122137776
A Model for Shock Waves in High Energy Heavy Ion Collisions
120691222
Superconductivity of Quark Matter at Finite Temperature
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.
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
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.
118969678
Tetraquark particle in the string model
We discuss the possibility of the existence of tetraquark states made of four quarks in the string (flux tube) model. The new particle is composed of a diquark and an antidiquark which are connected by a color flux. It is shown that the vibrational and rotational excited states of the string explain some non-qq mesons observed experimentally. Moreover we discuss the decay widths of such tetraquarks with the use of the Schwinger mechanism.
203024439
Recent results and current status of the muon g-2 experiment at BNL
The measurement of the (g−2) value of leptons provides a unique test of theory since it is the only quantity (unlike charge and mass) calculable in the framework of the Standard Model of elementary particles. The muon (g−2) experiment E821 is currently in progress at Brookhaven National Laboratory. Four data taking runs for positive muons and one run for negative muons were successfully accomplished in 1997–2000 and 2001, respectively. Results of the 1997–2000 runs have been published, thus completing our experiment for μ+. Data analysis for the 2001 run for μ− is currently in progress. To provide measurement of \(a_\mu = \tfrac{1} {2}(g - 2)_{\mu ^ - }\) at the same level of accuracy as for \(a_{\mu ^ + } = \tfrac{1} {2}(g - 2)_{\mu ^ + }\), we need to have one more data taking run.
185755181
The SuperKEKB accelerator status
120408377
Solving the kaonic-helium puzzle
We have measured the Balmer-series x-rays of kaonic 4He atoms using large-area silicon drift x-ray detectors (SDDs) in order to study the low-energy -nucleus strong interaction. The energy of the 3d → 2p transition was determined to be 6467 ± 3(stat) ± 2(syst) eV. The resulting strong-interaction energy-level shift is in agreement with theoretical calculations, thus eliminating a long-standing discrepancy between theory and experiment.
122815017
Statistical equations and methods applied to the precision muon (g-2) experiment at BNL
Abstract In the muon ( g - 2 ) experiment at Brookhaven National Laboratory, the spin precession frequency ω a is obtained from a standard χ 2 minimization fit applied to the time distribution of decay electrons. The unusually high accuracy ( ∼ 0.5 ppm ) of the experiment puts stringent requirements on the quality of the fit and the level of understanding of the statistical properties of the fitted parameters. We discuss the properties of the fits and their implications on the derived value for ω a , including estimates of the effect of an imperfect fit function, methods of including additional external information to reduce the error, the effects of splitting the data into many smaller subsets of data, applying different weighting methods to the data using energy information, and various tests of data suitability.
119456897
Spectroscopy of hypernuclei with stopped kaons — recent result of KEK experiment
Abstract Pion momentum spectra from K − absorption at rest on various nuclear targets were measured by means of a magnetic spectrometer with wide momentum range (100 ∼ 300 MeV/c). The ground state of Σ − hypernucleus, if well bound with a narrow width, is expected to be populated in 12 C(stopped K − , π + ) inclusive (untagged) spectrum, but such a peak was not observed. The spectrum is compared with the DWIA calculations by Morimatsu and Yazaki, indicating that the depth of the nuclear potential of Σ − is shallower than 12 MeV, and that its imaginary part is larger than 5 MeV if the potential depth is about 10 MeV. In the 12 C(stopped K − , π − ) spectrum, the ground state (( p 3 2 ) n −1 ( s 1 2 )Λ) and the excited states (( p3 2 ) n −1 ( p )Λ) of Λ 12 C were observed, and their formation probabilities were roughly in agreement with the results of DWIA calculations. In the π − spectra on 12 C, 9 Be, and 7 Li targets a distinct peak was observed at 132.1±0.7 MeV/c. It is ascribed to π − from the mesic decay of Λ 4 H; Λ 4 H → 4 He π − . The formation probability of Λ 4 H on C, Be, or Li target is much larger than those of the discrete states of Λ 12 C via the direct (stopped K − , π − ) reaction.