Negative Parity Baryons Research Articles

Analysis of the bottom-charm baryon states with QCD sum rules

In this work, we explore the ground state mass spectrum of the bottom-charm baryon states in the framework of the QCD sum rules in a comprehensive way. In calculations, we distinguish the contributions of the positive-parity and negative-parity baryon states unambiguously, and investigate the energy scale dependence of the QCD sum rules in detail and observe that the acceptable energy scales are [Formula: see text], while the best energy scale is [Formula: see text]. The predictions can be confronted to the experimental data in the future and shed light on the QCD low energy dynamics.

Novel pentaquark picture for singly heavy baryons from chiral symmetry

We propose a new type of structure for singly heavy baryons of $Qqq\overline{q}q$ in addition to the conventional one of $Qqq$. Based on chiral symmetry of the light quarks, we show that the $Qqq\overline{q}q$ baryon offers a novel picture for heavy-quark spin-singlet and flavor-antisymmetric baryons. By making use of the effective Lagrangian approach, we find that ${\mathrm{\ensuremath{\Lambda}}}_{c}(2765)$ and ${\mathrm{\ensuremath{\Xi}}}_{c}(2967)$ are mostly $Qqq\overline{q}q$, while ${\mathrm{\ensuremath{\Lambda}}}_{c}(2286)$ and ${\mathrm{\ensuremath{\Xi}}}_{c}(2470)$ are mostly $Qqq$. The masses of negative-parity baryons are predicted. We also derive a sum rule and the extended Goldberger-Treiman relation that the masses of the baryons satisfy. Furthermore, a mass degeneracy of parity partners of the baryons with the restoration of chiral symmetry is discussed. These are the unique features that the conventional picture of radial excitation in the quark model does not accommodate. Our findings provide useful information not only for future experiments but also for future lattice simulations on diquarks.

Parity doubling of baryons in QCD thermodynamics

Motivated by the recent lattice study, thermal masses of the baryon parity-doublers are explored for various pion masses. A general trend of the nucleon and delta parity-doublers is consistent with the lattice QCD results, whereas hyperon masses exhibit a qualitatively different behavior, traced back to the lattice set-up with mπ/mK∼1.We further investigate the fluctuations and correlations involving baryon number in hot hadronic matter with modified masses of negative-parity baryons, in the context of the hadron resonance gas. Confronting the baryon number susceptibility, baryon-charge correlation, and baryon-strangeness correlation and their ratios with the lattice QCD data, we show that the strong downward mass shift in the hyperons can accidentally reproduce some correlation ratios, however it also tends to overshoot the individual fluctuations and correlations. This indicates that in order to correctly account for the influence of the chiral symmetry restoration on the fluctuation observables, a consistent framework of in-medium effects beyond hadron mass shifts is required.

Weak decays of doubly heavy baryons: “decay constants”**Supported by National Natural Science Foundation of China (11575110, 11655002, 11735010), Natural Science Foundation of Shanghai (15DZ2272100, 15ZR1423100), Shanghai Key Laboratory for Particle Physics and Cosmology and Key Laboratory for Particle Physics, Astrophysics and Cosmology, Ministry of Education

Inspired by the recent observation of the by the LHCb Collaboration, we explore the “decay constants” of doubly heavy baryons in the framework of QCD sum rules. With the , and baryons interpolated by three-quark operators, we calculate the correlation functions using the operator product expansion and include the contributions from operators up to dimension six. On the hadron side, we consider both contributions from the lowest-lying states with and from negative parity baryons with . We find that the results are stable and the contaminations from negative parity baryons are not severe. These results are ingredients for the QCD study of weak decays and other properties of doubly-heavy baryons.

Form factors for the rare Λb(Λb*)→Nℓ+ℓ− decays in light cone QCD sum rules

Form factors of the rare $\Lambda_{b}(\Lambda_{b}^*)\to N\ell^{+}\ell^{-}$ decays are calculated in the framework of the light cone QCD sum rules by taking into account of the contributions from the negative parity baryons. Using the obtained results on the form factors, the branching ratios of the considered decays are estimated. The numerical survey for the branching ratios of the $\Lambda_b \rar N\ell^+\ell^- $ and $\Lambda_b^\ast \rar N\ell^+\ell^- $ decays indicate that these transitions could be measurable in LHCb in near future. Comparison of our predictions on the form factors and branching ratios with those existing in the literature is also performed.

29pWG-1 QCD sum rules for positive and negative-parity baryons

29pWG-1 QCD sum rules for positive and negative-parity baryons

Reanalysis of Ωc→Ξc+K- Decay in QCD

The strong coupling constants of newly observed Ωc0 baryons with spins J=1/2 and J=3/2 decaying into Ξc+K- are estimated within light cone QCD sum rules. The calculations are performed within two different scenarios on quantum numbers of Ωc baryons: (a) all newly observed Ωc baryons are negative parity baryons; that is, the Ωc(3000), Ωc(3050), Ωc(3066), and Ωc(3090) have quantum numbers JP=1/2- and JP=3/2- states, respectively; (b) the states Ωc(3000) and Ωc(3050) have quantum numbers JP=1/2- and JP=1/2+, while the states Ωc(3066) and Ωc(3090) have the quantum numbers JP=3/2- and JP=3/2+, respectively. By using the obtained results on the coupling constants, we calculate the decay widths of the corresponding decay. The results on decay widths are compared with the experimental data of LHC Collaboration. We found out that the predictions on decay widths within these scenarios are considerably different from the experimental data; that is, both considered scenarios are ruled out.

Overlap between Lattice QCD and HRG with in-medium effects and parity doubling

We investigate the fluctuations and correlations involving baryon number in hot hadronic matter with modified masses of negative-parity baryons, in the context of the hadron resonance gas. Temperature-dependent masses are adopted from the recent lattice QCD results and from a chiral effective model which implements the parity doubling structure with respect to the chiral symmetry. Confronting the baryon number susceptibility, baryon-charge correlation, and baryon-strangeness correlation and their ratios with the lattice QCD data, we show that the strong downward mass shift in hyperons can accidentally reproduce some correlation ratios, however it also tends to overshoot the individual fluctuations and correlations. This indicates, that in order to correctly account for the influence of the chiral symmetry restoration on the fluctuation observables, a consistent framework of in-medium effects beyond hadron mass shifts is required.

Mass and magnetic dipole moment of negative-parity heavy baryons with spin-3/2

We calculate the mass and residue of the heavy spin--3/2 negative parity baryons with single heavy bottom or charm quark by the help of a two-point correlation function. We use the obtained results to investigate the diagonal radiative transitions among the baryons under consideration. In particular, we compute corresponding transition form factors via light cone QCD sum rules which are then used to obtain the magnetic dipole moments of the heavy spin--3/2 negative parity baryons. We remove the pollutions coming from the positive parity spin--3/2 and positive/negative parity spin--1/2 baryons by constructing sum rules for different Lorentz structures. We compare the results obtained with the existing theoretical predictions.

Radiative decays of negative parity heavy baryons in the framework of the light cone QCD sum rules

The transition form factors responsible for the radiative ΣQ→ΛQγ and ΞQ′→ΞQγ decays of the negative parity baryons are examined within light cone QCD sum rules. The decay widths of the radiative transitions are calculated using the obtained results of the form factors. A comparison of our predictions on decay widths with the corresponding widths of positive parity baryons is given.

Strong coupling constant of negative parity octet baryons with light pseudoscalar mesons in light cone QCD sum rules

The strong coupling constants of the π and K mesons with negative parity octet baryons are estimated within the light cone QCD sum rules. It is observed that all strong coupling constants, similarly to the case for the positive parity baryons, can be described in terms of three invariant functions, where two of them correspond to the well known F and D couplings in the SU(3)f symmetry, and the third function describes the SU(3)f symmetry violating effects. We compare our predictions on the strong coupling constants of pseudoscalar mesons of negative parity baryons with those corresponding to the strong coupling constants for the positive parity baryons.

Magnetic moment for the negative parity Λ → Σ 0 transition in light cone QCD sum rules

The magnetic moment of the $\Lambda \to \Sigma^0$ transition between negative parity, baryons is calculated in framework of the QCD sum rules approach, using the general form of the interpolating currents. The pollution arising from the positive--to--positive, and positive to negative parity baryons are eliminated by constructing the sum rules for different Lorentz structures. Nonzero value of the considered magnetic moment can be attributed to the violation of the $SU(3)$ symmetry.

Magnetic moments of negative parity baryons in QCD

Using the most general form of the interpolating current for the octet baryons, the magnetic moments of the negative-parity baryons are calculated within the light-cone sum rules. The contributions coming from diagonal transitions of the positive-parity baryons, and also from non-diagonal transition between positive and negative-parity baryons are eliminated by considering the combinations of different sum rules corresponding to the different Lorentz structures. A comparison of our results on magnetic moments of the negative-parity baryons with the other approaches existing in literature is presented.

Magnetic moments of negative parity baryons from the effective Hamiltonian approach to QCD

Magnetic moments of $S_{11}(1535)$ and $S_{11}(1650)$ baryons are studied in the framework of the relativistic three-quark Hamiltonian derived in the Field Correlation Method. The baryon magnetic moments are expressed via the average current quark energies which are defined by the fundamental QCD parameters: the string tension $\sigma$, the quark masses, and the strong coupling constant $\alpha_s$. For the $J^P=1/2^+$ baryon octet the approach was shown to give a good first approximation to the experimental moments. Resulting magnetic moments for the $J^P=1/2^-$ nucleons are compared both to model calculations and to those from lattice QCD.

γ*N→N(1535)transition form factors in QCD

The form factors, as well as the helicity amplitudes for the ${\ensuremath{\gamma}}^{*}N\ensuremath{\rightarrow}N(1535)$ transition, are calculated in the framework of the QCD light-cone sum rules. The contamination coming from diagonal transition is eliminated by considering combinations of the sum rules corresponding to different Lorentz structures. A similar procedure is applied for the determination of the residue and mass of the negative-parity baryon. A comparison of our predictions on the helicity amplitudes with the existing theoretical and experimental results is also presented.

Effects of Instantons on P-Wave Multi-Quark Systems

We study noncentral parts of the flavor-singlet interquark interactions induced by the instanton-light quark coupling and their effects on the P-wave multiquark systems: the negative parity baryons and the relative P-wave two-nucleon systems. It is found that the noncentral force from the instanton induced interaction reduces that from the one-gluon exchange in the excited P-wave nucleons. This cancellation does not occur in the spin-orbit force between nucleons, where the flavor-symmetric q-q interaction plays a dominant role. Also, the cancellation is weakened in the flavor-singlet negative-parity baryons by the three-body part of instanton induced interaction, which may lead larger separation seen between Λ(1405) and Λ(1520).

[70,ℓ+]baryons in largeNcQCD revisited: The effect on Regge trajectories

A simple procedure within the $1/N_c$ expansion method where all the $N_c$ quarks are treated on the same footing has been found successful in describing mixed symmetric negative parity baryon states belonging to the $[{\bf 70},\ell^-]$ multiplets %with $\ell$ = 1, 2 or 3. of the $N$ = 1 and 3 bands. Presently it is applied to mixed symmetric positive parity $[{\bf 70},0^+]$ and $[{\bf 70},2^+]$ multiplets of the $N$ = 2 band. We search for the most dominant terms in the mass formula. The results are compared to those obtained in the procedure where the system is separated into a core and an excited quark. We find that both the spin and isospin operators of the entire system of $N_c$ quarks play dominant roles in describing the data, like for negative parity states. As a by-product we present the contribution of the leading spin-isospin singlet term as a function of the band number, which hints at distinct Regge trajectories for the symmetric and mixed symmetric states.

Simultaneous analysis of non-strange negative parity baryon properties in large Nc QCD

Non-strange excited baryons are analyzed within the Large QCD framework. The Large approach is used as an effective theory to simultaneously fit the masses and decays with corrections up to . Values of the mixing angles for the and nucleon mass eigenstates are obtained within the simultaneous analysis. The observed effective operator hierarchy is consistent with the previous studies conducted in this sector and improved results are obtained. DOI: http://dx.doi.org/10.4038/sljp.v13i2.5443 Sri Lankan Journal of Physics, Vol. 13 ( 2 ) ( 2012 ) 27 - 38

Production of negative parity baryons in the holographic Sakai-Sugimoto model

We extend our investigation of resonance production in the Sakai-Sugimoto model to the case of negative parity baryon resonances. Using holographic techniques we extract the generalized Dirac and Pauli baryon form factors as well as the helicity amplitudes for these baryonic states. Identifying the first negative parity resonance with the experimentally observed S_{11}(1535), we find reasonable agreement with experimental data from the JLab-CLAS collaboration. We also estimate the contribution of negative parity baryons to the proton structure functions.

Negative parity baryons in the1/Ncexpansion: The three towers of states revisited

We discuss the compatibility between the quark-shell picture and the meson-nucleon scattering picture in large $N_c$ QCD for mixed symmetric $\ell$ = 1 states previously analyzed by using a simple Hamiltonian including operators up to order $\mathcal{O}(N^0_c)$ defined in the standard ground state symmetric core + excited quark procedure. Here we introduce a Hamiltonian of order $\mathcal{O}(N^0_c)$ defined in a new approach where the separation of the system into two parts is not required. Three degenerate sets of states (towers) with the same quantum numbers as in the scattering picture and in the standard procedure are obtained. Thus the 0 is equally achieved. The eigenvalues of the presently chosen Hamiltonian also have simple analytic expressions, depending linearly on the three dynamical coefficients entering the Hamiltonian. This reinforces the validity of the new approach which had already 0 described excited negative parity baryons in a large energy range.