Interference and binding effects in decays of possible molecular component of X(3872)

It is pointed out that the internal structure of the narrow resonance X(3872) at the D^0 {\bar D}^{*0} threshold can be studied in some detail by measuring the rate and the spectra in the decays X(3872) \to D^0 {\bar D}^0 \pi^0 and X(3872) \to D^0 {\bar D}^0 \gamma. In particular, if this resonance contains a dominant `molecular' component D {\bar D^*} \pm {\bar D} D^*, this component can be revealed and studied by a distinct pattern of interference between the underlying decays of D^{*0} and {\bar D}^{*0} whose coherence is ensured by fixed (but yet unknown) C parity of the X(3872).Comment: 7 pages, 1 figur

Unitary and analytic model of nucleon EM structure, the puzzle with JLab proton polarization data and new insight into proton charge distribution

The Unitary and analytic model of nucleon electromagnetic structure, describing all existing nucleon form factor data, is briefly reviewed. Then in the framework of this model the problem of inconsistency of older proton electric form factor data in space-like region (obtained from $e^{-}p$ process by the Rosenbluth technique) with recent Jefferson Lab data on the ratio $G_{Ep}(t)/G_{Mp}(t)$ (measured in precise polarization $\overrightarrow{e}^{-}p\to e^{-}\overrightarrow{p}$ experiment) is suggested to be solved in favour of the latter data which, however, unlike older data cause an existence of the form factor zero, i.e. a difraction minimum in $|G_{Ep}(t)|$ around $t=-Q^{2}=-13$GeV$^{2}$. The new behaviour of $G_{Ep}(t)$ with the zero gives modified proton charge distribution with enlarged value of the mean square charge radius.Comment: 9 pages, 11 eps figures. Talk presented at the workshop on Lepton Scattering and the Structure of Hadrons and Nuclei, Erice (Italy), September 200

The onset of e^+e^- -> tau^+ tau^- at threshold revisited

The precise knowledge of the onset of the cross section $\sigma(e^+e^- \to \tau^+\tau^-)$ at the threshold is necessary for improving the accuracy of determination of the $\tau$ mass from the threshold measurements. The QED radiative corrections of relative order $\alpha$ and $\alpha^2$, additional to the well known Coulomb factor, are considered in the threshold region. The correction terms of order $\alpha^2$ are calculated, which contain coefficients enhanced by large parameters. As a result it is argued that the known $O(\alpha)$ corrections provide the accuracy of the description of the cross section close to $10^{-4}$, rather than $10^{-3}$ as claimed in a recent literature. Also analytical expressions are provided for some limiting cases of the corrections, previously calculated numerically.Comment: 16 page

The masses of Dsj∗D_{sj}^\ast(2317) and Dsj∗D_{sj}^\ast(2463) in the MIT bag model

The masses of the $D_{sj}^\ast$(2317)and $D_{sj}^\ast$(2463) were found in the MIT bag model in a reasonable agreement with the experimental values. The spectrum of ${0^\pm,1^\pm}$ for $D$ and $B$ mesons is presented. The equalities between the mass splittings $(1^+ - 1^-)(c\bar{q})\approx (1^+ - 1^-)(c\bar{s})$ and $(0^+ - 0^-)(c\bar{q})\approx (0^+ - 0^-)(c\bar{s})$, where $q=u, d$ are confirmed despite of the fact that $SU(3)_L\times SU(3)_R$ chiral symmetry is broken by the non-zero strange quark mass.Comment: 3 pages, change in the reference

Extra dimensions and invisible decay of orthopositronium

We point out that some models with infinite additional dimension(s) of Randall-Sundrum type predict the disappearance of orthopositronium (o-Ps) into additional dimension(s). The experimental signature of this effect is the o-Ps -> invisible decay of orthopositronium which may occur at a rate within three orders of magnitude of the present experimental upper limit. This result enhances existing motivations for a more sensitive search for this decay mode and suggests additional directions for testing extra dimensions in non accelerator experiments.Comment: 3 pages, to appear in Phys. Rev.