Octet magnetic Moments and their sum rules in statistical model

Physical Review D, 2008

A comprehensive study is made for the magnetic moments of octet baryons in the method of QCD sum rules. A complete set of QCD sum rules is derived using the external field method and generalized interpolating fields. For each member, three sum rules are constructed from three independent tensor structures. They are analyzed in conjunction with the corresponding mass sum rules. The performance of each of the sum rules is examined using the criteria of OPE convergence and ground-state dominance, along with the role of the transitions in intermediate states. Individual contributions from the u, d and s quarks are isolated and their implications in the underlying dynamics are explored. Valid sum rules are identified and their predictions are obtained. The results are compared with experiment and previous calculations.

Physics Letters B, 2005

Recently the µ ∆ ++ was found from a fit to π + p scattering [1]. This enable us to pinpoint condensate parameters more precisely in the context of QCD sum rules (QCDSR).

Physical Review D, 2005

Using generalized Sehgal equations for magnetic moments of baryon octet and taking into account Σ 0 − Λ mixing and two particle corrections to independent quark contributions we obtain very good fit using experimental values for errors of such moments. We present sum rules for quark magnetic moments ratios and for integrated spin densities ratios. Due to the SU (3) structure of our equations the results for magnetic moments of quarks and their densities depend on two additional parameters. Using information from deep inelastic scattering and baryon β-decays we discuss the dependence of antiquark polarizations on introduced parameters. For some plausible values of these parameters we show that these polarizations are small if we neglect angular momenta of quarks. Our very good fit to magnetic moments of baryon octet can still be improved by using specific model for angular momentum of quarks.

Physical Review D, 1996

The baryon magnetic moments are considered within the framework of the constituent quark model assuming charge symmetry d ϭϪ u /2. The baryons on the perimeter of the octet have two quarks of the same flavor, and a single quark of different flavor. The effective moments of the single flavor quarks were allowed to vary with I and Y. The resulting formulas predict eight magnetic moments in terms of four parameters. The average discrepancy is ͉͗ fit Ϫ expt ͉͘ϭ0.024 N .

Physical Review D

Lattice QCD calculations with background magnetic fields are used to determine the magnetic moments of the octet baryons. Computations are performed at the physical value of the strange quark mass, and two values of the light quark mass, one corresponding to the SU (3)F-symmetric point, where the pion mass is mπ ∼ 800 MeV, and the other corresponding to a pion mass of mπ ∼ 450 MeV. The moments are found to exhibit only mild pion-mass dependence when expressed in terms of appropriately chosen magneton units-the natural baryon magneton. A curious pattern is revealed among the anomalous baryon magnetic moments which is linked to the constituent quark model, however, careful scrutiny exposes additional features. Relations expected to hold in the large-Nc limit of QCD are studied; and, in one case, a clear preference for the quark model over the large-Nc prediction is found. The magnetically coupled Λ-Σ 0 system is treated in detail at the SU (3)F point, with the lattice QCD results comparing favorably with predictions based on SU (3)F symmetry. This analysis enables the first extraction of the isovector transition magnetic polarizability. The possibility that large magnetic fields stabilize strange matter is explored, but such a scenario is found to be unlikely.

1995

In quark potential models, two{body current contributions to baryon magnetic moments arise necessarily to satisfy the continuity equation for the electromagnetic current. On the other hand, the na ve additive quark model predicts the experimental octet magnetic moments to within 5%. We demonstrate that consistently derived two{body current contributions to the octet baryon magnetic moments are individually large, but tend to cancel each other globally.

EPJ Web of Conferences

Magnetic moments of the octet baryons are computed using lattice QCD in background magnetic fields, including the first treatment of the magnetically coupled ∑0- ⋀ system. Although the computations are performed for relatively large values of the up and down quark masses, we gain new insight into the symmetries and relations between magnetic moments by working at a three-flavor mass-symmetric point. While the spinflavor symmetry in the large Nc limit of QCD is shared by the naïve constituent quark model, we find instances where quark model predictions are considerably favored over those emerging in the large Nc limit. We suggest further calculations that would shed light on the curious patterns of baryon magnetic moments.

Il Nuovo Cimento A Series 10, 1966

Sum rules for the magnetic moments of baryons are obtained by using commutators of SU 3 generators with the electromagnetic current. The calculation is performed to first order in the medium-strong breaking of SU 3. The comparison of the results with the symmetry limit shows that SU 3 is a reasonably good symmetry group. The values of ~+ and A magnetic moments are in good agreement with experimental data.

Journal of Physics G: Nuclear and Particle Physics, 2010

We investigate the change of magnetic moments of octet baryons in nuclear matter at a finite density and temperature. Quark-meson coupling models are employed in describing properties of octet baryons and their interactions. Magnetic moments of octet baryons are found to increase non-negligibly as density and temperature increase, and we find that temperature dependence can be strongly correlated with the quark-hadron phase transition. Model dependence is also examined by comparing the results from the quark-meson coupling (QMC) model to those by the modified QMC (MQMC) model where the bag constant is assumed to depend on density. Both models predict sizable dependence on density and temperature, but the MQMC model shows a more drastic change of magnetic moments. Feasible changes of the nucleon mass by strong magnetic fields are also reported in the given models.

Physical Review D, 2007

Using the general QCD parametrization (GP) we display the magnetic moments of the octet baryons including all flavor breaking terms to any order. The hierarchy of the GP parameters allows to estimate a parameter g 0 related to the quark loops contribution of the proton magnetic moment; its magnitude is predicted to be inside a comparatively small interval including the value given recently by Leinweber et al. from a lattice QCD calculation.