The generalized parton distributions of the nucleon in the NJL model based on the Faddeev approach

We study the generalized parton distributions, including the helicity-flip ones, using Nambu-Jona-Lasinio model based on a relativistic Faddeev approach with `static approximation'. Sum rules relating the generalized parton distributions to nucleon electromagnetic form factors are satisfied. Moreover, quark-antiquark contributions in the region $-\xi<x<\xi$ are non-vanishing. Our results are qualitatively similar to those calculated with Radyushkin's double distribution ansatz using forward parton distribution functions calculated in the NJL model as inputs.Comment: 35 pages, 15 figure

A Faddeev Calculation for Pentaquark Θ+\Theta^+ in Diquark Picture with Nambu-Jona-Lasinio Type Interaction

A Bethe-Salpeter-Faddeev (BSF) calculation is performed for the pentaquark $\Theta^+$ in the diquark picture of Jaffe and Wilczek in which $\Theta^+$ is a diquark-diquark-${\bar s}$ three-body system. Nambu-Jona-Lasinio (NJL) model is used to calculate the lowest order diagrams in the two-body scatterings of ${\bar s}D$ and $D D$. With the use of coupling constants determined from the meson sector, we find that ${\bar s}D$ interaction is attractive while $DD$ interaction is repulsive, and there is no bound $\frac 12^+$ pentaquark state. A bound pentaquark $\Theta^+$ can only be obtained with unphysically strong vector mesonic coupling constants.Comment: 4 pages, 4 figure

Faddeev calculation of pentaquark Θ+\Theta^+ in the Nambu-Jona-Lasinio model-based diquark picture

A Bethe-Salpeter-Faddeev (BSF) calculation is performed for the pentaquark $\Theta^+$ in the diquark picture of Jaffe and Wilczek in which $\Theta^+$ is a diquark-diquark-${\bar s}$ three-body system. Nambu-Jona-Lasinio (NJL) model is used to calculate the lowest order diagrams in the two-body scatterings of ${\bar s}D$ and $D D$. With the use of coupling constants determined from the meson sector, we find that ${\bar s}D$ interaction is attractive in s-wave while $DD$ interaction is repulsive in p-wave. With only the lowest three-body channel considered, we do not find a bound $\frac 12^+$ pentaquark state. Instead, a bound pentaquark $\Theta^+$ with $\frac 12^-$ is obtained with a unphysically strong vector mesonic coupling constants.Comment: 22 pages, 11 figures, accepted version in Phys. Rev. C. Summary of main changes/corrections: 1. "which only holds at tree level" below the eq. (23) is added. 2. In the last paragraph of p.23 we added a remark that the coupling constant obtained from Lambda mass is different from the estimate as obtained from the meson spectru

A BeppoSAX observation of the super-soft source CAL87

We report on a BeppoSAX Concentrator Spectrometer observation of the super-soft source (SSS) CAL87. The X-ray emission in SSS is believed to arise from nuclear burning of accreted material on the surface of a white dwarf (WD). An absorbed blackbody spectral model gives a chi^2_v of 1.18 and a temperature of 42 +/- ^13 _11 eV. However, the derived luminosity and radius are greater than the Eddington limit and radius of a WD. Including an O viii edge at 0.871 keV gives a significantly better fit (at > 95% confidence) and results in more realistic values of the source luminosity and radius. We also fit WD atmosphere models to the CAL87 spectrum. These also give reasonable bolometric luminosities and radii in the ranges 2.7-4.8 10^{36} erg/s and 8-20 10^7 cm, respectively. These results support the view that the X-ray emission from CAL87 results from nuclear burning in the atmosphere of a WD.Comment: 4 pages. Accepted for publication in A&A (Letters

Baryon structure in a quark-confining non-local NJL model

We study the nucleon and diquarks in a non-local Nambu-Jona-Lasinio model. For certain parameters the model exhibits quark confinement, in the form of a propagator without real poles. After truncation of the two-body channels to the scalar and axial-vector diquarks, a relativistic Faddeev equation for nucleon bound states is solved in the covariant diquark-quark picture. The dependence of the nucleon mass on diquark masses is studied in detail. We find parameters that lead to a simultaneous reasonable description of pions and nucleons. Both the diquarks contribute attractively to the nucleon mass. Axial-vector diquark correlations are seen to be important, especially in the confining phase of the model. We study the possible implications of quark confinement for the description of the diquarks and the nucleon. In particular, we find that it leads to a more compact nucleon.Comment: 21 pages (RevTeX), 18 figures (eps

Liquid-gas phase transition in nuclear matter including strangeness

We apply the chiral SU(3) quark mean field model to study the properties of strange hadronic matter at finite temperature. The liquid-gas phase transition is studied as a function of the strangeness fraction. The pressure of the system cannot remain constant during the phase transition, since there are two independent conserved charges (baryon and strangeness number). In a range of temperatures around 15 MeV (precise values depending on the model used) the equation of state exhibits multiple bifurcates. The difference in the strangeness fraction $f_s$ between the liquid and gas phases is small when they coexist. The critical temperature of strange matter turns out to be a non-trivial function of the strangeness fraction.Comment: 15 pages, 7 figure

Luminosity Function of High-Mass X-ray Binaries and Anisotropy in the Distribution of Active Galactic Nuclei toward the Large Magellanic Cloud

In 2003-2012, the INTEGRAL observatory has performed long-term observations of the Large Magellanic Cloud (LMC). At present, this is one of the deepest hard X-ray (20-60 keV) surveys of extragalactic fields in which more than 20 sources of different natures have been detected. We present the results of a statistical analysis of the population of high-mass X-ray binaries in the LMC and active galactic nuclei (AGNs) observed in its direction. The hard X-ray luminosity function of high-mass X-ray binaries is shown to be described by a power law with a slope alpha~1.8, that in agreement with the luminosity function measurements both in the LMC itself, but made in the soft X-ray energy band, and in other galaxies. At the same time, the number of detected AGNs toward the LMC turns out to be considerably smaller than the number of AGNs registered in other directions, in particular, toward the source 3C 273. The latter confirms the previously made assumption that the distribution of matter in the local Universe is nonuniform.Comment: 5 pages, 5 figures, will be published in Astronomy Letters, 2012, Vol. 38, No. 8, p. 492--49

Detection of Toxoplasma gondii soluble antigen, SAG-1 (p30), antibody and immune complex in the cerebrospinal fluid of HIV positive or negative individuals

Active infection by T. gondii was evaluated by immunoassay for soluble SAG-1 (p30), the major surface antigen from T. gondii, specific antibodies and immune complexes in human cerebrospinal fluid (CSF) samples. A total of 263 samples of CSF were collected from hospitalized patients presenting neurological disorders and analyzed for antibodies to HIV. Patients were divided into two groups: HIV positive (n = 96) or HIV negative (n = 167). The results of the assays showed that 45% of all samples were positive for soluble SAG-1. Toxoplasma Ag/Ab immune complexes were detected in 19% of the CSF samples and 62% were positive for T. gondii- specific IgG. A combination of these assays in the presence of clinical findings consistent with active Toxoplasma infection may predict the presence of toxoplasmic encephalitis. Moreover, detection of soluble SAG-1 in the CSF of these individuals appears consistent with active infection