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.
67846515
A Modified Glauber Approximation and the Formation of Shock Waves in High-Energy Heavy Ion Collisions
Coherent features in high energy heavy ion collisions are investigated from a microscopic viewpoint. A modified Glauber approximation which enables us to include the slowing down of the relative motion between the centers of masses of both nuclei is presented. The generation of the shock wave is shown to be suppressed by this slowing down effect. As an application inclusive nucleon spectra and the two-particle correlation are calculated in the case of Ne+U collision at 400 Me V! A. l ) (which are referred to as I hereafter) we investigated a possible microscopic mechanism for shock wave generation in high energy heavy ion collisions. The nuclear excitation induced by a nuclear collision was de­ scribed in terms of phonons. It was shown that as the collision proceeds phonons are coherently excited and show a characteristic feature of the shock wave. In this treatment the action of the projectile on the target was replaced by that of a potential moving with a constant velocity. We may construct this potential by superposing the nucleonic potential between projectile nucleons and the target ones with amplitudes of nucleonic states in both nuclei. To treat both systems equally from a microscopic viewpoint, one of the authors (M.I) proposed a formalism which is essentially an application of the Glauber approximation to the process. 2 ) The assembly of nucleons in the projectile nucleus was assumed to move in a group during the collision and the Glauber approximation was applied to the relative motion between the centers of masses of the projectile and the target nucleus. In this treatment the deceleration of the relative motion due to the nuclear excitation was not taken into account. In this paper we extend the Glauber approximation so as to take into account the slowing down of the relative motion. In § 2 the formulation of the modified Glauber approximation is presented.
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.
6081502
Mass spectra and decay widths of hadrons in the relativistic string model
A relativistic string model for hadrons is presented. The center-of-mass motion is separated correctly. The vibrational and rotational motions of the string are solved by using the WKB approximation. Moreover, their decay widths are calculated by taking into account the pair creation of quarks inside the string. Both the mass spectra and the decay widths are reproduced fairly well in comparison with experimental data.
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.
123947708
A Search for Deeply-bound Kaonic Nuclear States by In-flight $^3$He($K^-, n$) Reaction at J-PARC
F. Sakuma, S. Ajimura, G. Beer, H. Bhang, M. Bragadireanu P. Buehler, L. Busso, M. Cargnelli, S. Choi, C. Curceanu S. Enomoto, D. Faso, H. Fujioka, Y. Fujiwara, T. Fukuda C. Guaraldo, T. Hashimoto, R.S. Hayano, T. Hiraiwa, M. Iio M. Iliescu, K. Inoue, Y. Ishiguro, T. Ishikawa, S. Ishimoto T. Ishiwatari, K. Itahashi, M. Iwai, M. Iwasaki, Y. Kato S. Kawasaki, P. Kienle, H. Kou, Y. Ma, J. Marton, Y. Matsuda Y. Mizoi, O. Morra , T. Nagae, H. Noumi, H. Ohnishi, S. Okada H. Outa, K. Piscicchia, M. Poli Lener, A. Romero Vidal Y. Sada, A. Sakaguchi, M. Sato, A. Scordo, M. Sekimoto, H. Shi D. Sirghi, F. Sirghi, K. Suzuki, S. Suzuki, T. Suzuki K. Tanida, H. Tatsuno, M. Tokuda, D. Tomono, A. Toyoda K. Tsukada, O. Vazquez Doce, E. Widmann, B.K. Wuenschek T. Yamaga, T. Yamazaki, H. Yim, Q. Zhang, J. Zmeskal
18985470
A search for deeply bound kaonic nuclear states
Abstract We have measured proton and neutron energy spectra by means of time-of-flight (TOF) from 4He( K stopped − , p / n ) reactions (KEK PS E471 experiment). In the proton spectrum, a clear mono-energetic peak was observed under semi-inclusive condition, which was assigned to the formation of a strange tribaryon S0(3115) with isospin T = 1 . The mass and width of the state were deduced to be 3117.7 −2.0 +3.8 ( syst . ) ± 0.9 ( stat . ) MeV / c 2 and 21.6 MeV / c 2 , respectively, and its main decay mode was Σ N N . In the neutron spectrum, a mono-energetic peak was found as the result of a detailed analysis, which was assigned to the formation of another kind of strange tribaryon S+(3140). The mass and width of the state were deduced to be 3140.5 −0.8 +3.0 ( syst . ) ± 2.3 ( stat . ) MeV / c 2 and 21.6 MeV / c 2 , respectively, and its main decay mode was Σ ± N N . The isospin of the state is assigned to be 0. The results are compared with recent theoretical calculations.
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.
122785400
Search for Heavy Neutrinos in Kaon Decay
We obtained a new constraint of | u . 1 * * versus m(v.), as shown in Fig.l. Because or the better resolution the lower end of the neutrino mass was reduced to 40 MeV. In Fig.l are also shown other upper limits. One is from R -» j/v done /3/ at SIN. Another comes from the 1 He(jf ,v ) reaction /4/. 1 For the first time we obtained e + spectrum with rejection of the three body decay mode. Hitherto only the e v peak region of 247 MeV/c was known /$/. From the analysis oj; the spectrum we obtained a new constraint, on I U | in a wide mass range between 140 and 350 MeV, as shown in Fig.2. The JL* -> e y experiment /6/ at TRIUMF covers a complementary mass region. A recent experiment to search for neutrino0decays at CERN /?/ gave a new constraint on |U | but the present experiment has yielded a one-order of magnitude better constraint. It should be noted that the deduction of | l I e i l from the CERN experiment requires a model for heavy neutrino decay, while in the present experiment it is given purely kmematically,
124123633
SEARCH FOR LORENTZ AND CPT VIOLATION EFFECTS IN MUON SPIN PRECESSION