123052618
Instability of the Chiral Quantum Baryon
The chiral quantum baryon which is stabilised by the quantum effect is discussed within the nonlinear σ-model with the pion mass term. It is shown that the quantum baryon does not exist mathematically even if the pion mass term is taken into account
121686024
Excited baryons in the MIT bag model
Abstract The Johnson-Thorn bag model which explains the rotational motion of the elongated MIT bag is extended so as to describe the longitudinal vibration along the elongated bag. Our model is a kind of string model for baryons but it reduces to the ordinary spherical MIT bag model in the ground states. It is shown that the mass spectra of the P 11 and P 33 resonances of baryons can be reproduced by the present model as well as the Regge trajectories.
120691222
Superconductivity of Quark Matter at Finite Temperature
25502171
Rotating Bag Model for Hadrons
The MIT bag model!) has been quite successful in reproducing the observed masses and other static properties of the low-lying hadrons. It is very important to discuss whether or not excited states of the hadrons (resonances) can be explained in the framework of the bag model. A number of excited states have been described successfully by considering collective excitations of the bag.) In particular, Johnson and Thorn) investigated a series of excited states known as the Regge trajectory by using the rotating bag model. They assumed that the rotating bag has stringlike shape with two ends by the centrifugal force and the transverse length is negligible compared with its longitudinal one. From this onedimensional bag model, they succeeded in reproducing the experimental value of the Regge slope very well. Furthermore it was showt: by Wakimaru and one of the present authors (M. I.) that this simple model can explain not only the Regge slope but also the energy spectra of the trajectories.) On the other hand, Eguchi and Migdal et aJ.5) also discussed the excited states by using their string models 'which are independent of the bag model. Any string model which has been proposed is based on the assumption that the shape is stringlike or one-dimensional. Is the assumption of the stringlike shape, however, surely true? section of the stringlike bag, which we call tube, can be given by
123223657
A Vibrational Bag Model for Baryons
Surface monopole vibration of baryons is investigated on the basis of the soliton bag model. We derive a relativistic Lagrangian for the surface motion whose mass parameter is proportional to square of the bag radius. With the use of the WKB approximation, the energy spectra of Pl1 and F" resonances are reproduced by our model fairly well. The static properties of the nucleon are alsO studied in our vibrational bag model and compared with those of the static bag model. Our model predicts that the nucleon consists of the central high·density part and the surrounding low-density part. It is also shown that our model is capable to predict the experimental data as well as the static bag model.
117897053
Shear viscosity and spectral function of the quark matter
We discuss the shear viscosity of the quark matter by using the Kubo-Mori formula. It is found that the shear viscosity is expressed in terms of the quark spectral function. If the spectral function is approximated by a modified Bright-Wigner type, the viscosity decreases as the width of the spectral function increases. We also discuss dependence of the shear viscosity on the temperature and the density.
125492698
A search for deeply-bound kaonic nuclear states at J-PARC
The J-PARC E15 experiment will be performed to search for the simplest kaonic nuclear bound state, K− pp , by the in-ﬂight 3 He(K − ,n) reaction. The exclusive measurement can be performed by a simultaneous measurement of the missing mass using the primary neutron and the invariant mass via the expected decay, K− pp → Λp → pπ− p . In this report, an overview of the experiment and the preparation status are presented.
119925353
Precise Muon Lifetime Measurement with a Pulsed Beam at the RIKEN-RAL Muon Facility
A precise measurement of the positive muon lifetime was performed at the RIKEN-RAL muon facility. We developed a new method to accumulate a large number of muon decays with a strong pulsed beam. A multi-wire proportional chamber was employed as a positron detector, which was finely segmented in order to reduce the systematic error due to the pile-up signal. Residual pile-up signals were corrected and a preliminary time spectrum was obtained in the off-line analysis. The pile-up correction analysis and the systematic error estimation are now in progress.
121515669
Generation of low-energy muons with laser resonant ionization
We have constructed a low-energy muSR spectrometer at RIKEN-RAL muon facility in ISIS, the UK. With low-background of pulsed muon beam, and short pulse width from laser resonant ionization method, it is hoped this instrument will open new possibilities for studies of material sciences with muon beam. It is enphasized that this method is well suited to the facility where intense pulsed proton beam is available.
124815658
Measure of the spatial size for the monopole excitation in proton scattering
124048289
A search for deeply bound kaonic nuclear states at J‐PARC
J‐PARC E15 experiment aims to search for the lightest kaonic nuclei, namely K−pp bound states, using in‐flight (K−, n) reactions. The advantage of this experiment is to perform exclusive measurement by missing mass study using the primary neutrons and invariant mass spectroscopy via such decay as K−pp→Λp→pπ−p, simultaneously. In this report, an overview of this experiment and the current status are presented.