arXiv subjects

K. Azizi

Publications and source records attributed to K. Azizi.

At least 73 records · Page 4Linked to original sources

arXiv2025

Eddington-inspired Born-Infeld gravity: Constraints from the generalized parton distributions (GPDs)

The Eddington-inspired Born-Infeld (EiBI) theory of gravity modifies general relativity in high-density regimes. It offers an alternative framework that avoids cosmological singularities and remodels gravitational dynamics within compact objects. An important feature of EiBI gravity is its additional parameter, $κ$, which governs deviations from standard gravitational behavior. In this study, we investigate constraints on $κ$ using the internal pressure distribution of the proton, derived from gravitational form factor (GFF) $ D(t) $ obtained through a QCD analysis of generalized parton distributions (GPDs). By comparing pressure profiles extracted from skewness-dependent GPDs with previous determinations based on deeply virtual Compton scattering (DVCS) data, we establish updated bounds on $κ$. Our results show that the choice of proton pressure model significantly impacts the constraints, with the strongest limits ($|κ| \leq 0.10\text{--}0.3\, \text{m}^5\, \text{kg}^{-1}\, \text{s}^{-2}$). We further demonstrate that constraints obtained based on the first and second moments of the pressure distribution yield competitive bounds compared to those derived from peak pressures or those derived from just the first moment. These findings highlight the importance of precise experimental and theoretical determinations of the proton's mechanical properties in testing alternative theories of gravity. The present study motivates future improvements in GPD reconstructions for stronger constraints on EiBI gravity and related modifications.

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arXiv2025

Mechanical properties of the nucleon from the generalized parton distributions

The proton's internal structure is characterized not only by its charge and magnetic distribution but also by its mechanical and mass properties, which are encoded in the energy-momentum tensor (EMT) of quantum chromodynamics (QCD). These properties provide insights into the spatial distributions of energy, pressure, and shear forces within the proton. Understanding the proton's internal structure, including properties such as its mechanical and mass radii, is essential for unraveling the complex interplay between quarks and gluons that govern its stability and dynamics. In this study, we investigate the gravitational form factors (GFFs) of the proton, particularly the D-term, which encodes key information about the internal stress distribution, pressure, and shear forces within the nucleon. Using a model for skewness-dependent generalized parton distributions constructed from the double-distribution representation, we extract the quark contribution to the $ D(t) $ GFF of the EMT by analyzing available data on Compton form factors. We then employ this extracted GFF to explore the mechanical properties of the proton, including its mechanical and mass radii, as well as the internal pressure and shear force distributions. Our results provide new insights into the proton's internal structure and contribute to the broader understanding of nucleon properties.

hep-ph↗

arXiv2025

Tensor hybrid charmonia

The mass and current coupling of the tensor hybrid charmonia $H_{\mathrm{c}} $ and $\widetilde{H}_{\mathrm{c}}$ with quantum numbers $J^{\mathrm{PC} }=2^{-+}$ and $2^{++}$, as well as their full widths are calculated in the context of the QCD sum rule method. The spectral parameters of these states are computed using the QCD two-point sum rule approach including dimension-12 terms $ \sim \langle g_{s}^{3}G^{3}\rangle ^{2} $. The full decay widths of the charmonia $H_{\mathrm{c}}$ and $\widetilde{H}_{\mathrm{c}}$ are evaluated by considering their kinematically allowed decay channels. In the case of the hybrid state $H_{\mathrm{c}} $ decays to $D^{(\pm )}D^{\ast (\mp )}$, $D^{0} \overline{D}^{\ast 0}$, and $D_{s}^{(\pm )}D_{s}^{\ast (\mp )} $ mesons are taken into account. The processes $\widetilde{H}_{\mathrm{c}} \to D^{(\ast)+}D^{(\ast )-}$, $D^{(\ast) 0}\overline{D}^{(\ast) 0}$, and $ D_{s}^{(\ast)+}D_{s}^{(\ast) -} $ are employed to estimate the full width of the hybrid charmonium $\widetilde{H}_{\mathrm{c}}$. The partial widths of these decays are computed by means of the QCD three-point sum rule method which is necessary to calculate strong couplings at the relevant hybrid-meson-meson vertices. Our predictions $m=(4.16\pm 0.14)~\mathrm{GeV}$ , and $\widetilde{m}=(4.5\pm 0.1)~\mathrm{GeV}$ for the masses and $Γ\left[ H_{\mathrm{c}}\right] =(160\pm 30)~\mathrm{MeV}$, and $Γ\left[ \widetilde{H }_{\mathrm{c}}\right] =(206\pm 33)~\mathrm{MeV}$ for the full width of these hybrid charmonia can be useful to study and interpret various resonances in the $4-5~\mathrm{GeV}$ mass range.

hep-ph↗

arXiv2025

Exploring fully-heavy tetraquarks through the CGAN framework: Mass and width

Fully-heavy tetraquark states, $QQ\bar{Q}\bar{Q} (Q=c,b)$, have garnered significant attention both experimentally and theoretically, due to their unique properties and potential to provide new insights into Quantum Chromodynamics (QCD). In this study, we employ Conditional Generative Adversarial Networks (CGANs) to predict the masses and decay widths of fully-heavy tetraquarks. To deepen our understanding of heavy multiquark structures, we prepare datasets based on two distinct approaches and train the CGAN model using both. The CGAN framework allows us to capture the complex relationships between input features, such as quark content, quantum numbers, and Clebsch-Gordan coefficients, and output properties, including mass and decay width. Our predictions, based on the CGAN framework, are consistent with existing data. By combining fundamental knowledge of QCD with advanced machine learning techniques, this work represents a significant step forward in the theoretical understanding of fully-heavy tetraquark states. Our CGAN approach has the potential to become a strong contender for future studies in heavy tetraquark systems, complementing existing theoretical models to deliver more precise results. Additionally, our findings could assist in the search for fully-heavy tetraquark systems in future experiments.

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arXiv2025

Fully heavy asymmetric scalar tetraquarks

The scalar tetraquarks $T_{b}$ and $T_{c}$ with asymmetric contents $bb \overline{b}\overline{c}$ and $cc \overline{c}\overline{b}$ are explored using the QCD sum rule method. These states are modeled as the diquark-antidiquarks composed of the axial-vector components. The masses and current couplings of $T_{b}$ and $T_{c}$ are calculated using the two-point sum rule approach. The predictions obtained for the masses of these four-quark mesons prove that they are unstable against the strong two-meson fall-apart decays to conventional mesons. In the case of the tetraquark $ T_{b}$ this is the decay $T_{\mathrm{b}}\to η_{b}B_{c}^{-}$. The processes $T_{\mathrm{c}}\rightarrow η_{c}B_{c}^{+}$ and $J/ψB_{c}^{\ast +}$ are kinematically allowed decay modes of the tetraquark $ T_{c}$. The widths of corresponding processes are evaluated by employing the QCD three-point sum rule approach which are necessary to estimate strong couplings at the tetraquark-meson-meson vertices of interest. The mass $ m=(15698 \pm 95)~\mathrm{MeV}$ and width $Γ[T_b]=(36.0 \pm 10.4)~ \mathrm{MeV}$ of the tetraquark $T_{b}$ as well as the parameters $ \widetilde{m}=(9680 \pm 102)~\mathrm{MeV}$ and $Γ[T_c]=(54.7 \pm 12.6)~ \mathrm{MeV}$ in the case of $T_{c}$ provide useful information to search for and interpret new exotic states.

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arXiv2025

Can we determine the exact size of the nucleon?: A comprehensive study of different radii

The concept of nucleon radii plays a central role in our understanding of the internal structure of protons and neutrons, providing critical insights into the non-perturbative regime of quantum chromodynamics (QCD). While the charge radius is often interpreted as the ``size" of the nucleon, this interpretation is an oversimplification that overlooks the multifaceted nature of nucleon structure. This paper provides a comprehensive overview of the different nucleon radii, including the charge and magnetic radii, the axial radius, and the emerging concepts of mechanical and mass radii. We discuss the definitions as well as the experimental, theoretical and phenomenological determinations of these radii, highlighting their distinct physical origins and implications. By synthesizing recent experimental results and theoretical advancements, we emphasize that each radius reflects a specific aspect of the nucleon's internal structure, such as its electric charge distribution, magnetic properties, weak interactions, or internal mechanical stress. In particular, we address the common but misleading interpretation of the proton radius as a simple measure of its size, underscoring the nuanced and context-dependent nature of nucleon radii. Through this exploration, we aim to clarify the roles of these radii in characterizing nucleon structure and to identify open questions that remain to be addressed. This work contributes to a deeper understanding of the nucleon and its significance in the broader context of particle and nuclear physics.

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arXiv2025

Future Circular Collider Feasibility Study Report: Volume 2, Accelerators, Technical Infrastructure and Safety

In response to the 2020 Update of the European Strategy for Particle Physics, the Future Circular Collider (FCC) Feasibility Study was launched as an international collaboration hosted by CERN. This report describes the FCC integrated programme, which consists of two stages: an electron-positron collider (FCC-ee) in the first phase, serving as a high-luminosity Higgs, top, and electroweak factory; followed by a proton-proton collider (FCC-hh) at the energy frontier in the second phase. FCC-ee is designed to operate at four key centre-of-mass energies: the Z pole, the WW production threshold, the ZH production peak, and the top/anti-top production threshold - delivering the highest possible luminosities to four experiments. Over 15 years of operation, FCC-ee will produce more than 6 trillion Z bosons, 200 million WW pairs, nearly 3 million Higgs bosons, and 2 million top anti-top pairs. Precise energy calibration at the Z pole and WW threshold will be achieved through frequent resonant depolarisation of pilot bunches. The sequence of operation modes remains flexible. FCC-hh will operate at a centre-of-mass energy of approximately 85 TeV - nearly an order of magnitude higher than the LHC - and is designed to deliver 5 to 10 times the integrated luminosity of the HL-LHC. Its mass reach for direct discovery extends to several tens of TeV. In addition to proton-proton collisions, FCC-hh is capable of supporting ion-ion, ion-proton, and lepton-hadron collision modes. This second volume of the Feasibility Study Report presents the complete design of the FCC-ee collider, its operation and staging strategy, the full-energy booster and injector complex, required accelerator technologies, safety concepts, and technical infrastructure. It also includes the design of the FCC-hh hadron collider, development of high-field magnets, hadron injector options, and key technical systems for FCC-hh.

physics.acc-ph↗

arXiv2025

Tensor hybrid mesons $\overline{b}gc$

Spectroscopic parameters and widths of the tensor hybrid mesons $H_{\mathrm{ bc}}$ and $\widetilde{H}_{\mathrm{bc}}$ with the structure $\overline{b}gc$ and spin-parities $J^{\mathrm{P}}=2^{-}$ and $J^{\mathrm{P}}=2^{+}$ are calculated with high accuracy in the QCD sum rule framework. Information on their masses $m=(7.214\pm 0.075)~\mathrm{GeV}$ and $\widetilde{m} =(7.685\pm 0.040)~\mathrm{GeV}$ enable us to determine decay channels of $H_{\mathrm{bc} }$ and $\widetilde{H}_{\mathrm{bc}}$. The full width of the meson $H_{ \mathrm{bc}}$ is estimated by considering the decays $H_{\mathrm{bc}} \to D^{+}\overline{B}^{\ast 0}$ and $D^{0}B^{\ast +}$. The channels $\widetilde{H }_{\mathrm{bc}}\to B^{+}D^{0}$, $B^{0}D^{+}$, $B^{\ast +}D^{\ast 0}$, $ B^{\ast 0}D^{\ast +} $, $B_{s}^{0}D_{s}^{+}$, and $B_{s}^{\ast 0}D_{s}^{\ast +}$ are studied to find the width of the $\widetilde{H}_{\mathrm{bc}}$ state. The widths of these processes are calculated using QCD three-point sum rule approach, which require estimation of the strong couplings at hybrid-meson-meson vertices. The results $(50.8 \pm 9.8)~\mathrm{MeV}$ and $ (184.3\pm 22.8)~\mathrm{MeV}$ for the full widths of the hybrid mesons $H_{ \mathrm{bc}}$ and $\widetilde{H}_{\mathrm{bc}}$ characterize them as relatively narrow and broad structures, respectively.

hep-ph↗

arXiv2025

Properties of the tensor state $bc\overline{b}\overline{c}$

Spectroscopic parameters and decays of the exotic tensor meson $T$ with content $bc \overline{b}\overline{c}$ are explored in the context of the diquark-antidiquark model. We treat it as a state built of axial-vector diquark $b^{T}Cγ_{μ}c$ and antidiquark $\overline{b}γ_{ν}C \overline{c}^{T}$, where $C$ is the charge conjugation matrix. The mass $m$ and current coupling $Λ$ of this tetraquark are extracted from two-point sum rules. Our result for $m=(12.70 \pm 0.09)~\mathrm{GeV}$ proves that $T$ is unstable against strong dissociations to two-meson final states. Its dominant decay channels are processes $T \to J/ψΥ$, $ η_{b}η_{c}$, and $B_{c}^{(\ast) +}B_{c}^{(\ast) -}$. Kinematically allowed transformations of $T$ include also decays $T\rightarrow D^{(\ast )+}D^{(\ast )-}$ and $D^{(\ast )0}\overline{D}^{(\ast )0}$, which are generated by $b\overline{b}$ annihilation inside of $T$. The full width of $ T $ is estimated by considering all of these channels. Their partial widths are calculated by invoking methods of three-point sum rule approach which are required to evaluate strong couplings at corresponding tetraquark-meson-meson vertices. Our predictions for the mass and width $ Γ_{T}=(117.4 \pm 15.9)~ \mathrm{MeV} $ of the tensor state $T$ provide useful information for experimental studies of fully heavy four-quark exotic structures.

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arXiv2025

Phenomenology of the semileptonic $Σ_{b}^{*0}\,\rightarrow\, Σ_{c}^{+}\,\ell\,\barν_{\ell}$ transition within QCD sum rules

We conduct an investigation on the spin $\frac{3}{2}\rightarrow \frac{1}{2}$ semileptonic weak transition of single heavy baryons for the exclusive decay $Σ_{b}^{*0}\,\rightarrow\, Σ_{c}^{+}\,\ell\,\barν_{\ell}$ in three possible lepton channels within the three point QCD sum rule method. We compute the responsible form factors of this semileptonic decay by incorporating both perturbative and nonperturbative contributions of the operator product expansion series up to a mass dimension six. Having acquired the form factors, the decay widths of the processes in all lepton channels are determined. Our findings as well as possible future experimental information can be employed in order to check the SM predictions and explore the possibility of new physics in heavy baryonic decay channels.

hep-ph↗

arXiv2025

Pseudoscalar and vector tetraquarks $bb\overline{c}\overline{c}$

The pseudoscalar and vector four-quark states $bb\overline{c}\overline{c}$ are studied in the context of the QCD sum rule method. We model $T_{\mathrm{ \ \ PS}} $ and $T_{\mathrm{V}}$ as structures built of diquarks $ b^{T}Cγ_{5}b$, $\overline{c}C\overline{c}^{T}$ and $b^{T}Cγ_{5}b$ , $\overline{c}Cγ_μγ_{5}\overline{c}^{T}$, respectively, with $ C$ being the charge conjugation matrix. The spectroscopic parameters of the tetraquarks $T_{\mathrm{PS}}$ and $T_{\mathrm{V}}$, i.e., their masses and current couplings are calculated using QCD two-point sum rule method. We evaluate the full widths of $T_{\mathrm{PS}}$ and $T_{\mathrm{V}}$ by taking into account their kinematically allowed decay channels. In the case of the pseudoscalar particle they are processes $T_{\mathrm{PS}} \to B_{c}^{-}B_{c}^{\ast -}$, $B_{c}^{-}B_{c}^{-}(1^{3}P_{0})$ and $B_{c}^{\ast -}B_{c}^{-}(1^{1}P_{1})$. The vector state $T_{\mathrm{V}}$ can dissociate to meson pairs $2 B_{c}^{-}$, $2 B_{c}^{\ast -}$ and $ B_{c}^{-}B_{c}^{-}(1^{1}P_{1})$. Partial widths of these decays are determined by the strong couplings at relevant tetraquark-meson-meson vertices, which evaluated in the context of the three-point sum rule approach. Predictions obtained for the mass and full width of the pseudoscalar $m =(13.092\pm 0.095)~\mathrm{GeV}$, $Γ_{\mathrm{PS} }=(63.7\pm 13.0)~\mathrm{MeV}$ and vector $\widetilde{m} =(13.15\pm 0.10)~ \mathrm{GeV}$, $Γ_{\mathrm{V}}=(53.5\pm 10.3)~\mathrm{MeV}$ tetraquarks can be useful for analyses of different four-quark resonances.

hep-ph↗

arXiv2025

The charge and magnetic radii of the nucleons from the generalized parton distributions

The proton-radius puzzle refers to the discrepancy observed in measurements of the proton's charge radius when using different methods. This inconsistency has prompted extensive research and debate within the physics community, as it challenges the understanding of quantum electrodynamics and the fundamental properties of protons. In the present study, we determine the charge and magnetic radii of the proton and neutron through a global analysis of the generalized parton distributions (GPDs) at zero skewness. We emphasize the importance of a simultaneous analysis of all available experimental data related to nucleon radii, rather than relying on individual experiments, specific observables, or limited kinematic regions. This comprehensive approach ensures robust and consistent results, avoiding values that are either too small or too large. Our analysis yields the following results: $ r_{pE} = 0.8558 \pm 0.0135~\textrm{fm} $, $ r_{pM} = 0.8268 \pm 0.0533~\textrm{fm} $, $ \left = -0.1181 \pm 0.0270~\textrm{fm}^2 $, and $ r_{nM} = 0.8367 \pm 0.0845~\textrm{fm} $.

hep-ph↗

arXiv2025

Hidden charm-bottom structures $bc\overline{b}\overline{c}$: Axial-vector case

Mass and width of a hidden charm-bottom axial-vector structure $T$ containing $bc \overline{b}\overline{c}$ quarks are calculated in QCD sum rule framework. It is treated as a diquark-antidiquark state built of scalar diquark and axial-vector antidiquark components. The mass of $T$ is computed using the two-point sum rule method. The width of this particle is evaluated by considering eight decay modes: The decays to $η_{b}J/ψ$, $η_{c}Υ(1S)$, $B_{c}^{-}B_{c}^{\ast +}$, and $B_{c}^{+}B_{c}^{\ast -}$ are dissociation processes, in which all initial quarks are distributed between the final-state particles. The decays to $DD$ and $BB$ mesons with appropriate charges and spin-parities are channels generated due to the annihilations of $b\overline{b}$ and $c\overline{c}$ quarks from $T$. Partial widths for all of these processes are obtained by employing the three-point sum rule approach necessary to find the strong couplings at relevant tetraquark-meson-meson vertices. Our results for the mass $ m=(12715\pm 90)~\mathrm{MeV}$ and width $Γ[T] =(140 \pm 13)~ \mathrm{MeV }$ of the tetraquark $T$, as well as its numerous decay channels explored in this article are useful for ongoing and future experimental investigations of fully heavy resonances.

hep-ph↗

arXiv2025

Unpolarized valence GPDs and form factors of pion in the modified chiral quark model

We calculate the valence generalized parton distribution functions (GPDs) of pion at zero skewness applying a theoretical approach in which the valence GPDs are related to valence quark distribution functions, directly. To this end, we use the results of modified chiral quark model ($χQM$) for the valence quark distributions of pion obtained in our previous work. We also determine the electromagnetic and gravitational form factors of pion and compare the results of our theoretical model for valence GPDs and form factors of pion with the results of some other models and available experimental data.

hep-ph↗

arXiv2025

Decays of the light hybrid meson $1^{\mathrm{-+}}$

The full width of the light isovector hybrid meson $H_{\mathrm{V}}$ with spin-parities $1^{\mathrm{-+}}$ and content $(\overline{u}gu-\overline{d}gd)/ \sqrt{2}$ is evaluated by considering the decays $H_{\mathrm{V}} \to ρ^{\pm}π^{\mp}$, $b_1^{\pm}π^{\mp}$, $f_1(1285)π$, $f_1(1420)π$, $ ηπ$, and $η^{\prime} π$. To calculate the partial widths of these channels, we use QCD three-point sum rule method which is necessary to determine strong couplings at the corresponding hybrid-meson-meson vertices. It turns out that the main contribution to the full width $Γ[H_{\mathrm{ V}}]=(109.7 \pm 16.0)~\mathrm{MeV}$ of the hybrid meson comes from the processes $H_{\mathrm{V}} \to ρ^{\pm}π^{\mp}$ partial width of which amounts to $\approx 67~\mathrm{MeV}$. The effects of the decays $H_{\mathrm{V }} \to b_1π$ and $H_{\mathrm{V}} \to f_1π, f_1^{\prime} π$ are also sizeable: Their partial widths are equal to $13~\mathrm{MeV}$ and $20~ \mathrm{MeV}$, respectively. The decays to $ηπ$ and $η^{\prime} π$ mesons are subdominant reactions, nevertheless they form $\approx 9\%$ of the full width $Γ[H_{\mathrm{V}}]$. Results obtained in this work may be interesting to unravel the tangle of predictions about $H_{\mathrm{V}}$ existing in the literature, as well as useful in analyses of different resonances.

hep-ph↗

arXiv2025

Investigation of full heavy $ QQQQ'\bar{Q}$ pentaquark candidates

Recent breakthroughs in research and experimentation have led to the identification of numerous exotic states in particle physics. Each new discovery not only sparks excitement for future findings but also fuels interest in uncovering additional unknown states. Motivated by this perspective and the recent identification of both standard and exotic hadrons with an increasing number of heavy quarks, this study conducts a spectroscopic analysis of possible pentaquark candidates with spin-parity $\frac{1}{2}^-$, and quark content of $cccb\bar{c}$ and $bbbc\bar{b}$. The masses of these states are calculated by considering the relevant Lorentz structures, including $\slashed{p}$ and $\mathbbm{1}$, yielding the following results, respectively: for the $P_{(4cb)}$ state, $m_{P_{(4cb)}} = 11388.30 \pm 107.79$~MeV and $m_{P_{(4cb)}} = 11368.30 \pm 112.68$~MeV, and for the $P_{(4bc)}$ state, $m_{P_{(4bc)}} = 20998.30 \pm 121.52$~MeV and $m_{P_{(4bc)}} = 20990.50 \pm 125.87$~MeV. Additionally, the current coupling constants of these states to the vacuum, which are essential for analyzing their potential decay modes, are also provided in this study.

hep-ph↗

arXiv2025

Semileptonic decay of the triply heavy $Ω_{ccb}$ to the observed $Ξ^{++}_{cc}$ state

We investigate the weak semileptonic decay of the $ Ω^{+}_{ccb} \rightarrow Ξ^{++}_{cc} ~{\ell}\barν_{\ell}$, where a triply heavy baryon with spin 1/2 decays into the observed doubly heavy baryon with spin 1/2, using QCD sum rule method in all lepton channels. We compute the six relevant vector and axial vector form factors entering the low energy matrix elements in full theory. The invariant form factors are building blocks, using the fit faction of which in terms of $ q^2 $ in whole physical region, we calculate the exclusive widths in three lepton channels. Our predictions may help the present and future experiments in the course of their search for doubly and triply heavy baryons.

hep-ph↗

arXiv2025

Impact of QCD sum rules coupling constants on neutron stars structure

We present a detailed investigation on the structure of neutron stars, incorporating the presence of hyperons within a relativistic model under the mean-field approximation. Employing coupling constants derived from QCD sum rules, we explore the particle fraction in beta equilibrium and establish the mass-radius relationship for neutron stars with hyperonic matter. Additionally, we compute the stellar Love number ($\mathcal{K}_{2}$) and the tidal deformability parameter ($\varLambda$), providing valuable insights into the dynamical properties of these celestial objects. Through comparison with theoretical predictions and observational data, our results exhibit good agreement, affirming the validity of our approach. These findings contribute significantly to refining the understanding of neutron star physics, particularly in environments containing hyperons, and offer essential constraints on the equation of state governing such extreme astrophysical conditions.

hep-ph↗