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.
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.
121309735
Casimir effect on quark-gluon plasma
We study the Casimir effect on baryon-free quark-gluon plasma confined in a slab region. The energy and entropy densities of confined QGP at the transition temperature are 2∼3 times as large as those of unconfined QGP when the width of the slab is about 1 fm.
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.
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.
120870231
L-band superconducting cavities at KEK for TESLA
An attractive future application of superconducting cavities is a TeV energy superconducting linear collider (TESLA). The substantial merits of TESLA compared to a normal conducting linear collider are to loosening of alignment tolerance and less wake field due to the lower frequency (1.3 GHz). The final focus also is easier to obtain by having the electron/positron population in bunches. TESLA demands upgrading field gradients to over 25 MV/m. KEK has been carrying out R&D on 1.3 GHz niobium superconducting cavities since 1990. So far, seven single cell cavities and two 9-cell cavities have been fabricated and tested. In parallel, input coupler design and niobium material studies are being conducted. This paper reports the present status of KEK's efforts for TESLA.<<ETX>>
56351344
RF SYSTEMS FOR JHF SYNCHROTRONS
Based on the measurements of the magnetic cores and R&D works, MA(Magnetic Alloy)-loaded cavity will be adopted for the RF cavity of JHF 50 GeV Main Ring and 3 GeV Booster. Because of high stability at large RF amplitude, high gradient of acceleration voltage (>50 kV/m) is available. By a test cavity, 2.5 kV/core has been already achieved in the CW operation using one MA core of 2.5 cm thickness. For the pulse operation, 5.5 kV/core has been obtained. Another advantage is that the system does not require the tuning system because of the cavity band width is wide enough to cover the RF frequency. A stability analysis shows that the RF system without the tuning loop has wider stable region than high Q cavity system with the loop. A multi-particle simulation shows that the RF system is also stable for the periodic transient and the RF bucket distortion. However, the distortion should be corrected when the Q value of the cavity is low (Q<2).
137182571
A New Material Evaluation Method on Niobium by Magnetization Measurement
As a new evaluation method for the material defects or surface contamination of niobium, we have tried magnetization measurement using very small niobium samples. We could see the hyst~resis curve varied depending on the sample's history. This method has a high sensitivity. Th~ m.f1uence ?y surface treatments was observed on the hysteresis curve; annealing, chemical p~hshmg, Q-dlsease due to hydrogen etc .. In this paper we will report several study results by this method.
9701286
Manufacture and assembly of the 6-meter-long cryomodules for superconducting RF Test Facility (STF) at KEK
A superconducting RF test facility (STF) is being constructed at KEK for R&D oriented toward the International Linear Collider (ILC). Under KEK's guidance, Hitachi, Ltd. has manufactured cryostat components at its factory and completed final assembly in the STF Linac Building at KEK. The STF cryomodule consists of two cryostats, each about six meters long based on the TESLA-TTF-type III design. Each cryostat can house four 9-cell cavities, each one meter in length. This report outlines the flow of manufacturing from the factory to final assembly, and describes the manufacturing of equipment, assembly precision, and other matters.
135524505
A New type of RF cavity for high intensity proton synchrotron using high permeability magnetic alloy
A new type of rf accelerating cavity using a high-permeability magnetic alloy (MA) core is proposed for a highintensity hadron synchrotron. The prototype of a single-gap high gradient cavity whose total length is only 40cm is under development and a maximum rf voltage of 20kV has been obtained so far.