8 research outputs found
Quark anomalous magnetic moment and its effects on the ρ meson properties
No full textThe authors acknowledge valuable comments from Jos ' e Rodriguez-Quintero. This work was supported by National Natural Science Foundation of China under Grant No. 12135007.A symmetry-preserving treatment of mesons, within a Dyson-Schwinger and Bethe-Salpeter equations
approach, demands an interconnection between the kernels of the quark gap equation and meson Bethe-
Salpeter equation. Appealing to those symmetries expressed by the vector and axial-vector Ward-Green-
Takahashi identitiges (WGTI), we construct a two-body Bethe-Salpeter kernel and study its implications in
the vector channel; particularly, we analyze the structure of the quark-photon vertex, which explicitly
develops a vector meson pole in the timelike axis and the quark anomlaous magnetic moment term, as well
as a variety of ρ meson properties: mass and decay constants, electromagnetic form factors, and valencequark
distribution amplitudes.National Natural Science Foundation of China (NSFC) 1213500
Bridging Electromagnetic and Gravitational Form Factors: Insights from LFHQCD
No full textWe propose an efficacious approach to derive the generalized parton
distributions for the pion and proton, based upon prior knowledge of their
respective parton distribution functions (PDFs). Our method leverages on
integral representations of the electromagnetic form factors derived from the
light-front holographic QCD (LFHQCD) formalism, coupled with PDFs computed from
continuum Schwinger functional methods at the hadronic scale. Using these
techniques, we calculate gravitational form factors and associated mass
distributions for each hadron. Remarkably, our calculations yield results that
closely match recent lattice QCD simulations conducted near the physical pion
mass. This work not only deepens our understanding of hadronic structure but
also highlights the efficacy of the LFHQCD approach in modeling fundamental
properties of hadrons.Comment: 6 pages, 5 figure
A fresh look at the generalized parton distributions of light pseudoscalar mesons
No full textWe present a symmetry-preserving scheme to derive the pion and kaon
generalized parton distributions (GPDs) in Euclidean space. The key to
maintaining crucial symmetries under this approach is the treatment of the
scattering amplitude, such that it contains both the traditional leading-order
contributions and the scalar/vector pole contribution automatically, the latter
being necessary to ensure the soft-pion theorem. The GPD is extracted
analytically via the uniqueness and definition of the Mellin moments and we
find that it naturally matches the double distribution; consequently, the
polynomiality condition and sum rules are satisfied. The present scheme thus
paves the way for the extraction of the GPD in Euclidean space using the
Dyson-Schwinger equation framework or similar continuum approaches.Comment: 5 pages, 2 figures, references adde
Sketching pion and proton mass distributions
No full textA light-front holographic model is used to illustrate an algebraic scheme for constructing a representation of a hadron's zero-skewness generalised parton distribution (GPD) from its valence-quark distribution function (DF) and electromagnetic form factor, FH, without reference to deeply virtual Compton scattering data. The hadron's mass distribution gravitational form factor, AH, calculated from this GPD is harder than FH; and, for each hadron, the associated mass-density profile is more compact than the analogous charge profile, with each pion near-core density being larger than that of its proton partner. These features are independent of the scheme employed.Work supported by: National Natural Science Foundation of China (grant no. 12135007); Spanish Ministry of Science and Innovation (MICINN grant no. PID2022-140440NB-C22); and Junta de Andalucía (grant no. P18-FR-5057).Ciencias Integrada
Chiral anomaly and the pion transition form factor: Beyond the cutoff
No full textIn the presence of a momentum cutoff, effective theories seem unable to faithfully reproduce the so-called chiral anomaly in the Standard Model. A novel prospect to overcome this related issue is discussed herein via the calculation of the γ*π0γ transition form factor Gγ*π0γ(Q2), whose normalization is intimately connected with the chiral anomaly and dynamical chiral symmetry breaking (DCSB). To compute such transition, we employ a contact interaction model of quantum chromodynamics (QCD) under a modified rainbow ladder truncation, which automatically generates a quark anomalous magnetic moment term, weighted by a strength parameter ξ. This term, whose origin is also connected with DCSB, is interpreted as an additional interaction that mimics the complex dynamics beyond the cutoff. By fixing ξ to produce the value of Gγ*π0γ(0) dictated by the chiral anomaly, the computed transition form factor, as well as the interaction radius and neutral pion decay width, turn out to be comparable with QCD-based studies and experimental data.Ciencias Integrada
QCD anomalies in electromagnetic processes: A solution to the puzzle
No full textIn this work, the form factor is calculated within the
Dyson-Schwinger equations framework using a contact interaction model within
the so-called modified rainbow ladder truncation. The present calculation takes
into account the pseudovector component in the pion Bethe-Salpeter amplitude
(BSA) and scattering effects, producing a anomaly
which is larger than the low energy prediction. Here
is the relative ratio of the pseudovector and pseudoscalar
components in the pion BSA; with our parameters input, this correction raises
the anomaly by around . The main outcome of this work is
the unveiling of the origin of such correction, which could be a possible
explanation of the discrepancy between the existing experimental data and the
low energy prediction. Moreover, it is highlighted how the magnitude of the
anomaly is affected in effective theories that require an irremovable
ultraviolet cutoff. We find that for both the anomalous processes
and , the missing contribution to the anomaly
can be compensated by the additional structures related with the quark
anomalous magnetic moment.Comment: 10 pages, 3 figures, references adde
QCD anomalies in electromagnetic processes: A solution to the γ → 3 π puzzle
No full textIn this work, the
γ
→
3
π
form factor is calculated within the Dyson-Schwinger equations framework using a contact interaction model within the so-called modified rainbow ladder truncation. The present calculation takes into account the pseudovector component in the pion Bethe-Salpeter amplitude (BSA) and
π
−
π
scattering effects, producing a
γ
→
3
π
anomaly that is
1
+
6
R
2
π
larger than the low energy prediction. Here
R
π
is the relative ratio of the pseudovector and pseudoscalar components in the pion BSA; with our parameters’ input, this correction raises the
γ
→
3
π
anomaly by around 10%. The main outcome of this work is the unveiling of the origin of such a correction, which could be a possible explanation of the discrepancy between the existing experimental data and the low energy prediction. Moreover, it is highlighted how the magnitude of the anomaly is affected in effective theories that require an irremovable ultraviolet cutoff. We find that for both the anomalous processes
π
→
2
γ
and
γ
→
3
π
, the missing contribution to the anomaly can be compensated by the additional structures related with the quark anomalous magnetic moment.This work was supported by National Natural Science
Foundation of China (Grant No. 12135007). K. R. is
supported by the Spanish MICINN Grant No. PID2022-
140440NB-C22, and regional Andalusian Project No. P18-
FR-5057.Ciencias Integrada
Pion scalar, vector and tensor form factors from a contact interaction
No full textThe pion scalar, vector and tensor form factors are calculated within a
symmetry-preserving contact interaction model (CI) of quantum chromodynamics
(QCD), encompassed within a Dyson-Schwinger and Bethe-Salpeter equations
approach. In addition to the traditional rainbow-ladder truncation, a modified
interaction kernel for the Bethe-Salpeter equation is adopted. The implemented
kernel preserves the vector and axial-vector Ward-Takahashi identities, while
also providing additional freedom. Consequently, new tensor structures are
generated in the corresponding interaction vertices, shifting the location of
the mass poles appearing in the quark-photon and quark tensor vertex and
yielding a notorious improvement in the final results. Despite the simplicity
of the CI, the computed form factors and radii are compatible with recent
lattice QCD simulations.Comment: 11 pages, 8 figure
