-flavor symmetry breaking in the levels of excited Baryons are studied to leading order in the 1/$N_c$ expansion. This breaking occurs at zeroth order. For non-strange Baryons with a single quark excited, it is shown that to first order of perturbation theory the breaking is given by one 1-body operator (spin-orbit), and three 2-body operators, all involving the orbital angular momentum of the excited quark. Higher-body operators can be reduced to that set of operators. As illustration, p-wave Baryons are briefly discussed.
We study baryon excited states for quark confinement and chiral symmetry breaking. In the first part we discuss spatially deformed baryon excitations. As signals of deformation, we study masses and electromagnetic transitions. Such a study of spatial structure is expected to provide information on quark binding mechanism and hence quark confinement. In the second part, we consider the chiral symmetry for baryons and study positive and negative parity baryons. We show that there are two distinctive representations of chiral symmetry for baryons. We investigate their phenomenological consequence…
We review results for the mass spectrum of orbitally excited baryons obtained in the $1/N_c$ expansion. We show the dependence of various contributions to the mass operator as a function of the excitation energy.
We derive a Bjorken sum rule for semileptonic $Ω_b$ decays to ground and low-lying negative-parity excited charmed baryon states, in the heavy quark limit. We discuss the restriction from this sum rule on form factors and compare it with some models.
The nature of the $ Λ(1405) $ has been a puzzle for decades, whether it is a standard three-quark baryon, a hybrid baryon or a baryon-meson molecule. More information on the decay channels of this particle and its strong, weak and electromagnetic interactions with other hadrons is needed to clarify its internal organization. The residue of this particle is one of the main inputs in investigation of its decay properties in many approaches. We calculate the mass and residue of $Λ(1405)$ state in the context of QCD sum rules considering it as a hybrid baryon with three-quark---one gluon content a…
We construct the interpolating currents for the fourteen p-wave excited heavy baryons in the framework of heavy quark effective theory (HQET). At the leading order in the 1/m_Q expansion these interpolating currents do not mix different states with the same J^P with each other. We use QCD sum rule to calculate the masses of the p-wave excited J=1/2 spin doublet heavy baryons in the m_Q~infinity limit. We discuss some implications of our results.
We analyze the photo-production helicity amplitudes for the positive parity excited baryons in the context of the $1/N_c$ expansion of QCD. The results show that sub-leading corrections in $1/N_c$ are important and that, while 1-body effective operators are dominant, there is some evidence for the need of 2-body effects.
We derive consistency conditions which constrain the possible form of the strong couplings of the excited baryons to the pions. The consistency conditions follow from requiring the pion-excited baryon scattering amplitudes to satisfy the large-N_c Witten counting rules and are analogous to consistency conditions used by Dashen, Jenkins and Manohar and others for s-wave baryons. The consistency conditions are explicitly solved, giving the most general allowed form of the strong vertices for excited baryons in the large-N_c limit. We show that the solutions to the large-N_c consistency condition…
In this work, we preform a systematic study of the strong decays for the higher singly heavy baryon resonances $Λ_Q(3S)$, $Λ_Q(2P)$, $Λ_Q(2D)$, $Λ_Q(1F)$, $Σ_Q(3S)$, $Σ_Q(2P)$, $Σ_Q(2D)$, and $Σ_Q(1F)$ within the $^3P_0$ model. Our results show that most of the $λ-$mode higher excited $Λ_Q$ and $Σ_Q$ states have a relatively narrow width, and mainly decay into two-body final states with one heavy meson plus one light baryon. Our calculations provide abundant theoretical information and demonstrate the general feature for these higher states, which may be valuable for future experimental search…
The decays of non-strange positive parity excited baryons via emission of a pseudo-scalar meson are studied in the framework of the 1/Nc expansion to order 1/Nc. In particular, the pionic decays of the l=0 Roper baryons and of the l=2 baryons in the mass interval 1680-1950 MeV are analyzed using the available partial decay widths. Decay widths by emission of an eta meson are shown to be suppressed by a factor 1/Nc^2 with respect to the pionic ones.
The LHCb Collaboration recently observed five narrow $Ω_c^{0}$ resonances, and measured their masses and widths through the decays $ Ω_c^{0} \to Ξ_c^{+}K^{-}$. Motivated by this discovery, and also by the fact that the ground-state bottom baryon $Ω_b^{-}$ with spin-1/2 was already found experimentally, we perform theoretical investigation of the spin-1/2 and spin-3/2, $Ω_b$, baryons by calculating decay width of their first orbitally and radially excited states to $Ξ_b^{0} K^{-}$. For this purpose, we employ QCD sum rule method on the light-cone by including into analysis the $K$ meson distrib…
Recently LHCb reported the discovery of five extremely narrow excited $Ω_c$ baryons decaying into $Ξ_c^+ K^-$. We interpret these baryons as bound states of a $c$-quark and a $P$-wave $ss$-diquark. For such a system there are exactly five possible combinations of spin and orbital angular momentum. The narrowness of the states could be a signal that it is hard to pull apart the two $s$-quarks in a diquark. We predict two of spin 1/2, two of spin 3/2, and one of spin 5/2, all with negative parity. Of the five states two can decay in $S$-wave and three can decay in $D$-wave. Some of the $D$-wave …
We argue that three-quark excited states naturally group into quartets, split into two parity doublets, and that the mass splittings between these parity partners decrease higher up in the baryon spectrum. This decreasing mass difference can be used to probe the running quark mass in the mid-infrared power-law regime. A measurement of masses of high-partial wave Delta* resonances should be sufficient to unambiguously establish the approximate degeneracy. We test this concept with the first computation of excited high-j baryon masses in a chirally invariant quark model.
The CLEO Collaboration recently has announced the discovery of an excited charmed and strange baryon. We estimate the expected width of this new member of the Xi_c family. We discuss the phenomenology of the excited csq and css states, and consider what additional charmed baryons might be observable in the future. We point out that the final state Xi_c + K could be an interesting new channel to examine.
We obtain the spectra of excited heavy baryons containing one heavy quark by quantizing the exactly-solved heavy meson bound states to Skyrme soliton. The results are comparable to the recent experimental observations and quark model predictions, and are consistent with the heavy quark spin symmetry. However, somewhat large dependence of the results on the heavy quark mass strongly calls for the incorporation of the soliton-recoil effects.
The "good" diquark is employed to study $Λ_c^{+}$ baryons within a mass loaded flux tube model. The study indicates that all $Λ_c^{+}$ baryons candidates in the 2008 review by the Particle Data Group (PDG) are well described in the mass loaded flux tube model. The quantum numbers $J^P$ of these $Λ_c^{+}$ candidates are assigned. If $Λ_c(2765)^{+}$ is an orbitally excited $Λ^+_c$, it is likely the $J^P={3\over 2}^+$ one. If $Λ_c(2765)^+$ is an orbitally excited $Σ_c$, there ought to be another $J^P={3\over 2}^+$ $Λ^+_c$ with mass $\approx 2770$ MeV. In the model, there exists no $J^P={1\over 2}…
The relativistic three-quark equations of the ${\bf (70,1^-)}$ baryons are found in the framework of the dispersion relation technique. The approximate solutions of these equations using the method based on the extraction of leading singularities of the amplitude are obtained. The calculated mass values of the ${\bf (70,1^-)}$ multiplet are in good agreement with the experimental ones.
This talk reviews recent developments in the use of large $N_c$ QCD in the description of baryonic resonances. The emphasis is on the model-independent nature of the approach. Key issues discussed include the spin-flavor symmetry which emerges at large $N_c$ and the direct use of scattering observables. The connection to quark model approaches is stressed.
Masses of the p-wave excited heavy baryons have been calculated to the Lambda_{QCD}/m_Q order using QCD sum rule method within the framework of heavy quark effective theory. Numerical results for kinetic energy lambda_1 and chromo-magnetic interaction lambda_2 are presented. The splitting between spin 1/2 and 3/2 doublet derived from our calculation is given, for which the agreement with the current experiment is desirable.
The mass spectra of the L=1 orbitally excited heavy baryons with light quarks in both the spin-flavor symmetric and the mixed representations are studied by the $1/N_c$ expansion method in the framework of the heavy quark effective theory. The mixing effect between the baryons in the two representations is also considered. The general pattern of the spectrum is predicted which will be verified by the experiments in the near future.
We calculate the mass and residue of the newly observed $Ω_c(3000)$ and $Ω_c(3066)$ states with quantum numbers $J^P = \frac{1}{2}^{-}$ and $\frac{3}{2}^{-}$ within QCD sum rules. Our predictions on masses are in good agreement with the experimental results.
The production of the excited charmed baryon doublet $Λ_c^*$ via fragmentation is studied. An analysis of the subsequent hadronic decays of the doublet within the framework of heavy hadron chiral perturbation theory produces expressions for both the angular distribution of the decay products and the polarization of the final state heavy baryon in terms of various nonperturbative fragmentation parameters. Future experimental investigation of this system will determine these parameters. In addition, recent experimental results are shown to fix one of the parameters in the heavy hadron chiral Lag…
We consider the strong decays of the lowest-lying radially excited baryons, in SU(6) language the states comprising the first excited 56-plet. Assuming a single-quark decay approximation, and negligible configuration mixing, we make model-independent predictions for the partial decay widths to final states with a single meson. Masses of unobserved states are predicted using results from large-N_c QCD, and the momentum dependence of the one-body decay amplitude is determined phenomenologically by fitting to observed decays, so that the baryon spatial wave functions are not assumed. We point out…
Spin dependent fragmentation functions for heavy flavor quarks to fragment into heavy baryons are calculated in a quark-diquark model. The production of intermediate spin 1/2 and 3/2 excited states is explicity included. The resulting $Λ_b$ production rate and polarization at LEP energies are in agreement with experiment. The $Λ_c$ and $Ξ_c$ functions are also obtained. The spin independent $f_1(z)$ is compared to data. The integrated values for production rates agree with the data.
The mass spectrum of the L=1 orbitally excited heavy baryons with light quarks in the spin-flavor symmetric representation is studied by the $1/N_c$ expansion method in the framework of the heavy quark effective theory. The mixing effect from the baryons in the mixed representation is considered. The general pattern of the spectrum is predicted which will be verified by the experiments in the near future. The $1/m_Q$ and SU(3) corrections are also considered. Mass relations for the baryons $Λ_{c1}^{(*)}$, $Σ_{c1}^{(*)}$, $Ξ_{c1}^{(')(*)}$, and $Ω_{c1}^{(*)}$ are derived.
In this paper, the mass spectra are obtained for doubly heavy $Ξ$ baryons, namely, $Ξ_{cc}^{+}$, $Ξ_{cc}^{++}$, $Ξ_{bb}^{-}$, $Ξ_{bb}^{0}$, $Ξ_{bc}^{0}$ and $Ξ_{bc}^{+}$. These baryons are consist of two heavy quarks($cc$, $bb$ and $bc$) with a light($d$ or $u$) quark. The ground, radial and orbital states are calculated in framework of Hypercentral constituent quark model with coul- omb plus linear potential. Our outcomes are also compared with other predictions, thus, the average possible range of excited states masses of these $Ξ$ baryons can be determined. The study of the Regge trajectori…
This is the first of two papers to study a new emergent symmetry which connects orbitally excited heavy baryons to the ground states in the combined heavy quark and large $N_c$ limit. The existence of this symmetry is shown in a model-independent way, and different possible realizations of the symmetry are discussed. It is also proved that this emergent symmetry commutes with the large $N_c$ spin-flavor symmetry.
The mass and residues of the first radial and orbital excitations of $J=\frac{1}{2}$ baryons containing two heavy quarks (b or c) are calculated within the QCD sum rules method. In calculations, the general forms of the interpolating currents with symmetric and anti-symmetric forms with respect to the exchange of heavy quarks have been used. Our results on the spectroscopic parameters of doubly heavy baryons are compared with the predictions of other theoretical approaches.
We study the conjectured "Insensitivity to Chiral Symmetry Breaking" in the highly excited light baryon spectrum. While the experimental spectrum is being measured at JLab and CBELSA/TAPS, this insensitivity remains to be computed theoretically in detail. As the only existing option to have both confinement, highly excited states and chiral symmetry, we adopt the truncated Coulomb gauge formulation of QCD, considering a linearly confining Coulomb term. Adopting a systematic and numerically intensive variational treatment up to 12 harmonic oscillator shells we are able to access several angular…
The effects of the spin-orbit and the tensor parts of the instanton-induced interaction on the excited nonstrange baryons up to $N$=2 and on the two-nucleon systems are investigated. The spin-orbit force from the instanton-induced interaction cancels most of that from the one-gluon exchange in the excited baryons while the spin-orbit force in the nucleon systems remains strong after the inclusion of the instanton-induced interaction. The model including the spin-orbit and the tensor terms of the instanton-induced interaction as well as the one-gluon exchange is found to reproduce successfully …
The physics of the orbitally excited baryons simplifies drastically in the large Nc limit. The states are arranged into irreducible representations of the contracted SU(4)_c symmetry, with mixing angles determined exactly. The ratios of the strong couplings N* -> [Nπ]_{S,D} are predicted in this limit, with results in agreement with those following from the quark model (with the large Nc mixing angles). We present a phenomenological analysis of the observed nonstrange baryons from the perspective of the 1/Nc expansion, including constraints from their masses and strong decays.
We consider decays of the lowest-lying radially excited baryons. Assuming a single-quark decay approximation, and negligible configuration mixing, we make model-independent predictions for the partial decay widths to final states with a single meson. Masses of unobserved states are predicted using an old mass formula rederived using large-$N_c$ QCD. The momentum dependence of the one-body decay amplitude is determined phenomenologically by fitting to observed decays. Comparison of these predictions to experiment may shed light on whether the Roper resonance can be interpreted as a three-quark …
The newly observed $Σ_b(6097)$ provides us a good chance to further construct the high excited states of the bottom baryon family. In this work, we explain the $Σ_b(6097)$ to be a $1P$ state with $J^P=5/2^-$ or $3/2^-$ by giving the mass spectrum analysis and the strong decay calculation, and predict the existence of $1P$ and $2S$ partners of the $Σ_b(6097)$, where their masses and the corresponding decay behaviors are presented. Because of the success of describing the $Σ_b(6097)$ and the former observed $Ξ_b(6227)$ under the quasi-two-body treatment to the bottom baryons, we continue to pred…
We show that excited baryons in large N_c QCD form multiplets, within which masses are first split at O(1/N_c). The dominant couplings of resonances to various mesons are highly constrained: The N(1535) decays at leading 1/N_c order exclusively to eta-N rather than pi-N, and vice versa for the N(1650). This multiplet structure is reproduced by a simple large N_c quark model, well studied in the literature, that describes resonances as single-quark excitations.
We present the first phenomenological study of the masses of orbitally excited baryons in large N_c QCD. Restricting here to the nonstrange sector of the L=1 baryons, the 1/N_c expansion is used to order and select a basis of effective operators that spans the nine observables (seven masses and two mixing angles). Fits are performed using subsets of the complete set of nine operators, including corrections up to O(1/N_c) where leading order is N_c^1. This study shows that the 1/N_c expansion provides an excellent framework for analyzing the mass spectrum, and uncovers a new hierarchy of operat…
We discuss the status of current dynamical lattice QCD simulations in connection to the emerging results on the strange and charmed baryon spectrum, excited states of the nucleon and the investigation of the structure of scalar mesons.
The discussion of the 70-plet of negative parity baryons illustrates the large Nc QCD approach to orbitally excited baryons. In the case of the l=1 baryons the existing data allows to make numerous predictions to first order in the SU(3) symmetry breaking. New relations between splittings are found that follow from the spin-flavor symmetry breaking. The Lambda(1405) is well described as a three-quark state and a spin-orbit partner of the Lambda(1520). Singlet states with higher orbital angular momentum are briefly discussed.
Mass spectra of excited states of the singly charmed baryons are calculated using the hypercentral description of three body system. The baryon consist of a charm quark and light quarks (u, d and s) are studied in the framework of QCD motivated constituent quark model. The form of confinement potential is hyper coloumb plus power potential with potential index $ν$, varying from 0.5 to 2.0. The first order correction to the confinement potential is also incorporated in this approach. The radial as well as orbital excited state masses of $Σ_{c}^{++}, Σ_{c}^+, Σ_{c}^0, Ξ_c^+, Ξ_c^0, Λ_c^+, Ω_c^0$…
The masses of positive parity $(70,0^+)$ and $(70,2^+)$ nonstrange and strange baryons are calculated in the relativistic quark model. The relativistic three-quark equations of the $(70,L^+)$ multiplets are found in the framework of the dispersion relation technique. The approximate solutions of these equations using the method based on the extraction of leading singularities of the amplitude are obtained. The calculated mass values of the $(70,L^+)$ multiplets are in good agreement with the experimental ones.
We summarize results obtained in the $1/N_c$ expansion method for the masses of baryon resonances belonging to the $[{\bf 70},\ell^+]$ multiplet. They represent an extension of our previous studies from two to three flavors. A better approach to mixed symmetric states of any angular momentum and parity is also outlined.
We present results for masses of excited baryons from a quenched calculation with Chirally Improved quarks at pion masses down to 350 MeV. Our analysis of the correlators is based on the variational method. In order to provide a large basis set for spanning the physical states, we use interpolators with different Dirac structures and Jacobi smeared quark sources of different width. Our spectroscopy results for a wide range of ground state and excited baryons are discussed.
The parton model relations in conjunction with quark-hadron duality in deep inelastic scattering suggests an asymptotic dominance of quark-diquark type of baryonic excited states with a radial Regge uniformly distributed mass squared spectrum $M_{n}^2 = μ^2 n + M_0^2$. We argue that this points to a lineary quark-diquark confining potential. We analyze the radial ($n$) and angular-momentum ($J$) Regge trajectories for all light-quark states with baryon number one listed in the 2016 edition of the Particle Data Tables. The parameters of the mass squared trajectories are obtained by linear regre…
