123091013
Masses of the Multiquark States in the MIT Bag Model with the Pion-Cloud
We study the masses of the low-lying multiquark states, especially the dibaryon states, within the framework of the MIT bag model with the pion-cloud, in which the non-local pion-quark· interaction is taken into account. We find that the pionic effect does not greatly alter the original predictions of the MIT bag model for the dibaryon states with Y = 1 and 2, while it increases the mass of the lowest Y = 0 dibaryon state. The Y = 0 dihyperon predicted by Jaffe may be either unbound or very weakly bound. In this letter we wish to study the low-lying multiquark states in the MIT bag model with the pion-cloud. In the original MIT bag model some authors calculated the masses of the multiquark states and discussed their properties. 1l • 2 ) Recent1y' however, it ~as pointed out that the contribu­ tion of the pion-cloud to the masses of the ordi­ nary hadrons amounts to about 100 MeV and especially the pion-cloud plays an important role in the origin of the N-LJ and the .E-A mass differences. 3 )A) We should, therefore, estimate the effect of the pion-cloud on the masses of the multiquark states. Of special interest is the deep­ ly bound state of the dihyperon UI"=OO+) predicted by Jaffe. 2 ) (This state is 70~80 MeV lower than the A-A threshold in the MIT bag model.) Here we will use the chiral and the cloudy bag models with the non-local interaction between the quark and pion,a) in which the extent of the pion is taken into account. The pionic corrections will be treated as a perturbation to the masses of the multiquark states. In the naive chiral S ) and cloudy 6) bag models there are two difficulties, i.e., the collapse of the bag and the divergence of the quark self-energy, which are due to the pion­ cloud. In the first order of the pionic correction we can, however, avoid these difficult problems by using the non-local description of the quark-pion interaction. In the limit of a static and spherical cavity with the radius R the usual mass formula for the N­ quark state is given by
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.
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.
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.
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.
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.
25242851
Test operation of ball-screw-type tuner for low-los high-gradient superconducting cavity at 77 K
Super-conducting Radio Frequency (SRF) 9-cell cavities have been developed in Low-Loss (LL) ICHIRO shape at KEK aiming at high-gradient operation for the International Linear Collider (ILC). One of the most important issues to realize high-gradient linac with SRF cavitiest in pulsed-mode operation is the compensation of the Lorentz detuning of cavities which amounts to 3 kHz at our goal of 45 MV/m acceleration field. None of tuners to date have achieved this specification. A coaxial ball- screw tuner was designed, fabricated and proven to reach this specification in room temperature. The performance was studied also at liquid-nitrogen temperature and the needed dynamic-range for 45 MV/m operation was proven at this temperature. The microphonic vibration was measured to be 100 Hz order in a test setup. In this paper, we describe these studies and evaluate the feasibility of ball-screw tuner operation at 2 K.
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.
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
114460174
SCRF test facilities toward the ILC
Since the ICFA selection of the superconducting linear collider technology in August 2004, many intensive ILC R&D programs are in the planning stage, or already underway; North America (ILCTA), Asia (STF), and Europe(TTF). In this paper, the global activities represented by the superconducting RF test facility will be reviewed. Their goals, schedules and possible complementarities will be presented. The performance expected from the different R&D efforts by 2009, or the corresponding contribution to the ILC Technical Design Report, will be especially emphasized.