119432599
Flavour asymmetry of anti-quarks in nuclei
Abstract:A novel nuclear effect on the flavour asymmetry of anti-quarks in the nucleon bound in a nucleus is discussed in terms of the meson cloud model and the Pauli exclusion principle. It is expected that the flavour asymmetry is enhanced in a nucleus.
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.
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.
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.
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.
33534124
Higher-Order-Mode Damping of L-Band Superconducting Cavity Using A Radial-Line HOM Damper
For the energy recovery linacs, strong damping of higher-order-modes (HOMs) is indispensable to avoid beam breakup instabilities. We studied a new HOM damping scheme using a radial-line HOM damper with a choke structure. Both models of the radial-line damper and the TESLA-type 9-cell cavity were prepared and the HOM characteristics of this scheme were experimentally investigated. Measurement results showed a promising performance of the radial-line HOM damper.
54770944
Degassing effect in water: sterilizing effect
Present ultrapure water making system requires a very high maintenance cost. One reason is its design philosophy with bacteria propagation in the system: kill bacteria in the system and filter the dead bodies. Filters in the system block frequently by the dead bodies and have to be exchanged so often. Deoxidization of water eliminates the condition for bacteria to be alive. Using this method, the maintenance should become very simple and cheap. In this paper we investigated quantitatively the effect of deoxidization of water on sterilizing and TOC level.
59129737
Development of a Superconducting Cavity for the High Intensity Proton Linac in JAERI
The R&D work of a superconducting (SC) cavity for the high intensity proton linac in JAERI has been started in collaboration with KEK. The RF field calculation and the structural analyses of the cavity have been made for the design in the proton energy range between 100 and 1500 MeV. The results indicate the feasibility of the SC proton linac, while more optimization is required. A vertical test stand with a cryostat, a clean room and a water rinsing system has been constructed. We present the preliminary cavity design and the overview of the test stand.
209505765
High Gradient Performance by Electropolishing with 1300 MHz Single and Multi-cell Niobium Superconducting Cavities
We reported the superiority of electropolishing on high gradient performance with 1300 MHz niobium bulk single cell cavities in the last SRF workshop in Abano in Italy. We are still doing the investigation. After the last workshop, we achieved the maximum field gradients of 40 MV/m in more five single cell cavities and Eacc > 30 MV/m in two 3-cell structures. For 9-cell cavities, tests are under going by a DESY/KEK collaboration. In the first test, the gradient was limited around 22 MV/m by multipacting. This contribution presents these results.
121387531
Binding Energies of Two-Delta Bound States