Negative Parity Resonances Research Articles

Decay properties of N*(1895)

The nature of nucleon resonances is still being debated, while much experimental data are accumulated. In this work, we focus on the negative parity resonance ${N}^{*}(1895)$ which is located in the scattering region of various meson-baryon coupled channels, and such dynamics can be crucial in understanding its properties. To test the relevance of such hadron dynamics, we investigate the decay properties of ${N}^{*}(1895)$ in detail. We examine how a two pole nature of ${N}^{*}(1895)$ is compatible with its observed decay properties. Moreover, we find that the resonance decays into final states involving $\mathrm{\ensuremath{\Lambda}}(1405)$ and $\mathrm{\ensuremath{\Sigma}}(1400)$, where the latter is not yet observed experimentally. Such decay processes can be useful to study the properties of the aforementioned hyperon resonances.

2p decays of O11

In a potential model, I have estimated decay widths for $^{11}\mathrm{O}$ to $^{9}\mathrm{C}+2p$ for sequential decay through $^{10}\mathrm{N}$ resonances and by simultaneous $2p$ ($^{2}\mathrm{He}$) decay by integrating over the relevant energy profiles. Results indicate that sequential decays through positive-parity resonances are only slightly smaller than those through negative-parity resonances. Simultaneous decay is predicted to be larger than sequential.

A covariant model for the negative parity resonances of the nucleon

We present a model for the γ*N → N* helicity amplitudes, where N is the nucleon and N* is a negative parity nucleon excitation, member of the SU(6)-multiplet [70, 1-]. The model combines the results from the single quark transition model for the helicity amplitudes with the results of the covariant spectator quark model for the γ*N → N* (1535) and γ*N → N* (1520) transitions. With the knowledge of the amplitudes A1/2 and A3/2 for those transitions we calculate three independent coefficients defined by the single quark transition model and make predictions for the helicity amplitudes associated with the γ*N → N* (1650), γ*N → N* (1700), γ*N → Δ (1620), and γ*N → Δ (1700) transitions. In order to facilitate the comparison with future experimental data at high Q2, we provide also simple parametrizations for the amplitudes, compatible with the expected falloff at high Q2.

Three-flavor chiral effective model with four baryonic multiplets within the mirror assignment

In the case of three quark flavors, (pseudo)scalar diquarks transform as antiquarks under chiral transformations. We construct four spin-1/2 baryonic multiplets from left- and right-handed quarks as well as left- and right-handed diquarks. The fact that two of these multiplets transform in a "mirror" way allows for chirally invariant mass terms. We then embed these baryonic multiplets into the Lagrangian of the so-called extended Linear Sigma Model, which features (pseudo)scalar and (axial-)vector mesons, as well as glueballs. Reducing the Lagrangian to the two-flavor case, we obtain four doublets of nucleonic states. These mix to produce four experimentally observed states with definite parity: the positive-parity nucleon $N(939)$ and Roper resonance $N(1440)$, as well as the negative-parity resonances $N(1535)$ and $N(1650)$. We determine the parameters of the nucleonic part of the Lagrangian from a fit to masses and decay properties of the aforementioned states. Studying the limit of vanishing quark condensate, we conclude that $N(939)$ and $N(1535)$, as well as $N(1440)$ and $N(1650)$ form pairs of chiral partners.

A solution to the old puzzle of 0+ resonances above the 0+2 Hoyle state in 12C — A new analysis with complex-scaled 3α OCM —

We have developed the complex-scaling method (CSM) by using the complex-range (or oscillating) Gaussian basis functions that are suited for describing highly oscillating few-body wave functions. The eigenvalue distribution of the complex scaled Hamiltonian becomes much more precise and the maximum scaling angle becomes drastically larger than those given by the use of real-range Gaussians. Owing to this advantage, we were able to isolate the S-matrix pole of the new broad 0+3 resonance from the 3α continuum. This confirms the Kurokawa-Kato's prediction (2005) of the new 0+3 resonance, which is considered to correspond to the newly observed 0+3 resonance (Ex = 9.04 MeV, Γ = 1.45 MeV) by Itoh et al. (2013). As a result the long-standing puzzle for the 0+ and 2+ resonances above the 0+ Hoyle state in 12C was solved. In this paper, the negative parity resonances with J = 1−, 2−, 3−, 4− and 5− are newly calculated.

Ground states and excitation spectra of baryons in a non-relativistic model with the anharmonic potential

In this work the mass spectra for some of the baryon resonances of the particle data group with three and four star status are obtained, and a unified description of the ground states and excitation spectra of baryons are provided in the framework of a non-relativistic potential model. For this goal we have analytically solved the radial Schrödinger equation for three identical interacting particles with the anharmonic potential by using the Ansatz method and then we have calculated the baryon resonances spectrum by using the Gürsey Radicati mass formula (GR) and with generalized Gürsey Radicati mass formula (GGR). The results of our model show that the calculated masses of baryon resonances by using the generalized Gürsey Radicati mass formula are found to be in good agreement with the tabulations of the Particle Data Group. The overall good description of the spectrum which we obtain shows that our model can also be used to give a fair description of the energies of the excited multiples up to 3 GeV mass and negative-parity resonance. Moreover, we have shown that our model reproduces the position of the Roper resonance of the nucleon.

The light and strange baryon spectrum in a non-relativistic hypercentral quark potential model and algebraic framework

In this paper, we studied the baryon resonances spectrum within a non-relativistically quark model using a simple approach based on the Gursey-Radicati mass formula (GR). The average energy value of each SU(6) multiplet is described using the SU(6) invariant interaction given by a hypercentral potential. In this paper the hypercentral potential is composed of four components: the oscillatory potential, color charge, the intraction quark and neutral gluon and the dipole-dipole electromagnetic interaction. The results of our model (the combination of our proposed hypercentral potential and the generalized GR mass formula to the description of the spectrum) show that the light and strange baryons spectrum are in general fairly well reproduced. The overall good description of the spectrum which we obtain shows that our model can also be used to give a fair description of the energies of the excited multiplets with more than 2GeV mass and negative-parity resonance.

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.

A new method for obtaining the spectrum of baryon resonances in the Killingbeck potential

In this paper, we investigate the spin- and flavor-dependent SU(6) violations in the baryon resonances spectrum using a simple approach based on the Gürsey–Radicati (GR) mass formula. The relativistic energy spectrum has some very important features that makes it vastly superior to the nonrelativistic one; so, in order to obtain the average energy value of each SU(6) multiplet, we have exactly solved the Dirac equation for the Killingbeck potential analytically by using the wave function ansatz method. The results of our model (the combination of our proposed hypercentral potential and the generalized GR mass formula for the description of the spectrum) show that the strange and nonstrange baryon spectra are, in general, fairly well reproduced. The overall good description of the spectrum which we obtain shows that our model can also be used to give a fair description of the energies of the excited multiplets with more than 2 GeV mass and negative-parity resonance. Moreover, we have shown that our model reproduces the position of the Roper resonance of the nucleon. Finally, we compare the results obtained by the Dirac equation for the Killingbeck potential with the corresponding results of the Schrödinger equation for the Cornell potential and we find that our model has improved the results of the nonrelativistic model.

A relativistic model for the light baryon masses in hypercentral potential and spin-flavor dependence

In this paper, we studied the light baryon resonances spectrum within a relativistically quark model based on Dirac equation and generalized Gursey Radicati mass formula (GR). For exact solving of the Dirac equation for our proposed hypercentral confining potential analytically, we used the Ansatz approach. The results of our model show that the light baryons spectrums are fairly well reproduced, thanks to the flavor-dependent interaction. The overall good description of the spectrums which we obtain shows that our model can also be used to give a fair description of the energies of the negativeparity resonance and excited multiplets, at least up to 3 GeV. Eventually, we compare the results obtained from our model with the corresponding results of the Schrodinger equation for the Coulombiclike term plus a linear confining term and we found out that our model has certainly improved the results of the non-relativistic model.

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).

Photoproduction of excited baryons in the 1 /Nc expansion of QCD

Baryon photo-couplings have been the subject of many studies over the last forty years, and are key elements in the understanding of baryon structure and dynamics. In this talk I will present the results of the photoproduction helicity amplitudes for excited baryons in the context of the 1=Nc expansion of QCD [1]. Such an expansion has been shown to provide a useful and systematic framework for the analysis of various baryon properties. This is mostly due to the existence of a contracted spin-flavor symmetry in the large Nc limit[2, 3]. Although SU(2N f) is not an exact symmetry in the excited baryon sector[4], its N 0 c breaking is small as several analyses of the baryon spectrum have shown[5‐7]. In this context the photoproduction helicity amplitudes for the negative parity excited baryons have been first analyzed in [8]. Here we report on an extension of such analysis which includes a systematic building of a complete basis of current operators to sub-leading order in the 1=Nc expansion, for both negative and positive parity resonances[9, 10].

Approach to Perturbative QCD Results in Transition Amplitudes of Nucleon Negative-Parity Resonances**The project supported by National Natural Science Foundation of China under Grant No. 10075056, the CAS Knowledge Innovation Project under Grant No. KC2-SW-N02, and Institute of Theoretical Physics

The scaling behaviors of the nucleon resonance transition amplitudes from perturbative QCD (PQCD) are utilized to parametrize the amplitudes of the first negative-parity nucleon resonance . Our analysis indicates that the constraints of the transition amplitude for the resonance at the limit by QCD sum rule calculations are not applicable at a moderate range of compared with the present available data if the contribution of is dominant in the limit.

Excited nucleons with chirally improved fermions

We study positive and negative parity nucleons on the lattice using the chirally improved lattice Dirac operator. Our analysis is based on a set of three operators chi_i with the nucleon quantum numbers but in different representations of the chiral group and with different diquark content. We use a variational method to separate ground state and excited states and determine the mixing coefficients for the optimal nucleon operators in terms of the chi_i. We clearly identify the negative parity resonances N(1535) and N(1650) and their masses agree well with experimental data. The mass of the observed excited positive parity state is too high to be interpreted as the Roper state. Our results for the mixing coefficients indicate that chiral symmetry is important for N(1535) and N(1650) states. We confront our data for the mixing coefficients with quark models and provide insights into the physics of the nucleon system and the nature of strong decays.

Three-body calculation of the structure ofΛ9Be

The hypernucleus ${}_{\ensuremath{\Lambda}}^{9}\mathrm{Be}$ is investigated using the $\ensuremath{\alpha}+\ensuremath{\Lambda}+\ensuremath{\alpha}$ cluster model. The corresponding Faddeev equations are solved for different $\ensuremath{\alpha}\ensuremath{-}\ensuremath{\alpha}$ and $\ensuremath{\Lambda}\ensuremath{-}\ensuremath{\alpha}$ interactions that describe both ${}^{8}\mathrm{Be}$ and ${}_{\ensuremath{\Lambda}}^{5}\mathrm{He}$ energy spectra. For the ground state ${J}^{\ensuremath{\pi}}={\frac{1}{2}}^{+}$ and excited states ${\frac{3}{2}}^{+}$ and ${\frac{5}{2}}^{+}$ we include the Coulomb repulsion between the $\ensuremath{\alpha}'\mathrm{s}$ and calculate, in addition to the energy eigenvalues, the Coulomb energy, the $\ensuremath{\alpha}$- and $\ensuremath{\Lambda}$-particle mean radius, the rms charge radius, the electric quadrupole moment $(Q),$ as well as the magnetic dipole $(\ensuremath{\mu})$ and octopole $({\ensuremath{\mu}}_{3})$ moments. To the best of our knowledge these observables have not yet been measured and, therefore, our calculation constitutes the first prediction. Structural differences between ${}^{9}\mathrm{Be}$ and ${}_{\ensuremath{\Lambda}}^{9}\mathrm{Be}$ lead to values of Q and $\ensuremath{\mu}$ that have opposite sign. Unlike previous theoretical work we find only two degenerate negative parity resonances ${\frac{1}{2}}^{\ensuremath{-}}({\frac{3}{2}}^{\ensuremath{-}})$ but, in addition, we get two degenerate positive parity resonances with ${J}^{\ensuremath{\pi}}={\frac{7}{2}}^{+}({\frac{9}{2}}^{+})$ at higher energy which, together with the bound states, complete the positive parity rotational band.

Chiral unitary approach to the [formula omitted] , [formula omitted] couplings for the [formula omitted] resonance

Using a chiral unitary model in which the negative parity nucleon resonance N ∗≡N ∗(1535) is generated dynamically by means of the Bethe–Salpeter equation with coupled meson–baryon channels in the S=0 sector, we have obtained the π 0N ∗N ∗ and ηN ∗N ∗ couplings. The π 0N ∗N ∗ coupling has smaller strength but the same sign as the π 0NN coupling. This rules out the mirror assignment of chiral symmetry where the ground state nucleon N and the negative parity resonance N ∗ are envisaged as chiral partners in the baryon sector.

Electromagnetic transition form factors of negative parity nucleon resonances

We have calculated the transition form factors for electromagnetic excitation of the negative parity resonances of the nucleon using different models previously proposed, and we discuss their results and limits by comparison with experimental data.

Neutron resonances in 166Ho.

We report the results of a high-resolution study of neutron resonances below 500 eV in $^{166}\mathrm{Ho}$. We find nine previously unreported weak resonances at energies 24.79, 75.08, 119.98, 187.94, 210.86, 227.87, 235.94, 248.60, and 264.98 eV. Bayesian probability analysis of the widths indicates they are formed primarily by s-wave capture and are therefore negative-parity resonances. If they have measurable d-wave neutron widths, they are candidates for the fivefold correlation test of time reversal. \textcopyright{} 1996 The American Physical Society.

Constituent quark model calculation for a possible JP = 0−, T = 0 dibaryon

There exists experimental evidence that a dibaryon resonance d' with quantum numbers J^P=0^-,T=0 and mass 2065 MeV could be the origin of the narrow peak in the (\pi^+ ,\pi^- ) double charge exchange cross--sections on nuclei. We investigate the six--quark system with these quantum--numbers within the constituent quark model, with linear confinement, effective one--gluon exchange at short range and chiral interactions between quarks (\pi and \sigma exchange). We classify all possible six quark states with J^P=0^-,T=0, and with N=1 and N=3 harmonic oscillator excitations, using different reduction chains. The six--quark Hamiltonian is diagonalized in the basis including the unique N=1 state and the 10 most important states from the N=3 shell. We find, that with most of the possible sets of parameters, the mass of such a "dibaryon" lies above the N(939)+N^\ast(1535) threshold. The only possibility to describe the supposed d'(2065) in the present context is to reduce the confinement strength to very small values, however at the expense of describing the negative parity resonances N^\ast. We also analyze the J^P=0^-,T=2,N=1 six--quark state.

Distribution amplitudes and electroproduction of the delta and other low-lying resonances.

Calculations are presented of certain moments of the wave function of the \ensuremath{\Delta} and of the lowest-lying negative-parity resonances. These are used to obtain model distribution amplitudes for these resonances and to calculate the size of the high-${Q}^{2}$ nucleon-resonance transition amplitude for each case. The I=(3/2 resonances are less asymmetric than the I=(1/2 ones, and indeed are compatible with total symmetry and even with being asymptotic; the agreement between calculation and measurement is good for the ${S}_{11}$(1535) transition amplitude although inconclusive for the \ensuremath{\Delta}. (For the isoquartet negative-parity ground state, the data presently hardly exist.)