Double charmonium production in exclusive bottomonia decays

This paper is devoted to the leading twist exclusive bottomonia decays with double charmonium in the final state. Using models of the twist-2 charmonia distribution amplitudes the widths of these decays are calculated within light cone formalism. In addition, the processes under consideration are studied within nonrelativistic QCD. In our analysis we have found that the production of some of the $P$-wave charmonia mesons with $L_z \neq 0$ is allowed already at the leading twist approximation. This means that the selection rules which predict the suppression of such decays are violated. The mechanism which lies behind this violation is discussed.Comment: Minor changes, some references adde

New Physics Effects and Hadronic Form Factor Uncertainties in B -> K^* l^+ l^-

It is well known that New Physics can contribute to weak decays of heavy mesons via virtual processes during its decays. The discovery of New Physics, using such decays is made difficult due to intractable strong interaction effects needed to describe it. Modes such as B -> K^* l^+ l^- offer an advantage as they provide a multitude of observables via angular analysis. We show how the multitude of "related observables" obtained from B -> K^* l^+ l^-, can provide many new "clean tests" of the Standard Model. The hallmark of these tests is that several of them are independent of the unknown universal form factors in heavy quark effective theory. We derive a relation between observables that is free of form factors and Wilson coefficients, the violation of which will be an unambiguous signal of New Physics. We also derive relations between observables and form factors that are independent of Wilson coefficients and enable verification of hadronic estimates. We show how form factor ratios can be measured directly from helicity fraction with out any assumptions what so ever. We find that the allowed parameter space for observables is very tightly constrained in Standard Model, thereby providing clean signals of New Physics. We examine both the large-recoil and low-recoil regions of the K^* meson and point out special features and derive relations between observables valid in the two limits. In the large-recoil regions several of the relations are unaffected by corrections to all orders in \alpha_s. We present yet another new relation involving only observables that would verify the validity of the relations between form-factors assumed in the low-recoil region. The several relations and constraints derived will provide unambiguous signals of New Physics if it contributes to these decays.Comment: 26 pages, 9 figures (20 pdf figure files). Several typos correcte

Compton Scattering on the Charged Pion and the Process \gamma\gamma \to \pi^0 \pi^0

The Compton scattering on a charged pion and the process \gamma\gamma \to \pi^0\pi^0 are studied using the dispersion relations. Unknown parameters of the S-wave \pi\pi interaction, represented as a board Breit-Wignar resonance, and a sum and a difference of the \pi^0 meson polarizabilities are found from a fit to the experimental data for the process \gamma+\gamma \to \pi^0+\pi^0. This fit gives \alpha+\beta=0.98\pm 0.03 and \alpha-\beta=-1.6\pm 2.2. The found parameters of the S-wave \pi\pi interaction are used for the calculation of the cross section of the Compton scattering on \pi^{\pm} meson. The analysis of the obtained results shows that the experimental data for the elastic \gamma\pi scattering in the energy region up to 1 GeV together with the data for the process \gamma+\gamma \to \pi^0+\pi^0 could be used both for a determination of the pion polarizability values with quite high accuracy and for study of the S-wave \pi\pi interaction.Comment: LaTex, 19 pages including 6 figures. Substantial revised versio

Study of exclusive processes e^+ e^- \to VP

This paper is devoted to consideration of the hard exclusive processes $e^+e^- \to VP$, where $V=\rho,\phi; P=\eta,\eta'$. Experimental measurement of the cross section of the process $e^+ e^- \to \phi\eta$ at BaBar collaboration at large center mass energy $\sqrt s=10.6$ GeV and some low energy experimental data $\sqrt s \sim 2-4$ GeV give us the possibility to study the cross section in the broad energy region. As the result, we have determined the asymptotic behavior of the cross section of $e^+ e^- \to \phi\eta$ in the limit $s \to \infty$, which is in agreement with perturbative QCD prediction. Assuming that the same asymptotic behavior is valid for the other processes under consideration and using low energy experimental data we have predicted the cross sections of these processes at energies $\sqrt s=3.67,~10.6$ GeV. In addition, we have calculated the cross sections of these processes at the same energies within perturbative QCD. Our results are in agreement with available experimental data.Comment: 10 pages, 2 tables, 6 figures; minor changes; article accepted to publication is Phys. Rev.

Non-Hamiltonian generalizations of the dispersionless 2DTL hierarchy

We consider two-component integrable generalizations of the dispersionless 2DTL hierarchy connected with non-Hamiltonian vector fields, similar to the Manakov-Santini hierarchy generalizing the dKP hierarchy. They form a one-parametric family connected by hodograph type transformations. Generating equations and Lax-Sato equations are introduced, a dressing scheme based on the vector nonlinear Riemann problem is formulated. The simplest two-component generalization of the dispersionless 2DTL equation is derived, its differential reduction analogous to the Dunajski interpolating system is presented. A symmetric two-component generalization of the dispersionless elliptic 2DTL equation is also constructed.Comment: 10 pages, the text of the talk at NEEDS 09. Notations clarified, references adde

Current in narrow channels of anisotropic superconductors

We argue that in channels cut out of anisotropic single crystal superconductors and narrow on the scale of London penetration depth, the persistent current must cause the transverse phase difference provided the current does not point in any of the principal crystal directions. The difference is proportional to the current value and depends on the anisotropy parameter, on the current direction relative to the crystal, and on the transverse channel dimension. An experimental set up to measure the transverse phase is proposed.Comment: 3 pages, 1 figur

Comment on "Polarizability of the pion: No conflict between dispersion theory and chiral perturbation theory"

The statement of the authors of the article Phys. Rev. C 77, 065211 (2008) that spurious singularities occur in the dispersion relation approach, where imaginary parts of the amplitudes of the process \gamma\gamma->\pi\pi are saturated by the contributions of meson resonances by using Breit-Wigner expressions, is analyzed. It is shown that there are no any additional singularities in this approach and the disagreement between the predictions of the dispersion relations and the chiral perturbation theory for (\alpha_1-\beta_1)_\pi^{\pm} remains.Comment: 3 pages, final version appeared in Phys. Rev.