arXiv subjects

Terry Mart

Publications and source records attributed to Terry Mart.

At least 19 recordsLinked to original sources

arXiv2026

Electromagnetic structure of strange vector mesons in nuclear medium

We investigate the in-medium modifications of the charge (electric) $G_C^{*}(Q^2)$, magnetic $G_M^{*}(Q^2)$, and quadrupole $G_Q^{*}(Q^2)$ form factors of the positively charged vector meson $K^{*+}$ in symmetric nuclear matter at zero temperature within the Schwinger proper-time Nambu-Jona-Lasinio (NJL) model. In this framework, both the nuclear medium effects and the electromagnetic structure of the $K^{*+}$ meson are described consistently in the NJL model at the quark level. We find that the charge, magnetic, and quadrupole form factors are suppressed with increasing nuclear density, indicating substantial in-medium modifications of the strange vector meson's internal structure. We further obtain a charge radius of $r_{K^{*+}}^{*}=0.74~\mathrm{fm}$ at normal nuclear density, which is slightly smaller than the corresponding value for the $\rho^{+}$ meson, $r_{\rho^{+}}^{*}\simeq0.75~\mathrm{fm}$.

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arXiv2026

Skewness dependence of the pion and kaon generalized parton distributions

We investigate the skewness dependence of the pion generalized parton distribution (GPD) at different momentum transfers $-t$ within the covariant Nambu-Jona-Lasinio (NJL) model, employing the Schwinger proper-time regularization scheme to regulate ultraviolet divergences and implement an effective description of quark confinement. We evolve the pion GPDs for various values of $-t$ and $\xi$ to the scales $\mu^2=4$ and $27~\mathrm{GeV}^2$. We find that the valence-quark distributions are suppressed with increasing $-t$ and $\xi$, with the suppression becoming more pronounced at the lower scale, $\mu^2=4~\mathrm{GeV}^2$. In the forward limit, $\xi=0$ and $-t=0$, the predicted pion valence-quark distribution at $\mu^2=27~\mathrm{GeV}^2$ is in good agreement with the available experimental data and the global JAM analysis. The corresponding pion gluon distribution at $\mu^2=4~\mathrm{GeV}^2$, obtained through next-to-leading-order (NLO) DGLAP evolution, is also consistent with the JAM analysis. We further find that the pion and kaon valence-quark distributions exhibit a strong dependence on $-t$ but only a weak dependence on $\xi$, whereas the corresponding gluon distributions show weak dependence on both $-t$ and $\xi$. The generalized form factors of the pion and kaon at $\mu^2=4~\mathrm{GeV}^2$ are in good agreement with the corresponding lattice-QCD results.

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arXiv2026

Electromagnetic structure of Bc and heavy quarkonia in the light-front quark model

We investigate the electromagnetic structure of heavy quarkonia and the $B_c$ meson within the light-front quark model (LFQM) to better understand the internal spatial charge distributions and QCD dynamics of heavy mesons. The light-front wave functions (LFWFs) are obtained using a variational approach with a few set of harmonic oscillator basis functions, providing a flexible yet tractable description of the bound-state dynamics. Using these LFWFs, we compute the electromagnetic form factors and compare our results with available lattice QCD data and other model calculations. Our results are roughly consistent with previous model predictions, showing that the electromagnetic radii of the $2S$ and $3S$ states are approximately 1.5 times and 1.9 times larger than those of their corresponding $1S$ states, reflecting the expected growth of spatial size in radial excitations.

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arXiv2026

Electromagnetic Production of Kaons on the Nucleon

Studies of the electromagnetic production of strange quarks began in the 1950s as something of a curiosity that puzzled experimentalists and theorists alike. As the datasets increased, concomitant advances in theoretical models were realized. A paradigm shift occurred in the 1990s with the development of second-generation facilities at ELSA, MAMI, SPring-8, and JLab, which brought nuclear physics experiments forward by orders of magnitude in counting statistics compared to the first-generation efforts. This was an utter boon to strangeness physics investigations, and to date, more than 50 dedicated experiments in kaon photo- and electroproduction have been completed at facilities around the world, leading to a host of experimental observables that have enabled significant advances in the exploration of strongly interacting systems that decay via $s\bar{s}$ quark pair creation. This review was designed to provide the first-ever in-depth overview of both the experimental and theoretical progress in the field of the electromagnetic production of strangeness. This work looks back over 70 years of past developments, discusses ongoing work and near-term plans, and details future possibilities being considered for third-generation facilities. Throughout this work, the primary impacts of these explorations are highlighted, along with connections to a wide range of related phenomenological applications. An important goal of this review is to provide a complete, self-contained guide into this field prepared at a level that is relevant for both new and seasoned scientists, whether experimentalists, phenomenologists, or theorists, to better understand what has been accomplished by so many dedicated folks-each building on what has come before-and to appreciate the exciting future potential for continued studies in this area. A more complete abstract is provided in the paper.

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arXiv2025

A Brief History and Outlook of Hadronic Physics in Indonesia

Hadronic physics has gradually emerged as one of the growing research frontiers in Indonesia, driven by efforts to better understand the properties of the strong interaction and the internal structure of hadrons from the fundamental principles of Quantum Chromodynamics. In the last few decades, Indonesian researchers have made significant contributions to developing various theoretical and phenomenological aspects of hadrons. In addition, on the experimental side, Indonesian scientists have participated in hadron experiment facilities overseas, such as the ALICE collaboration at CERN, which has strengthened the scientific activities and networks and has supported the training of young Indonesian researchers. In the present paper, we review Indonesian scientists' contributions to hadronic physics, highlight ongoing research directions in both experimental and theoretical, and outline strategies for future development toward integration into the international hadronic physics community.

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arXiv2025

Pion generalized parton distributions at zero skewness

In this paper, we systematically study the generalized parton distributions (GPDs) of the pion Goldstone Boson at zero skewness ($\xi =0$) in the framework of the covariant Nambu--Jona-Lasinio model with the help of the proper time regularization scheme to cure the divergence simultaneously to simulate the confinement. To this end, we evaluate the generalized form factors and parton distribution functions derived, respectively, from the first Mellin moments and the forward limit pion GPDs, in comparison to existing experimental data, recent lattice QCD simulations, and JAM global QCD analyses. We find that the pion parton distribution functions derived from the pion GPDs have excellent agreement with the experimental data and JAM analysis at renormalization scale $\mu^2 =$ 4 and 27 GeV$^2$. In addition, our results for the pion generalized form factors involving the scalar, vector, and tensor dressed form factors are consistent with recent lattice data and existing data. We then compute the charge radii for those dressed generalized form factors, and we obtain $r_{S}^{\pi} =$ 0.56 fm, $ r_V^{\pi} =$ 0.63 fm, and $r_{T}^{\pi} =$ 0.83 fm for the pion scalar, vector, and tensor form factors, respectively.

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arXiv2025

New Elementary Operator for Kaon Photoproduction on the Nucleon and Nuclei

A new elementary operator for kaon photoproduction on the nucleon and nuclei has been developed within a Feynman diagrammatic framework. By fitting the unknown coupling strengths at the electromagnetic and hadronic vertices of the baryon resonances to all available experimental data across the six isospin channels, the model achieves excellent agreement with the data. The operator includes 26 nucleon resonances in the $K\Lambda$ channels and 17 additional $\Delta$ resonances in the $K\Sigma$ channels. For applications to nuclear reactions, such as hypernuclear photoproduction, the operator is formulated in Pauli space, allowing a straightforward implementation of the nonrelativistic approximation. Several alternative forms for expressing the operator output are proposed. In one of them, the spin operators and photon polarization vectors are separated from the operator, since both are frame dependent, thereby enhancing its versatility in nuclear applications.

nucl-th↗

arXiv2025

Heavy Quarkonia in the Light-Front Quark Model

We present recent progress in constructing heavy quarkonia light-front wave functions from the light-front quark model, a relativistic framework well-suited for describing partonic structure and hadronic form factors. In this proceeding, we discuss the recent application of the model to the $M1$ radiative transition such as $J/\psi \to \eta_c \gamma$ among other transitions. Additionally, we compare our results on the transition form factor with available lattice QCD data. These show our efforts to deepen our understanding of the structure of heavy quarkonia from light-front model perspective.

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arXiv2025

Medium effects on the electromagnetic form factors of the $\rho$ meson

The dynamics of partons inside the light $\rho$ meson is found to be essential for its properties and internal structure, both in free space and in the nuclear medium. In this paper, we systematically investigate the in-medium structure changes of $\rho^+$ mesons within the covariant Nambu-Jona-Lasinio (NJL) model, utilizing the Schwinger proper-time regularization scheme. We solve the Bethe-Salpeter equations to guarantee the bound meson-state condition. At the quark level, the nuclear medium effects are also derived within the same NJL model to maintain a consistent approach with the in-medium $\rho^+$ meson electromagnetic form factors. To this end, we analyze the spacelike electromagnetic form factors of the $\rho^+$ meson in free space and in a nuclear medium. We find that the charge radius and quadrupole moment of the $\rho^+$ meson increase with increasing nuclear matter density, while the magnetic moment decreases, in agreement with the existing previous theoretical predictions. The enhancement of the $\rho^+$ meson charge radius at normal density relative to that in free space is about 11\% (0.08 fm), while the reduction of $\rho^+$ meson magnetic moment is about 8\% (0.20 $\mu_N$). Our predictions for the charge radius, magnetic moment, and quadrupole moment of the $\rho^+$ meson in both free space and nuclear medium, remain challenging to be verified experimentally.

nucl-th↗

arXiv2025

Triple-strangeness hidden-charm pentaquarks

We investigate the possible existence of triple-strangeness hidden-charm pentaquark states in the off-shell coupled-channel formalism. The open-charm meson-baryon $\bar{D}_s\Omega_c$, $\bar{D}_s\Omega_c^*$, $\bar{D}_s^*\Omega_c$, and $\bar{D}_s^*\Omega_c^*$ channels are considered, together with the hidden-charm $J/\psi\Omega$ channel. The two-body kernel Feynman amplitudes are constructed from an effective Lagrangian based on hidden local symmetry and heavy-quark spin symmetry. The coupled Blankenbecler-Sugar equation is solved in the partial-wave helicity basis. We observe two triple-strangeness hidden-charm pentaquark states: $P_{c\bar{c}sss}(4787)$ and $P_{c\bar{c}sss}(4841)$, both with $J^P=1/2^-$. The $P_{c\bar{c}sss}(4787)$ couples dominantly to the $\bar{D}_s^*\Omega_c$ and $\bar{D}_s^*\Omega_c^*$ channels, while the $P_{c\bar{c}sss}(4841)$ couples almost exclusively to the $\bar{D}_s^*\Omega_c^*$ channel. The total transition cross sections of $\bar{D}_s^{(\ast)}\Omega_c^{(\ast)}\to J/\psi\,\Omega$ indicate that the $P_{c\bar{c}sss}(4787)$ is clearly visible in the $J/\psi\,\Omega$ invariant mass spectrum, whereas the $P_{c\bar{c}sss}(4841)$ is obscured by cusp structures and background contributions.

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arXiv2025

New Isobar Models for $K^+\Lambda$ Electroproduction

The electroproduction of kaon on proton has been studied using two covariant isobar models. The models incorporate propagators and vertex factors developed in our previous works. In total, the current study includes 26 nucleon resonances and 20 hyperon resonances, with spins up to 13/2. In the electromagnetic vertices, we consider two alternative electromagnetic form factors alongside the commonly used dipole model. The unknown parameters in the models, such as longitudinal coupling constants and form factor cutoffs, are determined by fitting the calculated observables to nearly 2000 experimental data points. The resulting models demonstrate satisfactory consistency with the available experimental data.

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arXiv2025

$M1$ Radiative Transition of Light Mesons in the Light-Front Quark Model

We investigate the $M1$ radiative transitions between light vector $\mathcal{V}$ and pseudoscalar $\mathcal{P}$ mesons in the 1S and 2S states in the light-front quark model. To this end, we use the light-front wave functions (LFWFs) obtained from the QCD-motivated effective Hamiltonian that includes smeared spin-spin interactions, where a few harmonic oscillator basis functions were employed as trial wave functions. The results, including their couplings and widths, obtained from LFWFs with different trial wave functions are compared with the available experimental data and other theoretical predictions.

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arXiv2025

Double-strangeness hidden-charm pentaquarks

We investigate the possible existence of double-strangeness hidden-charm pentaquark states, denoted as $P_{c\bar{c}ss}$, within an off-shell coupled-channel formalism. Eleven meson-baryon channels with total strangeness $S = -2$ are constructed by combining charmed mesons and singly charmed baryons. The two-body scattering amplitudes are derived from an effective Lagrangian that respects heavy-quark spin symmetry, hidden local symmetry, and flavor SU(3) symmetry. The Bethe-Salpeter equation is solved using the Blankenbecler-Sugar reduction scheme, and resonances are identified as poles in the scattering amplitudes on the complex energy plane. We find five negative-parity $P_{c\bar{c}ss}$ states with spins $J = 1/2$, $3/2$, and $5/2$, all located below their relevant thresholds. Three positive-parity states are also found: two with $J = 1/2$ and one with $J = 3/2$, lying above the thresholds with substantial widths. The coupling strengths of each resonance to relevant meson-baryon channels are extracted. The sensitivity of the results to the cutoff parameter $\Lambda_0 = \Lambda - m$ is examined. These results provide theoretical predictions that may assist future experimental searches for $P_{c\bar{c}ss}$ states in the $J/\psi\,\Xi$ channel.

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arXiv2025

Production mechanism of hidden-charm pentaquark states $P_{c\bar{c}s}$ with strangeness $S=-1$

We investigate the hidden-charm pentaquark states with strangeness $S=-1$ ($P_{c\bar{c}s}$) within an off-shell coupled-channel approach based on effective Lagrangians that respect heavy-quark spin symmetry, SU(3) flavor symmetry, and hidden local symmetry. All relevant meson-baryon two-body channels composed of low-lying anti-charmed mesons and singly-charmed baryons with $S=-1$, as well as the $J/\psi \Lambda$ channel, are included. We find a total of eleven negative-parity states and three positive-parity states. Among the negative-parity states, the $P_{c\bar{c}s}(4338)$ and $P_{c\bar{c}s}(4459)$ can possibly be interpreted as $\bar{D}\Xi_c$ and $\bar{D}^* \Xi_c$ molecular states, respectively. We identify a second state, $P_{c\bar{c}s}(4472)$, located close to the $P_{c\bar{c}s}(4459)$ but with different spin and width, which may correspond to the structure observed by the Belle Collaboration. Both states are generated from the $\bar{D}^* \Xi_c$ channel and can be interpreted as spin partners. Their properties are consistent with recent experimental observations, providing strong support for the molecular interpretation of the $P_{c\bar{c}s}$ states. We also observe a two-pole structure near the $\bar{D}_s^* \Lambda_c$ and $\bar{D}\Xi_c^{'}$ thresholds, and find virtual and resonance states in the $\bar{D}^* \Xi_{c}^{'}$ channel depending on spin-parity.

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arXiv2024

Self-consistent $M1$ radiative transitions of excited $B_c$ and heavy quarkonia with different polarizations in the light-front quark model

In this study, we investigate the properties of pseudoscalar and vector charmonia, bottomonia, and $B_c$ mesons using the light-front quark model, focusing on the $M1$ radiative transition. For that purpose, we conduct a variational analysis with a QCD-motivated effective Hamiltonian, employing a trial wave function expanded in the harmonic oscillator basis functions up to the $3S$ state. We fit the model parameters to mass spectra and decay constants, obtaining reasonable agreement with experimental data and correctly reflecting the hierarchy of mass spectra and decay constants. In analyzing the $M1$ radiative transition, we consider both good ($\mu=+$) and transverse ($\mu={\perp}$) current components with both longitudinal $(h=0)$ and transverse $(h=\pm1)$ polarizations, demonstrating that the results from both components of currents and polarizations are identical. Self-consistency is achieved by substituting $M$ with $M_0$ when computing the operators for decay constants and radiative transitions. We also find that the difference between longitudinal and transverse polarizations of the observables may quantify the anisotropy of the model wave function. Our results on radiative transitions align reasonably well with experimental data, lattice QCD, and theoretical predictions. Furthermore, we also provide predictions for $B_c$ mesons that can be tested in experiments.

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arXiv2024

Production mechanism of the hidden charm pentaquark states $P_{c\bar{c}}$

We investigate hidden-charm pentaquark states using an off-shell coupled-channel formalism involving heavy meson and singly heavy baryon scattering. Our approach utilizes an effective Lagrangian to construct the kernel amplitudes, which respect both heavy quark symmetry and hidden local symmetry. After solving the coupled integral equations, we obtain the transition amplitudes for $J/\psi N$ scattering and various heavy meson and singly heavy baryon scattering processes. We identify seven distinct peaks related to molecular states of heavy mesons $\bar{D}$ ($\bar{D}^*$) and singly heavy baryons $\Sigma_c$ ($\Sigma_c^*$). Four of these peaks can be associated with the known $P_{c\bar{c}}$ states: $P_{c\bar{c}}(4312)$, $P_{c\bar{c}}(4380)$, $P_{c\bar{c}}(4440)$, and $P_{c\bar{c}}(4457)$. We predict two additional resonances with masses around 4.5 GeV, which we interpret as $\overline{D}^* \Sigma_c^*$ molecular states, and identify one cusp structure. Additionally, we predict two $P$-wave pentaquark states with positive parity, which may be candidates for genuine pentaquark configurations. Notably, these pentaquark states undergo significant modifications in the $J/\psi N$ elastic channel, with some even disappearing due to interference from the positive parity channel. The present investigation may provide insight into the absence of pentaquark states in $J/\psi$ photoproduction observed by the GlueX collaboration.

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arXiv2024

Global Data-Driven Determination of Baryon Transition Form Factors

Hadronic resonances emerge from strong interactions encoding the dynamics of quarks and gluons. The structure of these resonances can be probed by virtual photons parameterized in transition form factors. In this study, twelve $N^*$ and $\Delta$ transition form factors at the pole are extracted from data with the center-of-mass energy from $\pi N$ threshold to $1.8\,{\rm GeV}$, and the photon virtuality $0\leq Q^2/{\rm GeV}^2\leq 8$. For the first time, these results are determined from a simultaneous analysis of more than one state, i.e., $\sim 10^5$ $\pi N$, $\eta N$, and $K\Lambda$ electroproduction data. In addition, about $ 5\cdot 10^4$ data in the hadronic sector as well as photoproduction serve as boundary conditions. For the $\Delta(1232)$ and $N(1440)$ states our results are in qualitative agreement with previous studies, while the transition form factors at the poles of some higher excited states are estimated for the first time. Realistic uncertainties are determined by further exploring the parameter space.

nucl-th↗

arXiv2024

Nuclear medium meson structures from the Schwinger proper-time Nambu--Jona-Lasinio model

In this paper, we report the results of our study on the nuclear medium modifications of the meson electromagnetic form factors in the framework of the Nambu--Jona-Lasinio (NJL) model with the help of the Schwinger proper-time regularization scheme to tame the loop divergence and simulate the effect of QCD confinement. In our current approach, the meson structure and nuclear medium are constructed in the same NJL model at the quark level. We examine the free-space and in-medium charge radii of kaon and pion, the spacelike elastic electromagnetic form factors of kaon and pion, and their quark-sector form factors, which reflect their internal structures. By comparing our result to experimental data, we found that the free-space elastic electromagnetic form factors of the mesons are consistent with the data, while the in-medium elastic electromagnetic form factors of the mesons are found to decrease as the nuclear matter density increases, leading to a rise of meson charge radius, which is consistent with the prediction of other theoretical calculations. We also predict the axial nucleon coupling constant $g_A$ in nuclear medium computed via the Goldberger-Treiman relation (GTR), which is crucial for searching the neutrinoless double beta decay ($0\nu \beta \beta$).

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