Negative Parity Baryon Resonances Research Articles

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.

χ-SU(3) BETHE SALPETER MODEL: EXTENSION TO SU(6) AND SU(8) SPIN-FLAVOR SYMMETRIES

Consistent SU(6) and SU(8) spin-flavor extensions of the SU(3) flavor Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian are constructed, which incorporate vector meson degrees of freedom. In the charmless sector, the on-shell approximation to the Bethe-Salpeter (BS) approach successfully reproduces previous SU(3) WT results for the lowest-lying s–wave negative parity baryon resonances. It also provides some information on the dynamics of heavier ones and of the lightest d-wave negative parity resonances, as e.g. the Λ(1520). For charmed baryons the scheme is consistent with heavy quark symmetry, and our preliminary results in the strangeness-less charm C = +1 sector describe the main features of the three-star JP = 1/2− Λc(2595) and JP = 3/2− Λc(2625) resonances. We also find a second broad JP = 1/2− state close to the Λc(2595).

Resonances and the Weinberg-Tomozawa 56-baryon-35-meson interaction

Vector meson degrees of freedom are incorporated into the Weinberg-Tomozawa (WT) meson-baryon chiral Lagrangian by using a scheme which relies on spin--flavor SU(6) symmetry. The corresponding Bethe-Salpeter approximation successfully reproduces previous SU(3)--flavor WT results for the lowest-lying s--wave negative parity baryon resonances, and it also provides some information on the dynamics of the heavier ones. Moreover, it also predicts the existence of an isoscalar spin-parity $\frac32^-$ $K^*N$ bound state (strangeness +1) with a mass around 1.7--1.8 GeV, unstable through $K^*$ decay. Neglecting d-wave KN decays, this state turns out to be quite narrow ($\Gamma \le 15$ MeV) and it might provide clear signals in reactions like $\gamma p \to \bar K^0 p K^+\pi^-$ by looking at the three body $p K^+\pi^-$ invariant mass.

Spin effects in backward deuteron scattering and baryonic degrees of freedom in the deuteron

The effect of the baryon-resonance admixture to the deuteron wave function on the momentum dependences of the differential cross section, the tensor analyzing power T20, and the polarization-transfer coefficient κ0 for backward elastic deuteron-proton scattering at high energies is investigated. The reaction in question is assumed to proceed predominantly through nucleon and nucleon-resonance exchanges. The formalism used in this study is based on light-front dynamics. The effect of various parameters of the problem on the results of the calculations is analyzed, and it is shown that, even at a 1% level of the total admixture of nucleon resonances to the deuteron wave function, a description of experimental data that is superior to that within the one-nucleon-exchange approximation can be achieved by appropriately choosing the contributions of various resonances. For qualitative agreement between the results of the calculations and experimental data to be attained, it is sufficient to take into account the contributions of the lightest negative-parity baryon resonances. Upon taking into account baryon exchanges, results computed for observables with different deuteron wave functions show a smaller scatter than analogous results obtained within the one-nucleon-exchange approximation.

Negative parity non-strange baryons

Our previos study is extended to negative parity baryon resonances up to J = 9 2 − . The framework is a semi-relativistic constituent quark model. The quark-quark interaction contains a Coulomb plus linear confinement terms and a short distance spin-spin and tensor terms. It is emphasized that a linear confinement potential gives too large a mass to the D 35(1930) resonance.

Sextet string tension, mock baryonia and the U(3.1) resonance

We investigate the potential between static color sextet sources, a topic of central importance in connection with the existence or non-existence of mock-baryonia. The result is that these states should exist. We derive an effective potential for diquarks and discuss features of T- and M-baryonia which may help to clarify the nature of the U(3.1) in forthcoming experiments. The suggested decay mechanism predicts that decays into Λp plus pions prefer to proceed via the negative parity baryon resonances. The presented material is identical with that to be published in Zeitschrift für Physik C, Particles and Fields (in press). We therefore restrict ourselves to answering two questions that arose in the discussion.

Sextet string tension, mock baryonia and theU(3.1) resonance

We investigate the potential between static color sextet sources, a topic of central importance in connection with the existence or non-existence of mock-baryonia. The result is that these states should exist. We derive an effective potential for diquarks and discuss features ofT- andM-baryonia which may help to clarify the nature of theU(3.1) in forthcoming experiments. The suggested decay mechanism predicts that decays into Λ $$\bar p$$ plus pions prefer to proceed via the negative parity baryon resonances.

An su (6) w fit to the negative parity baryon decay rates

We present a least squares fit to the experimental data on decays of negative parity baryon resonances into a pseudoscalar meson and either a J P = 1/2 + stable baryon or a J P = 3/2 + decuplet member. We find that the s-waves and d-waves are separately in good agreement with the predictions of SU (6) w ⊗ O(2) L z . Predictions are given regarding several as yet unobserved decay processes, and for those which concern hitherto undetected resonances, their possible detection is discussed.

Extension of the Mass Operator in the Symmetric Quark Model for Negative-Parity Baryon Resonances

Extension of the Mass Operator in the Symmetric Quark Model for Negative-Parity Baryon Resonances

Formation and decay of negative-parity baryon resonances in a brokenU 6,6 model

Formation and decay of negative-parity baryon resonances in a brokenU 6,6 model

Reanalysis of the Lowest-Mass Negative-Parity Baryon Resonances Using the Symmetric Quark Model

Reanalysis of the Lowest-Mass Negative-Parity Baryon Resonances Using the Symmetric Quark Model

Negative parity baryon resonances in the SU(6) symmetry

The decay ratios of negative parity baryon resonances are compared with prediction of SU W (6) symmetry by assigning these resonances to the 540 supermultiplet. Some “semiempirical” mass formulae are also investigated. It turns out that the present experimental data are not inconsistent with such an assignment. Nevertheless, we believe that not all the negative parity baryon resonances of spins 1/2−, 3/2−, 5/2− fit into the 540-plet without contradicting experimental values.

Higher Meson and Baryon Resonances in aSU(18)Quark Model

The three-triplet model of Han and Nambu is extended to a broken $\mathrm{SU}(18)$ symmetry. Quarks are assumed to be fermions (only antisymmetric states are allowed). The corresponding representations of $\mathrm{SU}(18)$ are reduced with respect to the subgroup $\mathrm{SU}(6)\ensuremath{\bigotimes}\mathrm{SU}{(3)}^{\ensuremath{'}}$, and only $\mathrm{SU}{(3)}^{\ensuremath{'}}$ singlets are retained. This selects the permissible representations of $\mathrm{SU}(6)$. If all quarks are in $s$ states, the $q\overline{q}$ (quark-antiquark) system corresponds to 1+35, and the $\mathrm{qqq}$ system to 56, as expected (20 and 70 do not appear). The next higher meson resonances consist of $\mathrm{qq}\overline{q}\overline{q}$ and come in three sets, corresponding to 1, 35, and (1+35+189+405). Their parity is always positive, and their charge-conjugation properties are tabulated. The negative-parity baryon resonances ($\mathrm{qqq}\overline{q}\overline{q}$) can be classified according to 56 and (70+1134), while 700 does not appear. Still higher resonances can easily be obtained by the same method, but the results then become rather dubious, because of the competition of states with nonzero orbital angular momentum, and because of relativistic effects. Finally, we mention the possibility of creating stable isobars with strangeness -6.

Negative-parity baryon resonances and brokenSU 6×SU 6 symmetry

Negative-parity baryon resonances and brokenSU 6×SU 6 symmetry