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.
119441340
Relationship between the Quark-Meson Coupling Model and Quantum Hadrodynamics
Using the quark-meson coupling (QMC) model, we study nuclear matter from the point of view of quark degrees of freedom. Carrying out a re-definition of the scalar field in matter, we transform the QMC into a QHD-type model with a non-linear scalar potential. The potentials obtained from the QMC are compared with those of relativistic mean-field models. Since at present, rigorous studies of quantum chromodynamics (QCD) are limited to matter systems with high temperature and zero baryon density, it is important to build models that help to bridge the discrepancy between nuclear phenomenology and QCD. We have proposed a relativistic quark model for nuclear matter and finite nuclei that consists of non-overlapping nucleon bags bound by the self-consistent exchange of isoscalar, scalar (σ) and vector (ω) mesons in the mean-field approximation (MFA). This model is called the quark-meson coupling (QMC) model. 1) It has also been found in recent theoretical studies that various properties of finite nuclei can be described very well by relativistic mean-field (RMF) models, i.e., quantum hadrodynamics (QHD). 2) In this Letter, we consider the relationship between the QMC and the QHD and study howthe internal structure of the nucleon plays a role in effective nuclear models. In our previous works, 1) the MIT bag model has been used to describe the quark structure of the nucleon. Because the confined quarks interact with the scalar field σ in matter, the effective nucleon mass M � N in the QMC is given by a function of σ through the quark model of the nucleon. (Although the quarks also interact with the ω meson, it has no effect on the nucleon structure, except for a shift in the nucleon energy. 1) ) The (relativistic) constituent quark model (CQM) is an alternative model for the nucleon. Recently, Shen and Toki 3) have proposed a newversion of the QMC — the quark mean-field (QMF) model, in which the CQM is used to describe the nucleon. In the present study, in addition to the bag model (BM), we use the relativistic CQM with confining potentials V (r) of a square well (SW) and harmonic oscillator (HO) type to see the dependence of the matter properties on the quark model. It is assumed that the light (u or d) quark mass mq is 300 MeV in the CQM and 0 MeV in the BM. Furthermore, we introduce a Lorentz vector-type confining potential that is proportional to γ0, in addition to one of the scalar type, as
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.
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.
118503707
Toward construction of the unified lepton-nucleus interaction model from a few hundred MeV to GeV region
Next generation neutrino oscillation experiments will need a quantitative understanding of neutrino-nucleus interaction far better than ever. Kinematics covered by the relevant neutrino-nucleus interaction spans wide region, from the quasi-elastic, through the resonance region, to the deeply inelastic scattering region. The neutrino-nucleus interaction in each region has quite different characteristics. Obviously, it is essential to combine different expertise to construct a unified model that covers all the kinematical region of the neutrino-nucleus interaction. Recently, several experimentalists and theorists got together to form a collaboration to tackle this problem. In this contribution, we report the collaboration’s recent activity and a goal in near future.
11540608
The Nolen-Schiffer anomaly and isospin symmetry breaking in nuclear matter
Abstract The quark-meson coupling model which we have developed previously is extended to incorporate the δ meson. It is then used to study the Nolen-Schiffer anomaly and isospin symmetry breaking in nuclear matter. We find that, in combination with the u - d mass difference, the difference between quark scalar densities in protons and neutrons generates an effective neutron-proton mass difference of the right magnitude. Finally we find that isospin symmetry breaking in the quark condensates can be directly related to the δ meson field.
55249742
Activities on Superconducting Cavities at TOSHIBA
Abstructs R&D activities on superconducting cavities at TOSHIBA are presented. Two L-band single-cell niobium cavities and an L-band three-cell structure were fabricated in our company and measured at KEK. The maximum field gradient of Eacc,max>30MV/m in both single-cell cavities and Eacc,max =18MV/m in the three-cell structure were attained respectively. An optimization study on the annealing temperature for the hydrogen Q-disease is reported. R&D of hydroforming to fabricate seamless cavities is also presented.
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.
109094513
Development of a superconducting cavity for high gradient accelerators
A collaboration between KEK and CEBAF is pursuing the development of a superconducting high gradient accelerating structure for application in future accelerator which optimally requires the high field gradient above 25 MV/m. In the first phase of this collaboration three single cell 1300 MHz niobium cavities have been built and tested. In the second phase a full scale 9-cell niobium cavities was manufactured. This paper describes the fabrication and measurement result of the joint 9-cell Nb cavity.
7147715
Design of a Low Loss SRF Cavity for the ILC
An international team comprising SLAC, KEK, FNAL, JLAB and DESY is collaborating on the design, fabrication and test of a low loss, 1.3 GHz 9-cell SRF structure as a potential improvement for the ILC main linac. The advantages of this structure over the TESLA structure include lower cryogenic loss, shorter rise time, and less stored energy. Among the issues to be addressed in this design are HOM damping, Lorentz force detuning and multipacting. We will report on HOM damping calculations using the parallel finite element eigenmode solver Omega3P and the progress made towards an optimized design. Studies on multipacting and estimates of the Lorentz force detuning will also be presented.
56012808
Development of electropolishing technology for superconducting cavities
In this paper, a brief review is given for electropolishing (EP) of niobium superconducting (sc) cavities. KEK original EP method is introduced. This method can produce high gradient of 40MV/m, which will be the fundamental limit of high pure niobium sc cavities. A required surface smoothness is estimated to be less than 2/spl mu/m in order to prevent field enhancement problem in sc cavity.