arXiv subjects
Publications and source records attributed to M. Savci.
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.
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.
The radiative decays of the p-wave charmed heavy baryons to the ground state baryon states are studied in the framework of the light cone QCD sum rules method. Firstly, the transition form factors that describe these transitions are estimated, and then using these form factors the corresponding decay widths are calculated. A comparison of our results on the decay widths with those predicted by the other approaches existing in literature is performed.
The form factors of the $Λ_{b} \to N^\ast \ell^+ \ell^-$ decay are calculated in the framework of the light cone QCD sum rules. In the calculations the contribution of the negative parity $Λ_b^\ast$ baryon is eliminated by constructing the sum rules for different Lorentz structures. Furthermore the branching ratio of the semileptonic $Λ_b \to N^\ast \ell^+ \ell^-$ decay is calculated. The numerical study for the branching ratio of the $Λ_{b} \to N^\ast \ell^+ \ell^-$ decay indicates that it is quite large and could be measurable at future planned experiments to be conducted at LHCb.
The transition form factors of the radiative decays of the heavy tensor mesons to heavy pseudoscalar and heavy vector mesons are calculated in the framework of the light cone QCD sum rules method at the point $Q^2=0$. Using the obtained values of the transition form factors at the point $Q^2=0$ the corresponding decay widths are estimated. The results show that the radiative decays of the heavy--light tensor mesons can be measurable in the future planned experiments at LHCb.
Form factors of the rare $Λ_{b}(Λ_{b}^*)\to N\ell^{+}\ell^{-}$ decays are calculated in the framework of the light cone QCD sum rules by taking into account of the contributions from the negative parity baryons. Using the obtained results on the form factors, the branching ratios of the considered decays are estimated. The numerical survey for the branching ratios of the $Λ_b \rar N\ell^+\ell^- $ and $Λ_b^\ast \rar N\ell^+\ell^- $ decays indicate that these transitions could be measurable in LHCb in near future. Comparison of our predictions on the form factors and branching ratios with those existing in the literature is also performed.
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.
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.
The transition magnetic moments between negative parity, spin-1/2 heavy baryons are studied in framework of the light cone QCD sum rules. By constructing the sum rules for different Lorentz structures, the unwanted contributions coming from negative (positive) to positive (negative) parity transitions are removed. It is found that the magnetic moments between neutral negative parity heavy $Ξ_Q^{\prime 0}$ and $Ξ_Q^0$ baryons are very small. Magnetic moments of the $Σ_Q \to Λ_Q$ and $ Ξ_Q^{\prime \pm} \to Ξ_Q^\pm$ transitions are quite large and can be measured in further experiments.
The magnetic moments of the negative parity, spin-1/2 baryons containing single heavy quark are calculated. The pollution that occur from the transitions between positive and negative parity baryons are removed by constructing the sum rules from different Lorentz structures.
The magnetic moments of heavy sextet $J^P = {1\over 2}^+$ baryons are calculated in framework of the light cone QCD sum rules method. Linearly independent relations among the magnetic moments of these baryons are obtained. The results for the magnetic moments of heavy baryons obtained in this work are compared with the predictions of the other approaches.
If the $X(3872)$ is described by the picture as a mixture of the charmonium and molecular $D^{\ast} D$ states; $Y(3940)$ as a mixture of the $χ_{c0}$ and $D^\ast D^\ast$ states; and $X(4260)$ as a mixture of the tetra-quark and charmonium sates, their orthogonal combinations should also exist. We estimate the mass and residues of the states within the QCD sum rules method. We find that the mass splitting among $X$, $Y$ and their orthogonal states is at most $200MeV$. Experimental search of these new states can play critical role for establishing the nature of the new charmonium states.
Using the pictures for $X(3872)$ as a mixture of charmonium and molecular $D^{\ast 0}D^0$ states; $Y(3940)$ as a mixture of $χ_{c0}$ and $D^\ast D^{\prime\ast}$ states, and $Y(4260)$ as a mixture of the tetra-quark state with charmonium states, the corresponding mixing angles are estimated within the QCD sum rules. We obtain that our predictions for the mixing angles of the $X(3872)$, $Y(4260)$ and $Y(3940)$ states are considerably smaller compared to works in which mixing angles are estimated from the condition in reproducing the the mass of these states. Our conclusion is that the considered pictures for the $X(3872)$, $Y(4260)$ and $Y(3940)$ states are not successful in describing these states.
The $γ^\ast N \to N^\ast (1520)$ reaction is studied in framework of the light cone QCD sum rules method. The sum rules for the multipole form factors, namely, for the magnetic dipole $G_M(Q^2)$, electric quadrupole $G_E(Q^2)$, and Coulomb quadrupole $G_C(Q^2)$, form factors responsible for for the $γ^\ast N \to N^\ast (1520)$ transition are derived. Using these sum rules, the helicity amplitudes are presented as the combinations of these multipole form factors, and their $Q^2$ dependences are studied. We compare our results on the helicity amplitudes with those of the spectator model predictions, and with the existing experimental data.
The magnetic moments of the low lying, negative parity, spin-3/2 baryons are calculated within the light cone QCD sum rules method. The contributions coming from the positive parity, spin-3/2 baryons, as well as from the positive and negative parity spin-1/2 baryons are eliminated by constructing combinations of various invariant amplitudes corresponding to the coefficients of the different Lorentz structures.
The masses and residues of the triply heavy spin--3/2 baryons are calculated in framework of the QCD sum rule approach. The obtained results are compared with the existing theoretical predictions in the literature.
Light cone QCD sum rules for the electromagnetic transition form factors among positive and negative parity octet baryons are derived. The unwanted contributions of the diagonal transitions among positive parity octet baryons are eliminated by combining the sum rules derived from different Lorentz structures. The $Q^2$ dependence for the transversal and longitudinal helicity amplitudes are studied.
Using the most general form of the interpolating current for the octet baryons, the magnetic moments of the negative-parity baryons are calculated within the light-cone sum rules. The contributions coming from diagonal transitions of the positive-parity baryons, and also from non-diagonal transition between positive and negative-parity baryons are eliminated by considering the combinations of different sum rules corresponding to the different Lorentz structures. A comparison of our results on magnetic moments of the negative-parity baryons with the other approaches existing in literature is presented.