arXiv subjects

K. Azizi

Publications and source records attributed to K. Azizi.

At least 91 records · Page 5Linked to original sources

arXiv2024

Investigation of the semileptonic decay $ Ξ^{++}_{cc}\rightarrow Ξ^+_{c} \bar{\ell}ν_{\ell}$ within QCD sum rules

We study the semileptonic decay of the doubly heavy baryon $ Ξ^{++}_{cc} $ into the singly heavy baryon $ Ξ^+_{c}$ within the three-point QCD sum rule approach in two possible lepton channels. Our analysis includes perturbative as well as nonperturbative condensation contributions up to dimension 5. We evaluate the form factors of this semileptonic decay entering the amplitude described by the vector and axial vector transition currents. The fit functions of the form factors with respect to the transferred momentum squared are utilized to predict the decay widths and branching ratios of the $ Ξ^{++}_{cc}\rightarrow Ξ^+_{c} \bar{\ell}ν_{\ell}$ channels. We compare our findings with other predictions in the literature. Our outcomes can be useful for experimental groups in their search for the weak decays of doubly heavy baryons and may be checked via future experiments such as LHCb.

hep-ph↗

arXiv2024

Heavy four-quark mesons $bc\overline{b}\overline{c}$: Scalar particle

Parameters of the heavy four-quark scalar meson $T_{\mathrm{bc\overline{b} \overline{c}}}$ with content $bc \overline{b}\overline{c}$ are calculated by means of the sum rule method. This structure is considered as a diquark-antidiquark state built of scalar diquark and antidiquark components. The mass and current coupling of $T_{\mathrm{bc\overline{b} \overline{c}}}$ are evaluated in the context of the two-point sum rule approach. The full width of this tetraquark is estimated by taking into account two types of its possible strong decay channels. First class includes dissociation of $T_{\mathrm{bc\overline{b}\overline{c}}} $ to mesons $η_cη_{b}$, $B_{c}^{+}B_{c}^{-}$, $B_{c}^{\ast +}B_{c}^{\ast -}$ and $B_{c}^{+}(1^3P_{0})B_{c}^{\ast-}$. Another type of processes are generated by annihilations $\overline{b}b \to \overline{q}q$ of constituent $ b$-quarks which produces the final-state charmed meson pairs $D^{+}D^{-}$, $ D^{0} \overline{D}^{0}$, $D^{*+}D^{*-}$, and $D^{*0}\overline{D}^{*0}$. Partial width all of these decays are found using the three-point sum rule method which is required to calculate strong couplings at corresponding meson-meson-tetraquark vertices. Predictions obtained for the mass $m=(12697 \pm 90)~\mathrm{MeV}$ and width $Γ[T_{\mathrm{bc\overline{b}\overline{c} }}]=(142.4 \pm 16.9)~ \mathrm{MeV}$ of this state are compared with alternative results, and are useful for further experimental investigations of fully heavy resonances.

hep-ph↗

arXiv2024

Meson mass and width: Deep learning approach

It is fascinating to predict the mass and width of the ordinary and exotic mesons solely based on their quark content and quantum numbers. Such prediction goes beyond conventional methodologies traditionally employed in hadron physics for calculating or estimating these quantities. The relation between the quantum numbers and the properties of the mesons, such as the mass and width, is complicated in the world of particle physics. However, the deep neural network (DNN) as a subfield of machine learning techniques provides a solution to this problem. By analyzing large datasets, deep learning algorithms can automatically identify complex patterns among the particles' quantum numbers, and their mass and width, that would otherwise require complex calculations. In this study, we present two approaches using the DNNs to estimate the mass of some ordinary and exotic mesons. Also for the first time, the DNNs are trained to predict the width of ordinary and exotic mesons, whose widths have not been experimentally known. Our predictions obtained through the DNNs, will be useful for future experimental searches.

hep-ph↗

arXiv2024

Parameters of the tensor tetraquark $bb\overline{c}\overline{c}$

The mass and width of the tensor tetraquark $T=bb\overline{c}\overline{c}$ with spin-parity $J^{\mathrm{P}}=2^{+}$ are calculated in the context of the QCD sum rule method. The tetraquark $T$ is modeled as a diquark-antidiquark state built of components $b^{T}Cγ_{μ}b$ and $\overline{c}γ_{ν}C\overline{c}^{T}$ with $C$ being the charge conjugation matrix. The mass $m=(12.795\pm 0.095)~\mathrm{GeV}$ of the exotic tensor meson $T$ is found by means of the two-point sum rule approach. Its full width $Γ$ is evaluated by considering processes $T \to B_{c}^{-}B_{c}^{-}$, $ B_{c}^{-}B_{c}^{\ast -}$, and $B_{c}^{\ast -}B_{c}^{\ast -}$. Partial widths of these decays are computed by means of the three-point sum rule approach which is used to determine the strong couplings at relevant tetraquark-meson-meson vertices. Predictions obtained for the width $Γ_{\mathrm{T}}=55.5_{-9.9}^{+10.6}~\mathrm{MeV}$, as well as the mass of the tetraquark $T $ can be useful in investigations of fully heavy four-quark mesons.

hep-ph↗

arXiv2024

Investigation of full-charm and full-bottom pentaquark states

The continuous advancement of experimental techniques and investigations has led to observations of various exotic states in particle physics. Each addition to this family of states not only raises expectations for future discoveries but also focuses attention on such potential new states. Building upon this motivation and inspired by recent observations of various traditional and exotic particles containing an increased number of heavy quarks, our study provides a spectroscopic search for potential pentaquark states with spin-parity $\frac{3}{2}^-$ and composed entirely of charm or bottom quarks. We predict the masses for full-charm and full-bottom pentaquark states as $m = 7628 \pm 112$~MeV and $m = 21982 \pm 144$~MeV, respectively. We also compute the current couplings of these states to vacuum, which are main inputs in investigations of their various possible decays.

hep-ph↗

arXiv2024

Properties of the ground and excited states of triply heavy spin-1/2 baryons

We study the triply heavy spin-1/2 baryons with quark contents $ ccb $ and $ bbc $, and calculate their mass and residue using QCD sum rules. In the calculations, we consider the ground (1S), first orbitally excited (1P) and first radially excited (2S) states. Aiming to achieve higher accuracies in the results, we perform the computations by taking into account the non-perturbative operators up to eight mass dimensions. We compare our results with the predictions of other theoretical studies existing in the literature. The obtained results may help experimental groups in their search for these yet unseen, but previously predicted by the quark model, interesting particles.

hep-ph↗

arXiv2024

Mass spectra of heavy hybrid quarkonia and $\overline{b}gc$ mesons

Masses and current couplings of the charmonium and bottomonium hybrids $ \overline{c}gc$ and $\overline{b}gb$ with spin-parities $J^{\mathrm{PC} }=0^{++},\ 0^{+-},\ 0^{-+},\ 0^{--}$ and $1^{++},\ 1^{+-},\ 1^{-+},\ 1^{--}$ are calculated using QCD two-point sum rule method. Computations are performed by taking into account gluon condensates up to dimension 12 including terms $\sim \langle g_{s}^{3}G^{3}\rangle ^{2}$. The parameters of the bottom-charm hybrids $\overline{b}gc$ with quantum numbers $J^{\mathrm{PC }}=0^{+},\ 0^{-},\ 1^{+}$, and $1^{-}$ are calculated as well. In computations the dominance of the pole contribution to sum rule results is ensured. It is demonstrated that all charmonia hybrids decay strongly to two-meson final states. The bottomonium hybrids $0^{-+}$ and $1^{-+}$ as well as the bottom-charm hybrid mesons $0^{-(+)}$ and $1^{-(+)}$ may be stable against strong two-meson decay modes. Results of the present work are compared with ones obtained using the sum rule and alternative approaches. Our predictions for parameters of the heavy hybrid mesons may be useful to study their various decay channels which are important for interpretation of ongoing and future experiments.

hep-ph↗

arXiv2024

Semileptonic $Ω_{b}\rightarrow Ω_{c}{\ell}\barν_{\ell}$ transition in full QCD

We investigate the semileptonic decay of $Ω_b\toΩ_c~{\ell}\barν_{\ell}$ in three lepton channels. To this end, we use QCD sum rule method in three point framework to calculate the form factors defining the matrix elements of these transitions. Having calculated the form factors as building blocks, we calculate the decay widths and branching fractions of the exclusive decays in all lepton channels and compare the results with other theoretical predictions. The obtained results for branching ratios and ratio of branching fractions at different leptonic channels may help experimental groups in their search for these weak decays. Comparison of the obtained results with possible future experimental data can be useful to check the order of consistency between the standard model theory predictions and data on the heavy baryon decays.

hep-ph↗

arXiv2024

Electromagnetic properties of vector doubly charmed tetraquark states

We conduct a systematic study of the electromagnetic properties of multiquark systems with undetermined internal structures. Motivated by the recent observation of the $T_{cc}^+$ state, we apply the light-cone version of the QCD sum rule method to extract the magnetic dipole moments of several possible doubly-charmed vector tetraquark states. When analyzing the magnetic dipole moment of these states, they are modeled to have the diquark-antidiquark configurations. The magnetic dipole moments for the members are extracted as $ μ_{T_{cc \bar{u} \bar{d}}} = 1.17^{+0.44}_{-0.32} \, μ_N$, $ μ_{T_{cc \bar{u} \bar{s}}} = 1.35^{+0.50}_{-0.37} \, μ_N$, $ μ_{T_{cc \bar{d} \bar{s}}} = -2.69^{+1.02}_{-0.75} \, μ_N$, $ μ_{T_{cc \bar{u} \bar{u}}} = 1.33^{+0.56}_{-0.40} \, μ_N$, $ μ_{T_{cc \bar{d} \bar{d}}} = 1.41^{+0.57}_{-0.43} \, μ_N$ and $ μ_{T_{cc \bar{s} \bar{s}}} = 1.44^{+0.53}_{-0.41} \, μ_N$. Comparing the results obtained for the magnetic dipole moments of the $T_{cc \bar{u} \bar{d}}$ state with the $T_{cc \bar{u} \bar{s}}$ state, the $U$-symmetry is seen to be broken at about $\%15$, while for the $T_{cc \bar{d} \bar{d}}$ and $T_{cc \bar{s} \bar{s}}$ states, this symmetry is minimally broken. The obtained results may be useful to determine the true nature of these new interesting states.

hep-ph↗

arXiv2024

Light quarkonium hybrid mesons

We investigate the light quarkonium hybrid mesons of various spin-parities in QCD. Considering different interpolating currents made of the valence light quarks and single gluon, we calculate the mass and current coupling of the strange and nonstrange members of light hybrid mesons by including into computations the nonperturbative quark and gluon condensates up to ten dimensions in order to increase the accuracy of the results. The obtained results may be useful for future experimental searches of these hypothetical states. They can also be used in the calculations of different parameters related to the decays/interactions of light hybrid mesons to/with other states.

hep-ph↗

arXiv2024

Impact of JLab data on the determination of GPDs at zero skewness and new insights from transition form factors $ N\rightarrow Δ$

It is well established now that the generalized parton distributions (GPDs) at zero skewness are playing important roles in some physical process such as elastic electron-nucleon scattering, elastic (anti)neutrino-nucleon scattering, and wide-angle Compton scattering (WACS) via various types of form factors (FFs). In this study, we are going to utilize the recent JLab measurements of the elastic electron-nucleon scattering reduced cross-section, namely GMp12, as a touchstone to unravel the tension observed between the measurements of the WACS cross-section and the data of the proton magnetic FF $ G_M^p $. We also investigate the impact of GMp12 data on valence unpolarized GPDs $ H_v^q $ and $ E_v^q $ at zero skewness by performing some $ χ^2 $ analyses of the related experimental data. By calculating the electric and scalar quadrupole ratios, $ R_{EM} $ and $ R_{SM} $, and magnetic transition FF $ G^*_M/3G_D $ related to the nucleon-to-delta ($ N\rightarrow Δ$) transition using the extracted GPDs and comparing the results with corresponding experimental measurements, we show that our results are in an excellent consistency with experiments, indicating the universality property of GPDs. We emphasize that the inclusion of these data in the future analysis of GPDs can significantly affect the extracted GPDs especially their uncertainties at smaller values of $ Q^2 $.

hep-ph↗

arXiv2024

Investigations of $Λ$ states with spin-parity $\frac{3}{2}^{\pm}$

The present study provides spectroscopic investigations of spin-$\frac{3}{2}$ $Λ$ baryons with both positive and negative parities. The analysis mainly focuses on three states, namely $1P$, $2P$, and $2S$, and corresponding masses are calculated using the QCD sum rule method. To implement the method, we apply two types of interpolating currents with octet and singlet quantum numbers and compare the corresponding results with the reported masses of experimentally observed states. From the comparisons, it is extracted that the results of interpolating current with octet quantum numbers are in good agreement with the experimentally measured masses. The masses obtained with this interpolating current are $m=1513.64\pm 8.76$ MeV for $1P$ state with $J^P=\frac{3}{2}^-$, $m'=1687.91\pm 0.31$ MeV for $2P$ state with $J^P=\frac{3}{2}^-$ and $\tilde{m}=1882.37 \pm 11.95$ MeV for $2S$ state with $J^P=\frac{3}{2}^+$ and they are consistent with the experimental masses of $Λ(1520)$, $Λ(1690)$ and $Λ(1890)$, respectively, which confirm their spin-parity quantum numbers. Besides, we calculate the corresponding current coupling constants, which are utilized as inputs in the calculations of different form factors defining the widths of the states under study.

hep-ph↗

arXiv2024

Heavy axial-vector structures $bb\overline{c}\overline{c}$

The fully heavy axial-vector diquark-antidiquark structures $bb\overline{c} \overline{c}$ are explored by means of the QCD sum rule method. They are modeled as four-quark mesons $T_{\mathrm{1}}$ and $T_{\mathrm{2}}$ composed of $b^{T}Cσ_{μν}γ_{5}b$, $\overline{c}γ^{ν}C \overline{c}^{T}$ and $b^{T}Cγ_{μ}γ_{5}b$, $\overline{c}C \overline{c}^{T}$ diquarks, respectively. The spectroscopic parameters of the tetraquarks $T_{\mathrm{1}}$ and $T_{\mathrm{2}}$ are determined in the context of the QCD two-point sum rule method. Results obtained for masses of these states $m_{1} =(12715\pm 86)~\mathrm{MeV}$ and $m_{2}=(13383\pm 92)~ \mathrm{MeV}$ are used to fix their strong decay channels. The full width $ Γ(T_{\mathrm{1}})$ of the diquark-antidiquark state $T_{\mathrm{1}}$ is estimated by considering the processes $T_{\mathrm{1}} \to B_{c}^{-}B_{c}^{\ast -}$ and $T_{\mathrm{1}} \to B_{c}^{\ast -}B_{c}^{\ast -} $. The decays to mesons $B_{c}^{-}B_{c}^{\ast -}$, $B_{c}^{-}(2S)B_{c}^{ \ast -}$ and $B_{c}^{\ast -}B_{c}^{\ast -}$ are employed to evaluate $Γ(T_{\mathrm{2}})$. Results obtained for the widths $Γ(T_{\mathrm{1} })=(44.3\pm 8.8)~\mathrm{MeV}$ and $Γ(T_{\mathrm{2}})=(82.5\pm 13.7)~ \mathrm{MeV}$ of these tetraquarks in conjunction with their masses are useful for future experimental studies of fully heavy resonances.

hep-ph↗

arXiv2024

Properties of doubly heavy spin-$\frac{1}{2}$ baryons: The ground and excited states

We determine the masses and residues of the ground and excited spin-$\frac {1}{2} $ baryons consist of two heavy b or c quark utilizing the QCD sum rule formalism. In the calculations, we consider the nonperturbative operators up to ten mass dimensions in order to increase the accuracy compared to the previous calculations. We report the obtained results for both the symmetric and anti-symmetric currents defining the doubly heavy baryons of the ground state (1S), first orbitally excited state (1P) and first radially excited state (2S). We compare our results with the predictions of other nonperturbative approaches as well as existing experimental data which is available only for the ground state of $ Ξ_{cc}$ channel. These predictions can help the experimental groups in their searches for all members of the doubly heavy baryons in their ground and exited states.

hep-ph↗

arXiv2024

Decays of fully beauty scalar tetraquarks to $B_{q}\overline{B}_{q}$ and $B_{q}^{\ast}\overline{B}_{q}^{\ast}$ mesons

Decays of the fully beauty four-quark structures $X_{\mathrm{4b}}$ and $T_{ \mathrm{4b}}$ to $B$ meson pairs are investigated in the framework of QCD three-point sum rule method. We model the scalar exotic mesons $X_{\mathrm{4b }}$ and $T_{\mathrm{4b}}$ as diquark-antidiquark systems composed of the axial-vector and pseudoscalar diquarks, respectively. The masses $m=(18540 \pm 50)~\mathrm{MeV}$ and $\widetilde{m}=(18858 \pm 50)~\mathrm{MeV}$ of these compounds calculated in our previous articles, fix possible decay channels of these particles. In the present work, we consider their decays to $B_{q}\overline{B}_{q}$ and $B_{q}^{\ast }\overline{B}_{q}^{\ast } (q=u,d,s,c)$ mesons. In the case of $X_{\mathrm{4b}}$ the mass of which is below the $2η_{b}$ threshold, these channels determine essential part of its full width $Γ_{\mathrm{4b}}$. The tetraquark $T_{\mathrm{4b}}$ can decay to the pair $η_{b}η_{b}$, therefore partial widths of processes with $B (B^{\ast})$ mesons in the final state permit us to refine our estimate for the full width of this particle. The predictions $Γ_{ \mathrm{4b}}=(9.6\pm 1.1)~\mathrm{MeV}$ and $\widetilde{Γ}_{\mathrm{4b} }^{\mathrm{Full}}=(144 \pm 29)~\mathrm{MeV}$ obtained in this article can be used in future experimental investigations of four $b$-quark mesons.

hep-ph↗

arXiv2023

Charm content of the proton: An analytic calculation

According to general understanding, the proton as one of the main ingredients of the nucleus is composed of one down and two up quarks bound together by gluons, described by Quantum Chromodynamics (QCD). In this view, heavy quarks do not contribute to the primary wave function of the proton. Heavy quarks arise in the proton perturbatively by gluon splitting and the probability gradually increases as $Q^2$ increases (extrinsic heavy quarks). In addition, the existence of non-perturbative intrinsic charm quarks in the proton has also been predicted by QCD. In this picture, the heavy quarks also exist in the proton's wave function. In fact, the wave function has a five-quark structure $ \vert u u d c \bar{c}\rangle $ in addition to the three-quark bound state $ \vert u u d\rangle $. So far, many studies have been done to confirm or reject this additional component. One of the recent studies has been done by the NNPDF collaboration. They established the existence of an intrinsic charm component at the 3-standard-deviation level in the proton from the structure function measurements. Most of the studies performed to calculate the contribution of the intrinsic charm so far have been based on the global analyses of the experimental data. In this article, for the first time we directly calculate this contribution by an analytic method. We estimate a $x^{c\bar{c}} = (1.36 \pm 0.67)\% $ contribution for the $ \vert u u d c \bar{c}\rangle $ component of the proton.

hep-ph↗

arXiv2023

Scalar exotic mesons $bb\overline{c}\overline{c}$

Properties of doubly charged scalar tetraquarks $bb\overline{c}\overline{c}$ are investigated in the framework of the QCD sum rule method. We model them as diquark-antidiquark states $X_{\mathrm{1}}$ and $X_{\mathrm{2}}$ built of axial-vector and pseudoscalar diquarks, respectively. The masses and current couplings of these particles are computed using the QCD two-point sum rule method. Results $m_{1}=(12715 \pm 80)~\mathrm{MeV}$ and $m_{2}=(13370 \pm 95)~\mathrm{MeV}$ obtained for the masses of these particles are used to determine their kinematically allowed decay modes. The full width $Γ_{ \mathrm{1}}$ of the state $X_{\mathrm{1}}$ is evaluated by taking into account its strong decays to mesons $2B_{c}^{-}$, and $2B_{c}^{\ast -}$. The processes $X_{\mathrm{2}} \to 2B_{c}^{-}$, $2B_{c}^{\ast -}$ and $ B_{c}^{-}B_{c}^{-}(2S)$ are employed to estimate $Γ_{\mathrm{2}}$. Predictions obtained for the full widths $Γ_{\mathrm{1}}=(63 \pm 12)~ \mathrm{MeV}$ and $Γ_{\mathrm{2}}=(79 \pm 14)~\mathrm{MeV}$ of these structures and their masses may be utilized in experimental studies of fully heavy resonances.

hep-ph↗

arXiv2023

Gravitational form factors of $Δ$ baryon via QCD sum rules

The gravitational form factors of a hadron are defined through the matrix elements of the energy-momentum tensor current, which can be decomposed into the quark and gluonic parts, between the hadronic states. These form factors provide important information for answering fundamental questions about the distribution of the energy, the spin, the pressure and the shear forces inside the hadrons. Theoretical and experimental studies of these form factors provide exciting insights on the inner structure and geometric shapes of hadrons. Inspired by this, the gravitational form factors of $Δ$ resonance are calculated by employing the QCD sum rule approach. The acquired gravitational form factors are used to calculate the composite gravitational form factors like the energy and angular momentum multipole form factors, D-terms related to the mechanical properties like the internal pressure and shear forces as well as the mass radius of the system. The predictions are compared with the existing results in the literature.

hep-ph↗