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  • 1
    Electronic Resource
    Electronic Resource
    Three-hadron form factor via quark-triangle loop (1993)
    Springer
    Few body systems 15 (1993), S. 1-13 
    Details
    ISSN: 1432-5411
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An explicit construction in a manifestly Lorentz-invariant and cyclically symmetric form is given for a three-hadron (H) coupling through their respective (q $$\bar q$$ ) constituents interacting via a quark triangle loop under the most general conditions of unequal mass kinematics atboth the elementary quark and composite-hadron levels. The only ansatz employed is that theHq $$\bar q$$ vertex function ΓH at each vertexi is a function of $$\hat q$$ i , the relative momentumtransverse to the corresponding hadron momentumP i, an assumption which can be justified from several independent angles. The resulting structure $$\Gamma _H \approx D(\hat q) \otimes \phi (\hat q)$$ , withD( $$\hat q$$ ) being a model-independent function, has proved crucial for an explicit integration over the time-like component of the loop momentum, and thus provided an analytical, cyclically symmetric structure free of overlapping pole singularities. The applicational potential of this quantity is outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01344373
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  • 2
    Electronic Resource
    Electronic Resource
    Gluon-exchange currents: The nucleon axial-vector coupling constant and magnetic moments in bag models (1983)
    Springer
    The European physical journal 16 (1983), S. 331-338 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Possible numerical importance of the two-body currents arising from exchange of one hard gluon between two constituent quarks is investigated by studying the evaluation of the nucleon axial-vector coupling constantg A and magnetic moments μ p tot , μ n tot in the context of the MIT bag model. The double counting problem is resolved only to the extent that, in accord with the standard wisdom, hard gluons have nothing to do with the formation of bags (quark confinement) and so are not included in bag-model wave functions. For reasonable choices of the parameters, we find that (1) the contribution tog A arising from one-gluon-exchange currents (OGEC) could account for the discrepancy between the observed value and the one-body bag-model prediction, and that (2) whereas the OGEC contribution to μ n tot is negligible, the contribution to μ p tot could be important but does not allow further understanding of the observed μ p /μ n ratio.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01577102
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  • 3
    Electronic Resource
    Electronic Resource
    Recoil corrections to magnetic moments of octet baryons in the MIT bag model (1983)
    Springer
    The European physical journal 16 (1983), S. 327-330 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The presence of certain recoil corrections in the determination of baryon magnetic moments is described and taken into account for the octet members. Inclusion of these recoil corrections makes the MIT bag model, even in its zeroth-order version, very appealing, if the sum of many other corrections is not important by comparison.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01577101
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  • 4
    Electronic Resource
    Electronic Resource
    Dense stars with exotic configurations (1991)
    Springer
    The European physical journal 338 (1991), S. 223-232 
    Details
    ISSN: 1434-601X
    Keywords: 21.65.+ f
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper, we consider dense stars with configurations expected from the SU(3)C×SU(2)W× U(1) standard model of strong and electroweak interactions. Following a recent suggestion that strange matter, a form of (uds) quark matter, may be the true ground state of hadronic matter, we investigate the prospect for the existence of dense stars consisting partially, or entirely, of strange matter by comparing the relative stability between neutron matter and strange matter. It is found that the restriction on the maximum star mass holds in all cases, including a pure strange star, a pure neutron star, and a neutron star with a quark core. It is also found that the choice of both the bag constantB and the strong coupling constant αs has a decisive effect on the relative stability between strange matter and neutron matter. For currently accepted values of (B, αs), anA=∞ dense starcannot consist entirely,nor partially, of strange matter. Nevertheless, such conclusion may be subject to change if corrections ofO (α s 2 ) or other effects are taken into account. Finally, we use the framework of Tolman, Oppenheimer, and Volkoff to analyze two cases of boson stars: gluon stars and stars consisting of massive scalar particles (massive bosons). It is found that, in the case of gluon stars, the presence of the bag constant in the QCD vacuum yields results very similar to that found in quark stars. On the other hand, soliton stars consisting of massive bosons exist if there is some background pressure which plays the role similar to the bag constant for lowering the matter pressure. The stability problem for both gluon stars and soliton stars is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01284798
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  • 5
    Electronic Resource
    Electronic Resource
    Hard form factors for meson-baryon strong couplings as derived from deep inelastic lepton scattering (1991)
    Springer
    The European physical journal 339 (1991), S. 383-389 
    Details
    ISSN: 1434-601X
    Keywords: 13.75.Gx ; 13.75.Jz ; 13.60.Hb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract As stimulated by earlier attempts for obtaining theπNN andπNδ form factors from the deep inelastic lepton scattering data, we extend the analysis by taking into account effects of additional mesons includingρ, Ω, σ,K, andK *, with the coupling constants fixed by the lowenergy nucleon-nucleon and hyperon-nucleon scattering data. Contrary to an earlier claim that theπ NN andπNδ form factor must be very soft (e.g., with the cutoff mass less than 500 MeV in the monopole form), we find, for example, that with all form factors parametrized in the dipole form, a universal cutoff mass of 1150 MeV in theδ/N sector and 1400 MeV in theλ/σ sector yields predictions in excellent agreement with recently published neutrino data on the momentum fractions carried by thes, Ū, and¯d quarks, as well as consistent with the sea-to-valence ratio extracted from the CDHS data and the Femilab E615 experiment. Similar results can also be obtained by using exponential cutoffs for all couplings, or by using monopole forms for some vertices while retaining dipole forms for the rest. The success of the mesonexchange picture in generating the strangeness content in a proton suggests an alternative understanding of the origin of sea quarks in the proton.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01560641
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  • 6
    Electronic Resource
    Electronic Resource
    T-dependent Dyson-Schwinger equation in IR regime of QCD: the critical point (2005)
    Springer
    The European physical journal 39 (2005), S. 209-218 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The quark mass function $\Sigma(p)$ in QCD is revisited, using a gluon propagator in the form 1/(k 2 + m g 2) plus $2\mu^2/ (k^2 + m_g^2)^2$ , where the second (IR) term gives linear confinement for m g = 0 in the instantaneous limit, μ being another scale. To find $\Sigma(p)$ we propose a new (differential) form of the Dyson-Schwinger equation (DSE) for $\Sigma(p)$ , based on an infinitesimal subtractive renormalization via a differential operator which lowers the degree of divergence in integration on the RHS, by two units. This warrants $\Sigma(p-k)\approx \Sigma(p)$ in the integrand since its k-dependence is no longer sensitive to the principal term (p-k)2 in the quark propagator. The simplified DSE (which incorporates the Ward-Takahashi (WT) identity in the Landau gauge) is satisfied for large p 2 by $\Sigma(p)$ = $\Sigma(0)/(1 + \beta p^2)$ , except for Log factors. The limit p 2 = 0 determines $\Sigma_0$ . A third limit, p 2 = -m 0 2, defines the dynamical mass m 0 via $\Sigma({\mathrm {i}} m_0) = + m_0$ . After two checks ( $f_{\pi} = 93\pm 1$ MeV and $ \langle q{\bar{q}}\rangle $ = $(280 \pm 5 {\mathrm {MeV}})^3$ ), for $1.5 〈 \beta 〈 2$ with $\Sigma_0 = 300 $ MeV, the T-dependent DSE is used in the real time formalism to determine the “critical” index $\gamma = 1/3$ analytically, with the IR term partly serving as the H-field. We find $T_{\mathrm {c}} = 180 \pm 20 $ MeV and check the vanishing of $f_{\pi}$ and $ \langle q{\bar{q}}\rangle $ at T c.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjc/s2004-02072-3
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