arXiv subjects

K. Azizi

Publications and source records attributed to K. Azizi.

At least 55 records · Page 3Linked to original sources

arXiv2025

Prompt diphoton production compared to measurements at 13 TeV in $k_t$-factorization: A comparative analysis of unintegrated PDF models

We perform an in-depth comparative analysis of unintegrated parton distribution function (UPDF) models for isolated prompt diphoton production in proton-proton collisions at $\sqrt{s}=13$~TeV within the $k_t$-factorization framework. Predictions are obtained with three UPDF approaches: Parton Branching (PB), NLO-MRW, and Modified KMRW (MKMRW). Tree-level $q + \bar q\!\to\!γ+γ$, $q + \bar q\!\to\!γ+ γ+ g$, and $q + g\!\to\!γ+γ+ q$ subprocesses are generated with \textsc{KaTie} using off-shell initial states; the loop-induced $g + g\!\to\!γ+ γ$ channel is evaluated independently. We compare differential cross sections with ATLAS measurements across a broad set of observables, including the photon transverse momenta, diphoton invariant mass and transverse momentum, the Collins-Soper angle, acoplanarity, $ϕ^*_η$, and a transverse thrust-related variable. This comparative study quantifies the impact of the UPDF choice on the diphoton spectra. We find that the PB model provides the most consistent agreement over all distributions, whereas NLO-MRW tends to overshoot in regions correlated with larger factorization scales and MKMRW generally undershoots due to stronger Sudakov suppression. With standard scale variations, our results indicate that $k_t$-factorization with PB UPDFs can accurately describe diphoton production, while fixed-order collinear predictions typically require higher-order corrections together with parton-shower effects to achieve a comparable description.

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arXiv2025

Determination of the pion generalized parton distributions at zero skewness

We perform a global QCD analysis of the pion electromagnetic form factor (FF) data from pion electroproduction and elastic pion scattering to extract the valence pion generalized parton distributions (GPDs) at zero skewness. The analysis uses three different sets of pion parton distribution functions (PDFs), namely xFitter, JAM21, and MAP23, to construct the GPD ansatz. Through a $χ^2$ minimization and a careful parametrization scan, we determine the profile function parameters and find that only two parameters are sufficient to describe the data. The extracted valence pion GPDs from different analyses have similar $x$-dependence, with minor differences at small momentum transfer. The resulting theoretical predictions for the pion electromagnetic FF and its squared magnitude show good agreement with experimental measurements. Among the three analyses, the one using the MAP23 PDFs provides the best overall fit and is adopted as the final GPD set. Our results offer a consistent determination of the valence pion GPDs, indicating a minor impact of the choice of pion PDFs. The present study provides a solid foundation for future investigations of pion structure, including its charge radius, tomography, and mechanical properties.

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arXiv2025

Nonleptonic $Ω_{b}^{}\rightarrowΩ_{c}^{}P(V)$ weak transitions in QCD

We investigate the nonleptonic two-body weak decays of the single bottom baryon $Ω_{b}^{*}$ into $Ω_{c}^{*}P(V)$ final states within the factorization framework. Employing this framework and incorporating the contributions from the current-current operators, we compute the tree-level decay amplitudes and decay widths of the $Ω_{b}^{*}\rightarrowΩ_{c}^{*}P(V)$ processes in terms of the $Ω_{b}^{*}\rightarrowΩ_{c}^{*}$ transition form factors. Here, $P$ and $V$ denote pseudoscalar and vector mesons, respectively. Using the form factors obtained in our previous work, we evaluate the numerical values of the decay widths for the dominant nonleptonic weak channels. This study complements our previous analysis of the semileptonic weak transitions $Ω_{b}^{*}\rightarrowΩ_{c}^{*}\ell\barν_{\ell}$ reported in Ref. [1], thereby providing a detailed investigation of dominant $Ω_{b}^{*}\rightarrowΩ_{c}^{*}$ weak decays of the $Ω_{b}^{*}$ baryon.

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arXiv2025

Hadronic tensor molecule $B_c^{\ast +}B_c^{\ast -}$

Mass and full decay width of the hadronic tensor molecule $\mathcal{M}_{ \mathrm{T}}=B_c^{\ast +}B_c^{\ast -}$ are examined in the framework of QCD sum rule method. To find the mass $m$ and current coupling $Λ$ of this state, we use the two-point sum rules. The result $(12.87 \pm 0.08)~\mathrm{ GeV}$ for $m$ indicates that $\mathcal{M}_{\mathrm{T}}$ can easily decay to pairs of $J/ψΥ$, $η_{b}η_{c}$, $B_{c}^{+}B_{c}^{-}$, and $ B_{c}^{\ast +}B_{c}^{\ast -}$ mesons. Kinematically permitted ways for $ \mathcal{M}_{\mathrm{T}}$ to transform to conventional mesons include also processes $\mathcal{M}_{\mathrm{T}} \to D^{(\ast)+}D^{(\ast )-}$, $D^{(\ast )0}\overline{D}^{(\ast )0}$, and $D_{s}^{(\ast)+}D_{s}^{(\ast)-}$ triggered by annihilation of $b\overline{b}$ quarks in the molecule. The decays to meson pairs $B^{(\ast)+}B^{(\ast )-}$, $B^{(\ast )0}\overline{B}^{(\ast )0}$ , and $B_{s}^{(\ast)0}\overline{B}_{s}^{(\ast )0}$ generated by $c\overline{c } \to $ light quarks are also among possible channels of the hadronic molecule $\mathcal{M}_{\mathrm{T}}$. Technical tools of the three-point sum rule approach are applied to compute partial widths of these decays. Our results for the mass and width $Γ_{\mathcal{M}_{\mathrm{T}}}=(154 \pm 19)~ \mathrm{MeV} $ of the tensor molecule $\mathcal{M}_{\mathrm{T}}$ are important for experimental studies of fully heavy exotic structures.

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arXiv2025

Study of the semileptonic decay $Λ\to p\,\ell\,\barν_{\ell}$ in QCD

We conduct a comprehensive study of the semileptonic decay process $Λ\to p\,\ell\,\barν_{\ell}$, focusing on the determination of all six vector and axial-vector form factors that govern the low-energy hadronic matrix elements of the underlying theory. These invariant form factors constitute the essential inputs for describing the decay, and their dependence on the momentum transfer $q^{2}$ is analyzed across the entire physical kinematic region. To parametrize the $q^{2}$dependence, we adopt both the $z$-expansion formalism and a polynomial fitting approach. Utilizing parametrizations, we compute the exclusive decay widths for both the electron and muon channels, and subsequently extract the corresponding branching ratios. Furthermore, we evaluate the ratio of decay widths between the muon and electron channels defined as $R^{μe} \equiv \frac{Γ(Λ\to p\,μ\,\barν_μ)}{Γ(Λ\to p\,e\,\barν_{e})}$ obtaining $R^{μe} = 0.196^{+0.009}_{-0.012}$ from the polynomial fit and $R^{μe} = 0.174^{+0.002}_{-0.005}$ from the $z$ expansion. While both ratios are compatible with previously reported values in the literature, the result from the $z$ expansion exhibits particularly strong agreement with the averages reported by the Particle Data Group.

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arXiv2025

Investigation of triply heavy spin-3/2 baryons in their ground and excited states

We calculate the masses and residues of triply heavy baryons with spin-3/2, including $Ω^*_{ccc}$, $Ω^*_{ccb}$, $Ω^*_{bbc}$ and $Ω^*_{bbb}$, using the QCD sum rules method. Our calculations primarily focus on obtaining the masses of the first three resonances, that is, the ground state (1S), the first orbital excited state (1P), and the first radial excited state (2S), for the mentioned baryons. We additionally determine the residues of these baryons, which serve as key parameters for studying their possible decay channels and interactions with other particles. To achieve higher accuracy compared to previous studies, we consider nonperturbative operators up to eight mass dimensions. We present our calculated outcomes in two distinct energy schemes, referred to as pole and $\mathrm{\overline{MS}}$. Given the absence of experimental data for these states, we compare our results with previous theoretical calculations that are reported in relevant studies employing various approaches. These results may provide valuable insights for experimental groups searching for the triply heavy baryons.

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arXiv2025

Fresh look at the nuclear transparency using the generalized parton distributions

Color transparency (CT) is a fundamental phenomenon in QCD in which hadrons produced in high-energy exclusive processes traverse nuclear matter with minimal interactions. Nuclear transparency, which quantifies this attenuation suppression, is a quantity with high sensitivity to CT effects and provides critical insights into QCD dynamics in nuclear environments. In this study, we revisit nuclear transparency using the framework of generalized parton distributions (GPDs). By constructing nuclear GPDs (nGPDs) through the incorporation of nuclear parton distribution functions, we calculate the nuclear transparency $ T(Q^2) $ for the carbon nucleus as a function of momentum transfer $ Q^2 $ considering various definitions and compare the results obtained with available experimental data. Our finding highlights the importance of choosing a physically motivated definition of nuclear transparency. Moreover, we emphasize that a more reliable determination of nGPDs requires a dedicated global analysis incorporating nuclear data. Such an approach is essential for improving the theoretical understanding of CT and for achieving consistency with experimental observations in the high-$ Q^2 $ regime.

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arXiv2025

QCD sum rule study of the tensor $Δ^0Δ^0$ dibaryon state

We study the exotic $Δ^{0}Δ^{0}$ dibaryon state with quantum numbers $J^{P} = 2^{+}$ within the framework of QCD sum rules. A tensor interpolating current is constructed to determine the mass and residue of this state, including explicit calculations of contributions from quark, gluon, and mixed vacuum condensates up to dimension nine. The numerical analysis yields a mass of $m_{Δ^{0}Δ^{0}} = 2426^{+101}_{-108}~\mathrm{MeV}$ and a residue of $f_{Δ^{0}Δ^{0}} = \left( 2.30^{+0.49}_{-0.45} \right) \times 10^{-4}~\mathrm{GeV}^{8}$. The predicted mass lies about $38~\mathrm{MeV}$ below the $2m_{Δ^{0}}$ threshold, which indicates the possible existence of a bound molecular configuration. Consequently, the tensor $Δ^{0}Δ^{0}$ dibaryon may serve as a promising candidate for future experimental searches.

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arXiv2025

ECFA Higgs, electroweak, and top Factory Study

The ECFA Higgs, electroweak, and top Factory Study ran between 2021 and 2025 as a broad effort across the experimental and theoretical particle physics communities, bringing together participants from many different proposed future collider projects. Activities across three main working groups advanced the joint development of tools and analysis techniques, fostered new considerations of detector design and optimisation, and led to a new set of studies resulting in improved projected sensitivities across a wide physics programme. This report demonstrates the significant expansion in the state-of-the-art understanding of the physics potential of future e+e- Higgs, electroweak, and top factories, and has been submitted as input to the 2025 European Strategy for Particle Physics Update.

hep-ex↗

arXiv2025

CGAN-Based Framework for Meson Mass and Width Prediction

Mesons play a crucial role in understanding the strong interaction in the framework of quantum chromodynamics (QCD). However, the mass and decay width of several ordinary and exotic mesons remain experimentally undetermined. In this work, we propose a novel application of advanced machine learning techniques to deal with this challenge. Due to the limited available meson datasets, traditional data-driven methods are norm To overcome this, we employ a Conditional Generative Adversarial Network (CGAN) to generate synthetic meson data based on known physical parameters. This not only augments the dataset but also retain the underlying physics of the original mesons data. With the extended dataset, we train multiple copies of CGAN and apply a bagging technique to predict uncertainties, improving the robustness and reliability of the predictions. As our findings indicate, the CGAN models are capable of well describing meson properties and their structure relations, offering a potent novel instrument for hadron spectroscopy. This calculation opens a promising future for data-driven hadron physics studies.

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arXiv2025

Semileptonic decays of doubly charmed or bottom baryons to single heavy baryons

We investigate the semileptonic decays of baryons containing double charm or double bottom quarks, focusing on their transitions to single heavy baryons through three-point QCD sum rule framework. In our calculations, we take into account nonperturbative operators with mass dimensions up to five. We calculate the form factors associated with these decays, emphasizing the vector and axial-vector transition currents in the corresponding amplitude. By applying fitting functions for the form factors based on the squared momentum transfer, we derive predictions for decay widths and branching ratios in their possible lepton channels. These findings offer valuable insights for experimentalists exploring semileptonic decays of doubly charm or bottom baryons. Perhaps they can be validated in upcoming experiments like LHCb. These investigations contribute to a deeper understanding of the decay mechanisms in these baryonic channels.

hep-ph↗

arXiv2025

Axial-vector molecular structures $B_{c}^{\ast \pm} B_{c}^{\mp}$

The axial-vector molecular structure $\mathcal{M}_{\mathrm{AV}}=(B_{c}^{\ast +}B_{c}^{-} + B_{c}^{\ast - } B_{c}^{+})/2$ is explored in QCD sum rule framework. The mass and current coupling of this compound are found by means of the two-point sum rule method. It turns out that the mass of $\mathcal{M} _{\mathrm{AV}}$ is equal to $m=(12770 \pm 60)~\mathrm{MeV}$ making possible its dissociations to pairs of $J/ψη_b$, $Υη_c$, $ B_{c}^{\ast +} B_{c}^{-}$, and $B_{c}^{\ast - } B_{c}^{+}$ mesons. The partial widths of these decay modes contain the strong couplings at $ \mathcal{M}_{\mathrm{AV}}$-meson-meson vertices which are calculated by utilizing the three-point sum rule method. The full decay width of the molecule $\mathcal{M}_{\mathrm{AV}}$ is formed due to these dominant processes and amounts to $Γ[\mathcal{M}_{\mathrm{AV}}]=(93 \pm 14)~ \mathrm{MeV}$. Our results for parameters $m$ and $Γ[\mathcal{M}_{ \mathrm{AV}}]$ of the hadronic molecule $\mathcal{M}_{\mathrm{AV}}$ are useful for experimental studies of various fully heavy four-quark mesons.

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arXiv2025

Investigation of the semileptonic decays $Ξ^{(')}_{b}\rightarrow Ξ^{(')}_{c}{\ell}\barν_{\ell}$

We study the semileptonic decays of $Ξ^{(')}_{b}\rightarrowΞ^{(')}_{c}{\ell}\barν_{\ell}$ in all lepton channels. To do this, we first obtain the form factors defining these decay modes within the framework of QCD sum rules. Then, using the transferred momentum squared-dependent form factors, we compute the decay widths and branching fractions for all lepton channels and compare the results of our calculations with those obtained from other theoretical methods. We also estimate the branching ratios and the ratio of branching fractions at different leptonic channels to provide useful information for future experiments may be planned at different Colliders. Such comparison will provide valuable information about the consistency/inconsistency of the SM theory predictions with experimental data in weak semileptonic single heavy baryon decays.

hep-ph↗

arXiv2025

Heavy scalar molecule $B_{c}^{+} B_{c}^{-}$

Mass and full width of the heavy scalar molecule $\mathcal{M}$ composed of the mesons $B_{c}^{+}$ and $B_{c}^{-}$ are calculated in the QCD sum rule framework. To find its mass and current coupling, we apply the two-point sum rule method. The width of the hadronic molecule $\mathcal{M} =B_{c}^{+}B_{c}^{-}$ is evaluated by taking into account its dissociation to $η_cη_{b}, J/ψΥ$, and $B_{c}^{+}B_{c}^{-} $ mesons. Decays into $D$ and $B$ meson pairs with appropriate charges and quantum numbers triggered by $\overline{b}b$ and $\overline{c}c$ annihilations to light quark-antiquarks are also included in the analyses. Because the partial widths of $\mathcal{M}$ molecule's decay channels depend on the strong couplings at $\mathcal{M}$-meson-meson vertices, we estimate them by invoking tools of the three-point sum rule method. Our predictions $m=(12725 \pm 85)~\mathrm{ MeV}$ and $Γ[\mathcal{\ M}]=(155 \pm 23)~ \mathrm{MeV}$ for the parameters of the molecule $\mathcal{\ M}$ provide useful information for experimental studies of numerous heavy resonances.

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arXiv2025

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.

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arXiv2025

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↗

arXiv2025

The allowed baryon to baryon-meson strong transitions

We investigate the kinematically allowed baryon to baryon-meson strong transitions in all the light and heavy sectors. We consider only the ground state on-shell particles in the baryonic and mesonic channels. In the case of mesons, only the well-established pseudoscslar and vector nonets are involved. For the baryons, we consider the ground state spin 1/2 and 3/2 baryons. Using all the restrictions and conservation laws, a \texttt{mathematica}/ \texttt{python} code selects the allowed strong channels among many possible transitions. Using the strong coupling constants defining these transitions, we estimate the strong width and beaching fraction at each channel, that may help ongoing experimental and theoretical investigations.

hep-ph↗

arXiv2025

Z boson production in proton-lead collisions: A study utilizing MRW nuclear TMDs

This paper investigates the production of Z bosons in proton-lead collisions at a center of mass energy of $\sqrt{s} = 8.16$ TeV, utilizing various transverse momentum dependent parton distribution functions (TMDs), including the leading order Martin-Ryskin-Watt (LO-MRW), next-to-leading order MRW (NLO-MRW), and parton branching (PB) approaches. By comparing theoretical predictions with experimental data from the CMS collaboration, we assess the performance of these TMD models across different kinematic regions. Our analysis reveals that while both LO-MRW and NLO-MRW models generally align well with experimental data, the LO-MRW model tends to overestimate in certain kinematic regions. The NLO-MRW model, with its strong ordering constraint, provides better agreement in these areas. This study highlights the impact of different impositions of angular and strong ordering constraints in the LO-MRW and NLO-MRW approaches in describing Z boson production.

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