K. Tsushima - International Institute of Physics, Federal University of Rio Grande do Norte

K. Tsushima
Are you K. Tsushima?

Claim your profile, edit publications, add additional information:

Contact Details

Name
K. Tsushima
Affiliation
International Institute of Physics, Federal University of Rio Grande do Norte
Location

Pubs By Year

External Links

Pub Categories

 
Nuclear Theory (47)
 
High Energy Physics - Phenomenology (44)
 
Nuclear Experiment (35)
 
High Energy Physics - Experiment (33)
 
High Energy Physics - Lattice (20)
 
High Energy Astrophysical Phenomena (4)
 
Quantum Physics (3)
 
High Energy Physics - Theory (3)
 
General Relativity and Quantum Cosmology (2)
 
Solar and Stellar Astrophysics (1)
 
Mathematics - Mathematical Physics (1)
 
Mathematical Physics (1)

Publications Authored By K. Tsushima

$\phi$-meson--nucleus bound state energies and absorption widths are calculated for seven selected nuclei by solving the Klein-Gordon equation with complex optical potentials. Essential input for the calculations, namely the medium-modified $K$ and $\overline{K}$ meson masses, as well as the density distributions in nuclei, are obtained from the quark-meson coupling model. The attractive potential for the $\phi$-meson in the nuclear medium originates from the in-medium enhanced $K\overline{K}$ loop in the $\phi$-meson self-energy. Read More

The mass and decay width of the $\phi$ meson in cold nuclear matter are computed in an effective Lagrangian approach. The medium dependence of these properties are obtained by evaluating kaon-antikaon loop contributions to the $\phi$ self-energy, employing the medium-modified kaon masses, calculated using the quark-meson coupling model. The loop integral is regularized with a dipole form factor, and the sensitivity of the results to the choice of cutoff mass in the form factor is investigated. Read More

We investigate the production of charm-baryon hypernucleus $^{16}_{\Lambda_c^+}$O in the antiproton - $^{16}$O collisions within a fully covariant model that is based on an effective Lagrangian approach. The explicit ${\bar \Lambda}_c^ - \Lambda_c^+$ production vertex is described by the $t$-channel $D^0$ and $D^{*0}$ meson-exchanges in the initial collision of the incident antiproton with one of the protons of the target nucleus. The $\Lambda_c^+$ bound state spinors as well as the self-energies of the exchanged mesons employed in our calculations are derived from the quark-meson coupling model. Read More

We give a pedagogical introduction of the stochastic variational method by considering the quantization of a non-inertial particle system. We show that the effects of fictitious forces are represented in the forms of vector fields which behave analogous to the gauge fields in the electromagnetic interaction. We further discuss that the operator expressions for observables can be defined by applying the stochastic Noether theorem. Read More

2016Nov
Affiliations: 1Laboratorio de Fısica Teórica e Computacional - LFTC, Universidade Cruzeiro do Sul, 2Laboratorio de Fısica Teórica e Computacional - LFTC, Universidade Cruzeiro do Sul

Properties of \r{ho}-meson in symmetric nuclear matter are investigated within a light-front constituent quark model (LFCQM), using the in-medium input calculated by the quark-meson coupling (QMC) model. The LFCQM used here was previously applied in vacuum to calculate the \r{ho}-meson electromagnetic properties, namely, charge G 0 , magnetic G 1 , and quadrupole G 2 form factors, as well as the electromagnetic radius and decay constant. We predict the in-medium modifications of the \r{ho}-meson electromagnetic form factors in symmetric nuclear matter. Read More

After a brief review of the quark-based model for nuclear matter, and some pion properties in medium presented in our previous works, we report new results for the pion valence wave function as well as the valence distribution amplitude in medium, which are presented in our recent article. We find that both the in-medium pion valence distribution and the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant. Read More

2016Oct
Affiliations: 1Laboratório de Física Teórica e Computacional, LFTC, Universidade Cruzeiro do Sul, 2Laboratório de Física Teórica e Computacional, LFTC, Universidade Cruzeiro do Sul, 3Laboratório de Física Teórica e Computacional, LFTC, Universidade Cruzeiro do Sul

The pion electromagnetic form factor is calculated at lower and higher momentum transfer in order to explore constituent quark models and the differences among those models. In particular, the light-front constituent quark model is utilized here to calculate the pion electromagnetic form factor at lower and higher energies. The matrix elements of the electromagnetic current, are calculated with both "plus" and "minus" components of the electromagnetic current in the light-front. Read More

We study the $\bar D D$ (${\bar D}^0 D^0$ and $D^-D^+$) charm meson pair production in antiproton (${\bar p}$) induced reactions on nuclei at beam energies ranging from threshold to several GeV. Our model is based on an effective Lagrangian approach that has only the baryon-meson degrees of freedom and involves the physical hadron masses. The reaction proceeds via the $t$-channel exchanges of $\Lambda_c^+$, $\Sigma_c^+$, and $\Sigma_c^{++}$ baryons in the initial collision of the antiproton with one of the protons of the target nucleus. Read More

We study the effect of a hot and dense medium on the binding energy of hadronic molecules with open-charm mesons. We focus on a recent chiral quark-model-based prediction of a molecular state in the $N \bar D$ system. We analyze how the two-body thresholds and the hadron-hadron interactions are modified when quark and meson masses and quark-meson couplings change in a function of the temperature and baryon density according to predictions of the Nambu--Jona-Lasinio model. Read More

Pion valence distributions in nuclear medium and vacuum are studied in a light-front constituent quark model. The in-medium input for studying the pion properties is calculated by the quark-meson coupling model. We find that the in-medium pion valence distribution, as well as the in-medium pion valence wave function, are substantially modified at normal nuclear matter density, due to the reduction in the pion decay constant. Read More

2015Dec
Affiliations: 1Laboratorio de Fisica Teorica e Computacional, Universidade Cruzeiro do Sul, 2Laboratorio de Fisica Teorica e Computacional, Universidade Cruzeiro do Sul and National Center for Physics, Quaidi-i-Azam University Campus, 3Laboratorio de Fisica Teorica e Computacional, Universidade Cruzeiro do Sul

We compute the distribution amplitudes of the pion and kaon in the light-front constituent quark model with the symmetric quark-bound state vertex function. In the calculation we explicitly include the flavor-SU(3) symmetry breaking effect in terms of the constituent quark masses of the up (down) and strange quarks. To calculate the kaon parton distribution functions~(PDFs), we use both the conditions in the light-cone wave function, i. Read More

We study the weak interaction axial form factors of the octet baryons, within the covariant spectator quark model, focusing on the dependence of four-momentum transfer squared, Q^2. In our model the axial form factors G_A(Q^2) (axial-vector form factor) and G_P(Q^2) (induced pseudoscalar form factor), are calculated based on the constituent quark axial form factors and the octet baryon wave functions. The quark axial current is parametrized by the two constituent quark form factors, the axial-vector form factor g_A^q(Q^2), and the induced pseudoscalar form factor g_P^q(Q^2). Read More

2015Nov
Affiliations: 1Laboratório de Física Teórica e Computacional - LFTC - Universidade Cruzeiro do Sul, 2Laboratório de Física Teórica e Computacional - LFTC - Universidade Cruzeiro do Sul, 3Instituto Tecnológico da Aeronáutica/DCTA

The pion properties in symmetric nuclear matter are investigated with the Quark-Meson Coupling (QMC) Model plus the light-front constituent quark model~(LFCQM). The LFCQM has been quite successful in describing the properties of pseudoscalar mesons in vacuum, such as the electromagnetic elastic form factors, electromagnetic radii, and decay constants. We study the pion properties in symmetric nuclear matter with the in-medium input recalculated through the QMC model, which provides the in-medium modification of the LFCQM. Read More

We calculate Coulomb breakup of the neutron rich nucleus $^{37}$Mg on a Pb target at the beam energy of 244 MeV/nucleon within the framework of a finite range distorted wave Born approximation theory that is extended to include the effects of projectile deformation. In this theory, the breakup amplitude involves the full wave function of the projectile ground state. Calculations have been carried out for the total one-neutron removal cross section $(\sigma_{-1n})$, the neutron-core relative energy spectrum, the parallel momentum distribution of the core fragment, the valence neutron angular, and energy-angular distributions. Read More

We give a pedagogical introduction of the stochastic variational method and show that this generalized variational principle describes classical and quantum mechanics in a unified way. Read More

Quantization of electromagnetic fields is investigated in the framework of stochastic variational method (SVM). Differently from the canonical quantization, this method does not require canonical form and quantization can be performed directly from the gauge invariant Lagrangian. The gauge condition is used to choose dynamically independent variables. Read More

2014Apr
Affiliations: 1Laboratório de Física Teórica e Computacional, Universidade Cruzeiro do Sul, SP, Brazil, 2International Institute of Physics, Federal University of Rio Grande do Norte, 3Laboratório de Física Teórica e Computacional, Universidade Cruzeiro do Sul, SP, Brazil, 4Laboratório de Física Teórica e Computacional, Universidade Cruzeiro do Sul, SP, Brazil, 5Instituto Tecnológico da Aeronáutica/DCTA, São José dos Campos, SP, Brazil

Using the light-front pion wave function based on a Bethe-Salpeter amplitude model, we study the properties of the pion in symmetric nuclear matter. The pion model we adopt is well constrained by previous studies to explain the pion properties in vacuum. In order to consistently incorporate the constituent up and down quarks of the pion immersed in symmetric nuclear matter, we use the quark-meson coupling model, which has been widely applied to various hadronic and nuclear phenomena in a nuclear medium with success. Read More

In a relativistic quark model we study the structure of the $N(1710)$ resonance, and the $\gamma^\ast N \to N(1710)$ reaction focusing on the high momentum transfer region, where the valence quark degrees of freedom are expected to be dominant. The $N(1710)$ resonance, a state with spin 1/2 and positive parity ($J^P = \frac{1}{2}^+$), can possibly be interpreted as the second radial excitation of the nucleon, after the Roper, $N(1440)$. We calculate the $\gamma^\ast N \to N(1710)$ helicity amplitudes, and predict that they are almost identical to those of the $\gamma^\ast N \to N(1440)$ reaction in the high momentum transfer region. Read More

We study the effect of the meson cloud dressing in the octet baryon to decuplet baryon electromagnetic transitions. Combining the valence quark contributions from the covariant spectator quark model with those of the meson cloud estimated based on the flavor SU(3) cloudy bag model, we calculate the transition magnetic form factors at $Q^2=0$ ($Q^2=-q^2$ and $q$ the four-momentum transfer), and also the decuplet baryon electromagnetic decay widths. The result for the $\gamma^\ast \Lambda \to \Sigma^{\ast 0}$ decay width is in complete agreement with the data, while that for the $\gamma^\ast \Sigma^+ \to \Sigma^{\ast +}$ is underestimated the data by 1. Read More

We explore the equation of state for nuclear matter in the quark-meson coupling model, including full Fock terms. The comparison with phenomenological constraints can be used to restrict the few additional parameters appearing in the Fock terms which are not present at Hartree level. Because the model is based upon the in-medium modification of the quark structure of the bound hadrons, it can be applied without additional parameters to include hyperons and to calculate the equation of state of dense matter in beta-equilibrium. Read More

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. Read More

We study the octet to decuplet baryon electromagnetic transitions using the covariant spectator quark model, and predict the transition magnetic dipole form factors for those involving the strange baryons. Utilizing SU(3) symmetry, the valence quark contributions are supplemented by the pion cloud dressing based on the one estimated in the $\gamma^\ast N \to \Delta$ reaction. Although the valence quark contributions are dominant in general, the pion cloud effects turn out to be very important to describe the experimental data. Read More

The relatively small fraction of the spin of the proton carried by its quarks presents a major challenge to our understanding of the strong interaction. Traditional efforts to explore this problem have involved new and imaginative experiments and QCD based studies of the nucleon. We propose a new approach to the problem which exploits recent advances in lattice QCD. Read More

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. Read More

Studies of the structure of excited baryons are key to the N* program at Jefferson Lab. Within the first year of data taking with the Hall B CLAS12 detector following the 12 GeV upgrade, a dedicated experiment will aim to extract the N* electrocouplings at high photon virtualities Q2. This experiment will allow exploration of the structure of N* resonances at the highest photon virtualities ever yet achieved, with a kinematic reach up to Q2 = 12 GeV2. Read More

Our earlier Faddeev three-body study in the $K^-$-deuteron scattering length, $A_{K^-d}$, is revisited here in the light of the recent developments in two fronts: {\it (i)} the improved chiral unitary approach to the theoretical description of the coupled $\Kbar N$ related channels at low energies, and {\it (ii)} the new and improved measurement from SIDDHARTA Collaboration of the strong interaction energy shift and width in the lowest $K^-$-hydrogen atomic level. Those two, in combination, have allowed us to produced a reliable two-body input to the three-body calculation. All available low-energy $K^-p$ observables are well reproduced and predictions for the $\Kbar N$ scattering lengths and amplitudes, $(\pi \Sigma)^\circ$ invariant-mass spectra, as well as for $A_{K^-d}$ are put forward and compared with results from other sources. Read More

We study the $\gamma^\ast \Lambda \to \Sigma^0$ transition form factors by applying the covariant spectator quark model. Using the parametrization for the baryon core wave functions as well as for the pion cloud dressing obtained in a previous work, we calculate the dependence on the momentum transfer squared, $Q^2$, of the electromagnetic transition form factors. The magnetic form factor is dominated by the valence quark contributions. Read More

We study the production of $\Xi^-$-hypernuclei, $^{12}_{\Xi^{-}}$Be and $^{28}_{\Xi^{-}}$Mg, via the ($K^-,K^+$) reaction within a covariant effective Lagrangian model, employing the bound $\Xi^-$ and proton spinors calculated by the latest quark-meson coupling model. The present treatment yields the $0^\circ$ differential cross sections for the formation of simple s-state $\Xi^-$ particle-hole states peak at a beam momentum around 1.0 GeV/c with a value in excess of 1 $\mu$b. Read More

We investigate the variation with light quark mass of the mass of the nucleon as well as the masses of the mesons commonly used in a one-boson-exchange model of the nucleon-nucleon force. Care is taken to evaluate the meson mass shifts at the kinematic point relevant to that problem. Using these results, the corresponding changes in the energy of the 1 S0 anti-bound state, the binding energies of the deuteron, triton and selected finite nuclei are evaluated using a one-boson exchange model. Read More

We study the octet baryon electromagnetic form factors in nuclear matter using the covariant spectator quark model extended to the nuclear matter regime. The parameters of the model in vacuum are fixed by the study of the octet baryon electromagnetic form factors. In nuclear matter the changes in hadron properties are calculated by including the relevant hadron masses and the modification of the pion-baryon coupling constants calculated in the quark-meson coupling model. Read More

In the light of the recent discovery of a neutron star with a mass accurately determined to be almost two solar masses, it has been suggested that hyperons cannot play a role in the equation of state of dense matter in $\beta$-equilibrium. We re-examine this issue in the most recent development of the quark-meson coupling model. Within a relativistic Hartree-Fock approach and including the full tensor structure at the vector-meson-baryon vertices, we find that not only must hyperons appear in matter at the densities relevant to such a massive star but that the maximum mass predicted is completely consistent with the observation. Read More

We study the ground-state structure of nuclei in the vicinity of the one-neutron dripline within the latest version of the quark-meson coupling (QMC) model with a particular emphasis on 23O. For this nucleus the model predicts a [22O(0+) + n (2s_{1/2})] configuration for its ground state, with a one neutron separation energy in close agreement with the corresponding experimental value. The wave function describing the valence neutron-core relative motion was then used to calculate the Coulomb dissociation of 23O on a lead target at a beam energy of 422 MeV/nucleon. Read More

We study the effect of a $\Lambda$ hyperon immersed in the doubly magic nuclei, $^{16}$O, $^{40}$Ca, $^{48}$Ca, and $^{208}$Pb, as well as the neutron magic nucleus $^{90}$Zr. For a $\Lambda$ in the $1s$ and $1p$ states in $^{17}_{\Lambda}$O, $^{41}_{\Lambda}$Ca, $^{49}_{\Lambda}$Ca, $^{91}_{\Lambda}$Zr, and $^{209}_{\Lambda}$Pb, we compare the single-particle energies and density distributions of the core nucleons with those of the nuclei without the $\Lambda$, as well as the point proton and neutron radii. A remarkable finding is that the bound $\Lambda$ induces a significant asymmetry in the proton-neutron density distributions in the core nucleus. Read More

We estimate the valence quark contributions for the gamma* Y -> Lambda* (Y=Lambda, Sigma0) electromagnetic transition form factors. We focus particularly on the case Lambda*=Lambda(1670) as an analog reaction with gamma* N -> N(1535). The results are compared with those obtained from chiral unitary model, where the Lambda* resonance is dynamically generated and thus the electromagnetic structure comes directly from the meson cloud excitation of the baryon ground states. Read More

We study the production of bound cascade hypernuclei via the (K-,K+) reaction on 12C and 28Si targets within a covariant effective Lagrangian model, employing the cascade bound state spinors derived from the latest quark-meson coupling model as well as Dirac single particle wave functions. The K+-cascade production vertex is described by excitation, propagation and decay of Lambda and Sigma resonance states in the initial collision of a K- meson with a target proton in the incident channel. The parameters of the resonance vertices are fixed by describing the available data on total and differential cross sections for the cascade production in elementary (K-,K+) reaction. Read More

A covariant spectator quark model is applied to study the gamma N -> N*(1535) reaction in the large Q2 region. Starting from the relation between the nucleon and N*(1535) systems, the N*(1535) valence quark wave function is determined without the addition of any parameters. The model is then used to calculate the gamma N -> N*(1535) transition form factors. Read More

We study the octet baryon electromagnetic properties by applying the covariant spectator quark model, and provide covariant parametrization that can be used to study baryon electromagnetic reactions. While we use the lattice QCD data in the large pion mass regime (small pion cloud effects) to determine the parameters of the model in the valence quark sector, we use the nucleon physical and octet baryon magnetic moment data to parameterize the pion cloud contributions. The valence quark contributions for the octet baryon electromagnetic form factors are estimated by extrapolating the lattice parametrization in the large pion mass regime to the physical regime. Read More

It is shown that the helicity amplitudes A_1/2 and S_1/2 in the gamma N -> N(1535) reaction, can be well related by S_1/2 = -\frac{\sqrt{1+\tau}}{\sqrt{2}} \frac{M_S^2-M^2}{2 M_S Q} A_1/2 in the region Q^2 > 2 GeV^2, where M and M_S are the nucleon and N(1535) masses, q^2=-Q^2 the four-momentum transfer squared, and tau=\sfrac{Q^2}{(M_S+M)^2}. The observed relation is tested by the experimental data and the MAID parametrization. A direct consequence of the relation is that the assumption,|A_1/2| >> |S_1/2|, is not valid for high Q^2. Read More

Chiral symmetry is one of the most fundamental symmetries in QCD. It is closely connected to hadron properties in the nuclear medium via the reduction of the quark condensate , manifesting the partial restoration of chiral symmetry. To better understand this important issue, a number of Jefferson Lab experiments over the past decade have focused on understanding properties of mesons and nucleons in the nuclear medium, often benefiting from the high polarization and luminosity of the CEBAF accelerator. Read More

$J/\Psi$-nuclear bound state energies are calculated for a range of nuclei by solving the Proca (Klein-Gordon) equation. Critical input for the calculations, namely the medium-modified $D$ and $D^*$ meson masses, as well as the nucleon density distributions in nuclei, are obtained from the quark-meson coupling model. The attractive potential originates from the $D$ and $D^*$ meson loops in the $J/\Psi$ self-energy in nuclear medium. Read More

We calculate mass shift of the $J/\Psi$ meson in nuclear matter arising from the modification of $DD, DD^*$ and $D^*D^*$ meson loop contributions to the $J/\Psi$ self-energy. The estimate includes the in-medium $D$ and $D^*$ meson masses consistently. The $J/\Psi$ mass shift (scalar potential) calculated is negative (attractive), and complementary to the attractive potential obtained from the QCD color van der Waals forces. Read More

A covariant spectator quark model is applied to estimate the valence quark contributions to the$ F1*(Q2) and F2*(Q2) transition form factors for the gamma N -> P11(1440) reaction. The Roper resonance, P11(1440), is assumed to be the first radial excitation of the nucleon. The model requires no extra parameters except for those already fixed by the previous studies for the nucleon. Read More

A covariant spectator constituent quark model is applied to study the gamma N -> Delta(1600) transition. Two processes are important in the transition: a photon couples to the individual quarks of the Delta(1600) core (quark core), and a photon couples to the intermediate pion-baryon states (pion cloud). While the quark core contributions are estimated assuming Delta(1600) as the first radial excitation of Delta(1232), the pion cloud contributions are estimated based on an analogy with the gamma N -> Delta(1232) transition. Read More

A constituent quark model based on the spectator formalism is applied to the gamma N -> N* transition for the three cases, where N* is the nucleon, the Delta and the Roper resonance. The model is covariant, and therefore can be used for the predictions at higher four-momentum transfer squared, Q2. The baryons are described as an off-mass-shell quark and a spectator on-mass-shell diquark systems. Read More

The $J/\Psi$ mass shift in cold nuclear matter is computed using an effective Lagrangian approach. The mass shift is computed by evaluating $D$ and $D^*$ meson loop contributions to the $J/\Psi$ self-energy employing medium-modified meson masses. The modification of the $D$ and $D^*$ masses in nuclear matter is obtained using the quark-meson coupling model. Read More

We present results of hypernuclei calculated in the latest quark-meson coupling (QMC) model, where the effect of the mean scalar field in-medium on the one-gluon exchange hyperfine interaction, is also included self-consistently. The extra repulsion associated with this increased hyperfine interaction in-medium completely changes the predictions for {\Sigma} hypernuclei. Whereas in the earlier version of QMC they were bound by an amount similar to {\Lambda} hypernuclei, they are unbound in the latest version of QMC, in qualitative agreement with the experimental absence of such states. Read More

Using a covariant spectator quark model we estimate valence quark contributions to the F1*(Q2) and F2*(Q2) transition form factors for the gamma N -> P11(1440) reaction. The Roper resonance, P11(1440), is assumed to be the first radial excitation of the nucleon. The present model requires no extra parameters except for those already fixed by the previous studies for the nucleon. Read More

Using SU(3) symmetry to constrain the pion BB' couplings, assuming SU(3) breaking comes only from one-loop pion cloud contributions, and using the the covariant spectator theory to describe the photon coupling to the quark core, we show how the experimental masses and magnetic moments of the baryon octet can be used to set a model independent constraint on the strength of the pion cloud contributions to the octet, and hence the nucleon, form factors at Q2=0. Read More

We compute the Omega- electromagnetic form factors and the decuplet baryon magnetic moments using a quark model application of the Covariant Spectator Theory. Our predictions for the Omega- electromagnetic form factors can be tested in the future by lattice QCD simulations at the physical strange quark mass. Read More

We estimate the $D$, $\overline{D}$ and $J/\Psi$ meson potentials in nuclei. $J/\Psi$-nuclear potential (self-energy) is calculated based on the color-singlet mechanism, by the $DD$ and $DD^*$ meson loops. This consistently includes the in-medium properties of $D$ and $D^*$ mesons. Read More