arXiv subjects

R. Khosravi

Publications and source records attributed to R. Khosravi.

At least 19 recordsLinked to original sources

arXiv2024

Form factors of $B_{(s)}$ to light scalar mesons with the $B$-meson LCSR

In this work, the transition form factors of the semileptonic decays of $B_{(s)}$ to the light scalar mesons with masses close to $1.5~\rm{GeV}$ such as $K_0^*(1430), a_0(1450)$, and $f_0(1500)$ are calculated in the framework of the light-cone sum rules (LCSR). For this purpose, the two- and three-particle $B$-meson distribution amplitudes (DA's) are used. Note that it is possible to use the $B$-meson DA's for $B_{s}$-meson in the $\rm SU(3)_F$ symmetry limit. The transition form factors are obtained in terms of the two-particle DA's up to twist-five accuracy, and the three-particle up to twist-six level. We apply two classes of the phenomenological models for the DA's of $B$-meson. The longitudinal lepton polarization asymmetries and branching fractions for the semileptonic decays of $B_{(s)}$ to the light scalar mesons are estimated with the help of these form factors.

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arXiv2022

Semileptonic $B_{s}\to K_0^*(1430)$ transitions with the light-cone sum rules

In the $\rm SU(3)_F$ symmetry limit, using two- and three-particle distribution amplitudes of $B^{\pm}$-meson for $B_s$, the transition form factors of semileptonic $B_{s}\to K_{0}^*(1430)$ decays are calculated in the framework of the light-cone sum rules. The two-particle distribution amplitudes, $φ_{_{+}}(ω)$ and $φ_{_{-}}(ω)$ have the most important contribution in estimation of the form factors $f_{+}(q^2)$, $f_{-}(q^2)$ and $f_{T}(q^2)$. The knowledge of the behavior of $φ_{_+}(ω)$ is still rather limited. Therefore, we consider three different parametrizations for the shapes of $φ_{_+}(ω)$ that are derived from the phenomenological models. Using the form factors $f_{+}$, $f_{-}$ and $f_{T}$, the semileptonic $B_s \to K_0^*(1430) l \bar{ν_{l}}$ and $B_s \to K_0^*(1430) l \bar{l}/ν\barν$, $l=e, μ, τ$ decays are analyzed. The branching fractions for the aforementioned decays, in addition the longitudinal lepton polarization asymmetries are calculated. A comparison between our results with predictions of other approaches is provided.

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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.

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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.

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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.

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arXiv2018

Analysis of $D^_sD^K^$ and $ D_{s1} D_1 K^$ vertices in three-point sum rules

In this study, the coupling constant of $D^*_sD^*K^*$ and $D_{s1}D_1K^*$ vertices were determined within the three-point Quantum chromodynamics sum rules method with and without consideration of the $SU_{f}(3)$ symmetry. The coupling constants were calculated for off-shell charm and K$^*$ cases. Considering the non-perturbative effect of the correlation function, as the most important contribution, the quark-quark, quark-gluon, and gluon-gluon condensate corrections were estimated and were compared with other predictive methods.

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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).

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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.

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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.

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arXiv2017

Analysis of $D_s D K^$ and $D_s D^{} K^$ vertices and branching ratio of $B^+\to {K^}^0 π^+$

In this paper, the strong form factors and coupling constants of $D_sDK^*$ and $D_sD^*K^*$ vertices are investigated within the three-point QCD sum rules method with and without the $SU_{f}(3)$ symmetry. In this calculation, the contributions of the quark-quark, quark-gluon, and gluon-gluon condensate corrections are considered. As an example of specific application of these coupling constants, the branching ratio of the hadronic decay $B^+\to {K^*}^0 π^+$ is analyzed based on the one-particle-exchange which is one of the phenomenological models. In this model, $B$ decays into a $D_s D^*$ intermediate state, and then these two particles exchange a $D (D^*)$ producing the final $K^*$ and $π$ mesons. In order to compute the effect of these interactions, the $D_s D K^*$ and $D_s D^* K^*$ form factors are needed.

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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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arXiv2015

Vertices of the $D_s^{()}D^{()}K^*$

Taking into account the contributions of the quark-quark, quark-gluon, and gluon-gluon condensate corrections, the strong form factors and coupling constants of $D^*_{s0}D^*_0K^*$, $D_sDK^*$, $D^*_sD^*K^*$, $D_{s1}D_1K^*$, $D_sD^*K^*$, and $D_{s0}D_1K^*$ vertices are investigated within the three-point QCD sum rules method, without and with the $SU_{f}(3)$ symmetry.

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arXiv2015

Semileptonic decays of $B (B_s)$ to light tensor mesons

The semileptonic $B_s (B) \to K_2^*(a_2, f_2) \ellν$, $\ell=τ, μ$ transitions are investigated in the frame work of the three-point QCD sum rules. Considering the quark condensate contributions, the relevant form factors of these transitions are estimated. The branching ratios of these channel modes are also calculated and compared with the obtained data for other approaches.

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arXiv2015

Form factors and branching ratios of the FCNC $B \to a_1 \ell^{+}\ell^{-}$ decays

We analyze the semileptonic $B \to a_1 \ell^+\ell^-$, $\ell=τ, μ, e$ transitions in the frame work of the three-point QCD sum rules in the standard model. These rare decays governed by flavor-changing neutral current transition of $b \to d$. Considering the quark condensate contributions, the relevant form factors as well as the branching fractions of these transitions are calculated.

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arXiv2015

Analysis of the semileptonic $B_c\to D_1^0$ transition in QCD sum rules and HQET

We investigate the structure of the $D_{1}^0(2420[2430]) (J^P=1^+)$ mesons via analyzing the semileptonic $B_{c}\to D_{1}^0 lν$ transition in the frame work of the three--point QCD sum rules and the heavy quark effective theory. We consider the $D_{1}^0$ meson in three ways; the pure $|c\bar{u}\rangle$ state, a mixture of two $|^3P_1\rangle$ and $|^1P_1\rangle$ states with a mixing angle $θ$ and a combination of two mentioned states with mixing angle $θ=35.3^\circ$ in the heavy quark limit. Taking into account the gluon condensate contributions, the relevant form factors are obtained for the three above conditions. These form factors are numerically calculated for $|c\bar{u}\rangle$ and the heavy quark limit cases. The obtained results for the form factors are used to evaluate the decay rates and the branching ratios. Also for mixed states, all of the mentioned physical quantities are plotted with respect to the unknown mixing angle $θ$.

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arXiv2014

Decay constants and masses of light tensor mesons ($J^P =2^+$)

We calculate the masses and decay constants of the light tensor mesons with quantum numbers $J^P =2^+$ in the framework of the QCD sum rules in the standard model. The non-perturbative contributions up to dimension-$5$ as important terms of the operator product expansion are considered.

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arXiv2011

Exclusive $D_{s} \to (η,η^{\prime}) l ν$ decays in light cone QCD

Probing the $\bar ss$ content of the $η$ and $η'$ mesons and considering mixing between these states as well as gluonic contributions, the form factors responsible for semileptonic $D_s \to (η, η') l ν$ transitions are calculated via light cone QCD sum rules. Corresponding branching fractions and their ratio for different mixing angles are also obtained. Our results are in a good consistency with experimental data as well as predictions of other nonperturbative approaches.

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arXiv2010

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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