arXiv subjects

S. Momeni

Publications and source records attributed to S. Momeni.

9 recordsLinked to original sources

arXiv2020

Charm meson couplings in hard-wall Holographic QCD

The four-flavor hard-wall holographic QCD is studied to evaluate the couplings of $(D^{_{-(*-)}}, \bar{D}^{_0}, a_1^{_-})$, $(D^{_{-(*-)}}, \bar{D}^{_0}, b_1^{_-})$, $(D_{s}^{_{-(*-)}},\bar{D}^{_0}, K_{1A}^{_-})$, $(D_s^{_{-(*-)}}, \bar{D}^{_0}, K_{1B}^{_{-(*-)}})$, $(D_s^{_{+(*+)}}, D^{_+}, K_{1A}^{_0})$, $(D_s^{_{+(*+)}}, D^{_+}, K_{1B}^{_0})$, $(D^{_{-(*-)}}, \bar{D}^{_{0(*0)}}, ρ^{_-})$, $(D_s^{_{-(*-)}}, \bar{D}^{_{0(*0)}}, K^{_{*-}})$, $(D^{_{0(*0)}}, \bar{D}^{_{0(*0)}}, ψ)$, $(D_1^{_-}, \bar{D}_1^{_0}, π^{_-})$, $(D_{s1}^{_-}, \bar{D}_1^{_0}, K^{_{-}})$, $(D_1^{_0}, \bar{D}_1^{_0}, η_c)$, $(ψ, D^{_{0(*0)}}, D^{_+}, π^{_-})$, $(ψ, D^{_{0(*0)}}, \bar{D}^{_0}, π^{_0})$, $(ψ, D_{s}^{_{+(*+)}}, D^{_-}, K^{_0})$, $(ψ, D^{_{0(*0)}}, D^{_+}, a_1^{_-})$, $(ψ, D^{_{0(*0)}}, D^{_+}, b_1^{_-})$, $(ψ, D_s^{_{+(*+)}}, D^{_-}, K_{1B}^{_0})$ and $(ψ, D_s^{_{+(*+)}}, D^{_-}, K_{1B}^{_0})$ vertices. Moreover, the values of the masses of $D^{_{0(*0)}}$, $D_s^{_{-(*-)}}$, $ω$, $ψ$, $D_1^{_0}$, $D_1^{_{-}}$, $K^0$, $η_{c}$, $D_{s1}^{_-}$ and $χ_{_{c1}}$ as well as the decay constant of $π^-$, $D^{_{-(*-)}}$, $K^-$, $ρ^-$, $D_1^{_-}$ , $a_1^-$ and $D_s^{_{-(*-)}}$ are estimated in this study. A comparison is also made between our results and the experimental values of the masses and decay constants. Our results for strong couplings are also compared with the 3PSR and LCSR predictions.

hep-ph↗

arXiv2020

Helicity form factors for $D_{(s)} \to A \ell ν$ process in the light-cone QCD sum rules approach

The helicity form factors of the $D_{(s)}\to A \ell^+ ν$ with $A=a_{1}^{-}, a_{1}^{0}, b_{1}^{-}, b_{1}^{0}, K_{1}(1270)$ and $K_{1}(1400)$ are calculated in the light-cone sum rules approach, up to twist-3 distribution amplitudes of the axial vector meson $A$. In the helicity form factors parametrization the unitarity constraints are applied to the fitting parameters. In addition, the effects of the low-lying resonances are included in series expansions of aforementioned form factors. The properties of the $D_{(s)}\to A \ell^+ ν$ semileptonic decays are studied by extending the form factors to the whole physical region of $q^2$. For a better analysis, a comparison is also made between our results and the predictions obtained using transition form factors via LCSR, 3PSR and CLFQM methods.

hep-ph↗

arXiv2020

$D D A$, $D^{}D^{}A$ and $D^{*} D A$ vertices in the light-cone QCD and considering $B^0\to {K}_{1}^{+} π^-$ branching ratio

We investigate the strong coupling constants of $D D A$, $D^{*}D^{*}A$ and $D^{*} D A$ vertices in the framework of the light-cone QCD sum rules, where $A$ is an axial vector meson such as $a_1, b_1, K_{1A}, K_{1B}, K_1(1270)$ and $K_1(1400)$. Using the strong coupling constants of $D_s D K_1$, $D_s^* D K_1$ and $D_s^* D^* K_1$ vertices for $K_1(1270)$ and $K_1(1400)$ mesons, we evaluated the branching ratios of the non-leptonic decays $B^0\to {K}_{1}^{+}(1270,1400) π^-$. Our results for the branching ratios of these decays are a good agreement with the experimental values.

hep-ph↗

arXiv2019

Semileptonic $D_{(s)} \to A \ell^+ ν$ and nonleptonic $D\to K_1(1270,1400) π$ decays in LCSR

In this work, the transition form factors are calculated for the semileptonic $D_{(s)} \to A \ell^+ ν$ where $A=a_{1}, b_{1}, K_{1}(1270,1400)$, i.e., $D^{+} \to a^{0}_{1} (b^{0}_{1}, K^{0}_{1}) \ell^+ ν$, $D^{0} \to a^{-}_{1} (b^{-}_{1}) \ell^+ ν$, and $D^{+}_{s}\to K^{0}_{1} \ell^+ ν$ in the frame work of the light-cone QCD sum rules (LCSR) approach up to the twist-3 distribution amplitudes (DAs). Since the masses of these axial vector mesons are comparable to the charm quark mass, we keep out in our calculations all terms including ${m_{A}}/{m_c}$ in expansion of two--parton DAs. Branching ratio values are estimated for the semileptonic $D_{(s)} \to A \ell ν$ and nonleptonic $D\to K_1 (1270,1400) π$ decays. A comparison is also made between our results and predictions of other methods and the existing experimental values.

hep-ph↗

arXiv2019

Semileptonic and nonleptonic decays of $D$ into tensor mesons with light-cone sum rule

Form factors of $D$ decays into $J^{PC}=2^{++}$ tensor mesons are calculated in the light-cone sum rules approach up to twist-4 distribution amplitudes of the tensor meson. The masses of the tensor mesons are comparable to that of the charm quark mass $m_c$; therefore all terms including powers of $m_T/m_c$ are kept out in the expansion of the two-particle distribution amplitude $\langle T|\bar q_{1α}(x) \, q_{2δ}(0)|0\rangle$. Branching ratios of the semileptonic $D \to T\,μ\,\barν_μ$ decays and nonleptonic $D\to T~ P ~(P=K, π)$ decays are taken into consideration. A comparison is also made between our results and predictions of other methods and the existing experimental values for the nonleptonic case. The semileptonic branching ratios are typically of the order of $10^{-5}$, and the nonleptonic ones show better agreement with the experimental data in comparison to the Isgur-Scora-Grinstein-Wise predictions.

hep-ph↗

arXiv2018

Analysis of the semileptonic $B\to K_1 \ell^+ \ell^-$transitions and non-leptonic $B \to K_1 γ$ decay in the AdS/QCD correspondence

We consider the axial-vector mesons $K_1(1270)$ and $K_1(1400)$ as a mixture of two $|^3P_1\rangle$ and $|^1P_1\rangle$ states with the mixing angle $θ$ that equal to $(-34\pm 13)^\circ$. We calculate the light-front distribution amplitudes (LFDAs) and decay constant formulas for both the axial-vector mesons $K_1$ in the AdS/QCD correspondence. The transition form factors of the semileptonic $B\to K_1$ decays are derived in terms of the LFDAs for $K_1$ mesons. Using these form factors and decay constant values, the differential branching ratios of $B\to K_1 (1270, 1400) \ell^+ \ell^-$,~$\ell=μ,τ$ transitions are plotted with respect to the four-momentum transfer squared, $q^2$. In addition, the branching ratio values of these decays and the non-leptonic $B \to K_1(1270, 1400) γ$ decays are estimated. A comparison is made between our results for the branching ratios of $B\to K_1(1270, 1400) γ$ decays in the AdS/QCD model and predictions obtained from the light-cone sum rules (LCSR) as well as the experimental values. Finally, the forward-backward asymmetries for the aforementioned semileptonic decays are plotted on $q^2$ in both the AdS/QCD correspondence and two Higgs doublet model (2HDM) in order to test the standard model (SM) and search for the new physics (NP).

hep-ph↗

arXiv2018

Semileptonic $B_{(s)}\to a_1(K_1)\ell^+ \ell^-$ decays via the light-cone sum rules with $B$-meson distribution amplitudes

The form factors of semileptonic $B_{(s)}\to a_{1}(K_1)\, \ell^{+}\ell^{-}$, $ \ell=τ,μ,e$ transitions are investigated in the framework of the light-cone sum rules with $B$-meson distribution amplitudes, which play an important role in exclusive $B$ decays. The $B$-meson distribution amplitudes, $φ_{\pm}(ω)$ are a model-dependent form, so we consider four different parameterizations which can provide a reasonable description of $φ_{\pm}(ω)$ from QCD corrections. The branching fractions of these transitions are calculated. For a better analysis, a comparison of our results with the prediction of other models is provided.

hep-ph↗

arXiv2018

Form Factors and Differential Branching Ratio of $B \to K μ^+ μ^-$ in AdS/QCD

The light-front distribution amplitudes (LFDAs) and the decay constant of the $K $ pseudoscalar meson are extracted within the framework of the AdS/QCD correspondence. For the LFDAs calculation, we consider a momentum-dependent (dynamical) helicity wave function which contains the dynamical spin effects. We use the LFDAs to predict the transition form factors of the semileptonic $B\to K \ell^{+}\ell^{-}$ decay. With the help of these form factors, the differential branching ratio of the $B\to K\, μ^+ μ^-$ on $q^2$ is plotted. A comparison is made between our prediction in AdS/QCD and the results obtained from two models including the light-cons sum rules (LCSR) and lattice QCD as well as the experimental values.

hep-ph↗

arXiv2016

FCNC transition of $B$ to $a_1$ with LCSR

The $B\to a_1 \ell^+ \ell^-$ decays occur by the electroweak penguin and box diagrams which can be performed through the flavor changing neutral current (FCNC). We calculate the form factors of the FCNC $B \to a_1$ transitions in the light--cone sum rules approach, up to twist--4 distribution amplitudes of the axial vector meson $a_1$. Forward--backward asymmetry, as well as branching ratios of $B\to a_1\ell^{+}\ell^{-}$, and $B\to a_1 γ$ decays are considered. A comparison is also made between our results and the predictions of other methods.

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