Effects of Instanton Induced Interaction on the Pentaquarks

Roles of instanton induced interactions (III) in the masses of pentaquark baryons, Theta^+ (J=1/2 and 3/2) and Xi^{--}, and a dibaryon, H, are discussed using the MIT bag model in the negative parity case. It is shown that the two-body terms in III give a strong attraction mainly due to the increase of the number of pairs in multi-quark systems. In contrast, the three-body u-d-s interaction is repulsive. It is found that III lowers the mass of Theta^+ as much as 100 MeV from the mass predicted by the bag model without III.Comment: 11 pages, 3 figure

P-wave Pentaquark and its Decay in the Quark Model with Instanton Induced Interaction

P-wave pentaquarks with strangeness +1, I=0 and J^P=1/2^+ are studied in the non-relativistic quark model with instanton induced interaction (III). We present their mass splittings and orbital-spin-isospin-color structures. It is found that decompositions of the wave functions are sensitive to III, while the mass splittings are insensitive. The decay of the lowest energy pentaquark, \Theta^+, is found to be suppressed when the contribution of III is increased. Its wave function is dominated by Jaffe-Wilczek-type configuration at large III.Comment: 9 pages, 5 figure

Spectral Statistics and Local Luminosity Function of a Hard X-ray Complete Sample of Brightest AGNs

We have measured the X-ray spectral properties of a complete flux-limited sample of bright AGNs from HEAO-1 all-sky catalogs to investigate their statistics and provide greater constraints on the bright-end of the hard X-ray luminosity function (HXLF) of AGNs and the AGN population synthesis model of the X-ray background. Spectral studies using data from ASCA, XMM-Newton and/or Beppo-SAX observations have been made for almost all AGNs in this sample. The spectral measurements enable us to construct the neutral absorbing column density (Log nH) distribution and separate HXLFs for absorbed (Log nH[cm-2]> 21.5) and unabsorbed AGNs in the local universe. Our results show evidence for a difference in the shapes of HXLFs of absorbed and unabsorbed AGNs in that absorbed AGN HXLF drops more rapidly at higher luminosities than that of unabsorbed AGNs, which is similar to that previously reported. In the Lx - nH plot, we found no AGN in the high-luminosity high-intrinsic absorption regime (Log Lx[erg/s]> 44.5, Log nH[cm-2]> 21.5) in our sample, where we expect about 5 AGNs if we assume that absorbed and unabsorbed having identical AGN HXLF shapes. We also find that the observed flux with ASCA or XMM-Newton is smaller than that with HEAO-1 by a factor of 0.29 on average, which is expected for re-observation of sources with a factor 2.5 variability amplitude scale.Comment: 43 pages(one column), 10 figures(5 electronic only figures have been included in the preprint source (tar.gz file)), accepted by The Astronomical Journal, 9. Mar 200