arXiv subjects

S. Bilmis

Publications and source records attributed to S. Bilmis.

32 records · Page 2Linked to original sources

arXiv2021

Semileptonic $Ξ_c$ baryon decays in the light cone QCD sum rules

Form factors of the weak $Ξ_c \to Ξ(Λ)$ transitions are calculated within the light cone QCD sum rules. The pollutions coming from the contribution of the negative parity $Ξ_c^*$ baryon is eliminated by considering the combinations of sum rules corresponding to the different Lorentz structures. Having obtained the form factors, the branching ratios of the $Ξ_c \to Ξ(Λ) \ell ν$ decays are also calculated, and our predictions are compared with the results of other approaches as well as the measurements done by BELLE and ALICE Collaborations.

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arXiv2020

Light-cone sum rules for radial excitation of decuplet to octet baryons electromagnetic transition form factors

Magnetic dipole moment form factor, $G_M^{(2)}(Q^2)$, describing the radial excitation of decuplet baryons to octet baryons electromagnetic transitions as well as the ratios, $R_{SM} = -\frac{1}{4 m_2^2} \sqrt{4 m_2^2 Q^2 + (m_2^2 - Q^2 -m_1^2)^2} \frac{G_C^{(2)}(Q^2)}{G_M^{(2)}(Q^2)}$ and $R_{EM} = -\frac{G_E^{(2)}(Q^2)}{G_M^{(2)}(Q^2)}$ are calculated in the framework of light-cone sum rules. We also estimate the degree of the violation of U-spin symmetry. The obtained results for the multipole form factors can be useful in searching the properties of radially excited baryon states.

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arXiv2020

$γ^* N \rightarrow Δ^{+}(1600)$ transition form factors in light-cone sum rules

The form factors of $γ^* N \rightarrow Δ(1600)$ transition is calculated within the light-cone sum rules assuming that $Δ^+(1600)$ is the first radial excitation of $Δ(1232)$. The $Q^2$ dependence of the magnetic dipole $\tilde{G}_M(Q^2)$, electric quadrupole $\tilde{G}_E(Q^2)$, and Coulomb quadrupole $\tilde{G}_c(Q^2)$ form factors are investigated. Moreover, the $Q^2$ dependence of the ratios $R_{EM} = -\frac{\tilde{G}_E(Q^2)}{\tilde{G}_M{Q^2}}$ and $R_{SM} = - \frac{1}{4 m_{Δ(1600)}^2} \sqrt{4 m_{Δ(1600)}^2 Q^2 + (m_{Δ(1600)}^2 - Q^2 - m_N^2)^2} \frac{\tilde{G}_c(Q^2)}{\tilde{G}_M(Q^2)}$ are studied. Finally, our predictions on $\tilde{G}_M(Q^2)$, $\tilde{G}_E(Q^2)$, and $\tilde{G}_C(Q^2)$ are compared with the results of other theoretical approaches.

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arXiv2020

Multipole Moments of Heavy Vector and Axial-Vector Mesons in QCD

The magnetic and quadrupole moments of the vector and axial-vector mesons containing heavy quark are estimated within the light cone sum rules method. Our predictions on magnetic moments for the vector mesons are compared with the results obtained by other approaches.

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arXiv2019

Properties of excited $B_c$ states in QCD

The mass and leptonic decay constants of recently observed two new excited $B_c$ states at LHC are studied within the QCD sum rules. Considering the contributions of the ground and radially excited states, the mass and residues of the excited states of pseudoscalar and vector mesons are calculated in the framework of two different approaches of the QCD sum rules, namely, linear combinations of the corresponding sum rules and its derivatives as well as QCD sum rules with the incorporation of the least square fitting method. The obtained results on mass $m_{B_c^+}(2S) = 6.88 \pm 0.03~\rm{GeV} $ and $m_{B_c^{*+}}(2S) = 6.94 \pm 0.03~\rm{GeV} $ are in good agreement with the experimental data. Our predictions for the decay constants of these states are: $f_{B_c^+}(2S) = 0.42 \pm 0.02~\rm{GeV} $ and $f_{B_c^{*+}}(2S) = 0.46 \pm 0.01~\rm{GeV}$, which can be checked at future experiments to be conducted at the LHC. Comparison of our results with the predictions of the other approaches on mass and residues is also presented.

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arXiv2019

Are the new excited $Ω_c$ baryons negative parity states?

We calculate the mass and residue of the newly observed $Ω_c(3000)$ and $Ω_c(3066)$ states with quantum numbers $J^P = \frac{1}{2}^{-}$ and $\frac{3}{2}^{-}$ within QCD sum rules. Our predictions on masses are in good agreement with the experimental results.

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arXiv2019

The mass and residues of radially and orbitally excited doubly heavy baryons in QCD

The mass and residues of the first radial and orbital excitations of $J=\frac{1}{2}$ baryons containing two heavy quarks (b or c) are calculated within the QCD sum rules method. In calculations, the general forms of the interpolating currents with symmetric and anti-symmetric forms with respect to the exchange of heavy quarks have been used. Our results on the spectroscopic parameters of doubly heavy baryons are compared with the predictions of other theoretical approaches.

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arXiv2018

Determination of $f_0 - a_0^0$ mixing angle from QCD sum rules

By assuming that the $f_0$ and $a_0^0$ mesons are mixed states of the two-quark - tetraquark, the mixing angle between them is estimated within QCD sum rules method, and it is obtained that the mixing angle is $(6.03 \pm 0.08)^\circ$. Our prediction on mixing angle can be checked in further experiments which can shed light on choosing the "right" structure of $f_0$ and $a_0^0$ mesons.

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arXiv2018

Reanalysis of $Ω_c \rightarrow Ξ_c^+ K^-$ decay in QCD

The strong coupling constants of newly observed $Ω_c^0$ baryons with spin $J = \frac{1}{2}$ and $J = \frac{3}{2}$ decaying into $Ξ_c^{+} K^{-}$ are estimated within light cone QCD sum rules. The calculations are performed within two different scenarios on quantum numbers of $Ω_c$ baryons: a) all newly observed $Ω_c$ baryons are negative parity baryons, i.e., the $Ω_c(3000)$, $Ω_c(3050)$, $Ω_c(3066)$, and $Ω_c(3090)$ have quantum numbers $J^P = \frac{1}{2}^-$ and $J^P = \frac{3}{2}^-$ states respectively; b) the states $Ω_c(3000)$ and $Ω_c(3050)$ have quantum numbers $J^P = \frac{1}{2}^-$ and $J^P = \frac{1}{2}^+$, while the states $Ω_c(3066)$ and $Ω_c(3090)$ have the quantum numbers $J^P = \frac{3}{2}^-$ and $J^P = \frac{3}{2}^+$, respectively. By using the obtained results on the coupling constants, we calculate the decay widths of the corresponding decays. The results on decay widths are compared with the experimental data of LHC Collaboration. We found out that the predictions on decay widths within these scenarios are considerably different from the experimental data, i.e., both considered scenarios are ruled out.

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arXiv2017

Light-Cone Distribution Amplitudes of Light $J^{PC}=2^{--}$ Tensor Mesons in QCD

We present a study for two-quark light-cone distribution amplitudes for the $1^3D_2$ light tensor meson states with quantum number $J^{PC}=2^{--}$. Because of the G-parity, the chiral-even two-quark light-cone distribution amplitudes of this tensor meson are antisymmetric under the interchange of momentum fractions of the quark and antiquark in the SU(3) limit, while the chiral-odd ones are symmetric. The asymptotic leading-twist LCDAs with the strange quark mass correction are shown. We estimate the relevant parameters, the decay constants $f_T$ and $f_T^\perp$, and first Gegenbauer moment $a_1^\perp$, by using the QCD sum rule method. These parameters play a central role in the investigation of $B$ meson decaying into the $2^{--}$ tensor mesons.

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arXiv2017

Strong coupling constants of negative parity heavy baryons with $π$ and $K$ mesons

The strong coupling constants of negative parity heavy baryons belonging to a sextet and antitriplet representations of $SU_f(3)$ with light $π$ and $K$ mesons are estimated within the light cone QCD sum rules. It is observed that each class of the sextet-sextet, sextet-antitriplet, and antitriplet-antitriplet transitions can be described by only one corresponding function. The pollutions arising from the positive to positive, positive to negative, and negative to positive parity baryons transitions are eliminated by constructing sum rules for different Lorentz structures. The obtained coupling constants are compared with the ones for the positive parity heavy baryons.

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arXiv2016

Analysis of radial excitations of octet baryons in QCD sum rules

Using the QCD sum rules method, we estimate the mass and residues of the first radial excitations of octet baryons. The contributions coming from the ground state baryons are eliminated by constructing the linear combinations of the sum rules corresponding to different Lorentz structures. Our predictions of the masses of the first radial excitations of octet baryons are in good agreement with the data.

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arXiv2015

Constraints on Dark Photon from Neutrino-Electron Scattering Experiments

A possible manifestation of an additional light gauge boson $A^\prime$, named as Dark Photon, associated with a group $U(1)_{\rm B-L}$ is studied in neutrino electron scattering experiments. The exclusion plot on the coupling constant $g_{\rm B-L}$ and the dark photon mass $M_{A^\prime}$ is obtained. It is shown that contributions of interference term between the dark photon and the Standard Model are important. The interference effects are studied and compared with for data sets from TEXONO, GEMMA, BOREXINO, LSND as well as CHARM II experiments. Our results provide more stringent bounds to some regions of parameter space.

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arXiv2012

Constraints on Non-Commutative Physics Scale with Neutrino-Electron Scattering

Neutrino-electron scatterings ($ν- e$) are purely leptonic processes with robust Standard Model (SM) predictions. Their measurements can therefore provide constraints to physics beyond SM. Non-commutative (NC) field theories modify space-time commutation relations, and allow neutrino electromagnetic couplings at the tree level. Their contribution to neutrino-electron scattering cross-section was derived. Constraints were placed on the NC scale parameter $Λ_{NC}$ from $ν- e$ experiments with reactor and accelerator neutrinos. The most stringent limit of $Λ_{NC} > 3.3 TeV$ at 95% confidence level improves over the direct bounds from collider experiments.

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