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Atsushi Hosaka

Publications and source records attributed to Atsushi Hosaka.

175 records · Page 10Linked to original sources
arXiv2005

Production of Lambda(1520)

We investigate the Lambda(1520) photoproduction via the reaction process, gamma N -> K Lambda(1520). We employ the Born approximation and the Rarita Schwinger formalism is used for Lambda(1520). We reproduce the total cross sections and the various angular distributions qualitatively well for the proton target and estimate them for the neutron one. We find that the contact term contributes much more to the process than the other kinematical channels. Taking into account this fact, we reanalyze the K^*--exchange dominance hypothesis suggested by the previous experiments.

hep-ph↗
arXiv2005

Phenomenology of spin 3/2 baryons with pentaquarks

We examine several assignments of spin and parity for the pentaquark Theta+ state (J^P=1/2^{+,-}, 3/2^{+,-}) in connection with known baryon resonances. Assuming that the Theta+ belongs to an antidecuplet representation which mixes with an octet, we calculate the mass spectra of the flavor partners of the Theta+ based on the SU(3) symmetry. The decay widths of the Theta+ and nucleon partners are analyzed for the consistency check of the mixing angle obtained from the masses. It is found that a suitable choice of the mixing angle successfully reproduces the observed masses of Theta(1540) and Xi_{3/2}(1860), when their spin and parity are assigned to be J^P=3/2^-, together with other J^P=3/2^- resonances. The decay widths of Theta -> KN, N(1520) -> pi N, and N(1700) -> pi N are also reproduced simultaneously.

hep-ph↗
arXiv2005

Photoproduction of Lambda(1520,3/2^-)

We investigate the photoproduction of Lambda(1520,3/2^-) via the gamma N -> K Lambda^* reaction using the Born approximation and the Rariata-Schwinger vector-spinor field for the spin 3/2 particle. We reproduce the experimental data of the total cross section and the angular dependence for the proton target qualitatively well and estimate them for the neutron target. For the neutron target, we find much smaller total cross section than that of the proton and the significant K^*-exchange contribution.

hep-ph↗
arXiv2005

Determination of the parity of the pentaquark baryons : Theta^+ and Xi_5

We study determination of the parity of the pentaquark baryons in two different processes. First, we investigate the Theta^+ production via the vec{p} vec{p} -> Sigma^+ Theta^+ reaction process which was proposed to determine unambiguously the parity of Theta^+. We observe the clear differences in the total cross sections and the spin observable A_{xx}. As for the Xi_5 in the bar{K} N -> K Xi_5 reaction process, the total cross section for the positive parity presents about one hundred times lager than that of the negative one due to the huge destructive interference.

hep-ph↗
arXiv2004

Theta^+ baryon production from gamma N and NN scattering

We investigate Theta^+ production via gamma N and NN reactions in order to obtain information on the structure of Theta^+, especially its parity. We observe that the positive parity. Theta^+production provides about ten times total cross sections than those of the negative parity one in both photon and nucleon induced reactions due to P-wave enhancement of the KNTheta vertex. We also consider the model independent method in the nucleon induced reaction to determine the parity of Theta^+ and show clearly distinguishable signals for the two parities.

nucl-th↗
arXiv2004

Photon and nucleon induced production of Theta^+

We investigate Theta^+ production via photon and nucleon induced reactions. We observe that the positive parity Theta^+ production provides about ten times larger total cross sections than those of the negative parity one in both photon and nucleon induced reactions due to P-wave enhancement of the K-N-Theta vertex. We also consider the model independent method in the nucleon induced reaction to determine the parity of Theta^+ and show clearly distinguishable signals for the two parities.

nucl-th↗
arXiv2004

Photo-production of the pentaquark $Θ^{+}$ with positive and negative parities

We investigate the production of the pentaquark $Θ^+$ baryon via the $γn\to K^-Θ^+$ and $γp\to \bar{K}^0 Θ^+$ processes, focusing on the parity of the $Θ^+$. Using the effective Lagrangians, we calculate the total and differential cross sections with the spin of the $Θ^+$ presumed to be 1/2. We employ the coupling constant of the $KNΘ$ vertex determined by assuming its mass and the decay width to be $1540 {\rm MeV}$ and $15 {\rm MeV}$. That of the $K^*NΘ$ is taken to be about a half of the $KNΘ$ coupling constant. We estimate the cutoff parameter by reproducing the total cross section of the $γp \to K^+ Λ$ reaction. It turns out that the total cross section for the $γn\to K^- Θ^+$ process is about four times larger than that of the $γp\to\bar{K}^0Θ^+$. We also find that the cross sections for the production of the positive-parity $Θ$ are about ten times as large as those for the negative-parity ones.

hep-ph↗
arXiv2003

Pentaquark states in a chiral potential

We discuss a possible interpretation for the pentaquark baryon $Θ^+$ which has an exotic quantum number of strangeness $S = +1$. The role of the pion which modifies the structure of single-particle levels of quarks is examined. When the pion field is sufficiently strong, the ground state of five quarks for $Θ^+$ acquires positive parity. If this is the case, an excited state may appear slightly above the ground state with negative parity.

hep-ph↗
arXiv2001

Chiral Symmetry of Baryons

We study chiral symmetry aspects of the positive and negative parity baryons by identifying them with linear representations of the chiral group $SU(N_{f}) \otimes SU(N_{f})$. It is shown that there are two distinctive schemes: naive and mirror assignments. We construct linear sigma models for baryons in the two assignments and examine their physical implications. Then we investigate properties of the naive and mirror nucleons microscopically by using QCD interpolating fields. Finally, we propose experiments to distinguish the two chiral assignments for the nucleon.

hep-ph↗
arXiv2000

Electromagnetic transitions of excited baryons in a deformed oscillator quark model

We study electromagnetic transitions of excited baryons in a deformed oscillator quark model, where baryon excited states are described as rotational bands of deformed intrinsic states. We describe all necessary tools to compute transition amplitudes in multipole basis, which are then related to the commonly used helicity amplitudes. We pay a special attention on the sign of the amplitudes as well as their absolute values by computing the photon and pion couplings simultaneously. We have found that the effect of deformation on the transition amplitudes is rather weak. The difficulty in reproducing the empirical amplitude of the Roper state is discussed.

hep-ph↗
arXiv2000

Probing chiral symmetry of nucleon by threshold $ηπ$ production

Double meson production of the eta and pion at the threshold region is investigated in order to determine chiral property of the nucleon. The eta can be used as a probe for the negative parity nucleon $N^* \equiv N^*(1535)$ produced in the intermediate state. The coupling of the low energy pion in the final state is then used to extract the sign of the Yukawa coupling, $\gpRR$, which distinguishes the two realizations of chiral symmetry, either naive or mirror, for the nucleon.

hep-ph↗
arXiv1995

The large-$N_c$ limit and the behavior of $g_A^{(0)}$ and $g_A$

We investigate the isoscalar and isovector components of the axial vector coupling constants, $g_A^{(0)}$ and $g_A$, using algebraic models that lead to the correct symmetries of large-$N_c$ QCD. Results obtained previously in various chiral models are interpreted from this algebraic point of view. The results of the Skyrme model and the valence quark model are explained by simple realizations of the algebra.

hep-ph↗