Search

We utilize an exact quantum calculation to explore axion emission from electrons and protons in the presence of the strong magnetic field of magnetars. The axion is emitted via transitions between the Landau levels generated by the strong magnetic field. The luminosity of axions emitted by protons is shown to be much larger than that of electrons and becomes stronger with increasing matter density. Cooling by axion emission is shown to be much larger than neutrino cooling by the Urca processes. Consequently, axion emission in the crust may significantly contribute to the cooling of magnetars. In the high-density core, however, it may cause heating of the magnetar., Comment: 14 pages, 3 figures

Adopting the 3+1 neutrino mixing parameters by the IceCube and shortbase line experiments, we investigate the sterile-active neutrino oscillation effects on the supernova neutrino process. For the sterile neutrino ($\nu_s$), we study two different luminosity models. First, we presume that the $\nu_s$ does not interact with other particles through the standard interactions apart from the oscillation with the active neutrinos. Second, we consider that $\nu_s$ can be directly produced by $\nu_e$ scattering with matter. In both cases, we find that the pattern of neutrino oscillations can be changed drastically by the $\nu_s$ in supernova environments. Especially multiple resonances occur, and consequently affect thermal neutrino-induced reaction rates. As a result, $^7$Li, $^7$Be, $^{11}$B, $^{11}$C, $^{92}$Nb, $^{98}$Tc and $^{138}$La yields in the $\nu$-process are changed. Among those nuclei, $^7$Li and $^{11}$B yields can be constrained by the analysis of observed SiC X grains. Based on the meteoritic data, we conclude that the second model can be allowed while first model is excluded. The viability of the second model depends on the sterile neutrino temperature and the neutrino mass hierarchy.

Recently, a tetraquark mixing framework has been proposed for light mesons and applied more or less successfully to the isovector resonances, $a_0(980), a_0(1450)$, as well as to the isodoublet resonances, $K^*_0(800), K^*_0(1430)$. In this work, we present a more extensive view on the mixing framework and extend this to the isoscalar resonances, $f_0 (500)$, $f_0(980)$, $f_0 (1370)$, $f_0(1500)$. 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 the two nonets, which, in fact, coincide roughly with the experimental observation. We identify that $f_0 (500)$, $f_0(980)$ are the isoscalar members in the light nonet, and $f_0 (1370)$, $f_0(1500)$ 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 $f_0 (500), f_0 (1370)$ among the members in light mass, and $f_0(980), f_0(1500)$ in heavy mass. The complication arises because the isoscalar members of each nonet are subject to an additional flavor mixing known as OZI rule so that $f_0 (500), f_0 (980)$, and similarly $f_0 (1370), f_0 (1500)$, are the mixture of two isoscalar members belonging to an octet and a singlet in SU$_f$(3). 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., Comment: 16 pages, 2 figures, slightly modified, 2 references added

In this work, we investigate additional signatures to support the tetraquark mixing framework that has been recently proposed as a possible structure for the two nonets, namely $a_0 (980)$, $K_0^* (800)$, $f_0 (500)$, $f_0 (980)$ in the light nonet, $a_0 (1450)$, $K_0^* (1430)$, $f_0 (1370)$, $f_0 (1500)$ in the heavy nonet. First, we advocate that the two nonets form the flavor nonet approximately satisfying the Gell-Mann--Okubo mass relation. Then we reexamine the mass ordering generated from the tetraquark nonets and show that this mass ordering is satisfied by the two nonets although the ordering in the heavy nonet is marginal. The marginal mass ordering however can be regarded as another signature for tetraquarks because it can be explained partially by the hyperfine masses calculated from the tetraquark mixing framework. The tetraquark mixing parameters are found to be independent of isospins giving additional support for the formation of the flavor nonets. In addition, we discuss the other approaches like two-quark pictures or meson-meson bound states, and their possible limitations in explaining the two nonets. As a peculiar signature distinguished from other approaches, we investigate the fall-apart coupling strengths into two vector mesons from our tetraquarks. Coupling strengths into the two-vector modes are found to enhance strongly in the heavy nonet while they are suppressed in the light nonet. The coupling ratios, which depend on the isospin channel, are found to be huge around $\sim 15$. This trend in the two-vector modes, which is opposite to that in the two-pseudoscalar fall-apart modes, can provide another testing ground for the tetraquark mixing framework. Some experimental evidences related to the phenomena are discussed particularly from the resonances belonging to the heavy nonet., Comment: 15 pages, 2 figures, revised slighltly, version accepted for publication in PRD

We investigated pion production near threshold by the weak current in terms of multipole amplitudes. By exploiting the chiral Ward identity based on the QCD Lagrangian, we derived relevant multipole amplitudes in closed forms and presented their numerical results. In the amplitudes, scalar and pseudo scalar (PS) form factors, which represent the scalar and the PS quark density distributions, manifest by themselves. We applied these amplitudes to the cross sections for the weak- and electro-production near threshold. Both pion and PS form factor contributions are shown to account for the t-channel contribution in the charged pion electro-production near threshold. The asymmetry on the pion production by the neutrino and anti-neutrino is also discussed with their longitudinal and transverse cross sections.

By assuming the existence of extra-dimensional sterile neutrinos in big bang nucleosynthesis (BBN) epoch, we investigate the sterile neutrino ($\nu_{\rm s}$) effects on the BBN and constrain some parameters associated with the $\nu_{\rm s}$ properties. First, for cosmic expansion rate, we take into account effects of a five-dimensional bulk and intrinsic tension of the brane embedded in the bulk, and constrain a key parameter of the extra dimension by using the observational element abundances. Second, effects of the $\nu_{\rm s}$ traveling on or off the brane are considered. In this model, the effective mixing angle between a $\nu_{\rm s}$ and an active neutrino depends on energy, which may give rise to a resonance effect on the mixing angle. Consequently, reaction rate of the $\nu_{\rm s}$ can be drastically changed during the cosmic evolution. We estimated abundances and temperature of the $\nu_{\rm s}$ by solving the rate equation as a function of temperature until the sterile neutrino decoupling. We then find that the relic abundance of the $\nu_{\rm s}$ is drastically enhanced by the extra-dimension and maximized for a characteristic resonance energy $E_{\rm res}\gtrsim 0.01$ GeV. Finally, some constraints related to the $\nu_{\rm s}$, mixing angle and mass difference, are discussed in detail with the comparison of our BBN calculations corrected by the extra-dimensional $\nu_{\rm s}$ to observational data on light element abundances., Comment: Secs. 2B, 2C, 3, and 4D revised, Fig. 10 added, Figs. 2-13 revised with updated calculations, Appendices A & B added

Production of a neutrino source through a proton-induced reaction is studied by using the particle transport code geant4. Unstable isotopes such as $^{27}\mathrm{Si}$ can be produced when the $^{27}\mathrm{Al}$ target is bombarded by 15-MeV energetic proton beams. Through the $\ensuremath{\beta}$-decay process of the unstable isotope, a new electron-neutrino source in the 0--5.0 MeV energy range is obtained. Proton-induced reactions are simulated with JENDL-4.0 High Energy File (JENDL-4.0/HE). For radioactive decay processes, we use the G4 radioactive decay model based on the Evaluated Nuclear Structure Data File (ENSDF). We suggest detailed target systems required for future solar neutrino experiments, in particular for the vacuum-matter transition region. As for a detection system of the new neutrino source, we evaluate reaction or event rates for available radiochemical detectors and Low Energy Neutrino Astronomy (LENA)--type scintillator detector and discuss effects due to possible sterile neutrinos as an application.

We report the constraints from primordial nucleosynthesis on a possible time-dependent quark mass. The variation may affect binding energies and Q values as well as resonance properties of light elements through the hadron mass variation in the nucleon–nucleon interaction. Updated light-element abundances and uncertainties along with a new detailed analysis of the resonance properties on the crucial 3He(d, p)4He reaction imply a narrower range on the possible quark-mass variations in the early universe. The optimum concordance region reduces to a value consistent with no variation.

Neutrino (antineutrino) [Formula: see text] scattering off 12 C is one of key reactions for the ν-process in the nucleosysnthesis of light nuclei, which usually assumes indirect two-step processes within the energy range from a few to tens of MeV. We investigate the direct [Formula: see text] quasi-elastic scattering off 12 C around the energy region liberating one nucleon and evaluate effects of the direct processes in the abundances. The direct processes might be comparable to the indirect processes if the final state interactions between outgoing nucleons and residual nuclei are explicitly taken into account.

We investigate the structure of neutron star within the framework of the quark-meson coupling model, considering hyperons and kaon condensation. In order to compare the EoS with that from quark matter, the MIT bag model is used. We calculate the mass and radius of a neutron star by using Tolman-Oppenheimer-Volkov equations.

We evaluate mass differences between a neutron and a proton, and between a charged and a neutral meson by using a gauged linear sigma model retaining the chiral SU (2) L × SU (2) R × U (1)V symmetry. Masses of nucleons and relevant mesons are generated through the spontaneous and the explicit chiral symmetry breaking. Since our Lagrangian includes explicitly SU(2) isospin symmetry breaking term, it enables us to simultaneously consider the mass differences of a neutron and a proton, and a charged meson and a neutral one. Their reciprocal relations of the mass differences are also derived, where radiative corrections due to electromagnetic interactions are deliberately taken into account to exactly obtain the isospin symmetry breaking effect in the particle mass differences.

We present the neutral-current (NC) and charged-current (CC) reactions by incident neutrino (antineutrino) scattering on the nucleon, and also on the 12 C target in quasi-elastic region within the framework of a relativistic single particle model. Effects of the strangeness are studied on the cross sections, the ratios between the NC and CC reactions, and the asymmetries. We found that there exists some cancellation of the strange quark contributions between the knocked-out protons and neutrons in the neutrino (antineutrino)-nucleus scattering. The effect of the strangeness on the asymmetry exhibits larger than that on the ratio and the cross section.

The neutral-current neutrino-nucleus scattering is calculated through the neutrino-induced knocked-out nucleon process in the quasielastic region by using a relativistic single particle model for the bound and continuum states. The incident energy range between 500 MeV and 1.0 GeV is used for the neutrino (antineutrino) scattering on the 12 C target nucleus. The effects of the final state interaction of the knocked-out nucleon are studied not only on the cross section but also on the asymmetry due to the difference between neutrinos and antineutrinos, within a relativistic optical potential. We also investigate the sensitivity of the strange quark contents in the nucleon on the asymmetry. (Some figures in this article are in colour only in the electronic version)

Assuming four-quark structure for the $X$ resonances in low-lying region, we calculate their masses using the color-spin interaction. In specific, the hyperfine masses of the color-spin interaction are calculated for the possible states in spin-0, spin-1, spin-2 channels. The two states in spin-0 channel as well as the two states in spin-1 channel are diagonalized in order to generate the physical hyperfine masses. By matching the difference in hyperfine masses with the splitting in corresponding hadron masses and using the $X(3872)$ mass as an input, we estimate the masses corresponding to the states $J^{PC}=0^{++}, 1^{+-},2^{++}$. We find the masses of two states in $1^{+-}$ are close to those of $X(3823)$, $X(3900)$, and the mass of the $2^{++}$ state is close to that of $X(3940)$. For them, the discrepancies are about $\sim 10$ MeV. This may suggest that the quantum numbers of the controversial states are $X(3823)=1^{+-}, X(3900)=1^{+-}, X(3940)=2^{++}$. In this work, we use the same inputs parameters, the constituent quark masses and the strength of the color-spin interaction, that have been adopted in the previous work on the $D$ or $B$-meson excited states. There, it was shown that the four-quark structure can be manifested in their excited states. Thus, our results in this work provide a consistent treatment on open- and hidden-charm mesons as far as the four-quark model is concerned., 8 pages, substantially revised, more references are added, the version to be published in EPJA

We reviewed present status regarding theoretical approaches for neutrino-induced reactions and neutrino scattering. With a short introduction of relevant data, our recent calculations by distorted-wave Born approximation (DWBA) for quasielastic region are presented for MiniBooNE data. We also discussed that one step-process estimated by the DWBA is comparable to the two-step process, which has been usually used in the neutrino-nucleosynthesis. For much higher energy neutrino data, such as NOMAD data, elementary process approach was shown to be useful instead of using complicated nuclear models. But, in the low energy region, detailed nuclear structure model, such as QRPA and shell model, turn out to be inescapable to explain the reaction data.

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 ($\bar{\bm{3}}_c$, $\bar{\bm{3}}_f$). 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, $|J,J_{12},J_{34}\rangle=|000\rangle$, 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 ($\bm{6}_c$, $\bar{\bm{3}}_f$) 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 $|J,J_{12},J_{34}\rangle=|011\rangle$. The two configurations, $|000\rangle$ and $|011\rangle$, 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, $|111\rangle$ and $|211\rangle$, and discuss possible candidates in the physical spectrum., Comment: 9 pages, no figures, revised slightly

The pseudo-scalar form factor, which represents the pseudo-scalar quark density distribution due to finite quark masses on the nucleon, is shown to manifest itself with the induced pseudo-scalar form factor in the L 0 + amplitude for the charged pion electro-production. Both form factors show their own peculiar momentum dependence. Under the approximation on which the Goldberger–Treiman relation holds, a sum of both form factors' contributions accounts for the t-channel contribution in the charged pion electro-production near threshold.

Possible ambiguities in the theoretical interpretation of exclusive ( e , e ' p ) reactions are discussed on the basis of realistic model calculations. Gauge ambiguity, medium effects, and contribution of the Δ current are evaluated in distorted wave Born approximation (DWBA) where the four momentum transfer square | q µ | 2 is less than 0.5 (GeV/c) 2 . The gauge ambiguity effects are shown to be about 10% in the small missing momentum region and about 20% maximally in the high missing momentum region. Medium effects of about 6–10% appear mainly in the small missing momentum region. The Δ-resonance current influences the high missing momentum region by about 10% maximally.

Radiative muon capture is studied to investigate the induced pseudoscalar coupling constant gP in nuclear matter. According to the recent TRIUMF experiment for μ−p → nνμγ, the gP was surprisingly larger than the value obtained from μ−p → nνμ experiment by as much as 44%. The result may affect seriously theoretical interpretations of the experimental results for the radiative muon captures in finite nuclei. In view of the recent TRIUMF result, the radiative muon capture in nuclear matter is revisited in a framework of the relativistic mean field theory.

The recent TRIUMF experiment for μ−p → nνμγ gave a surprising result that the induced pseudoscalar coupling constant gP was larger than the value obtained from μ−p → nνμ experiment by as much as 44%. Subsequent debates on the result gave rise to many theoretical calculations. Most of them were skeptical for the enlarged coupling constant gP. Therefore, one needs to reexamine the theoretical analysis of the matrix element of Beder and Fearing which was exploited for the extraction of the value in the experiment. In this report we analyse the matrix element from the viewpoint of electro-magnetic coupling schemes and suggest an additional term. This additional term plays an important role in restoring the standard value of gP.

We construct the equation of state (EoS) for neutron stars explicitly including hyperons and quarks. Using the quark-meson coupling model with relativistic Hartree-Fock approximation, the EoS for hadronic matter is derived by taking into account the strange ($\sigma^{\ast}$ and $\phi$) mesons as well as the light non-strange ($\sigma$, $\omega$, $\vec{\pi}$ and $\vec{\rho}$) mesons. Relevant coupling constants are determined to reproduce the experimental data of nuclear matter and hypernuclei in SU(3) flavor symmetry. For quark matter, we employ the MIT bag model with one-gluon-exchange interaction, and Gibbs criteria for chemical equilibrium in the phase transition from hadrons to quarks. We find that the strange vector ($\phi$) meson and the Fock contribution make the hadronic EoS stiff, and that the maximum mass of a neutron star can be consistent with the observed mass of heavy neutron stars even if the coexistence of hadrons and quarks takes place in the core. However, in the present calculation the transition to pure quark matter does not occur in stable neutron stars. Furthermore, the lower bound of the critical chemical potential of the quark-hadron transition at zero temperature turns out to be around 1.5 GeV in order to be consistent with the recent observed neutron star data., Comment: 37 pages, 11 figures, 7 tables

A role of the axial-vector mesons, such as K1 and a1, on the emitted-photon spectrum in hot hadronic matter is studied through the channels πρ→a1→πγ and Kρ→K1→Kγ. Both channels could be dominant over the region lower than Eγ∼ 0.5 GeV, while the role of the K1 meson is diminished in the higher Eγ region. This study is carried out with an SUL(3) ⊗SUR(3) effective chiral Lagrangian which includes vector and axial-vector mesons systematically and explains well their hadronic and radiative decays simultaneously.

The injections of energetic hadrons could have occurred in the early universe by decays of hypothetical long-lived exotic particles. The injections induce the showers of nonthermal hadrons via nuclear scattering. Neutrons generated at these events can react with $^7$Be nuclei and reduce $^7$Be abundance solving a problem of the primordial $^7$Li abundance. We suggest that thermal neutron injection is a way to derive a model independent conservative limit on the relation between abundances of D and $^7$Li in a hadronic energy injection model. We emphasize that an uncertainty in cross sections of inelastic $n+p$ scattering affects the total number of induced neutrons, which determines final abundances of D and $^7$Li. In addition, the annihilations of antinucleons with $^4$He result in higher D abundance and trigger nonthermal $^6$Li production. It is concluded that a reduction of $^7$Li abundance from a value in the standard big bang nucleosynthesis (BBN) model down to an observational two $\sigma$ upper limit is necessarily accompanied by an undesirable increase of D abundance up to at least an observational 12 $\sigma$ upper limit from observations of quasi-stellar object absorption line systems. The effects of antinucleons and secondary particles produced in the hadronic showers always lead to a severer constraint. The BBN models involving any injections of extra neutrons are thus unlikely to reproduce a small $^7$Li abundance consistent with observations.

We study the effects of density-dependent electromagnetic, axial, and weak vector form factors on the inclusive $(e,{e}^{\ensuremath{'}})$ reaction and the charged-current neutrino-nucleus scattering in the quasi-elastic region within the framework of a relativistic single-particle model. The density-dependent form factors obtained from a quark-meson coupling model are applied into the $(e,{e}^{\ensuremath{'}})$ reaction and the neutrino-nucleus scattering via charged current. The effects of the density-dependent form factors increase the $(e,{e}^{\ensuremath{'}})$ cross sections by a few percent. However, the effects may reduce the differential cross sections up to 20% (60%) at $\ensuremath{\rho}=1.0{\ensuremath{\rho}}_{0}\phantom{\rule{4pt}{0ex}}(2.0{\ensuremath{\rho}}_{0})$ for the antineutrino scattering and also reduce the cross section up to 20% (30%) at $\ensuremath{\rho}=1.0{\ensuremath{\rho}}_{0}\phantom{\rule{4pt}{0ex}}(2.0{\ensuremath{\rho}}_{0})$ for the neutrino scattering around the peak positions, where the normal density is ${\ensuremath{\rho}}_{0}\ensuremath{\sim}0.15$ ${\mathrm{fm}}^{\ensuremath{-}3}$. For the density of finite nuclei such as $^{12}\mathrm{C}$, $^{40}\mathrm{Ca}$, and $^{208}\mathrm{Pb}$ as 0.6, 0.7, and 1.0 of ${\ensuremath{\rho}}_{0}$, the in-medium effects are 20% to 30%, even in the antineutrino case. Our theoretical double-differential and total cross sections are compared with the recent MiniBooNE data for $^{12}\mathrm{C}({\ensuremath{\nu}}_{\ensuremath{\mu}},{\ensuremath{\mu}}^{\ensuremath{-}})$ scattering.

We calculate the neutrino production cross-section through the direct URCA process in proto-neutron star matter in the presence of a strong magnetic field. We assume isoentropic conditions and introduce a new equation of state parameter-set in the relativistic mean-field approach that can reproduce neutron stars with $M > 1.96$ M$_\odot$ as required by observations. We find that the production process increases the flux of emitted neutrinos along the direction parallel to the magnetic field and decreases the flux in the opposite direction. This means that the neutrino flux asymmetry due to the neutrino absorption and scattering processes in a magnetic field becomes larger by the inclusion of the neutrino production process., 9 pages, 3 figures

Using various kinds of relativistic mean-field models as well as the quark-meson coupling model, we study in detail the properties of neutron stars. We find that the equation of state in SU(3) flavor symmetry can support a neutron star with mass of $(1.8 \sim 2.1) M_{\odot}$ even if hyperons exist inside the core of a neutron star., 4 pages, 4 figures, 2 table, accepted to the proceedings of the 12th Asia Pacific Physics Conference (APPC12) in JPS Conference Proceedings

A SU(2) effective Lagrangian is extended to a SU L(3) ⊗SU R(3) by including the vector and axial vector meson. With this effective Lagrangian, electromagnetic form factors of charged pion and kaon are calculated in both time- and space-like regions. The pseudoscalar meson loops are taken into account. Good agreement with experimental data is obtained for those form factors and charged pseudoscalar meson radii. Decay widths of ρ→ππ and φ→K + K - are also calculated and shown to agree with experimental data very well.

We calculate the spin deceleration of proto-neutron stars by asymmetric neutrino absorption in the context of a fully relativistic mean field theory. We calculate for the first time the spin deceleration of neutron stars due to asymmetric neutrino absorption in a toroidal magnetic field configurations. We find a surprising effect that the deceleration can much larger for asymmetric neutrino absorption in a toroidal magnetic field than the usually presumed braking due to magnetic dipole radiation. This may explain the observation that magnetars appear to have had a more rapid deceleration in the past., Comment: 13 pages, 1 figure, 1 table

We addressed possible ambiguities on the properties of neutron stars (NSs) estimated in theoretical sides. First, roles of hyperons inside the NS are discussed through various relativistic mean field (RMF) theories. In particular, the extension of SU(6) spin-flavor symmetry to SU(3) flavor symmetry is shown to give rise to the increase of hyperon threshold density, similarly to the Fock term effects in RMF theories. As a result, about 2.0 solar mass is obtained with the hyperons. Second, the effect by the modified f(R) gravity, which leaves a room for the dark energy in the Einstein equation to be taken into account, is discussed for the NS in a strong magnetic field (MF). Our results show that the modified gravity with the Kaluza-Klein electro-magnetism theory expanded in terms of a length scale parameter may reasonably describe the NS in strong MF, so called magnetar. Even the super-soft equation of state is shown to be revived by the modified f(R) gravity.

The nucleon form factors in free space are usually thought to be modified when a nucleon is bound in a nucleus or immersed in a nuclear medium. We investigated effects of the density-dependent axial and weak-vector form factors on the electro-neutrino (νe) and anti-electro-neutrino (νe) reactions with incident energy Ev ≤ 80 MeV via neutral current (NC) and charged current (CC) for a nucleon in a nuclear medium or 12C. For the density-dependent form factors, we exploited the quark-meson-coupling (QMC) model, and apply them to the νe and νe induced reactions by NC and CC. In CC reaction, about 5 % decrease of the electro neutrino (νe) reaction cross section on the nucleon is shown to be occurred in normal density, ρ = ρ0∼0.15fm−3, and also about 5 % reduction of total νe cross section on 12C is obtained by the modification of the weak form factors for bound nucleons. Density effects for both cases are relatively small, but they are as large as the effect by the Coulomb distortion of outgoing leptons in t...

We construct the equation of state in a wide-density range for neutron stars within relativistic Hartree-Fock approximation. The properties of uniform and nonuniform nuclear matter are studied consistently. The tensor couplings of vector mesons to baryons due to exchange contributions (Fock terms) are included, and the change of baryon internal structure in matter is also taken into account using the quark-meson coupling model. The Thomas-Fermi calculation is adopted to describe nonuniform matter, where the lattice of nuclei and the neutron drip out of nuclei are considered. Even if hyperons exist in the core of a neutron star, we obtain the maximum neutron-star mass of 1.95M⊙, which is consistent with the recently observed massive pulsar, PSR J1614-2230. In addition, the strange vector (φ) meson also plays a important role in supporting a massive neutron star.

We propose a four-quark structure for some of the excited states of heavy mesons containing a single charm or bottom quark. The four-quark wave functions are constructed based on a diquark-antidiquark form under the constraint that they form an antitriplet $\bar{\bf{3}}_f$ in $\mbox{SU(3)}_f$, which seems to be realized in some of the excited states listed in Particle Data Group. Depending on the structure of antidiquark, we construct two possible models for its wave functions: Model I) the antidiquark is symmetric in flavor ($\bar{\bf{6}}_f$) and antisymmetric in color ($\bf{3}_c$) and Model II) the antidiquark is antisymmetric in flavor ($\bf{3}_f$) and symmetric in color ($\bar{\bf{6}}_c$). To test phenomenological relevance of these wave functions, we calculate the mass differences among the excited states of spin $J=0,1,2$ using color-spin interactions. The four-quark wave functions based on Model~I is found to reproduce the observed mass of the excited states of heavy mesons. Also, our four-quark model provides an interesting phenomenology relating to the decay widths of the excited states. To further pursue the possibility of the four-quark structure, we make a few predictions for open charm and open bottom states that may be discovered in future experiments. Most of them are expected to have broad widths, which would make them difficult to be identified experimentally. However, one resonance with $J=1$ containing bottom and strange quarks is expected to appear as a sharp peak with its mass around $B^{\bar s}_{1N} \sim 5753$~MeV. Confirmation of the existence of such states in future experiments will shed light on our understanding of the structure of heavy meson excited states., Comment: 15 pages, REVTeX

The Big Bang nucleosynthesis (BBN) and the cosmic microwave background (CMB) anisotropies are the pillars of modern cosmology. It has recently been suggested that axion which is a dark matter candidate in the framework of the standard model could condensate in the early universe and induce photon cooling before the epoch of the photon last scattering. Although this may render a solution to the overproduction problem of primordial {sup 7}Li abundance, there arises another serious difficulty of overproducing D abundance. We propose a hybrid dark matter model with both axions and relic supersymmetric (SUSY) particles to solve both overproduction problems of the primordial D and {sup 7}Li abundances simultaneously. The BBN also serves to constrain the nature of neutrinos. Considering non-thermal photons produced in the decay of the heavy sterile neutrinos due to the magnetic moment, we explore the cosmological constraint on the strength of neutrino magnetic moment consistent with the observed light element abundances. Core-collapse supernovae eject huge flux of energetic neutrinos which affect explosive nucleosynthesis of rare isotopes like {sup 7}Li, {sup 11}B, {sup 92}Nb, {sup 138}La and {sup 180}Ta and r-process elements. Several isotopes depend strongly on the neutrino flavor oscillation due to the Mikheyev-Smirnov-Wolfenstein (MSW) effect.more » Combining the recent experimental constraints on θ{sub 13} with predicted and observed supernova-produced abundance ratio {sup 11}B/{sup 7}Li encapsulated in the presolar grains from the Murchison meteorite, we show a marginal preference for an inverted neutrino mass hierarchy. We also discuss supernova relic neutrinos (SRN) that may indicate the softness of the equation of state (EoS) of nuclear matter and adiabatic conditions of the neutrino oscillation.« less

We calculate the neutrino production cross-section in the proto-neutron-star matter under a strong magnetic field in the relativistic mean-field approach. We introduce a new parameter-set which can reproduce the 1.96 solar mass neutron star. We find that the production process increases emitted neutrinos along the direction parallel to the magnetic field and decrease those along its opposite direction. It means that resultant asymmetry due to the neutrino absorption and scattering process in the magnetic field becomes larger by the addition of the neutrino production process.

The nucleon form factors in free space are usually thought to be modified when a nucleon is bound in a nucleus or immersed in a nuclear medium. We investigate effects of the density-dependent axial and weak-vector form factors on the electro-neutrino ($\nu_e$) and anti-electro-neutrino $({\bar \nu_e})$ reactions via neutral current (NC) for a nucleon in nuclear medium or $^{12}$C. For the density-dependent form factors, we exploit the quark-meson-coupling (QMC) model, and apply them to the $\nu_e$ and ${\bar \nu_e}$ induced reactions by NC. About 12% decrease of the total cross section by $\nu_e$ reaction on the nucleon is obtained at normal density, $\rho = \rho_0 \sim 0.15 {fm}^{-3} $, as well as about 18% reduction of total ${\nu}_e$ cross section on $^{12}$C, by the modification of the weak form factors of the bound nucleon. However, similarly to the charged current reaction, effects of the nucleon property change in the ${\bar \nu}_e$ reaction reduce significantly the cross sections about 30% for the nucleon in matter and $^{12}$C cases. Such a large asymmetry in the ${\bar \nu}_e$ cross sections is addressed to originate from the different helicities of ${\bar \nu}_e$ and ${\nu}_e$.

Using several relativistic mean field models (such as GM1, GM3, NL3, TM1, FSUGold and IU-FSU) as well as the quark-meson coupling model, we calculate the particle fractions, the equation of state, the maximum mass and radius of a neutron star within relativistic Hartree approximation. In determining the couplings of the isoscalar, vector mesons to the octet baryons, we examine the extension of SU(6) spin-flavor symmetry to SU(3) flavor symmetry. Furthermore, we consider the strange ($\sigma^{\ast}$ and $\phi$) mesons, and study how they affect the equation of state. We find that the equation of state in SU(3) symmetry can sustain a neutron star with mass of $(1.8 \sim 2.1) M_{\odot}$ even if hyperons exist inside the core. In addition, the strange vector ($\phi$) meson and the variation of baryon structure in matter also play important roles in supporting a massive neutron star., Comment: 28 pages, 12 figures, 5 tables

{ital g}{sub {ital KN}}{Lambda} and {ital g}{sub {ital KN}{Sigma}} are calculated using a QCD sum rule motivated method used by Reinders, Rubinstein, and Yazaki to extract hadron couplings to Goldstone bosons. The SU(3) symmetry breaking effects are taken into account by including the contributions from the strange quark mass and assuming different values for the strange and the up-down quark condensates. We find {ital g}{sub {ital KN}}{Lambda}/{radical}4{pi}={minus}1.96 and {ital g}{sub {ital KN}{Sigma}}/{radical}4{pi}=0.33. {copyright} {ital 1996 The American Physical Society.}

We study the effect of the density-dependent axial and vector form factors on the electro-neutrino ($\nu_e$) and anti-neutrino $({\bar \nu}_e)$ reactions for a nucleon in nuclear matter or in $^{12}$C. The nucleon form factors in free space are presumed to be modified for a bound nucleon in a nuclear medium. We adopt the density-dependent form factors calculated by the quark-meson coupling (QMC) model, and apply them to the $\nu_e$ and ${\bar \nu}_e$ induced reactions with the initial energy $E = $ 8 $\sim$ 80 MeV. We find that the total ${\nu}_e$ cross sections on $^{12}$C as well as a nucleon in nuclear matter are reduced by about 5% at the nuclear saturation density, $\rho_0$. This reduction is caused by the modification of the nucleon structure in matter. Although the density effect for both cases is relatively small, it is comparable with the effect of Coulomb distortion on the outgoing lepton in the $\nu$-reaction. In contrast, the density effect on the ${\bar \nu}_e$ reaction reduces the cross section significantly in both nuclear matter and $^{12}$C cases, and the amount maximally becomes of about 35% around $\rho_0$. Such large asymmetry in the $\nu_e$ and ${\bar \nu}_e$ cross sections, which seems to be nearly independent of the target, is originated from the difference in the helicities of ${\bar \nu}_e$ and ${\nu}_e$. It is expected that the asymmetry influences the r-process and also the neutrino-process nucleosynthesis in core-collapse supernovae., Comment: 12 pages, 12 figures

The Gamow Teller (GT) transition strengths deduced from charge exchange reactions (CEXRs) are very helpful for understanding the nuclear reaction induced by neutrinos, in particular, by the solar neutrino. For further study of supernovae (SNe) neutrinos in the cosmos, one needs to study high-lying GT states around a few tens of MeV region as well as other multipole transitions because of the high energy tail in the neutrino spectra emitted from the neutrino sphere. In this report, we address the importance of the high-lying GT excited states, whose data now become available from various CEXR experiments. For example, GT(± strengths up to 70MeV are successfully extracted by 90Zr(n, p) and 90Zr(p, n) reactions. Our discussions are extended to investigate roles of the high-lying states beyond a few low-lying states known in the old experiment on the reaction induced by SNe neutrinos particularly on 40Ar target. The nucleus was originally exploited to identify the solar neutrino emitted from 8B produced in the pp-chains on the Sun, and now lots of applications for more energetic neutrino detection are under progress. The expected large difference between the cross-sections of \( \nu_{e}^{}\) and \( \bar{{\nu}}_{e}^{}\) reactions on 40Ar , whose differences were anticipated because of the large Q-value in the \( \bar{{\nu}}_{e}^{}\) reaction, is significantly diminished compared to previous results. Our calculations are carried out by the Quasi-particle Random Phase Approximation (QRPA), which takes the neutron-proton pairing into account to the standard proton-neutron QRPA (pnQRPA) where only proton-proton and neutron-neutron pairing correlations are considered.

It has recently been proposed that ${}_{41}^{92}$Nb and ${}_{43}^{98}$Tc may have been formed in the $\ensuremath{\nu}$-process. We investigate the neutrino induced reactions related to the $\ensuremath{\nu}$-process origin of these two odd-odd nuclei. We find that the main neutrino reactions to produce ${}_{41}^{92}$Nb are the charged-current (CC) ${}^{92}$Zr(${\ensuremath{\nu}}_{e},{e}^{\ensuremath{-}}$)${}^{92}$Nb and the neutral-current (NC) ${}^{93}$Nb[$\ensuremath{\nu}(\overline{\ensuremath{\nu}}),{\ensuremath{\nu}}^{\ensuremath{'}}{(\overline{\ensuremath{\nu}})}^{\ensuremath{'}}$ $n$]${}^{92}$Nb reactions. Similarly, the main reactions for ${}_{43}^{98}$Tc, are the CC reaction ${}^{98}$Mo(${\ensuremath{\nu}}_{e},{e}^{\ensuremath{-}}$)${}^{98}$Tc and the NC reaction ${}^{99}$Ru[$\ensuremath{\nu}(\overline{\ensuremath{\nu}}),{\ensuremath{\nu}}^{\ensuremath{'}}{(\overline{\ensuremath{\nu}})}^{\ensuremath{'}}$$p$]${}^{98}$Tc. Our calculations are carried out using the quasiparticle random phase approximation. Numerical results are presented for the energy and temperature dependent cross sections. Since charge exchange reactions by neutrons may also lead to the formation of ${}_{41}^{92}$Nb and ${}_{43}^{98}$Tc, we also discuss the feasibility of the ${}^{92}$Mo($n,p$)${}^{92}$Nb and ${}^{98}$Ru($n,p$)${}^{98}$Tc reactions to produce these nuclei.