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Zeinab Dehghan

Publications and source records attributed to Zeinab Dehghan.

7 recordsLinked to original sources

Mechanical properties of the $Ω^-$ baryon from gravitational form factors

We present a comprehensive investigation of the mechanical properties of the $Ω^-$ baryon by analyzing its gravitational form factors (GFFs) within the framework of QCD sum rules. These form factors encode rich information about the internal structure of hadrons and offer deep insights into the dynamics that govern their stability. The spin-3/2 nature of the $Ω^-$ baryon manifests in its gravitational form factors as intricate multipole structures, which encapsulate higher-order deformations and demonstrate the influence of intrinsic spin on internal dynamics. We extract the GFFs of the $Ω^-$ baryon and apply their specific multipole combinations, gravitational multipole form factors (GMFFs), to quantify key mechanical observables-including energy density, angular momentum, pressure and shear force distributions, mass and mechanical radii, and D-terms-associated with different multipole orders. Notably, this work provides the first determination of several of these observables, such as the mechanical radii and the quadrupole contributions to the pressure and shear force distributions. Our analysis shows that the quadrupole contributions to the mechanical properties are generally subdominant compared to those from the monopole component. We further investigate the mechanical stability of the $Ω^-$ through a multipole analysis of its internal force distributions. These results enhance our understanding of the mechanical structure of spin-3/2 hadrons and provide useful benchmarks for future theoretical and lattice QCD studies.

hep-ph

Mechanical properties of proton using flavor-decomposed gravitational form factors

We investigate the mechanical properties of the proton by extracting its flavor-decomposed gravitational form factors (GFFs) using Light-Cone QCD sum rules (LCSR). These form factors encode critical information about the internal dynamics and spatial distribution of energy, momentum, and internal forces within the proton. The flavor decomposition of the quark sector indicates the role of each flavor in the proton's pressure and shear force distributions. Our results show that the up quark contributes more significantly compared to the down quark in the three conserved proton GFFs, as well as in the energy and shear force distributions. Additionally, we define the non-conserved form factor $\bar{c}^q (t)$, which takes part in the distributions of energy and pressure; the latter is essential for maintaining proton stability. Furthermore, we determine the proton's mass and mechanical radii, providing valuable insight into its internal structure and dynamics.

hep-ph

What do we know about the confinement mechanism?

Color confinement is a fundamental phenomenon in quantum chromodynamics. In this work, the mechanisms underlying color confinement are investigated in detail, with a particular focus on the role of non-perturbative phenomena such as center vortices and monopoles in the QCD vacuum. By exploring lattice QCD approaches, including the Maximal Center Gauge and center projection methods, we examine how these topological structures contribute to the confining force between color charges. We also address the limitations of conventional methods and suggest improvements to the gauge fixing prescription to enhance the accuracy of string tension predictions. Our findings support the validity of the center vortex model as a key candidate for understanding the dynamics of the confining QCD vacuum.

hep-lat

Investigation of the ensemble of maximal center gauge

Maximal Center Gauge (MCG) aims to detect center vortices by maximizing a gauge functional and then projecting onto the center elements of the respective group. The requirement for unrestricted maximization of the gauge functional has proven to be untenable because it was shown that it leads to an underestimation of the string tension. To counter this problem, the ensemble of local gauge maxima is investigated and it is found that the unrestricted maximization can be replaced by a maximization restricted to the Gaussian distributed part of the ensemble. Such restricted maximization weakens the problem of an underestimated string tension.

hep-lat

A first analysis of the ensemble of local maxima of maximal center gauge

Maximal center gauge (MCG) aims to detect some of the most important vacuum configurations, suggesting thick magnetic flux tubes quantised to non-trivial center elements of the gauge group being responsible for confinement. Due to the NP-hardness of a global maximization of the gauge functional only numeric procedures aiming for local maxima are possible. We observe a linear decrease of the string tension with increasing gauge functional value of the local maxima. This implies that the request to get as close as possible to the absolute maximum is untainable. We compare global properties of the ensemble of local maxima with other methods to detect center vortices and with determinations of the string tension from full configurations. This comparison indicates that the information about the number and positions of center vortices is contained in the structure of the ensemble of local maxima. This may pave the way for a future more successful formulation of the gauge condition.

hep-lat

Influence of Fermions on Vortices in SU(2)-QCD

Gauge fields control the dynamics of fermions, also a back reaction of fermions on the gauge field is expected. This back reaction is investigated within the vortex picture of the QCD vacuum. We show that the center vortex model reproduces the string tension of the full theory also with the presence of fermionic fields.

hep-lat

Cho decomposition, Abelian gauge fixing and monopoles in G(2) Yang-Mills theory

By extending the Cho decomposition method to G(2) gauge group, monopoles of this group are studied. Since SU(2) and SU(3) are subgroups of G(2), discussions are done mostly based on these subgroups of G(2). A direct relation between root vectors of G(2) and the associated magnetic charges is presented by group theoretical issues. In addition, G(2) monopoles are obtained by an Abelian gauge fixing method, and it is shown that the results agree with the ones we obtain by the Cho decomposition method.

hep-ph