摘要:

A hybrid emulsion experiment E373 at KEK has been carried out to study doubly strange nuclear system. By the 8&percent; data analysis of all, one twin single-&Lgr; hypernuclei event and two events of double-&Lgr; hypernucleus have been successfully detected. The twin single-&Lgr; event is uniquely interpreted as&Ygr;−+14N→&Lgr;5He+&Lgr;5He+4He+nfor the first time. In the first double-&Lgr; hypernucleus event, “Demachi-Yanagi,” it is interpreted as&Ygr;−+12C→&Lgr;&Lgr;10Be*(or&Lgr;&Lgr;10Be*)+t.The second double-&Lgr; hypernucleus event, “NAGARA,” shows a clearly recognized topology and the interpretation is unique as&Ygr;−+12C→&Lgr;&Lgr;6He+4He+t,&Lgr;&Lgr;6He→&Lgr;5He+&pgr;−+p,&Lgr;5He→p+d+2netc. By the preliminary result of the&Lgr;&Lgr;6He,the attractive &Lgr;&Lgr; interaction has been confirmed with the&Dgr;B&Lgr;&Lgr;∼1 MeV.©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425502

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The four-body calculations for&Lgr;4Heand&Lgr;4Hwith high accuracy have been performed in the framework of the variational method with Jacobian-coordinate Gaussian-basis functions. All the rearrangement channel of bothNNN&Lgr;andNNN&Sgr;are explicitly taken into account for the first time using realisticNNandYNinteractions. The important role of&Lgr;−&Sgr;conversion and the amount of the virtual &Sgr;-component in&Lgr;4Heand&Lgr;4Hare discussed. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425503

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We explore a question of whether quark Pauli principle plays an important role or not in the binding mechanism of &Lgr; hypernuclei. We introduce a special five-baryon configuration which is forbidden by the Pauli principle at the quark level. By excluding the forbidden state, we show that the &Lgr; separation energy of&Lgr;5Heor&Lgr;&Lgr;6Heis significantly reduced for a baryon size of 0.86 fm, while it is unchanged for a smaller size of 0.6 fm. We also show a qualitative estimation of the energy reduction for more heavier systems,&Lgr;9Beand&Lgr;&Lgr;10Be,by an &agr; cluster model. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425504

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Shell-model calculations in a large model space are performed for the low-lying1/2+,3/2−and1/2−states in&Lgr;17O,introducing effective interactions among the &Lgr;, &Sgr; and nucleons. The effective interactions are derived from hyperon-nucleon and nucleon-nucleon interactions given in free space in the framework of the unitary-model-operator approach. The results are compared with those obtained in a perturbative method studied previously, and reliability of the present method is discussed. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425505

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The weak&pgr;−-decay of&Lgr;&Lgr;4Hare theoretically analyzed with the recent experimental data by BNL-E906. The two-body&pgr;−-decay width of&Lgr;&Lgr;4His calculated to be 0.69&Ggr;&Lgr;,and its branching ratio to the total&pgr;−decay is about 25&percent;. The branching ratio of decay channels accompanied with a &Lgr; particle to the total&pgr;−-decay is about 43&percent;. The calculated&pgr;−spectrum of&Lgr;&Lgr;4Hhas a broad peak around 100 MeV/cin nuclear continuum region, whose value is inconsistent with the experimental results of a peak structure around 103 MeV/c. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425506

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

In this work we investigate an SU(3) extension of the axially symmetricB=2chiral quark soliton model. The classical soliton is extended to the SU(3) by trivial embedding. We expand the quark determinant in terms of the collective angular velocity up to the second order as well as in the quark mass difference of the first order. The diagonalization of the collective SU(3) hamiltonian is estimated by the method of Yabu-Ando. Finally the mass spectrum and the binding energy of the baryon-baryon channels down to strangenessS=−6are obtained. Absolute mass are considerably larger than the values of experimental candidates because of the absence of all Casimir effects. The results suggest the possibility of several bound states especially for lower strangeness. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425507

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We present the centrality dependence of proton and deuteron rapidity distributions inRu+Rucollisions at400A MeV.The ratio of baryon rapidity distributions in isospin asymmetric collision systems shows incomplete mixing and transparency of the projectile and target nucleons at this beam energy. In addition, we also present the results of thermal model calculations including both a modification of the &Dgr;(1232) spectral function and the Coulomb interaction. The model calculations are compared with the published pion spectra for centralAu+Aucollisions at1A GeV.©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425508

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

The time evolution of quantum many body systems in the relativistic quantum field theory is studied. We use Shibata-Hashitsume’s projection operator method which gives a systematic expansion of the Heisenberg equation of motion in terms of the interaction Hamiltonian. We calculate the time evolution of expectation values of creation and annihilation operators in a renormalizable model with unstable particles in a vacuum and in a medium. It is shown how to renormalize the ultraviolet divergences appearing in the equation of motion and calculate the medium effects on the time evolution. The mass and the wavefunction renormalizations are carried out in the lowest order. We find that the results coincide with the on-mass-shell values of the self-energy and its derivative which are calculated by the usual Feynman rule. We also discuss the initial divergence which remains at the initial time after mass renormalization. It is suggested that the projection operator method can be applied to the relativistic quantum field theory. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425509

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

Using the Nambu-Jona-Lasinio (NJL) model we study responses of the pion and kaon masses to changes in the chemical potential,∂m/∂&mgr;,at zero and finite chemical potential. We find that the behavior of∂m/∂&mgr;for the pion is quite different from that for the kaon. Our results can give a clue for future studies of∂m/∂&mgr;on the lattice. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425510

出版商:AIP    

年代:1901

数据来源: AIP

摘要:

We calculate the Wilson coefficients of all dimension 6 gluon operators with non zero spin in the correlation function between two heavy vector currents. We apply our results to investigate the mass ofJ/&psgr;in nuclear matter. Using an upper bound estimate on the matrix elements of the dimension 6 gluon operators to linear order in density, we find that the density dependent contribution from dimension 6 operators is less than 40&percent; of the dimension 4 operators with opposite sign. ©2001 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1425511

出版商:AIP    

年代:1901

数据来源: AIP