On the Application of Gluon to Heavy Quarkonium Fragmentation Functions

We analyze the uncertainties induced by different definitions of the momentum fraction $z$ in the application of gluon to heavy quarkonium fragmentation function. We numerically calculate the initial $g \to J / \psi$ fragmentation functions by using the non-covariant definitions of $z$ with finite gluon momentum and find that these fragmentation functions have strong dependence on the gluon momentum $\vec{k}$. As $| \vec{k} | \to \infty$, these fragmentation functions approach to the fragmentation function in the light-cone definition. Our numerical results show that large uncertainties remains while the non-covariant definitions of $z$ are employed in the application of the fragmentation functions. We present for the first time the polarized gluon to $J/\psi$ fragmentation functions, which are fitted by the scheme exploited in this work.Comment: 11 pages, 7 figures;added reference for sec.

Universal decay law in charged-particle emission and exotic cluster radioactivity

A linear universal decay formula is presented starting from the microscopic mechanism of the charged-particle emission. It relates the half-lives of monopole radioactive decays with the $Q$-values of the outgoing particles as well as the masses and charges of the nuclei involved in the decay. This relation is found to be a generalization of the Geiger-Nuttall law in $\alpha$ radioactivity and explains well all known cluster decays. Predictions on the most likely emissions of various clusters are presented.Comment: 2 figure

Black hole production at lepton colliders

Production of black holes has been discussed in a variety of extensions of the Standard Model, and related bounds have been established from data taken at the Large Hadron Collider. We show that, if the Higgs particle has a fully gravitational content via the equivalence principle, enhanced cross-sections of black holes at colliders should be expected within the Standard Model itself. The case of black hole production by precision measurements at electron colliders is discussed. The Coulomb repulsion strongly suppresses the related cross-section with respect to the one based on the hoop conjecture, making the possible production of black holes still unfeasible with current beam technology. At the same time, this suggests the reanalysis of the bounds, based on the hoop conjecture, already determined in hadronic collisions for extra-dimensional models.Comment: 10 pages, 6 figure

Local Dielectric Measurements of BaTiO3-CoFe2O4 Nano-composites Through Microwave Microscopy

We report on linear and non-linear dielectric property measurements of BaTiO3 - CoFe2O4 (BTO-CFO) ferroelectro-magnetic nano-composites and pure BaTiO3 and CoFe2O4 samples with Scanning Near Field Microwave Microscopy. The permittivity scanning image with spatial resolution on the micro-meter scale shows that the nano-composites have very uniform quality with an effective dielectric constant \epsilon_r = 140 +/- 6.4 at 3.8 GHz and room temperature. The temperature dependence of dielectric permittivity shows that the Curie temperature of pure BTO was shifted by the clamping effect of the MgO substrate, whereas the Curie temperature shift of the BTO ferroelectric phase in BTO-CFO composites is less pronounced, and if it exists at all, would be mainly caused by the CFO. Non-linear dielectric measurements of BTO-CFO show good ferroelectric properties from BTO.Comment: 6 pages, 6 figures, to be published in the Journal of Materials Researc

Calculation of the spectrum of 12Li by using the multistep shell model method in the complex energy plane

The unbound nucleus $^{12}$Li is evaluated by using the multistep shell model in the complex energy plane assuming that the spectrum is determined by the motion of three neutrons outside the $^9$Li core. It is found that the ground state of this system consists of an antibound $1/2^+$ state and that only this and a $1/2^-$ and a $5/2^+$ excited states are physically meaningful resonances.Comment: 9 pages, 5 tables, 7 figures, printer-friendly versio

Dynamical Axion Field in Topological Magnetic Insulators

Axions are very light, very weakly interacting particles postulated more than 30 years ago in the context of the Standard Model of particle physics. Their existence could explain the missing dark matter of the universe. However, despite intensive searches, they have yet to be detected. In this work, we show that magnetic fluctuations of topological insulators couple to the electromagnetic fields exactly like the axions, and propose several experiments to detect this dynamical axion field. In particular, we show that the axion coupling enables a nonlinear modulation of the electromagnetic field, leading to attenuated total reflection. We propose a novel optical modulators device based on this principle.Comment: 5 pages, 3 figure