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K. Azizi

Publications and source records attributed to K. Azizi.

At least 109 records · Page 6Linked to original sources
arXiv2023

Exploring fully heavy scalar tetraquarks $QQ\overline{Q}\overline{Q}$

The masses, current couplings and widths of the fully heavy scalar tetraquarks $X_{\mathrm{4Q}}=QQ\overline{Q}\overline{Q}$, $Q=c, b$ are calculated by modeling them as four-quark systems composed of axial-vector diquark and antidiquark. The masses $m^{(\prime)}$ and couplings $ f^{(\prime)}$ of these tetraquarks are computed in the context of the QCD sum rule method by taking into account a nonperturbative term proportional to the gluon condensate $\langle α_{s}G^{2}/ π\rangle$. Results $ m=(6570 \pm 55)~\mathrm{MeV}$ and $m^{\prime}=(18540 \pm 50)~\mathrm{MeV}$ are used to fix kinematically allowed hidden-flavor decay channels of these states. It turns out that, the processes $X_{\mathrm{4c}}\rightarrow J/ψJ/ψ$, $X_{\mathrm{4c}}\rightarrow η_{c}η_{c}$, and $X_{\mathrm{4c }}\rightarrow η_{c}χ_{c1}(1P)$ are possible decay modes of $X_{ \mathrm{4c}}$. The partial widths of these channels are evaluated by means of the couplings $g_{i}, i=1,2,3$ which describe strong interactions of tetraquark $X_{\mathrm{4c}}$ and mesons at relevant vertices. The couplings $ g_{i}$ are extracted from the QCD three-point sum rules by extrapolating corresponding form factors $g_{i}(Q^2) $ to the mass-shell of a final meson. The mass of the scalar tetraquark $X_{\mathrm{4b}}$ is below the $η_b η_b$ and $Υ(1S)Υ(1S)$ thresholds, therefore it does not fall apart to these bottomonia, but transforms to conventional particles through other mechanisms. Comparing $m=(6570 \pm 55)~\mathrm{MeV}$ and $ Γ_{\mathrm{4c}}=(110 \pm 21)~\mathrm{MeV}$ with parameters of structures observed by the LHCb, ATLAS and CMS collaborations, we interpret $ X_{4c}$ as the resonance $X(6600)$ reported by CMS. Comparisons are made with other theoretical predictions.

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arXiv2023

Resonance $X(7300)$: excited $2S$ tetraquark or hadronic molecule $χ_{c1}χ_{c1}$?

We explore the first radial excitation $X_{\mathrm{4c}}^{\ast}$ of the fully charmed diquark-antidiquark state $X_{\mathrm{4c}}=cc\overline{c}\overline{c} $ built of axial-vector components, and the hadronic molecule $\mathcal{M} =χ_{c1}χ_{c1}$. The masses and current couplings of these scalar states are calculated in the context of the QCD two-point sum rule approach. The full widths of $X_{\mathrm{4c}}^{\ast}$ and $\mathcal{M}$ are evaluated by taking into account their kinematically allowed decay channels. We find partial widths of these processes using the strong couplings $g_i^{\ast}$ and $G_i^{(\ast)}$ at the $X_{\mathrm{4c}}^{\ast}$($\mathcal{M}$ )-conventional mesons vertices computed by means of the QCD three-point sum rule method. The predictions obtained for the parameters $m=(7235 \pm 75)~ \mathrm{MeV}$, $Γ=(144 \pm 18)~\mathrm{MeV}$ and $\widetilde{m}=(7180 \pm 120)~\mathrm{MeV}$, $\widetildeΓ=(169 \pm 21)~\mathrm{MeV}$ of these structures, are compared with the experimental data of the CMS and ATLAS Collaborations. In accordance to these results, within existing errors of measurements and uncertainties of the theoretical calculations, both the excited tetraquark and hadronic molecule may be considered as candidates to the resonance $X(7300)$. Detailed analysis, however, demonstrates that the preferable model for $X(7300)$ is an admixture of the molecule $\mathcal{M}$ and sizeable part of $X_{\mathrm{4c}}^{\ast}$.

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arXiv2023

Investigation of $Λ(1405)$ as a molecular pentaquark state

$Λ(1405)$ is one of the interesting particles with its unclear structure and distinct properties. It has a light mass compared to its non-strange counterpart, despite the strange quark it carries. This situation puts the investigation of this resonance among the hot topics in hadron physics and collects attention to clarify its properties. In this study, we focus on the calculation of the mass and residue of the $Λ(1405)$ resonance within the framework of QCD sum rules. We assign a structure in the form of a molecular pentaquark composed from admixture of $K^-$ meson-proton and $\bar{K}^0$ meson-neutron. Using an interpolating current in this form, the masses and the current coupling constant are attained as $m=1406\pm 128~\mathrm{MeV}$ and $λ=(3.35\pm 0.35)\times10^{-5}~\mathrm{GeV}^6$ for $\slashed{q}$ and $m=1402\pm 141~\mathrm{MeV}$ and $λ=(4.08\pm 1.08)\times10^{-5}~\mathrm{GeV}^6$ for $I$ Lorentz structures entering the calculations, respectively. The obtained mass values agree well with the experimental data supporting the plausibility of the considered structure.

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arXiv2023

Properties of kaon at non-zero temperature and baryon chemical potential

We investigate the spectroscopic properties of the strange particle kaon in the framework of hot and dense QCD. To this end, first, we find the perturbative spectral density, which is connected with both the temperature $T$ and the baryon chemical potential $μ_{B}$. We include the non-perturbative operators as functions of temperature and baryon chemical potential up to mass dimension five. We perform the calculations in momentum space and use the quark propagator in the hot and dense medium. The numerical results at non-zero temperature and baryon chemical potential demonstrate that the mass of the particle rises considerably by increasing the baryon chemical potential at a fixed temperature (for both the zero and non-zero temperatures) up to approximately $μ_{B}=0.4$ GeV. After this point, it starts to fall by increasing the baryon chemical potential and it apparently vanishes at $μ_{B}=(1.03-1.15)$ GeV for finite temperatures: The point of apparent vanishing moves to lower baryon chemical potentials by increasing the temperature. At zero temperature, the mass reaches to roughly a fixed value at higher baryon chemical potentials. On the other hand, the decay constant decreases considerably with respect to baryon chemical potential up to roughly $μ_{B}=0.4$ GeV, but after this point, it starts to increase in terms of the baryon chemical potential at finite temperatures. At $T=0$, the decay constant reaches to a fixed value at higher chemical potentials, as well. Regarding the dependence on the temperature we observe that, at fixed values of baryon chemical potentials, the mass and decay constant remain roughly unchanged up to $T=50$ MeV and $T=70$ MeV respectively, but after these points, the mass starts to fall and the decay constant starts to rise up to a critical temperature $T=155$ MeV, considerably.

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arXiv2023

Impact of recent MINERvA measurement of the antineutrino-proton scattering cross-section on the generalized parton distributions

We investigate the impact of the new measurement of the antineutrino-proton scattering cross-section from the MINERvA Collaboration on generalized parton distributions (GPDs), particularly the polarized GPDs denoted as $\widetilde{H}^q$. To achieve this, we perform some QCD analyses of the MINERvA data, in addition to all available data of the proton's axial form factors. We demonstrate that MINERvA data lead to consistent results with other related experimental data, confirming the universality of GPDs. Our results indicate that MINERvA data can impose new constraints on GPDs, particularly on $\widetilde{H}^q$. Our predictions for the proton's axial charge radius, WACS cross-section, and axial form factor show good consistency with those of other studies and measurements. This leads us to conclude that the result of a more comprehensive analysis, considering all related experimental data, is not only reasonable but also more reliable, even in light of existing tensions among the data. The present study can be considered as a guideline for performing a new and comprehensive QCD global analysis of GPDs including the MINERvA measurements like that presented in Phys. Rev. D \textbf{107}, 096005 (2023).

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arXiv2023

Hadronic molecules $η_c η_c$ and $χ_{c0}χ_{c0}$

The fully charmed hadronic scalar molecules $\mathcal{M}_1=η_c η_c$ and $\mathcal{M}_2=χ_{c0}χ_{c0}$ are studied in the context of the QCD sum rule method. The masses $m$, $\widetilde{m}$ and current couplings $f$, $ \widetilde{f}$ of these states are calculated using the two-point sum rule approach. The obtained results $m=(6264 \pm 50)~\mathrm{MeV}$ and $ \widetilde{m}=(6954 \pm 50)~\mathrm{MeV}$ are employed to determine their decay channels. It is demonstrated that the processes $\mathcal{M}_1\to J/ψJ/ψ$ and $\mathcal{M}_1\to η_{c}η_{c}$ are kinematically allowed decay modes of $\mathcal{M}_1$. The molecule $\mathcal{M}_2$ decays to $J/ψJ/ψ$, $J/ψψ^{\prime}$, $η_{c}η_{c}$, $η_{c}η_{c}(2S)$, $η_{c}χ_{c1}(1P)$, and $χ_{c0} χ_{c0}$ mesons. The partial widths all of these processes are evaluated by means of the three-point sum rule calculations, which are necessary to extract the strong couplings $g_i$ at vertices $\mathcal{M}_1J/ψJ/ψ$, $\mathcal{M }_1η_{c}η_{c}$, and others. Our estimates for the full widths of the molecules $Γ_{\mathcal{M}_1}=(320 \pm 72)~\mathrm{MeV}$ and $Γ_{ \mathcal{M}_2}=(138 \pm 18)~\mathrm{MeV}$, as well as their masses are compared with parameters of the $X$ resonances discovered by the LHCb-ATLAS-CMS Collaborations in the di-$J/ψ$ and $J/ψψ^{\prime}$ invariant mass distributions. We argue that the molecule $\mathcal{M}_1$ can be considered as a real candidate to the resonance $X(6200)$. The structure $ \mathcal{M}_2$ may be interpreted as $X(6900)$ or one of its components in combination with a scalar tetraquark.

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arXiv2023

Fully charmed resonance $X(6900)$ and its beauty counterpart

The fully heavy scalar tetraquarks $T_{\mathrm{4Q}}=QQ\overline{Q}\overline{Q }$, ($Q=c, b$) are explored in the context of QCD sum rule method. We model $ T_{\mathrm{4Q}}$ as diquark-antidiquark systems composed of pseudoscalar constituents, and calculate their masses $m^{(\prime)}$ and couplings $ f^{(\prime)}$ within the two-point sum rule approach. Our results $m=(6928 \pm 50)~\mathrm{MeV}$ and $m^{\prime}=(18858 \pm 50)~\mathrm{MeV}$ for masses of the tetraquarks $T_{\mathrm{4c}}$ and $T_{\mathrm{4b}}$ prove that they can decay to hidden-flavor heavy mesons. The full width $Γ_{ \mathrm{4c}}$ of the $T_{\mathrm{4c}}$ is evaluated by taking into account the decay channels $T_{\mathrm{4c}} \to J/ψJ/ψ$, $J/ψψ^{\prime}$, $η_{c}η_{c}$, $η_{c}η_{c}(2S)$, $η_{c}χ_{c1}(1P)$, and $χ_{c0}χ_{c0}$. The partial widths of these processes depend on strong couplings $g_{i}$ at vertices $T_{\mathrm{4c} }J/ψJ/ψ$, $T_{\mathrm{4c}}J/ψψ^{\prime} $ etc., which are computed using the QCD three-point sum rule method. The decay $T_{\mathrm{4b} } \to η_{b}η_{b}$ is used to find the width $Γ_{\mathrm{4b}}$ of the $T_{\mathrm{4b}}$. The predictions for $m$ and $Γ_{\mathrm{4c} }=(128 \pm 22)~\mathrm{MeV}$ are compared with parameters of the fully charmed resonances reported by the LHCb, ATLAS, and CMS Collaborations. Based on this analysis, we interpret the tetraquark $T_{\mathrm{4c}}$ as a candidate to the resonance $X(6900)$. The mass $m^{\prime} $ and width $ Γ_{\mathrm{4b}}=(94 \pm 28)~\mathrm{MeV}$ of the exotic meson $T_{ \mathrm{4b}}$ can be used in future experimental investigations of these

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arXiv2023

Investigation of the strange pentaquark candidate $P_{ψs}^Λ(4338){}^0$ recently observed by LHCb

The recently observed strange pentaquark candidate, $P_{ψs}^Λ(4338){}^0$, is investigated to provide information about its nature and substructure. To this end, its mass and width through the decay channels $P_{ψs}^Λ(4338){}^0 \rightarrow J/ψΛ$ and $P_{ψs}^Λ(4338){}^0 \rightarrow η_c Λ$ are calculated by applying two- and three-point QCD sum rules, respectively. The state is considered as a $Ξ_c\bar{D}$ meson-baryon molecular structure with spin-parity quantum numbers $J^P=\frac{1}{2}^-$. The obtained mass, $m_{P_{ψs}^Λ(4338){}^0}=4338\pm 130~\mathrm{MeV}$, and width, $Γ_{P_{ψs}^Λ(4338){}^0}= 10.40\pm 1.93~\mathrm{MeV}$, are consistent with the experimental data within the presented uncertainties. This allows us to assign a $Ξ_c\bar{D}$ molecular structure of $J^P=\frac{1}{2}^-$ for the $P_{ψs}^Λ(4338){}^0$ state.

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arXiv2023

Strange partners of the doubly charmed tetraquark $T^{+}_{cc}$

The spectroscopic parameters and widths of the axial-vector $T_{cc:s}^{ \mathrm{AV}}$ and scalar $T_{cc:s}^{\mathrm{S}}$, $\widetilde{T}_{cc:s}^{ \mathrm{S}}$ strange partners of the doubly charmed exotic meson $T_{cc}^{+}$ with the content $cc\overline{u}\overline{s}$, are calculated in the framework of the QCD sum rule method. We model $T_{cc:s}^{\mathrm{AV}}$ as the diquark-antidiquark state composed of axial-vector and scalar components, whereas scalar particles $T_{cc:s}^{\mathrm{S}}$ and $\widetilde{ T}_{cc:s}^{\mathrm{S}}$ are built of axial-vector and scalar diquarks, respectively. The masses and current couplings of these tetraquarks are calculated in the context of the two-point sum rule approach by taking into account the quark, gluon and mixed condensates up to dimension $10$. The full width of the state $T_{cc:s}^{\mathrm{AV}}$ is found from analysis of the processes $T_{cc:s}^{\mathrm{AV}} \to D^{0}D_{s}^{\ast +}$ and $ T_{cc:s}^{\mathrm{AV}} \to D^{\ast}(2007)^{0}D_{s}^{+}$. Decays to $ D^{0}D_{s}^{+}$, $D^{\ast}(2007)^{0}D_{s}^{\ast+}$ and $D^{0}D_{s}^{+}$ mesons are utilized in the case of the scalar tetraquarks $T_{cc:s}^{\mathrm{ S}}$ and $\widetilde{T}_{cc:s}^{\mathrm{S}}$, respectively. The partial widths of the aforementioned decays are determined via the strong couplings $ g_1$, $g_2 $, $G_1$, $G_2$ and $\widetilde{G}$, which describe the strong interactions of the particles at the relevant tetraquark-meson-meson vertices. These couplings are computed using the QCD three-point sum rule method, most appropriate for the strong decays under study. ....

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arXiv2023

Generalized parton distributions at zero skewness

We present a new determination of the generalized parton distributions (GPDs) with their uncertainties at zero skewness, $ ξ=0 $, through a simultaneous analysis of all available experimental data of the nucleon electromagnetic form factors (FFs), nucleon charge and magnetic radii, proton axial FFs (AFFs) and wide-angle Compton scattering (WACS) cross sections for the first time, and we investigate whether there is any tension between these data. This can be considered the most comprehensive analysis of GPDs at $ ξ=0 $ performed so far. We show that such an analysis provides the simultaneous determination of three kinds of GPDs, namely $ H^q $, $ \widetilde{H}^q $ and $ E^q $, considering also the sea-quark contributions. As a result, we find that the inclusion of the WACS and AFF data at larger values of the momentum transfer squared $ Q^2=-t $ can put new constraints on GPDs and change them drastically in some cases. We show that there is a considerable tension between the WACS and the proton magnetic form factor ($ G_M^p $) data, especially at larger values of $ -t $. However, we indicate that the results for the gravitational FF $ M_2 $ and the proton total angular momentum $ J^p $ calculated using the extracted GPDs are in relatively good agreement with the light-cone QCD sum rules (LCSRs) and lattice QCD predictions when the sea-quark contributions are considered and both WACS and $ G_M^p $ data are included in the analyses simultaneously.

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arXiv2023

Near-threshold structures in the $D_{s}^{+}D_{s}^{-}$ mass distribution of the decay $B^{+}\rightarrow D_{s}^{+}D_{s}^{-}K^{+}$

Two near-threshold peaking structures with spin-parities $J^{\mathrm{PC} }=0^{++}$ were recently discovered by the LHCb Collaboration in the $ D_{s}^{+}D_{s}^{-}$ invariant mass distribution of the decay $ B^{+}\rightarrow D_{s}^{+}D_{s}^{-}K^{+}$. The first of them is the resonance $X(3960)$, whereas the second one, $X_0(4140)$, is a structure with the mass around $4140~\mathrm{MeV}$. To explore their natures and model them, we study the hadronic molecule $\mathcal{M}=D_s^{+}D_s^{-}$ and calculate its mass, current coupling, and width. The mass and current coupling of the molecule are extracted from the QCD two-point sum rule analyses by taking into account vacuum condensates up to dimension $10$. To evaluate its full width, we consider the processes $\mathcal{M} \to D_{s}^{+}D_{s}^{-}$, $\mathcal{M} \toη_{c}η^{(\prime)}$, and $\mathcal{ M} \to J/ψϕ$. Partial widths of these decays are determined by the strong couplings $g_i, \ i=1,2,3,4 $ at vertices $\mathcal{M} D_{s}^{+}D_{s}^{-}$, $\mathcal{M}η_{c} η^{(\prime)}$, and $\mathcal{M} J/ψϕ$. They are computed by means of the three-point sum rule method. Predictions for the mass $m=(4117 \pm 85)~\mathrm{MeV}$ and width $Γ_{ \mathcal{M}}=(62 \pm 12)~\mathrm{MeV}$ of the molecule $\mathcal{M}$ are compared with the corresponding LHCb data, and also with our results for the diquark-antidiquark state $X=[cs][\overline{c}\overline{s}]$. We argue that the structure $X_0(4140)$ may be interpreted as the hadronic molecule $ D_s^{+}D_s^{-}$, whereas the resonance $X(3960)$ can be identified with the tetraquark $X$.

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arXiv2023

Modeling the resonance $T_{cs0}^{a}(2900)^{++}$ as a hadronic molecule $D^{\ast +}K^{\ast +}$

The doubly charged scalar resonance $T_{cs0}^{a}(2900)^{++}$ is studied in the context of the hadronic molecule model. We consider $ T_{cs0}^{a}(2900)^{++}$ as a molecule $M=D^{\ast +}K^{\ast +}$ composed of vector mesons, and calculate its mass, current coupling and full width. The spectroscopic parameters of $M$, i.e., its mass and current coupling, are found by means of the QCD two-point sum rule method by taking into account vacuum expectation values of quark, gluon and mixed operators up to dimension $10$. The width of the molecule $M$ is evaluated through the calculations of the partial widths of the decay channels $M \to D_{s}^{+}π^{+}$, $M \to D_{s}^{\ast +}ρ^{+}$, and $M \to D^{\ast +}K^{\ast +}$. Partial widths of these processes are determined by strong couplings $g_1$, $g_2$, and $g_3$ of particles at vertices $ MD_{s}^{+}π^{+} $, $MD_{s}^{\ast +}ρ^{+}$, and $M D^{\ast +}K^{\ast +}$ , respectively. We calculate the couplings $g_i$ by employing the QCD light-cone sum rule approach and technical tools of the soft-meson approximation. Predictions obtained for the mass $m=(2924 \pm 107)~\mathrm{ MeV}$ and width $Γ=(123 \pm 25)~\mathrm{MeV}$ of the hadronic molecule $ M$ allow us to consider it as a possible candidate of the resonance $ T_{cs0}^{a}(2900)^{++}$.

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arXiv2023

On the structures of new scalar resonances $T_{cs0}^{a}(2900)^{++}$ and $T_{cs0}^{a}(2900)^{0}$

We investigate properties of the new scalar resonances $ T_{cs0}^{a}(2900)^{++}$ and $T_{cs0}^{a}(2900)^{0}$, which were recently reported by the LHCb collaboration. These states were observed as resonant structures in $D_{s}^{+}π^{+}$ and $D_{s}^{+}π^{-}$ invariant mass distributions in $B^{+}$ meson decays. We argue that $T_{cs0}^{a}(2900)^{++} $ and $T_{cs0}^{a}(2900)^{0}$ may be modeled as molecules $\mathcal{M} ^{++}=D_{s}^{\ast+}ρ^{+}$ and $\mathcal{M}^{0}=D_{s}^{\ast+}ρ^{-} $ of conventional vector mesons, respectively. The mass $m$ and current coupling $ f $ of the molecule $\mathcal{M}^{++}$ are calculated using two-point sum rule method. The sum rule analysis is performed by taking into account vacuum condensates up to dimension $8$. The obtained result for the mass, $ m=(2917 \pm 135)~\mathrm{MeV}$, permits us to consider the molecule $ \mathcal{M}^{++}$ as one of possible models of the resonance $ T_{cs0}^{a}(2900)^{++}$. Because the second structure $T_{cs0}^{a}(2900)^{0}$ is isospin partner of the doubly charged state, it should have the mass close to $m$.

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arXiv2023

X(3872): propagating in a dense medium

In cold nuclear matter, the shifts in the mass and current-meson coupling as well the vector self energy of the exotic $X(3872)$ are calculated using the diquark-antidiquark current within the framework of the in-medium two-point QCD sum rule. At the rest frame of the medium, the three momentum of the considered particle is fixed to remove the contributions of the particles with negative energy. In the calculations, we include the in-medium condensates of quark-quark, gluon-gluon and quark-gluon. It is observed that, the shift due to the nuclear matter is negative and is about $25\%$ when the saturation density is used. Such shift is considerably large and comparable with the nucleon' mass shift due to the nuclear medium. The negative shift in the current-meson coupling due to nuclear matter is approximately $10\%$. At the saturation density, the vector self energy of the exotic $X(3872)$ state is found to be $Σ_\upsilon=1.31$ GeV. It is shown that the mass, current-meson coupling and vector self energy of $X(3872)$ strongly depend on the density of cold nuclear matter.

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arXiv2023

Axial-vector and pseudoscalar tetraquarks $[ud][\bar{c}\bar{s}]$

Spectroscopic parameters and widths of the fully open-flavor axial-vector and pseudoscalar tetraquarks $X_{\mathrm{AV}}$ and $X_{\mathrm{PS}}$ with content $[ud][\overline{c}\overline{s}]$ are calculated by means of the QCD sum rule methods. Masses and current couplings of $X_{\mathrm{AV}}$ and $X_{ \mathrm{PS}}$ are found using two-point sum rule computations performed by taking into account various vacuum condensates up to dimension $10$. The full width of the axial-vector state $X_{\mathrm{AV}}$ is evaluated by including into analysis $S$-wave decay modes $X_{\mathrm{AV}}\to D^{\ast }(2010)^{-}K^{+}$, $\overline{D}^{\ast }(2007)^{0}K^{0}$, $D^{-}K^{\ast }(892)^{+}$, and $\overline{D}^{0}K^{\ast }(892)^{0}$. In the case of $X_{ \mathrm{PS}}$, we consider $S$-wave decay $X_{\mathrm{PS}}\to \overline{D} _{0}^{\ast }(2300)^{0}K^{0}$, and $P$-wave processes $X_{\mathrm{PS}}\to D^{-}K^{\ast}(892)^{+}$ and $X_{\mathrm{PS}}\to \overline{D} ^{0}K^{\ast}(892)^{0}$. To determine partial widths of these decay modes, we employ the QCD light-cone sum rule method and soft-meson approximation, which are necessary to estimate strong couplings at tetraquark-meson-meson vertices $X_{\mathrm{AV}}D^{-}D^{\ast }(2010)^{-}K^{+} $, etc. Our predictions for the mass $m_{\mathrm{AV}}=(2800 \pm 75)~\mathrm{MeV}$ and width $Γ_{\mathrm{AV}}=(58 \pm 10)~\mathrm{MeV}$ of the tetraquark $X_{ \mathrm{AV}}$, as well as results $m_{\mathrm{PS}}=(3000 \pm 60)~\mathrm{MeV} $ and $Γ_{\mathrm{PS}}=(65 \pm 12)~\mathrm{MeV}$ for the same parameters of $X_{\mathrm{PS}}$ may be useful in future experimental studies of multiquark hadrons.

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arXiv2023

Exploring the magnetic dipole moments of $T_{QQ \bar q \bar s}$ and $T_{QQ \bar s \bar s}$ states in the framework of QCD light-cone sum rules

Motivated by the recent observation of the tetraquark $ T_{cc}^{+}$, we investigate the magnetic dipole moments of the possible single and double strange partners, $T_{QQ \bar q \bar s}$ and $T_{QQ \bar s \bar s}$, with the spin-parity $ J^{P} = 1^{+}$ by means of the QCD light-cone sum rules. To this end, we model these states as diquark-antidiquark states with different organizations and interpolating currents. The results of magnetic dipole moments obtained using different diquark-antidiquark structures differ from each other, considerably. The magnetic dipole moment is the leading-order response of a bound system to a soft external magnetic field. Therefore, it provides an excellent platform for investigation of the inner structures of hadrons governed by the quark-gluon dynamics of QCD.

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arXiv2023

Resonance $X(3960)$ as a hidden charm-strange scalar tetraquark

We investigate features of the hidden charm-strange scalar tetraquark $c \overline{c}s\overline{s}$ by calculating its spectral parameters and width, and we compare the obtained results with the mass and width of the resonance $ X(3960)$ discovered recently in the LHCb experiment. We model the tetraquark as a diquark-antidiquark state $X=[cs][\overline{c}\overline{s}]$ with spin-parities $J^{\mathrm{PC}}=0^{++}$. The mass and current coupling of $X$ are calculated using the QCD two-point sum rules by taking into account various vacuum condensates up to dimension $10$. The width of the tetraquark $X$ is estimated via the decay channels $X \to D_{s}^{+}D_{s}^{-}$ and $X \to η_{c} η^{(\prime)}$. The partial widths of these processes are expressed in terms of couplings $G$, $g_1$ and $g_2$ which describe the strong interactions of particles at the vertices $XD_{s}^{+}D_{s}^{-}$, $ Xη_{c}η^{\prime}$ and $Xη_{c}η$, respectively. Numerical values of $G$, $g_1$ and $g_2$ are evaluated by employing the three-point sum rule method. Comparing the results $m=(3976 \pm 85)~\mathrm{MeV}$ and $Γ_{ \mathrm{X}}=(42.2 \pm 12.0)~\mathrm{MeV}$ obtained for parameters of the tetraquark $X$ and experimental data of the LHCb Collaboration, we conclude that the resonance $X(3960)$ can be considered as a candidate to a scalar diquark-antidiquark state.

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arXiv2023

Gravitational transition form factors of $N \rightarrow Δ$ via QCD light-cone sum rules

We present the first direct calculation on the gravitational form factors (GFFs) of the $N \rightarrow Δ$ transition using an analytic method, the QCD light-cone sum rules. The matrix element of the quark part of the energy momentum tensor current sandwiched between the nucleon and $Δ$ states are parameterized in terms of five independent conserved and four independent non-conserved GFFs, for calculation of which we use the distribution amplitudes (DAs) of the on-shell nucleon expanded in terms of functions with different twists. We present the results for two sets of light-cone input parameters. The results indicate that the behavior of the form factors with respect to $Q^2$ are described by multipole fit functions. Our results may be checked by other phenomenological models including the Lattice QCD as well as future related experiments.

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