arXiv subjects
Publications and source records attributed to V. V. Braguta.
In this paper we have analyzed the production of pair charmonium mesons in the reactions $e^+ e^- \to J/ Ψχ_{c0}, e^+ e^-\to Ψ(2S) χ_{c0}$ at energy $\sqrt s = 10.6$GeV in the framework of the light cone formalism. In comparison with NRQCD the numerical results for the cross sections are in better agreement with experiment.
In this article we consider the three-particle decays $χ_{b0,2}\to J/ψc\bar c\to J/ψD\bar D+X$. We present the analytical formulae for the differential widths of these decays, the numerical values of their integrated widths and check the duality relation that connects the decays $χ_{b0,2}\toψc\bar c$ with the two-particle decays $χ_{b0,2}\to J/ψ(c\bar c)$. We also study the possibility of observing the $χ_{b0,2}\to J/ψDD+X$ mode at Tevatron and LHC colliders.
The calculation of the transverse muon polarization in $K^+ \to μ^+ νγ$ decay due to the final state interaction up to $O(p^6)$ CHPT level has been carried out. It is shown that $O(p^6)$ corrections to the observable is much less than $O(p^4)$ contribution.
We confirm the results of previous works that the internal motion of quarks inside charmonium mesons increases the cross section of the process $e^+e^-\to $J/ψη_c$. We also show, that this effect increases the widths of the scalar meson decay into two vector ones and state that the decays $χ_{b0,2}\to2J/ψ$ can be used to detect these scalar mesons at Tevatron and LHC colliders.
In this paper the production of excited vector and pseudoscalar charmonium mesons in $\epem$ annihilation is analyzed in the framework of light cone. In particular the cross sections $\epem \to ψ(2S)η_c(1S), ψ(1S)η_c(2S),ψ(2S)η_c(2S)$ have been calculated. It is shown, that contrary to NRQCD the cross sections calculated in the framework of light cone agree with experimental data.
In this paper transverse positron polarization in the $μ^+ \to e^+ \bar {ν_μ} ν_e$ decay in the framework of SM is considered. It is shown that the final state interaction effect leads to nonzero transverse polarization. Numerical value of the considered effect proved to be negligible. Thus SM contribution to the transverse positron polarization in the $μ^+ \to e^+ \bar {ν_μ} ν_e$ decay will not be the obstacle to a new physics searches.
We present an analysis of QCD sum rules for pion form factor in next-to-leading order of perturbation theory for the case of axial-vector pion currents. The theoretical predictions for Q^2-dependence of pion form factor are in good agreement with available experimental data. It is shown, that NLO corrections are large in this case and should be taken into account in rigorous theoretical analysis.
We present predictions for rho-meson form factors obtained from the analysis of QCD sum rules in next-to-leading order of perturbation theory. The radiative corrections turn out to be sizeable and should be taken into account in rigorous theoretical analysis.
We present an analysis of QCD sum rules for pion form factor in next-to-leading order of perturbation theory for the case of pseudoscalar pion currents. The essential instanton contribution is reanalysed with account for present more accurate values of parameters entering Single Instanton Approximation (SIA). The theoretical curve obtained for Q^2 dependence of pion form factor is in a good agreement with existing experimental data. To calculate NLO corrections for double spectral densities we developed an effective computational technic. The details of the method together with the results for pion form factor in a more theoretically clean case of axial interpolating currents will be presented elsewhere.
The dependence of the T-odd correlation on the effective Lagrangian parameters in the $K^+ \to πl νγ, l=e, μ$ decays is analyzed. It is shown that the introduced observable is perspective in a search for new physics in the vector and pseudovector sector of the Lagrangian. As for scalar and pseudoscalar sectors, the T-odd correlation studies will not allow one to improve current restrictions on parameters of models beyond SM.
The effect of lepton transverse polarization in the B^0 --> D^- l^+ nu_l, B^+ --> bar(D^0) l^+ nu_l decays (l= tau, mu) is analyzed within the framework of Standard Model in the leading order of HQET. It is shown that the non-zero transverse polarization appears due to the electromagnetic final state interaction. The diagrams with intermediate D, D^* - mesons contributing to the non-vanishing P_T are considered. Regarding only the contribution of these mesons, values of the tau-lepton transverse polarization, averaged over the physical region, in the B^0 --> D^- tau^+ nu_l and B^+ --> bar(D^0) tau^+ nu_l decays are equal to $2.60 cdot 10^{-3} and -1.59 cdot 10^{-3}, correspondingly. In the case of muon decay modes the values of are equal to 2.97 cdot 10^{-4} and -6.79 cdot 10^{-4}.
The muon transverse polarization in the $K^+ \to μ^+ νγ$ process induced by the electromagnetic final state interaction is calculated in the framework of Standard Model. It is shown that one loop contributions lead to a nonvanihing muon transverse polarization. The value of the muon transverse polarization averaged over the kinematical region of $E_γ\geq 20$ MeV is equal to $5.63 \times 10^{-4}$.
We consider two possible sources of the $T$-violating muon transverse polarization in the process $K^+ \to μ^+ νγ$: electromagnetic final state interaction in the SM and contribution due to charged-Higgs exchange diagrams in the framework of the Weinberg three doublets model. It is shown that at the one-loop level of the SM the muon transverse polarization, $P_T^{SM}$, varies within $(0.0 ÷1.1 \cdot 10^{-3})$ in the Dalitz plot region. Averaged value of the muon polarization, $ $, in the kinematic region of $E_γ\geq 20$ MeV is equal to $4.76\cdot 10^{-4}$. In the case of the model with three Higgs doublets the muon transverse polarization is calculated as a function of charged Higgs masses, imaginary part of the Yukawa coupling constants product and vacuum expectation values of the Higgs doublets. The averaged value of the transverse polarization in the Weinberg model is $ = - 6.62 \cdot 10^{-5}$. Perspectives to probe the effect caused by the charged Higgs exchange diagrams in planned kaon experiments are discussed.
The dependence of the $K^+ \to π^0 l^+ ν_l γ$ decay width on the $T$-odd kinematical variable, $ ξ= {\vec q \cdot [\vec p_l \times \vec p_π]} / {M^3}$, is studied at the tree and one-loop levels of Standard Model. It is shown that at the tree level this decay width is the even function of $ξ$, while the odd contribution arises due to the electromagnetic final state interaction. This contribution is determined by imaginary parts of one-loop diagrams. The calculations performed show that the $ξ$-odd contribution to the $K^+ \to π^0 e^+ ν_e γ$ and $K^+ \to π^0 μ^+ ν_μγ$ decay widths is four orders of magnitude smaller than even contribution coming from the tree level of SM.
We analytically calculate the total and differential cross sections for the pair production of doubly heavy baryons in the framework of diquark model. The processes of electron-positron and quark-antiquark annihilations are considered. The fractions of doubly heavy baryons in the yields of heavy quarks are evaluated numerically.