18878762
Nucleon structure effect on the longitudinal response function
Using the quark-meson coupling model, we study the longitudinal response function for quasielastic electron scattering from nuclear matter within relativistic RPA. In QMC the coupling constant between the scalar meson and the nucleon is expected to decrease with increasing nuclear density. Furthermore, since the electromagnetic form factors of the in-medium nucleon are modified at the same time, the longitudinal response function and the Coulomb sum are reduced by a total of about 20% in comparison with the Hartree contribution.
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.
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.
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.
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.
107821728
Characteristics of the results of measurement on 1.3 GHz high gradient superconducting cavities
55112672
Improvement of cavity performance by electropolishing in the 1.3 GHz Nb superconducting cavities
A steep drop of the cavity quality factor (Q/sub 0/) at high electric field has been observed frequently in chemically-polished and high-pressure-rinsed Saclay cavities, even in the absence of field emission. Three single-cell cavities from Saclay were tested at KEK following electropolishing and high pressure rinsing. This treatment eliminated the steep Q/sub 0/ drop, the quench field increased to an accelerating gradient of more than 30 MV/m with a quality factor above 2/spl times/10/sup 10/. No dependence of the quench field on the niobium RRR was observed between RRR=200 and 320 in electropolished cavities.
23554524
A New Design for A Super-Conducting Cavity Input Coupler
An attractive structure using capacitive coupling has been found for the input coupler for the 45 MV/m versions of the International Linear Collider (ILC) project. The coupler supports an electrical field gradient of ∼1 kV/m around the rf window ceramic with 500 kW through power, a VSWR of 1.1 and a frequency bandwidth of 460 MHz. No unwanted resonances were found in the rf window near the first and second harmonics of the operation frequency.
25781443
Analysis of induced radionuclides in low-activation concrete (limestone concrete) using the 12 GeV proton synchrotron accelerator facility at KEK.
22Na is one of the long-lived radionuclides induced in shielding concrete of a beam-line tunnel of a high-energy particle accelerator facility and poses a problem of radiation wastes at the decommissioning of the facility. In order to estimate the 22Na concentration induced in shielding concrete, chemical reagents such as NaHCO3, MgO, Al203, SiO2 and CaCO3 were irradiated at several locations in the beam-line tunnel of the 12 GeV proton synchrotron accelerator at KEK, and the 22Na concentrations induced in those chemical reagents were measured. Low-activation concrete made up of limestone aggregates was also irradiated by secondary particles in the beam-line tunnel and the long-lived radionuclide, such as 22Na, concentrations induced in the concrete were measured. It was confirmed that 22Na concentrations induced in Mg, Al, Si and Ca were lower than that in Na, and that 22Na concentrations induced in the low-activation concrete was lower than those induced in ordinary concrete made up of sandstone aggregates.
134525019
Status of The Seamless L-band Cavity Fabrication at KEK
For the future superconducting RF cavity project like TESLA, reduction of the fabrication cost is a great concern. Elimination of electron beam welding in the present fabrication process is one way to do so. Spinning(1), explosive forming or hydro-bulge forming is a candidate to fabricate such a seamless cavity. As a feasibility study, explosive forming was tried for the L-band three cell copper structures and could successfully expand copper tubes by 60 % of the final cell shape. The study of hydro-bulge forming has also started to get enough thickness at the equator section of cavities. Both method need intermediate annealing to form the final cell shape. If one applies these methods to the Nb/Cu clad cavities, large merits are expected on not material cost reduction but also cavity performance.