17033717
A Relativistic Mean-Field Model with Density-Dependent Meson-Nucleon Couplings
Within the relativistic mean-field approach, we extend the Miyazaki model, where the NN$\sigma$ and NN$\omega$ interactions are modified to suppress the couplings between positive- and negative-energy states of a nucleon in matter. Assuming appropriate density-dependence of the meson-nucleon couplings, we study nuclear matter and finite nuclei. The model can reproduce the observed properties of $^{16}$O and $^{40}$Ca well. We also examine if the model is natural.
119311709
A new molecular dynamics calculation and its application to the spectra of light and strange baryons
A new approach based on antisymmetrized molecular dynamics is proposed to correctly take account of the many-body correlations. We applied it to the spectra of low-lying, light and strange baryons. The inclusion of the quark–quark correlation is important to predict the precise spectra, and the semi- relativistic kinematics is also vital to correct the level ordering. The baryon spectra calculated by the present method is as precise as the Faddeev calculation.
10938062
Composite nucleons in scalar and vector mean fields.
We emphasize that the composite structure of the nucleon may play quite an important role in nuclear physics. It is shown that the momentum-dependent repulsive force of second order in the scalar field, which plays an important role in Dirac phenomenology, can be found in the quark-meson coupling (QMC) model, and that the properties of nuclear matter are well described through the quark-scalar density in a nucleon and a self-consistency condition for the scalar field. The difference between theories of pointlike nucleons and composite ones may be seen in the change of the {omega}-meson mass in nuclear matter if the composite nature of the nucleon suppresses contributions from nucleon-antinucleon pair creation.
15022310
A Deformable Bag Model of Hadrons. I
As a generalization of the MIT spherical bag model, we construct the spheroidal bag model of hadron with an arbitrary eccentricity. This generalization is made by slightly modifying the MIT linear boundary condition: The linear boundary condition is examined in detail. Our model always satisfies two necessary requirements of the MIT bag model --i. e., n-j=O, no quark colour flux leaves the bag, and ijq =0, the scalar density of quark should vanish on the bag surface-- and it reduces to the MIT spherical bag model in the limit of zero-eccentricity. Lagrangian formalism of our model is briefly described. The eigenfrequencies of a single massless quark confined in this spheroidal bag are numer­ ically calculated. We obtain the level-splitting of the excited quark orbits, which is just analogous to the well-known Nilsson's splitting of single particle orbits in deformed nuclei. By using the numerical results of the lowest orbit, the effect of the bag-deformation on the mass of low-lying hadrons is estimated. It is found that, although the spherical bag is stable, tbe quark bag is extremely soft against the quadrupole deformation. Brief discussions are added on the mechanisms which make the spherical bag more stable.
121131573
New Scaling Phenomena in Nuclear Structure Functions
We consider the nuclear mass-number (A) dependence of the nuclear structure functions. We restrict ourselves to a two-component model, in which we assume the existence of an exotic component other than the normal nucleon component in nuclei. We find that there exist scaling phenomena and that the structure function of the exotic component should be independent of A. We also show that the A dependence of the nuclear structure function can be attributed to that of the surface-to-volume ratio which is incorporated in the probability of finding the exotic component in the nucleus.
119162077
The quark-meson coupling model and chiral symmetry
We extend the quark‐meson coupling (QMC) model to incorporate chiral symmetry. The relationship between the QMC model and chiral perturbation theory is also discussed. The nuclear central potential is modified by the effect of internal structure of the nucleon.
118654996
Analytic Formulae for the Off-Center CMB Anisotropy in a General Spherically Symmetric Universe
The local void model has recently attracted considerable attention because it can explain the apparent accelerated expansion of the present universe without introducing dark energy. However, in order to justify this model as an alternative to the standard ΛCDM cosmology, the model should be tested by various observations, such as the CMB temperature anisotropy, besides the distance-redshift relation of SNIa. For this purpose, we derive analytic formulae for the dipole and quadrupole moments of the CMB temperature anisotropy that hold for any spherically symmetric universe model and can be used to compare consequences of such a model with observations of the CMB temperature anisotropy rigorously. We check that our formulae are consistent with the numerical studies previously made for the CMB temperature anisotropy in the void model. We also update the constraints concerning the location of the observers in the void model by applying our analytic dipole formula with the latest WMAP data. Subject Index: 400, 401, 402, 403, 468
55513765
Investigation on Barrel Polishing for Superconducting Niobium Cavities
Barrel polishing was applied to L-band niobium cavities instead of buffing. For the TRISTAN superconducting cavities, buffing had been used for every half cell as the pre-finishing of electropolishing. It demands specialists and a rather high cost. For the mass-production as a superconducting linear collider like TESLA, an easier and cheaper method has to be developed. Barrel polishing seems to satisfy these requirements. Using combination of this method and electropolishing, field gradient higher than 30 MV/m with Qo - 1010 has achieved by a comparatively small amount of removal thickness.
20108614
SUPERIORITY OF ELECTROPOLISHING OVER CHEMICAL POLISHING ON HIGH GRADIENTS
Electropolishing (EP) offers a smoother surface, and that makes us expect high gradients in superconducting niobium cavities. EP has a little bit complicated procedure and needs annealing to avoid the hydrogen Q-disease. On the other hand, chemical polishing (CP) is easier and cheaper, so widely used in many laboratories. For the conventional field gradients ( ∪ 5 MV/m) in storage rings (TRISTAN-MR, HERA), no difference was seen on the cavity performance between EP and CP. In the high gradients research for TESLA, we have to establish the surface treatment method which has a high reliability on the high gradients over than 25 MV/m and is cheaper in the preparation cost. So far, CP has offered a nice cavity performance, but a concern on "European Headache" was developed recently on the high gradients at Saclay. KEK has intensively investigated the difference between the effect of CP and EP on high gradient performance since the last SRF workshop at Saclay. In this investigation "European headache" was also seen in chemically polished cavities at KEK, in addition these cavities often showed a new Q-degradation without x-ray signals which seriously limited the high gradient. EP offers the high gradient over than 30 MV/m reliably. At the moment, EP seems to have a superiority over CP on the high gradient over than 25 MV/m.
14603783
A Measurement System Using Gp-Ib For A Magnetic Core Test Cavity
In the design of the RF system of the JHF (Japan Hadron Facilit y) proton synchrotrons, it is very important to find a magnetic core to which satisfies the required condition of the JHF accelerators[1]. Ferrite cores are usually used for the magnetic core of the proton synchrotron, however there are some problems. Generally, some ferrite cores have non-linear characteristics which depend on the RF magnetic field. And, there is a size-dependence of the characteristics. Thus, it is required to measure the characteristics of large size magnetic cores. To measure characteristics of the magnetic cores, we have developed a test cavity which is capable of measuring an actual size one, and measurement system using software ‘HP-VEE’[ 2,3] which is possible to control the measurement devices by using a GP-IB command directly. In this measuring system, the acquisition of data and calculation of the characteristics of the magnetic cores are automatically processed.
121098853
X-band prebunched FEL amplifier
Abstract We have designed and constructed a prebunched FEL amplifier consisting of a prebuncher and a standard FEL. Microwave power saturation with a short wiggler length has been realized by a prebunched beam. We have also examined microwave phase evolutions. It has been demonstrated the adjustable range of the output microwave phase by changing the input microwave phase is restricted within a narrow band due to spontaneous emission radiated by the prebunched beam.