Baryon States Research Articles

Nonlocal chiral contributions to generalized parton distributions of the proton at nonzero skewness

We compute the one-loop contributions to spin-averaged generalized parton distributions (GPDs) in the proton from pseudoscalar mesons with intermediate octet and decuplet baryon states at nonzero skewness. Our framework is based on nonlocal covariant chiral effective theory, with ultraviolet divergences regularized by introducing a relativistic regulator derived consistently from the nonlocal Lagrangian. Using the splitting functions calculated from the nonlocal Lagrangian, we find the nonzero skewness GPDs from meson loops by convoluting with the phenomenological pion GPD and the generalized distribution amplitude, and verify that these satisfy the correct polynomiality properties. We also compute the lowest two moments of GPDs to quantify the meson loop effects on the Dirac, Pauli, and gravitational form factors of the proton. Published by the American Physical Society 2024

Out-of-time-order correlator as a detector of baryonic phase structure in holographic QCD with instanton

We study the out-of-time-order correlators (OTOC) of Skyrmion as baryon in the D0-D4/D8 model which is expected to be holographically dual to QCD with instantons as D0-branes or with a non-zero theta angle. Baryon states are identified to the excitations of the Skyrmion which are described by a holographic quantum mechanical system in this model. By employing the definition of OTOC in quantum mechanics, we derive the formulas and demonstrate explicitly the numerical calculations of the OTOC. Our calculation illustrates the quantum OTOC with imaginary Lyapunov coefficient indicates the possibly metastable baryonic status in the presence of the instanton while the classical OTOC can not, thus it reveals the instantonic or theta-dependent features of QCD are dominated basically by its quantum properties. Furthermore, the OTOC also implies the baryonic phase becomes really chaotic with real Lyapunov exponent if the instanton charge increases sufficiently which agrees with the unstable baryon spectrum presented in this model. In this sense, we believe the OTOC may be treated as a tool to detect the baryonic phase structure of QCD.

Hadronic spectrum in the chiral large Nc extension of quantum chromodynamics

We study quantum chromodynamics in the chiral large Nc limit which contains a left-handed Weyl fermion in the fundamental representation, a left-handed Weyl fermion in the two index antisymmetric representation and (Nc−3) left-handed Weyl fermions in the antifundamental representation of the SU(Nc) gauge group. We construct gauge singlet composite operators and study their masses and correlation functions at large Nc. It is shown that all hadron masses scale as ∼Nc0nq where nq is the number of constituent quarks in the hadron. In addition by simple gluon exchange considerations it is seen that scattering amplitudes between hadrons have the same Nc scaling as the mass of the lightest hadron involved. This is the case provided the hadrons in the scattering amplitude share a sufficiently large number of constituent quarks. The chiral large Nc extension also allows for other nontrivial processes. For instance we consider two different baryonium states that are unique to this extension and that decay via emissions of two- and three-quark hadrons. Also other nontrivial scattering processes are considered. Finally, we study composites made of a mix of left- and right-handed fields. We categorize multiple groups of hadrons within the full spectrum according to their flavor structure. Within these groups all n-point functions scale the same. Published by the American Physical Society 2024

Nonleptonic three-body charmed baryon weak decays with H(15)

We study the nonleptonic three-body charmed baryon weak decays of Bc→BnPP′ under the SU(3)F flavor symmetry, where Bc denotes the antitriplet charmed baryon, comprising (Ξc0,−Ξc+,Λc+), and Bn and P(P′) represent octet baryon and pseudoscalar meson states, respectively. In addition to 12 parameters from the contributions of the color-antisymmetric part of the effective Hamiltonian, denoted as H(6¯), there are 4 parameters from the color-symmetric one, H(15), which were not included in the previous study. With 16 parameters in total and 28 experimental data points, we obtain the minimal χ2 over degree of freedom of χ2/d.o.f=1.5, which is a great improvement comparing to that without H(15). With the better fitting values, we evaluate the branching ratios and up-down asymmetries of Bc→BnPP′, which present some interesting results such as B(Λc+→(Ξ(1690)0→Σ+K−)K+)≡(1.5±0.4)×10−3 and potential SU(3) breaking effects in Ξc+→pπ+K− and Λc+→Σ+π−K+ to be verified by the experiments at BESIII, Belle-II, and LHCb. Published by the American Physical Society 2024

Color symmetry and confinement as an underlying superconformal structure in holographic QCD

Dedicated to the memory of our colleague, Harald Fritzsch, who, together with Murray Gell-Mann, introduced the color quantum number as the exact symmetry responsible for the strong interaction, thus establishing quantum chromodynamics (QCD) as a fundamental non-Abelian gauge theory. A basic understanding of hadron properties, however, such as confinement and the emergence of a mass scale, from first principles QCD has remained elusive: Hadronic characteristics are not explicit properties of the QCD Lagrangian and perturbative QCD, so successful in the large transverse momentum domain, is not applicable at large distances. In this article, we shall examine how this daunting obstacle is overcome in holographic QCD with the introduction of a superconformal symmetry in anti de Sitter (AdS) space which is responsible for confinement and the introduction of a mass scale within the superconformal group. When mapped to light-front coordinates in physical spacetime, this approach incorporates supersymmetric relations between the Regge trajectories of meson, baryon and tetraquark states which can be visualized in terms of specific [Formula: see text] color representations of quarks. We will also briefly discuss here the implications of holographic models for QCD color transparency in view of the present experimental interest.

Effects of multiple single-particle basis states in scattering systems

Low-lying baryon resonances have been explored using Hamiltonian Effective Field Theory (HEFT), in a formalism where resonances with a three-quark component are described by both two-particle meson–baryon states and a bare basis state. Here, we investigate the use of multiple bare states in the Hamiltonian, to extend the formalism to higher energy ranges, and represent a larger portion of the low-lying baryon spectrum. Introducing a second bare state into a toy model extension of the low-energy Δ(1232) system, we explore the influence of the second bare state on the position of poles in the infinite-volume T-matrix. Considering the same system in a finite-volume, we analyse the finite-volume energy spectrum in the presence of a second bare state, providing insight into the interplay between two bare basis states, representing quark-model states, and the relationship between infinite-volume poles and finite-volume eigenstates.

Heavy and baryons in the quark model

We present a study of the low-lying and baryon states based on masses, strong and radiative decays. In a harmonic oscillator quark model analysis it is found that the majority of the detected states can be interpreted as S- and P-wave excitations.

Four-body baryonic [formula omitted] decays

LHCb has recently reported the first observation of a four-body baryonic B→B1B¯1′B2B¯2′ decay, where B1B¯1′ and B2B¯2′ represent the two pairs of octet baryon states. In our classification, the measured B¯0→pp¯pp¯ decay is a tree dominated process via internal W-boson emission, whose branching fraction is explained as small as 2.2×10−8. We investigate for the first time the phenomenology of other tree and penguin dominated B→B1B¯1′B2B¯2′ decays, and predict the presence of a double threshold effect, manifested as two peaks around mB1B¯1′∼mB1+mB¯1′ and mB2B¯2′∼mB2+mB¯2′ in the invariant mass spectra of B1B¯1′ and B2B¯2′, respectively. Moreover, we predict the following branching fractions: B(B−→np¯pp¯)=(1.7−0.2+0.4±0.1−0.4+0.7)×10−7, B(B−→Λp¯pp¯)=(7.4−0.2+0.6±0.03−2.6+3.6)×10−7, and B(B¯s0→ΛΛ¯pp¯)=(1.9−0.1+0.3±0.01−0.6+1.1)×10−7, which are accessible to experimental facilities.

Analysis of the D-wave Sigma -type charmed baryon states with the QCD sum rules

We construct the Sigma -type currents to investigate the D-wave charmed baryon states with the QCD sum rules systematically. The predicted masses M=3.35^{+0.13}_{-0.18},textrm{GeV} (3.33^{+0.13}_{-0.16},textrm{GeV}), 3.34^{+0.14}_{-0.18},textrm{GeV} (3.35^{+0.13}_{-0.16},textrm{GeV}) and 3.35^{+0.12}_{-0.13}, textrm{GeV} (3.35^{+0.12}_{-0.14},textrm{GeV}) for the Omega _c(0,2,{frac{1}{2}}^+), Omega _c(0,2,{frac{3}{2}}^+) and Omega _c(0,2,{frac{5}{2}}^+) states are in excellent agreement with the experimental data 3327.1pm 1.2 text{ MeV } from the LHCb collaboration, and support assigning the Omega _c(3327) to be the Sigma -type D-wave Omega _c state with the spin-parity J^P={frac{1}{2}}^+, {frac{3}{2}}^+ or {frac{5}{2}}^+.

Mass predictions of triply heavy hybrid baryons via QCD sum rules

In this article, we study the mass spectrum of the low-lying triply heavy hybrid baryon, which consists of three valence heavy quarks in a color octet and one valence gluon, with spin-parity J^P=(frac{1}{2})^+ via QCD sum rules. This is the first study on the triply heavy hybrid baryons in the framework of QCD sum rules. After performing the QCD sum rule analysis, we find that the mass of cccg hybrid baryon lies in M_{cccg}= 5.91–6.13 GeV. As a byproduct, the mass of the triply bottom hybrid baryon state is extracted to be around M_{bbbg}= 14.62–14.82 GeV. The contributions up to dimension eight at the leading order of alpha _s (LO) in the operator product expansion are taken into account in the calculation. The triply charmed hybrid baryon predicted in this work can decay into one doubly charmed baryon and one charmed meson. Especially, we propose to search for cccg hybrid baryon with J^{P}= (1/2)^+ in the P-wave decay channels Xi _{cc}^{++} D^0, Xi _{cc}^{+} D^+, and Xi _{ccs}^{+} D_s^+, which may be accessible in future BelleII, Super-B, PANDA, and LHCb experiments.

The Λ-type P-wave bottom baryon states via the QCD sum rules* *Supported by the National Natural Science Foundation of China (12175068) and the Postgraduate Students Innovative Capacity Foundation of Education Department of Hebei Province, China (CXZZBS2023146)

Our study focuses on the Λ-type P-wave bottom baryon states with spin-parity , . We introduce an explicit P-wave between the two light quarks in the interpolating currents (these light quarks are antisymmetric in the flavor space, thus giving rise to the designation of Λ-type baryon) to investigate the and states within the framework of the full QCD sum rules. The predicted masses show that and could be the P-wave bottom-strange baryon states with spin-parity and , respectively; meanwhile, and could be the P-wave bottom baryon states with spin-parity and , respectively. Moreover, and may have two remarkable under-structures or Fock components at least.

QCD angular momentum in N → Δ transitions

N→Δ transitions offer new possibilities for exploring the isovector component of the QCD quark angular momentum (AM) operator causing the Ju−d flavor asymmetry in the nucleon. We extend the concept of QCD AM to transitions between baryon states, using light-front densities of the energy-momentum tensor in transversely localized states. We calculate the N→Δ transition AM in the 1/Nc expansion, connect it with the Ju−d flavor asymmetry in the nucleon, and estimate the values using lattice QCD results. In the same setup we connect the transition AM to the transition GPDs sampled in hard exclusive electroproduction processes with N→Δ transitions, enabling experimental study of the transition AM.

Mass spectra of bottom-charm baryons

In this paper, we investigate the mass spectra of bottom-charm baryons systematically, where the relativistic quark model and the infinitesimally shifted Gaussian basis function method are employed. Our calculation shows that the [Formula: see text]-mode appears lower in energy than the other excited modes. According to this feature, the allowed quantum states are selected and a systematic study of the mass spectra for [Formula: see text] ([Formula: see text]) and [Formula: see text] ([Formula: see text]) families is performed. The root mean square radii and quark radial probability density distributions of these baryons are analyzed as well. Next, the Regge trajectories in the [Formula: see text] plane are successfully constructed based on the mass spectra. At last, we present the structures of the mass spectra, and analyze the difficulty and opportunity in searching for the ground states of bottom-charm baryons in experiment.

Baryonic states in mathbf {{mathcal {N}}=1} supersymmetric SU(2) Yang–Mills theory on the lattice

We extend our analysis of bound states in {mathcal {N}}=1 supersymmetric Yang–Mills theory by the consideration of baryonic operators, which are composed of three gluino fields. The corresponding states are similar to the baryons in QCD, but due to the difference between gluino and quark fields, their properties and the fermion line contractions involved in their correlation functions are different from QCD. In this work, we first explain the derivation of these operators and the contractions needed in numerical calculations of their correlators. In contrast to QCD the correlators contain a spectacle piece, which requires methods for all-to-all propagators. We provide a first estimate of the two-point function and the mass of the lightest baryonic state in {mathcal {N}}=1 supersymmetric Yang–Mills theory.

Mass spectroscopy and decay properties of Ξcb, Ξbb baryons

Using the Hypercentral Constituent Quark Model (hCQM), the mass spectra of doubly heavy baryons [Formula: see text] and [Formula: see text] are determined. The model describes an interaction inside the baryonic system. Screened potential has been considered as confining potential with color-Coulomb potential to enumerate the masses of baryonic states. Regge trajectories have been plotted in [Formula: see text] plane. The properties like magnetic moment and radiative decay width have been determined using the obtained results.

Symmetry analysis of charmonium two-body decay

In the light of SU(3) flavor symmetry, the effective interaction Hamiltonian in tensor form is obtained by virtue of group representation theory. The strong and electromagnetic breaking effects are treated as a spurion octet so that the flavor singlet principle can be utilized as the criterion to determine the form of effective Hamiltonian. Two body decays of both baryonic and mesonic final states are parameterized in the uniform scheme, based on which the relative phase between the strong and electromagnetic amplitudes is studied for various charmonium decay modes, including psi' and/or J/jpsi decay to octet baryon pair, decuplet baryon pair, decuplet-octet baryon final state, and pseudoscalar-pseudoscalar meson final state. In data analysis of samples taken in $e^+e^-$ collider, the details of experimental effects, such as energy spread and initial state radiative correction are taken into consideration in order to make full use of experimental information and acquire the accurate and delicate results.

Emergence of high-energy dynamics from cascade-baryon detections at the LHC

We propose the inclusive detection at the LHC of a cascade Xi ^-/bar{Xi }^+ baryon in association with a jet, as a novel probe channel for the QCD dynamics at high energies. We investigate the behavior of a selection of distributions, differential in rapidity, azimuthal angle and/or transverse momenta, calculated via the hybrid high-energy/collinear factorization encoding the full next-to-leading BFKL resummation of energy logarithms. We come out with the conclusion that the fragmentation mechanism underlying the production of Xi ^-/bar{Xi }^+ baryon states leads to stabilization effects of the resummation, similar to those recently observed in the context of heavy-flavor studies within the same formalism.

Further study of within a chiral quark model* *Supported by the National Natural Science Foundation of China (12175065, 12005060, 12075288, 11735003, 11961141012). Ju-Jun Xie is also supported by the Youth Innovation Promotion Association CAS

In our previous studies, we analyzed the two-body strong decays of the low-lying Ω baryon states within a chiral quark model. The results showed that the mass, total width, and two body decay could be well reproduced with the spin-parity state classified in the quark model. Stimulated by the new observations of the three-body decay process at Belle, in the present study, we further investigate the three-body strong decay within the chiral quark model. It is found that the has a sizeable decay rate into the three-body final states . When considering as the resonance, the predicted ratio is close to the upper limit measured by the Belle Collaboration in 2019; however, it is too small to be comparable to the recent measurement . In addition, the coupled-channel effects on the bare three-quark state from nearby channels , , and are studied. Our theoretical results show that the coupled-channel effects on are not very large, and the molecular component is no more than . To clarify the nature of resonance, precise measurements on the ratio are needed, and further investigation on the effects of coupled channels is recommended.

Entanglement between valence and sea quarks in hadrons of 1+1 dimensional QCD

The conceptual interpretation of valence- and sea-quark separation, which is a key aspect of the parton model and of an intuitive picture of hadron structure, becomes obscured by quantum effects in QCD. This suggests that there may be measures of entanglement between quark degrees of freedom that are present in QCD, but absent in the intuitive picture with a clear valence-sea (VS) separation. In this paper, we define the first rigorous measure of VS entanglement in QCD in an attempt to bring conceptual clarity to this issue, and, potentially, to find a measure of the applicability of the parton model to QCD bound states. This VS entanglement vanishes in the large-Nc limit, and it remains low when finite-Nc states resemble their large-Nc counterparts. We perform a numerical study of VS entanglement in 1 + 1 dimensional discrete light-cone quantized QCD, and in the process develop a method for building the color-singlet basis of 1 + 1d QCD that is manifestly complete and orthogonal by construction. We calculate this VS entanglement entropy for the first time and find that it is relatively low for the first few excited states of both mesons and baryons compared to all other states in the spectrum, with the VS entropy of ground state hadrons providing a minimum. We also see that for ground state mesons the entropy is well described in the 1/Nc approximation. These results suggest that low energy hadrons may be the only QCD bound states for which the large-Nc expansion, and perhaps the parton model, provide an accurate description. This work also provides the first evidence that the VS entanglement entropy of QCD in 3 + 1d, which would likely serve as an order parameter for the transition between quark and hadron degrees of freedom, may be perturbatively accessible through a large-Nc expansion.

Mass spectra of double-bottom baryons

Based on the relativistic quark model and the infinitesimally shifted Gaussian basis function method, we investigate the mass spectra of double-bottom baryons systematically. In the [Formula: see text]-mode which appears lower in energy than the other excited modes, we obtain the allowed quantum states and perform a systematic study of the mass spectra of the [Formula: see text] and [Formula: see text] families. We analyze the root mean square radii and quark radial probability density distributions to deeply understand the structure of the heavy baryons. Meanwhile, the mass spectra allow us to successfully construct the Regge trajectories in the [Formula: see text] plane. We also predict the masses of the ground states of double-bottom baryons and discuss the differences between the structures of our spectra and those from other theoretical methods. At last, the shell structure of the double-bottom baryon spectra is shown from which one could get a bird’s-eye view of the mass spectra. In this paper, we also make a hypothesis that the heavy baryon excitation may be dominated by the excitation of heavy quarks in the heavy quark limit. It could help to deepen the understanding of heavy baryons structure.