We study the photoproduction of K * (892) vector meson from both the charged and neutral reactions, γp → K * + Λ and γn → K * 0 Λ. The production mechanisms that we consider include t-channel K * , K, κ exchanges, s-channel nucleon diagram, and u-channel Λ, Σ, Σ * diagrams. These could constitute important backgrounds for future investigation of "missing" resonances that can be searched for especially in these reactions. The t-channel K meson exchange is found to dominate both reactions. The total and differential cross sections are presented together with some spin asymmetries.

Differential cross sections for neutrino-(and antineutrino-) induced nucleon knockout are calculated for neutral-current reactions from nuclei. A relativistic Fermi gas model with binding energy corrections is used. We examine the accuracy with which strange quark axial and vector current parameters can be extracted from both existing and (possible) future experiments. Both high (above 1 GeV) and low (near 150 MeV) neutrino energies and the knockout of neutrons and protons are considered.PACS number(s): 25.30.Pt, 24.85. +p

Recently, a tetraquark mixing framework has been proposed for light mesons and applied more or less successfully to the isovector resonances, a 0 ð980Þ, a 0 ð1450Þ, as well as to the isodoublet resonances,. In this work, we present a more extensive view on the mixing framework and apply this framework to the isoscalar resonances, f 0 ð500Þ, f 0 ð980Þ, f 0 ð1370Þ, f 0 ð1500Þ. Tetraquarks in this framework can have two spin configurations containing either spin-0 diquark or spin-1 diquark and each configuration forms a nonet in flavor space. The two spin configurations are found to mix strongly through the color-spin interactions. Their mixtures, which diagonalize the hyperfine masses, can generate the physical resonances constituting two nonets, which, in fact, coincide roughly with the experimental observation. We identify that f 0 ð500Þ, f 0 ð980Þ are the isoscalar members in the light nonet, and f 0 ð1370Þ, f 0 ð1500Þ are the similar members in the heavy nonet. This means that the spin configuration mixing, as it relates the corresponding members in the two nonets, can generate f 0 ð500Þ, f 0 ð1370Þ among the members in light mass, and f 0 ð980Þ, f 0 ð1500Þ in heavy mass. The complication arises because the isoscalar members of each nonet are subject to an additional flavor mixing known as Okubo-Zweig-Iizuka rule so that f 0 ð500Þ, f 0 ð980Þ, and similarly f 0 ð1370Þ, f 0 ð1500Þ, are the mixture of two isoscalar members belonging to an octet and a singlet in SU f ð3Þ. The tetraquark mixing framework including the flavor mixing is tested for the isoscalar resonances in terms of the mass splitting and the fall-apart decay modes. The mass splitting among the isoscalar resonances is found to be consistent qualitatively with their hyperfine mass splitting strongly driven by the spin configuration mixing, which suggests that the tetraquark mixing framework works. The fall-apart modes from our tetraquarks also seem to be consistent with the experimental modes. We also discuss possible existence of the spin-1 tetraquarks that can be constructed by the spin-1 diquark.

No abstract

Charged-current cross sections are calculated for quasielastic neutrino and antineutrino scattering using a relativistic meson-nucleon model. We examine how nuclear-structure effects, such as relativistic random-phaseapproximation (RPA) corrections and momentum-dependent nucleon selfenergies, influence the extraction of the axial form factor of the nucleon. RPA corrections are important only at low-momentum transfers. In contrast, the momentum dependence of the relativistic self-energies changes appreciably the value of the axial-mass parameter, M A , extracted from dipole fits to the axial form factor. Using Brookhaven's experimental neutrino spectrum we estimate the sensitivity of M A to various relativistic nuclear-structure effects. *

In the paper above, we have proposed a tetraquark picture with the mixing scheme for the I z = 1 members of the isovector (I = 1) resonances, a + 0 (980), a + 0 (1450). In particular, their mass splittings fit relatively well with the hyperfine mass splittings if they are viewed as mixtures of two spin-configurations of diquark-antidiquark constituents, |J, J 12 , J 34 = |000 , |011 , where J is the tetraquark spin, J 12 the diquark spin, J 34 the antidiquark spin. The second configuration involving the spin-1 diquark, |011 , is found to be an important ingredient in explaining the resonances of our concern in this tetraquark picture. However, the existence of the |011 component requires additional tetraquarks to be found in J = 1 and J = 2 resonances with the spin configurations, |J, J 12 , J 34 = |111 and |211 , respectively.In this erratum, we point out that our assignment of a + 1 (1260) as a candidate for the J = 1 tetraquark with the |111 configuration is incorrect because of the C-parity for its corresponding member in I z = 0. Specifically, we would like to demonstrate that the |111 state with I = 1, I z = 0 must have the C-parity odd and, in this regard, a relevant candidate for the |111 state should be b 0 1 (1235). So its charged member (I = 1, I z = 1), which in fact was considered in our paper, must be b To demonstrate that C|111 = −|111 for the isospin member of I = 1, I z = 0, we take the state with J = 1 and the spin projection M = 1 among three spin states in |111 , and we denote this state as |J M = |11 . The same proof can be done for the other spin states, |J M = |10 , |1 − 1 . The flavor structure of the member I = 1, Now it is straightforward to prove that the state above has C = − by applying the charge conjugation [Eq. (2) 123

We apply a mixing framework to the light-meson systems and examine tetraquark possibility in the scalar channel. In the diquark-antidiquark model, a scalar diquark is a compact object when its color and flavor structures are in (3 c , 3 f ). Assuming that all the quarks are in an S-wave, the spin-0 tetraquark formed out of this scalar diquark has only one spin configuration, |J, J 12 , J 34 = |000 , where J is the spin of the tetraquark, J 12 the diquark spin, J 34 the antidiquark spin. In this construction of the scalar tetraquark, we notice that another compact diquark with spin-1 in (6 c ,3 f ) can be used although it is less compact than the scalar diquark. The spin-0 tetraquark constructed from this vector diquark leads to the spin configuration |J, J 12 , J 34 = |011 . The two configurations, |000 and |011 , are found to mix strongly through the color-spin interaction. The physical states can be identified with certain mixtures of the two configurations which diagonalize the hyperfine masses of the color-spin interaction. Matching these states to two scalar resonances a 0 (980), a 0 (1450) or to K * 0 (800), K * 0 (1430) depending on the isospin channel, we find that their mass splittings are qualitatively consistent with the hyperfine mass splittings, which can support their tetraquark structure. To test our mixing scheme further, we also construct the tetraquarks for J = 1, J = 2 with the spin configurations |111 and |211 , and we discuss possible candidates in the physical spectrum.

We improve so called "naive" and "mirror" models for the positive and negative parity nucleons, N and N * , by introducing nonlinear terms allowed by chiral symmetry. Both models in this improvement reproduce the observed nucleon axial charge in free space and reveal interesting density dependence of the axial charges for N and N * , and the doublet masses. A remarkable difference between the two models is found in the off-diagonal axial charge, g AN N * , which could appear either as suppression or as enhancement of N * → πN decay in the medium.