34447702
Collective modes in hot and dense matter.
We propose a model for a relativistic many-body system at finitetemperature in the framework of thermo field dynamics, which is a real-timeformalism of finite-temperature field theory. Our model contains the scalar(sigma) and the vector (..omega..) mesons as well as the Dirac nucleon. Thefull propagator and self-energy for each particle are presented in terms ofspectral representations. The Feynman rules for a perturbation expansion areshown. They are applied to the study of collective modes in hot and densematter within the random-phase approximation. The dispersion relations of thelongitudinal and transverse collective modes in the meson branch arecalculated. We also estimate the effective meson mass which is defined as theenergy needed to create one meson at rest in extreme matter. The effects ofvacuum fluctuations are also examined. They contribute a fair amount to thecollective modes through the effective nucleon mass.
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.
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.
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.
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.
55538978
HIGH GRADIENT BEHAVIORS OF LARGE GRAIN ICHIRO SINGLE CELL CAVITY BY CHEMICAL POLISHING
We have started high gradient R&D with the combination of ICHIRO shape, sliced large grain niobium, and buffered chemical polishing (BCP). We fabricated one large grain ICHIRO single cell cavity that had end cell shape of ICHIRO 9-cell but no end group. We processed this cavity surface by centrifugal barrel polishing (CBP) and BCP. This cavity successfully achieved the high gradient of 42MV/m at the first vertical test. We made series test by repeating BCP on this cavity. The results of the series test will be reported. INTRODUCTION Large grain niobium SRF cavities have been developed in many laboratories, Jlab, DESY, IHEP, KEK, and so on. Our KEK LL group made breakthrough of LG Nb sheet production in 2008 [1]. We have successfully developed the multi-wire slicing method for niobium ingots with 270mm diameter collaborating with KEK, Tokyo Denkai Co. Ltd., TKX Co.Ltd., and Toyo Advanced Technologies Co. Ltd. This technology can reduce the cost of Nb sheet productions. LG cavity also can achieve high gradient of 40MV/m by BCP, not by electro polishing (EP) [2]. In order to make the breakthrough of ILC cavity cost, we are proposing the combination of sliced LG Nb materials + ICHIRO shape + BCP. This could promise the cheap, easy, and high reliable performance cavity production. In this paper, we will describe about our R&D on LG single cell cavity made of sliced Nb sheets.
27396914
Properties of strange quark matter.
Assuming that the novel nuclei of [ital A]=370 amu and [ital Z]=14 recently observed in high-energy cosmic rays are really strange quark matter (SQM), the relationship between parameters describing SQM is discussed and the mass formula for SQM is derived by requiring that it yields the observed value of [ital A]=370 amu and [ital Z]=14.
132588620
HIGH FIELD Q-SLOPE PROBLEM IN END GROUP CAVITIES N=3
In our high gradient R&D of ICHIRO cavities at KEK, we have found some problems related to HOM coupler and high power RF input coupler port on beam tube: end group. One is the difficulty of rinsing in complex structures like HOM coupler. The other is Q-slope at high filed more than 40MV/m. The cavities without end group did not show such a high field Q-slope. At first step, we tested much stronger and aggressive rinsing method; wiping, brushing, and mega-sonic rinsing on the end group. The details and results of these rinsing effects will be reported. INTRODUCTION We have successfully demonstrated the principle proof of 50MV/m with KEK Low Loss (ICHIRO) single cell cavities (IS cavities) [1]. IS cavity has the centre cell shape of ICHIRO 9cell cavity (I9 cavity), but no end group. End group includes HOM coupler, high power RF input coupler port, and transmitted RF power pick up port on beam tube. For the pilot study of I9 cavity, we also made end single cell cavities (ISE cavities) that have end cell shape of I9 cavity. ISE#3 that has end cell shape but no end group successfully achieved 50MV//m using same recipe as IS cavities. It will be described later about the recipe. ISE#5, and #7, those have full end group except transmitted RF power pick up port, have achieved around 48MV/m with modified recipe but limited by Q-slope so far (Figure 2). We confirmed that RF design of ICHIRO cavity has no problem for 50MV/m, but end group has Qslope problem at more than 40MV/m. In this paper we focused on Q-slope problem of ISE cavities. ISE CAVITY AND RECIPE Our standard recipe for IS cavities consists of centrifugal barrel polishing (CBP, ~100μm), chemical polishing (CP, 10μm), annealing (AN, 750Cx3hrs), electropolishing (EP, 80μm+20μm), flash EP (3μm, new acid, no circulation), HPR, and Baking (120Cx48hrs). This recipe achieved 46.7±1.9MV/m with 6 IS cavities [2]. The key of this recipe is flash EP. We have found that sulphur contaminations generated during EP made scatter of performance. Some of sulphur remains underneath of the SRF niobium surface as niobium sulphide (NbxSy) after long EP durations [3]. The combination of light EP (20μm) + flash EP can remove NbxSy most effectively. We also understood the mechanism of sulphur generation during EP and how to reduce it [4]. For ISE cavities with end group, standard recipe did not work. They were limited by field emission (FE) at first. We considered one of the FE seeds of ISE cavities was sulphur contaminations remained at end group. End group has a complex structur, so it might be difficult to remove contamination by HPR only. We tried ethanol rinsing after EP which can dissolve sulphur. ISE#5 was improved but still limited around 40MV/m. We also tried wiping cavity inner surface directly. In common sense, RF surface is very sensitive, so nobody favours to touch the SRF surface after EP and before VT. We tried it to another cavity which limited by heavy FE as a pilot study. It was successfully improved. Then we tried it to ISE#5. We used very smooth cloth soaked in degreaser as wiper. ISE#5 was wiped whole SRF surface; cell, beam tubes, HOM cylinder and antenna by hand. The antenna was even rubbed by teeth brash. ISE#5 have achieved 48MV/m by combination of ethanol rinsing and wiping so far. We understood the problem of end group relates to the difficulties of rinsing in complex structures and post EP cleaning like ethanol rinsing and wiping are effective to rinse end group [5]. SERIES TEST OF POST EP CLEANINGS From the experience of ethanol rinsing and wiping, we confirmed that the contaminations generated during EP process is very sticky and stronger rinsing is needed for the complex structure like end group to remove them. In ___________________________________________ *fumio.furuta@kek.jp Proceedings of IPAC’10, Kyoto, Japan WEPE005 03 Linear Colliders, Lepton Accelerators and New Acceleration Techniques A03 Linear Colliders 3347 this chapter we will describe about 4 kinds of post EP cleanings we tried; ethanol rinsing, wiping, steam cleaning and Horn rinsing. Ethanol Rinsing Figure 3 shows the results of the yield test for ethanol rinsing. The tested recipe consists of light EP, flash EP, ethanol rinsing, degreasing, HPR, and baking. We repeated this recipe + VT 6times for ISE#5. The average of maximum gradient is 39.2±5.7MV/m, scatter is 15%. The average of FE onset is 35.2± 6.7MV/m. In our measurements, FE onset corresponded to the gradient where the level of radiation reached more than 0.3μSv/hr. It is radiation monitor’s sensitivity. The average Qo value at 40MV/m is (0.97±0.11)e10. Wiping Figure 3 shows the results of the yield test of wiping. Figure 4 shows the picture of wiping. The tested recipe consists of light EP, flash EP, ethanol rinsing, wiping with degreaser, HPR, and baking. We repeated this 5times for ISE#5. The average of maximum gradient is 42.6± 3.7MV/m, scatter is 9%. The average of FE onset is 31.8 ±7.1MV/m. The average Qo value at 40MV/m is (1.12± 0.21)e10. The Qo value is 15% higher than that of ethanol rinsing. Steam Cleaning Figure 4 shows steam cleaner and steam cleaning for end group. This steam cleaner is commercial one. We used pure water for the steam. Hot steam, about 100C, come out from nozzle of steam cleaner, we sprayed it all around end groups. The recipe for series test of steam cleaning did not include EP. It consists of steam cleaning, degreasing, HPR, short baking for degassing, and VT. We applied this for ISE#5, #7, and #8. We repeated this twice for ISE#7 and #8 to check the reproducibility. Qo vs. Eacc curves are summarized in figure 5. The average of maximum gradient is 41.6±3.9MV/m, scatter is 9%. The average of FE onset is 33.3±5.0MV/m. The average Qo value at 40MV/m is (0.93±0.19)e10.