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K. Azizi

Publications and source records attributed to K. Azizi.

At least 289 records · Page 16Linked to original sources

Strong coupling constants of bottom and charmed mesons with scalar, pseudoscalar and axial vector kaons

The strong coupling constants, $g_{D_{s}DK_0^*}$, $g_{B_{s}BK_0^*}$, $g_{D^{\ast}_{s}D K}$, $g_{B^{\ast}_{s}BK}$, $g_{D^{\ast}_{s}D K_1}$ and $g_{B^{\ast}_{s}BK_1}$, where $K_0^*$, $K$ and $K_1$ are scalar, pseudoscalar and axial vector kaon mesons, respectively are calculated in the framework of three-point QCD sum rules. In particular, the correlation functions of the considered vertices when both $B(D)$ and $K_0^*(K)(K_1)$ mesons are off-shell are evaluated. In the case of $K_1$, which is either $K_1(1270)$ or $K_1(1400)$, the mixing between these two states are also taken into account. A comparison of the obtained result with the existing prediction on $g_{D^{\ast}_{s}D K}$ as the only coupling constant among the considered vertices, previously calculated in the literature, is also made.

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Analysis of heavy spin--3/2 baryon--heavy spin--1/2 baryon--light vector meson vertices in QCD

The heavy spin--3/2 baryon--heavy spin--1/2 baryon vertices with light vector mesons are studied within the light cone QCD sum rules method. These vertices are parametrized in terms of three coupling constants. These couplings are calculated for all possible transitions. It is shown that correlation functions for these transitions are described by only one invariant function for every Lorenz structure. The obtained relations between the correlation functions of the different transitions are structure independent while explicit expressions of invariant functions depend on the Lorenz structure.

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Spin--3/2 to spin--1/2 heavy baryons and pseudoscalar mesons transitions in QCD

The strong coupling constants of light pseudoscalar mesons with spin--3/2 and spin--1/2 heavy baryons are calculated in the framework of light cone QCD sum rules. It is shown that each class of transitions among members of the sextet spin--3/2 to sextet spin--1/2 baryons and that of the sextet spin--3/2 to spin--1/2 anti--triplet baryons is described by only one invariant function. We also estimate the widths of kinematically allowed transitions. Our results on decay widths are in good agreement with the existing experimental data, as well as predictions of other nonperturbative approaches.

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Thermal QCD Sum Rules Study of Vector Charmonium and Bottomonium States

We calculate the masses and leptonic decay constants of the heavy vector quarkonia, $J/ψ$ and $Υ$ mesons at finite temperature. In particular, considering the thermal spectral density as well as additional operators coming up at finite temperature, the thermal QCD sum rules are acquired. Our numerical calculations demonstrate that the masses and decay constants are insensitive to the variation of temperature up to $T\cong 100 ~MeV$, however after this point, they start to fall altering the temperature. At deconfinement temperature, the decay constants attain roughly to 45% of their vacuum values, while the masses are diminished about 12%, and 2.5% for $J/ψ$ and $Υ$ states, respectively. The obtained results at zero temperature are in good consistency with the existing experimental data as well as predictions of the other nonperturbative models. Considerable decreasing in the values of the decay constants can be considered as a sign of the quark gluon plasma phase transition.

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A comparative study on $B \rar K^\ast \ell^+ \ell^-$ and $B \rar K_0^\ast (1430) \ell^+ \ell^-$ decays in the Supersymmetric Models

In this paper, we compare the branching ratio and rate difference of electron channel to muon channel of $B \rar K_0^\ast (1430) \ell^+ \ell^-$ and $B \rar K^\ast \ell^+ \ell^-$decays, where $K_0^\ast (1430)$ is the p--wave scalar meson, in the supersymmetric models. MSSM with $R$ parity is considered since considerable deviation from the standard model predictions can be obtained in $B\rightarrow X_s \ell^-\ell^+$. Taking $C_{Q1}$ and $C_{Q2}$ about one which is consistent with the $B\to K^\astμ^+μ^-$ rate at low dileptonic invariant mass region($1\leq q^2\leq 6$GeV$^2$). It is found that, firstly, the $B \rar K_0^\ast (1430) \ell^+ \ell^-$ $(\ell = μ,\, τ)$ decay is measurable at LHC, secondly, in comparison with $B \rar K^\ast \ell^+ \ell^-$ decay a greater deviation in the $B \rar K_0^\ast (1430) \ell^+ \ell^-$ decay can be seen. Measurement of these observables for the semileptonic rare $B \rar K_0^\ast (1430) \ell^+ \ell^-$, in particular, at low $q^2$ region can give valuable information about the nature of interactions within Standard Model or beyond.

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$g_{D^{\ast}_{s}D K^{\ast}(892)}$ and $g_{B^{\ast}_{s}B K^{\ast}(892)}$ coupling constants in QCD sum rules

The coupling constants $g_{D^{\ast}_{s}D K^{\ast}(892)}$ and $g_{B^{\ast}_{s}B K^{\ast}(892)}$ are calculated in the framework of three-point QCD sum rules. The correlation functions responsible for these coupling constants are evaluated considering contributions of both $D(B)$ and $K^*(892)$ mesons as off-shell states, but in the absence of radiative corrections. The results, $g_{D^{\ast}_{s}D K^{\ast}(892)}=(4.31\pm1.42) GeV^{-1}$ and $g_{B^{\ast}_{s}B K^{\ast}(892)}=(3.24\pm1.08) GeV^{-1}$ are obtained for the considered strong coupling constants.

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Investigation of the $Λ_b \rightarrow Λ\ell^+ \ell^-$ transition in universal extra dimension using form factors from full QCD

Using the related form factors from full QCD which recently are available, we provide a comprehensive analysis of the $Λ_b \rightarrow Λ\ell^+ \ell^-$ transition in universal extra dimension model in the presence of a single universal extra dimension called the Applequist-Cheng-Dobrescu model. In particular, we analyze some related observables like branching ratio, forward-backward asymmetry, double lepton polarization asymmetries and polarization of the $Λ$ baryon in terms of compactification radius and corresponding form factors. We present the sensitivity of these observables to the compactification parameter, 1/R up to 1/R=1000 GeV. We also compare the results with those obtained using the form factors from heavy quark effective theory as well as the SM predictions.

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Double-Lepton Polarization Asymmetries and Branching Ratio in $B \rar K_{0}^{*}(1430) l^+ l^- $ transition from Universal Extra Dimension Model

We investigate the $B \rar K_{0}^{*}(1430) l^+ l^- $ transition in the Applequist-Cheng-Dobrescu model in the presence of a universal extra dimension. In particular, we calculate double lepton polarization asymmetries and branching ratio related to this channel and compare the obtained results with the predictions of the standard model. Our analysis of the considered observables in terms of radius $R$ of the compactified extra-dimension as the new parameter of the model show a considerable discrepancy between the predictions of two models in low $\frac{1}{R}$ values.

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Strong coupling constants of light pseudoscalar mesons with heavy baryons in QCD

We calculate the strong coupling constants of light pseudoscalar mesons with heavy baryons within the light cone QCD sum rules method. It is shown that sextet--sextet, sextet--antitriplet and antitriplet--antitriplet transitions are described by one universal invariant function for each class. A comparison of our results on the coupling constants with the predictions existing in literature is also presented.

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Heavy baryon--light vector meson couplings in QCD

The strong coupling constants of heavy baryons with light vector mesons are calculated in the framework of the light cone QCD sum rules using the most general form of the interpolating currents for the heavy baryons. It is shown that the sextet--sextet, sextet--antitriplet and antitriplet--antitriplet transitions are described by one invariant function for each class of transitions. The values of the electric and magnetic coupling constants for these transitions are obtained.

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Rare Semileptonic $B_{s}$ Decays to $η$ and $η'$ mesons in QCD

We analyze the rare semileptonic $B_s \to (η, η') l^+ l^-$, $(l=e, μ, τ)$ and $B_s \to (η, η') ν\barν$ transitions probing the $\bar s s$ content of the $η$ and $η'$ mesons via three--point QCD sum rules. We calculate responsible form factors for these transitions in full theory. Using the obtained form factors, we also estimate the related branching fractions and longitudinal lepton polarization asymmetries. Our results are in a good consistency with the predictions of the other existing nonperturbative approaches.

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Scalar Quarkonia at Finite Temperature

Masses and decay constants of the scalar quarkonia, $χ_{Q0} (Q=b,c)$ with quantum numbers $I^G(J^{PC})=0^{+}(0^{++})$ are calculated in the framework of the QCD sum rules approach both in vacuum and finite temperature. The masses and decay constants remain unchanged up to $T\simeq100~MeV$ but they start to diminish with increasing the temperature after this point. At near the critic or deconfinement temperature, the decay constants reach approximately to 25% of their values in vacuum, while the masses are decreased about 6% and 23% for bottom and charm cases, respectively. The results at zero temperature are in a good consistency with the existing experimental values and predictions of the other nonperturbative approaches. Our predictions on the decay constants in vacuum as well as the behavior of the masses and decay constants with respect to the temperature can be checked in the future experiments.

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The $g_{Σ_QΣ_Qπ}$ Coupling Constant via Light Cone QCD Sum Rules

Using the most general form of the interpolating currents, the coupling constants $g_{Σ_bΣ_bπ}$ and $g_{Σ_cΣ_cπ}$ are calculated within the light cone QCD sum rules approach. It is found that $g_{{Σ_{c}Σ_{c}π}}=-8.0\pm1.7$ and $g_{{Σ_{b}Σ_{b}π}}=-11.0\pm2.1$.

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Strong Coupling Constants of Decuplet Baryons with Vector Mesons

We provide a comprehensive study of strong coupling constants of decuplet baryons with light nonet vector mesons in the framework of light cone QCD sum rules. Using the symmetry arguments, we argue that all coupling constants entering the calculations can be expressed in terms of only one invariant function even if the $SU(3)_f$ symmetry breaking effects are taken into account. We estimate the order of $SU(3)_f$ symmetry violations, which are automatically considered by the employed approach.

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Strong transitions of decuplet to octet baryons and pseudoscalar mesons

The strong coupling constants of light pseudoscalar $π$, $K$ and $η$ mesons with decuplet--octet baryons are studied within light cone QCD sum rules, where $SU(3)_f$ symmetry breaking effects are taken into account. It is obtained that all coupling constants under the consideration are described by only one universal function even if $SU(3)_f$ symmetry breaking effects are switched into the game.

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Heavy $χ_{Q_2}$ tensor mesons in QCD

The masses and decay constants of the ground state heavy $χ_{Q2}(Q=b,c)$ tensor mesons are calculated in the framework of the QCD sum rules approach. The obtained results on the masses are in good consistency with the experimental values. Our predictions on the decay constants can be verified in the future experiments.

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Flavor Changing Neutral Currents Transition of the $Σ_{Q}$ to Nucleon in Full QCD and Heavy Quark Effective Theory

The loop level flavor changing neutral currents transitions of the $Σ_{b}\to n l^+l^-$ and $Σ_{c}\to p l^+l^-$ are investigated in full QCD and heavy quark effective theory in the light cone QCD sum rules approach. Using the most general form of the interpolating current for $Σ_{Q}$, $Q=b$ or $c$, as members of the recently discovered sextet heavy baryons with spin 1/2 and containing one heavy quark, the transition form factors are calculated using two sets of input parameters entering the nucleon distribution amplitudes, namely, QCD sum rules and lattice QCD inputs. The obtained results are used to estimate the decay rates of the corresponding transitions. Since such type transitions occurred at loop level in the standard model, they can be considered as good candidates to search for the new physics effects beyond the SM.

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Analysis of the $Λ_{b}\rar Λ\ell^+\ell^- $ decay in QCD

Taking into account the $Λ$ baryon distribution amplitudes and the most general form of the interpolating current of the $Λ_{b}$, the semileptonic $Λ_{b}\rar Λ\ell^+\ell^- $ transition is investigated in the framework of the light cone QCD sum rules. Sum rules for all twelve form factors responsible for the $Λ_{b}\rar Λ\ell^+\ell^- $ decay are constructed. The obtained results for the form factors are used to compute the branching fraction. A comparison of the obtained results with the existing predictions of the heavy quark effective theory is presented. The results of the branching ratio shows the detectability of this channel at the LHCb in the near future is quite high.

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