Heavy Baryons Research Articles

1Dand 2D Ξ b and Λ b baryons * *Supported by the Fundamental Research Funds for the Central Universities (016MS133), Natural Science Foundation of HeBei Province (A2018502124)

Recently, scientists have achieved significant progress in experiments searching for excited and baryons such as , , , , , , and . Motivated by these achievements, we systematically analyze the and states of and baryons using the method of quantum chromodynamics sum rules. By constructing three types of interpolating currents, we calculate the masses and pole residues of these heavy baryons with different excitation modes: , , and . Subsequently, we decode the inner structures of , , , and and favor assigning these states as the baryons with the quantum numbers and , , , and , respectively. In addition, the predictions for the masses and pole residues of the other and and baryons in this paper will be useful for studying D-wave bottom baryons in the future.

Lifetimes of singly charmed hadrons

We provide an extensive study of the lifetimes of singly charmed baryons and mesons, within the heavy quark expansion with all known corrections included. A special attention is devoted to the choice of the charm mass and wavefunctions of heavy baryons. We give our predictions for lifetimes, lifetime ratios, and semileptonic branching ratios of singly charmed baryons. Our results accommodate the experimentally-favoured hierarchy of singly charmed baryon lifetimesτΞc0<τΛc+<τΩc0<τΞc+,\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \ au \\left({\\Xi}_c^0\\right)<\ au \\left({\\Lambda}_c^{+}\\right)<\ au \\left({\\Omega}_c^0\\right)<\ au \\left({\\Xi}_c^{+}\\right), $$\\end{document}in contrast to earlier theoretical findings. Predictions for charmed meson lifetimes and semileptonic decay rates are in agreement with a recent comprehensive study and experimental results within uncertainties.

Delta-resonances and hyperons in proto-neutron stars and merger remnants

The equation of state (EoS) and composition of dense and hot varDelta -resonance admixed hypernuclear matter is studied under conditions that are characteristic of neutron star binary merger remnants and supernovas. The cold, neutrino free regime is also considered as a reference for the astrophysical constraints on the EoS of dense matter. Our formalism uses the covariant density functional (CDF) theory successfully adapted to include the full J^P=1/2^+ baryon octet and non-strange members of J^P=3/2^+ decouplet with density-dependent couplings that have been suitably adjusted to the existing laboratory and astrophysical data. The effect of varDelta -resonances at finite temperatures is to soften the EoS of hypernuclear matter at intermediate densities and stiffen it at high densities. At low temperatures, the heavy baryons varLambda , varDelta ^-, varXi ^-, varXi ^0 and varDelta ^0 appear in the given order if the varDelta -meson couplings are close to those for the nucleon-meson couplings. As is the case for hyperons, the thresholds of varDelta -resonances move to lower densities with the increase of temperature indicating a significant fraction of varDelta ’s in the low-density subnuclear regime. We find that the varDelta -resonances comprise a significant fraction of baryonic matter, of the order of 10% at temperatures of the order of several tens of MeV in the neutrino-trapped regime and, thus, may affect the supernova and binary neutron star dynamics by providing, for example, a new source for neutrino opacity or a new channel for bulk viscosity via the direct Urca processes. The mass-radius relation of isentropic static, spherically symmetric hot compact stars is discussed.

Heavy baryons in hot stellar matter with light nuclei and hypernuclei

The production of light nuclei and hypernuclei together with heavy baryons, both hyperons and $\Delta$-baryons, in low density matter as found in stellar environments such as supernova or binary mergers is studied within relativistic mean-field models. Five light nuclei were considered together with three light hypernuclei. The presence of both hyperons and $\Delta$-baryons shift the dissolution of clusters to larger densities and increase the abundance of clusters. This effect is larger the smaller the charge fraction and the higher the temperature. The couplings of the $\Delta$-baryons were chosen imposing that the nucleon effective mass remains finite inside neutron stars.

Heavy-flavor-conserving hadronic weak decays of charmed and bottom baryons

Three decades ago, heavy-flavor-conserving (HFC) weak decays of heavy baryons such as ${\mathrm{\ensuremath{\Xi}}}_{Q}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{Q}\ensuremath{\pi}$ and ${\mathrm{\ensuremath{\Omega}}}_{Q}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{Q}\ensuremath{\pi}$ for $Q=c$, $b$ had been studied within the framework that incorporates both heavy quark and chiral symmetries. It was pointed out that if the heavy quark in the HFC process behaves as a spectator, then the $P$-wave amplitude of ${\mathcal{B}}_{\overline{3}}\ensuremath{\rightarrow}{\mathcal{B}}_{\overline{3}}+\ensuremath{\pi}$, with ${\mathcal{B}}_{\overline{3}}$ being an antitriplet heavy baryon, will vanish in the heavy quark limit. Indeed, this is the case for ${\mathrm{\ensuremath{\Xi}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{b}\ensuremath{\pi}$ decays. For ${\mathrm{\ensuremath{\Xi}}}_{c}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}\ensuremath{\pi}$ decays, they receive additional nonspectator contributions arising from the $W$-exchange diagrams through the $cs\ensuremath{\rightarrow}dc$ transition. Spectator and nonspectator $W$-exchange contributions to the $S$-wave amplitude of ${\mathrm{\ensuremath{\Xi}}}_{c}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}\ensuremath{\pi}$ are destructive, rendering the $S$-wave contribution even smaller. However, the nonspectator effect on the $P$-wave amplitude was overlooked in all the previous model calculations until a very recent investigation within the framework of a constituent quark model in which the parity-conserving pole terms were found to be dominant in ${\mathrm{\ensuremath{\Xi}}}_{c}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}\ensuremath{\pi}$ decays. Since the pion produced in the HFC process is soft, we apply current algebra to study both $S$- and $P$-wave amplitudes and employ the bag and diquark models to estimate the matrix elements of four-quark operators. We confirm that ${\mathrm{\ensuremath{\Xi}}}_{c}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}\ensuremath{\pi}$ decays are indeed dominated by the parity-conserving transition induced from nonspectator $W$-exchange and that they receive largest contributions from the intermediate ${\mathrm{\ensuremath{\Sigma}}}_{c}$ pole terms. We also show that the $S$-wave of ${\mathrm{\ensuremath{\Omega}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{b}\ensuremath{\pi}$ decays vanishes in the heavy quark limit, while ${\mathrm{\ensuremath{\Omega}}}_{c}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{c}\ensuremath{\pi}$ receive additional $W$-exchange contributions via $cs\ensuremath{\rightarrow}dc$ transition. The $P$-wave contribution to ${\mathrm{\ensuremath{\Omega}}}_{c}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{c}\ensuremath{\pi}$ is enhanced by the ${{\mathrm{\ensuremath{\Xi}}}^{\ensuremath{'}}}_{c}$ pole, though it is not so dramatic as in the case of ${\mathrm{\ensuremath{\Xi}}}_{c}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}\ensuremath{\pi}$. The asymmetry parameter $\ensuremath{\alpha}$ is found to be positive, of order 0.70 and 0.74 for ${\mathrm{\ensuremath{\Xi}}}_{c}^{0}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and ${\mathrm{\ensuremath{\Xi}}}_{c}^{+}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Lambda}}}_{c}^{+}{\ensuremath{\pi}}^{0}$, respectively. The predicted branching fraction is of order $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ for ${\mathrm{\ensuremath{\Omega}}}_{c}^{0}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{c}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and $3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$ for ${\mathrm{\ensuremath{\Omega}}}_{c}^{0}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{c}^{0}{\ensuremath{\pi}}^{0}$ both with the asymmetry parameter close to $\ensuremath{-}1$.

Radiative correction to lepton proton scatterings in manifestly Lorentz-invariant chiral perturbation theory

Manifestly lorentz-invariant baryon chiral perturbation theory is used to calculate the radiative correction of low energy elastic lepton proton scatterings. Corrections of differential cross section and charge asymmetry are given at next-to-leading order with nonzero lepton mass, in which both are infrared and ultraviolet finite. The results are basically consistent with previous predictions based on hadron model, but somewhat different from calculations based on heavy baryon chiral perturbation theory, especially in charge asymmetry.

Strong decays of multistrangeness baryon resonances in the quark model

Decay properties of multistrangeness $\mathrm{\ensuremath{\Xi}}$ and $\mathrm{\ensuremath{\Omega}}$ baryon resonances are investigated within the constituent quark model by including relativistic corrections. The strong decay widths of various $\mathrm{\ensuremath{\Xi}}$ and $\mathrm{\ensuremath{\Omega}}$ resonances are computed and tested for internal quark configurations to pin down their spin-parity (${J}^{P}$) quantum numbers and internal structures. We found that the Roper-like resonances in the multistrangeness sector have large decay widths bearing resemblances to their siblings in light and heavy baryon sectors. In addition, we obtained the decay ratio for the $\mathrm{\ensuremath{\Omega}}(2012)$ as $\mathrm{\ensuremath{\Gamma}}(\mathrm{\ensuremath{\Omega}}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Xi}}\overline{K}\ensuremath{\pi})/\mathrm{\ensuremath{\Gamma}}(\mathrm{\ensuremath{\Omega}}\ensuremath{\rightarrow}\mathrm{\ensuremath{\Xi}}\overline{K})=4.5%$, which is consistent with the experimental data when ${J}^{P}=3/{2}^{\ensuremath{-}}$ is assigned. This observation holds the possibility that the $\mathrm{\ensuremath{\Omega}}(2012)$ could naturally be explained as a three-quark state in the quark model. The decays of other low-lying $\mathrm{\ensuremath{\Xi}}$ and $\mathrm{\ensuremath{\Omega}}$ resonances are systematically analyzed, which would be useful to unveil the structure of these resonances in future experiments.

Landscape of heavy baryons from the perspective of the chiral quark-soliton model

We employ the chiral quark-soliton model and the heavy quark symmetry to describe spectra of charm and beauty baryons. Heavy baryons can be classified according to the SU(3) representations of the light sector. We argue that recently discovered $\Xi_b$ states can be interpreted as negative parity excited anti-triplets or sextets, and the $\Sigma_b$ states as negative parity sextets. Consequences of such assignments for the decay patterns are discussed and also predictions of masses of the yet unmeasured sextet members are given.

Resonances in heavy meson–heavy baryon coupled-channel interactions

The interactions of {bar{D}}^{(*)} Lambda _c - {bar{D}}^{(*)}Sigma _c^{(*)} are studied within the framework of a dynamical coupled-channel approach. A series of bound states and resonances with different spin and parity are dynamically generated in the hidden charm sector. Four S-wave bound states are found in the mass range of 4.3–4.5 GeV, close to the pentaquark states observed by LHCb. Two of the states have a spin parity of J^P= 1/2^- and the other two have J^P=3/2^-. In addition, several resonances with different spin and parity in higher partial waves are predicted.

Mass spectra and decay properties of singly heavy bottom-strange baryons

In this paper, we enumerated ground and excited state masses of singly heavy bottom-strange baryons using the hypercentral constituent quark model (hCQM). The screening potential is used with color-Coulomb potential, as the confining potential. We determine the possible [Formula: see text] values to recently observed excited states like, [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] and four [Formula: see text] states. The Regge trajectories are plotted in [Formula: see text] plane to assign the [Formula: see text] values and quantum numbers to recently observed states. Using the calculated spectroscopic data, properties such as magnetic moment, transition magnetic moment, radiative decay width, and strong decay width are also investigated for all singly heavy bottom-strange baryonic system.

Decays of Roper-like singly heavy baryons in a chiral model

We present a chiral model describing decays of the Roper-like ${\mathrm{\ensuremath{\Lambda}}}_{c}(2765)$ and ${\mathrm{\ensuremath{\Xi}}}_{c}(2970)$ as well as those of the heavy quark spin-doublet ${{\mathrm{\ensuremath{\Sigma}}}_{c}(2455),{\mathrm{\ensuremath{\Sigma}}}_{c}(2520)}$ and ${{\mathrm{\ensuremath{\Xi}}}_{c}^{\ensuremath{'}},{\mathrm{\ensuremath{\Xi}}}_{c}(2645)}$, by focusing on chiral representations of diquarks inside the heavy baryons. Based on our chiral model together with the heavy quark spin symmetry, we derive a relation satisfied by axial charges of the heavy baryons that controls the magnitude of their one pion (kaon) decays. Besides, it is shown that the large decay widths of the Roper-like ${\mathrm{\ensuremath{\Lambda}}}_{c}(2765)$ and ${\mathrm{\ensuremath{\Xi}}}_{c}(2970)$, which cannot be implemented by conventional nonrelativistic quark models, are explained by reasonable values of the axial charges. In addition, we apply the chiral model to bottom baryons and predict decay widths of the undiscovered Roper-like ${\mathrm{\ensuremath{\Xi}}}_{b}$. We expect that our present investigation leads to elucidation of dynamical properties of the excited heavy baryons from the viewpoint of chiral symmetry.

Excitation spectra of heavy baryons in diquark models

Abstract The excitation energy spectra of heavy baryons consisting of a heavy quark and two light quarks are investigated using diquark models in order to examine the nature of the diquark as a constituent of single heavy baryons. We consider two diquark models; in Model A the diquark is treated as a point-like particle, while it has a spatial size in Model B. We determine the masses of scalar and axial vector diquarks by the mass difference of the ground-state charmed baryons and the Λc baryon, while the mass of the ud scalar diquark in the Λc baryon is assumed to be 500 MeV as a reference. The parameters of these models are fixed by the 1p excitation energy of Λc. We find that Model A reproduces well the excitation energy spectra of the charmed and bottomed baryons, although the string tension of the confinement potential in Model A should be half of that of the charmonium, while Model B suggests degeneracy of the 2s and 1d states, which is not seen in the Λc spectrum.

Magnetic moments of spin–1/2 triply heavy baryons: a study of light-cone QCD and quark–diquark model

In this study, the magnetic moments of the spin-1/2 triply-heavy baryons have been calculated using both light-cone QCD sum rules and Quark-diquark model. Theoretical investigations on magnetic moments of the triply-heavy baryons, are crucial as their results can help us better understand their internal structure and the dynamics of the QCD as the theory of the strong interaction. We compare the results extracted for the magnetic moment with the existing theoretical predictions. It is seen that the obtained magnetic moment values are quite compatible with the results in the literature.

Mass spectra of Ξ cc , Ξ bc , Ω cc , and Ω bc baryons in Regge phenomenology

In this article, we study the mass spectra of baryons containing two heavy quarks; charm-charm (cc) and bottom-charm (bc) with a light quark (u, d, s) within the framework of Regge phenomenology. With the assumption of linear Regge trajectories we have derived the relations between slope ratios, intercepts, and baryon masses. Using these relations, the ground state masses of Ξ cc , Ξ bc , Ω cc , and Ω bc baryons are obtained. The values of Regge slopes and Regge intercepts are extracted for these baryons to estimate the excited state masses in both the (J, M 2) and (n, M 2) planes. Our obtained results are compared with the experimental observations where available and other theoretical predictions, which could be a valuable addition to the interpretations of experimentally unknown heavy baryon spectra.

Test of the hyperon-nucleon interaction within leading order covariant chiral effective field theory

Motivated by the recent experimental measurements of differential cross sections of the $\Sigma^{-}p$ elastic scattering in the momentum range of $470$ to $850$ MeV$/c$ by the J-PARC E$40$ experiment, we extend our previous studies of $S=-1$ hyperon-nucleon interactions to relatively higher energies up to $900$ MeV$/c$ for both the coupled-channel $\Lambda p\rightarrow(\Lambda p, \Sigma^{+}n, \Sigma^{0}p)$, $\Sigma^{-}p\rightarrow(\Lambda n, \Sigma^{0}n, \Sigma^{-}p)$ and single-channel $\Sigma^{+}p\rightarrow\Sigma^{+}p$ reactions. We show that although the leading order covariant chiral effective field theory is only constrained by the low energy data, it can describe the high energy data reasonably well, in particular, the J-PARC E40 differential cross sections. The predicted cusp structure close to the $\Sigma N$ threshold in the $\Lambda p\to \Lambda p$ reaction agrees with the latest ALICE observation as well as with the results of the next-to-leading order heavy baryon chiral effective theory. On the other hand, the comparison with the latest CLAS data on the $\Lambda p$ cross sections between 0.9 and 2.0 GeV$/c$ clearly indicates the need of higher order chiral potentials for such high momenta. This is also the case for the latest J-PARC data on the $\Sigma p \rightarrow \Lambda n$ differential cross sections. Nevertheless, even for these cases, the predictions are in qualitative agreement with the data, albeit with large uncertainties, implying that the predicted total and differential cross sections are of relevance for ongoing and planned experiments.

Mass spectra of doubly heavy tetraquarks in an improved chromomagnetic interaction model

Doubly heavy tetraquark states are the prime candidates for tightly bound exotic states. We present a systematic study of the mass spectra of the $S$-wave doubly heavy tetraquark states $QQ\bar{q}\bar{q}$ ($q=u, d, s$ and $Q=c, b$) with different quantum numbers $J^P=0^+$, $1^+$, and $2^+$ in the framework of the improved chromomagnetic interaction (ICMI) model. The parameters in the ICMI model are obtained by fitting the conventional hadron spectra and are used directly to predict the masses of the tetraquark states. For heavy quarks, the uncertainties of the parameters are obtained by comparing the masses of doubly and triply heavy baryons with those given by lattice QCD, QCD sum rules, and potential models. Several compact and stable bound states are found in both the doubly charmed and doubly bottomed tetraquark systems. The predicted mass of the $cc\bar u\bar d$ state is consistent with the recent measurement from the LHCb collaboration.

Nonperturbative two-pion exchange contributions to the nucleon-nucleon interaction in covariant baryon chiral perturbation theory

We calculate the nonperturbative two-pion exchange (TPE) contributions to the $NN$ interaction in covariant baryon chiral perturbation theory. We study how the nonperturbative resummation affects the $NN$ phase shifts for partial waves with $J \geq 3$ and $L \leq 6$. No significant differences are observed between the nonperturbative phase shifts and perturbative ones for most partial waves except for $^3D_3$, for which the nonperturbative resummation greatly improves the description of the phase shifts. However, a significant cutoff dependence is found for this partial wave and a reasonable description of the phase shifts can only be obtained with a particular cutoff. Furthermore, we compare the so-obtained nonperturbative phase shifts with those obtained in the heavy baryon chiral perturbation theory. We show that the contributions from relativistic nonperturbative TPE are more moderate than those from the nonrelativistic TPE obtained in the dimensional regularization scheme. A proper convergence pattern is observed for most of the partial waves studied except for $^3F_3$, $^3F_4$, and $^3H_6$, for which the subleading TPE contributions are a bit strong. We find that for $H$ and $I$ partial waves, the OPE alone can already describe the phase shifts reasonably well.

Sterile neutrinos in Λb0→(Λc+,p+)ℓ1−ℓ2−ℓ3+ν decays

We study lepton number violating and lepton number conserving semi-leptonic decays of heavy baryons $\Lambda_b^0$ to three charged leptons and a neutrino. The decays occur through two intermediate quasi-degenerate GeV-scale sterile neutrinos of either Majorana or Dirac type that can be on-shell. Interference between the intermediate heavy neutrinos leads to CP violation in the final states. Effect of neutrino oscillations between the heavy states are also considered in observables of interests, \emph{i.e.,} branching ratio, and the CP-asymmetry. Given the present constraints on the heavy-to-light mixing elements $|V_{eN}|$ and $|V_{\mu N}|$, CP-averaged branching ratio of $\Lambda_b^0\to (\Lambda_c,p)\mu\mu e\nu$ with intermediate Majorana neutrinos is almost two orders of magnitude larger than for the same with Dirac neutrinos, whereas, CP-averaged branching ratio of $\Lambda_b^0\to (\Lambda_c,p)ee\mu\nu$ is of the same order of magnitude for both Majorana and Dirac neutrino induced decays. CP-violation is found to be appreciable when the neutrino mass difference is comparable with the average decay widths.

Triply heavy baryon spectroscopy in the relativistic quark model

Triply heavy baryons are investigated in the framework of the relativistic quark model based on the quark-diquark picture in the quasipotential approach in QCD. Masses of the ground and excited states of the ${\mathrm{\ensuremath{\Omega}}}_{ccc}$, ${\mathrm{\ensuremath{\Omega}}}_{bbb}$, ${\mathrm{\ensuremath{\Omega}}}_{ccb}$, and ${\mathrm{\ensuremath{\Omega}}}_{cbb}$ baryons are calculated. Orbital and radial excitations between the diquark and quark as well as between quarks inside the diquark are considered. The diquark internal structure is consistently taken into account by the form factor of the diquark-gluon interaction expressed through the overlap integral of the diquark wave functions. A detailed comparison with previous calculations is given.

Restudy of the color-allowed two-body nonleptonic decays of bottom baryons Ξb and Ωb supported by hadron spectroscopy

In this work, we calculate the branching ratios of the color-allowed two-body nonleptonic decays of the bottom baryons, which include the ${\mathrm{\ensuremath{\Xi}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Xi}}}_{c}^{(*)}$ and ${\mathrm{\ensuremath{\Omega}}}_{b}\ensuremath{\rightarrow}{\mathrm{\ensuremath{\Omega}}}_{c}^{(*)}$ weak transitions by emitting a pseudoscalar meson (${\ensuremath{\pi}}^{\ensuremath{-}}$, ${K}^{\ensuremath{-}}$, ${D}^{\ensuremath{-}}$, and ${D}_{s}^{\ensuremath{-}}$) or a vector meson (${\ensuremath{\rho}}^{\ensuremath{-}}$, ${K}^{*\ensuremath{-}}$, ${D}^{*\ensuremath{-}}$, and ${D}_{s}^{*\ensuremath{-}}$). For achieving this aim, we adopt the three-body light-front quark model with the support of hadron spectroscopy, where the spatial wave functions of these heavy baryons involved in these weak decays are obtained by a semirelativistic potential model associated with the Gaussian expansion method. Our results show that these decays with the ${\ensuremath{\pi}}^{\ensuremath{-}}$, ${\ensuremath{\rho}}^{\ensuremath{-}}$, and ${D}_{s}^{(*)\ensuremath{-}}$-emitted mode have considerable widths, which could be accessible at the ongoing LHCb and Belle II experiments.