RESUMO
Experimental evidence exists that the Ξ-nucleus interaction is attractive. We search for NNΞ and NNNΞ bound systems on the basis of the AV8 NN potential combined with either a phenomenological Nijmegen ΞN potential or a first principles HAL QCD ΞN potential. The binding energies of the three-body and four-body systems (below the d+Ξ and ^{3}H/^{3}He+Ξ thresholds, respectively) are calculated by a high precision variational approach, the Gaussian expansion method. Although the two ΞN potentials have significantly different isospin (T) and spin (S) dependence, the NNNΞ system with quantum numbers (T=0, J^{π}=1^{+}) appears to be bound (one deep for Nijmegen and one shallow for HAL QCD) below the ^{3}H/^{3}He+Ξ threshold. Experimental implications for such a state are discussed.
RESUMO
The nucleon-nucleon (NN) potential is studied by lattice QCD simulations in the quenched approximation, using the plaquette gauge action and the Wilson quark action on a 32(4) [approximately (4.4 fm)(4)] lattice. A NN potential V(NN)(r) is defined from the equal-time Bethe-Salpeter amplitude with a local interpolating operator for the nucleon. By studying the NN interaction in the (1)S(0) and (3)S(1) channels, we show that the central part of V(NN)(r) has a strong repulsive core of a few hundred MeV at short distances (r approximately < 0.5 fm) surrounded by an attractive well at medium and long distances. These features are consistent with the known phenomenological features of the nuclear force.
RESUMO
Thermal color superconducting phase transitions in high density three-flavor quark matter are investigated in the Ginzburg-Landau approach. The effects of nonzero strange quark mass, electric and color charge neutrality, and direct instantons are considered. Weak coupling calculations show that an interplay between the mass and electric neutrality effects near the critical temperature gives rise to three successive second-order phase transitions as the temperature increases: a modified color-flavor locked (mCFL) phase (ud, ds, and us pairings) --> a d-quark superconducting (dSC) phase (ud and ds pairings) --> an isoscalar pairing phase (ud pairing) --> a normal phase (no pairing). The dSC phase is novel in the sense that while all eight gluons are Meissner screened as in the mCFL phase, three out of nine quark quasiparticles are always gapless.
RESUMO
Analyzing correlation functions of charmonia at finite temperature (T) on 32(3)x(32-96) anisotropic lattices by the maximum entropy method (MEM), we find that J/psi and eta(c) survive as distinct resonances in the plasma even up to T approximately 1.6T(c) and that they eventually dissociate between 1.6T(c) and 1.9T(c) (T(c) is the critical temperature of deconfinement). This suggests that the deconfined plasma is nonperturbative enough to hold heavy-quark bound states. The importance of having a sufficient number of temporal data points in MEM analyses is also emphasized.
RESUMO
Baryon resonances with even and odd parity are collectively investigated from the viewpoint of chiral symmetry (ChS). We propose a quartet scheme where Delta's and N(*)'s with even and odd parity form a chiral multiplet. This scheme gives parameter-free constraints on the baryon masses in the quartet, which are consistent with observed masses with spin 1 / 2,3 / 2,5 / 2. The scheme also gives selection rules in the one-pion decay: The absence of the parity nonchanging decay N(1720)-->piDelta(1232) is a typical example which should be confirmed experimentally to unravel the role of ChS in baryon resonances.
RESUMO
A 53-year-old woman whose history was noncontributory for rheumatoid arthritis and collagen disease had bilateral necrotizing inflammation of the sclera. The left eye had necrotizing nodular scleritis and the right eye, massive granuloma of the sclera. In the right eye the orbital adnexae were also involved by granulomatous infiltration and developed a mass of fibroadipose tissue simulating an orbital tumor within a week after enucleation.
