Ratios of heavy hadron semileptonic decay rates

Ratios of charmed meson and baryon semileptonic decay rates appear to be satisfactorily described by considering only the lowest-lying (S-wave) hadronic final states and assuming the kinematic factor describing phase space suppression is the same as that for free quarks. For example, the rate for $D_s$ semileptonic decay is known to be $(17.0 \pm 5.3)$ lower than those for $D^0$ or $D^+$, and the model accounts for this difference. When applied to hadrons containing $b$ quarks, this method implies that the $B_s$ semileptonic decay rate is about 1% higher than that of the nonstrange $B$ mesons. This small difference thus suggests surprisingly good local quark-hadron duality for $B$ semileptonic decays, complementing the expectation based on inclusive quark-hadron duality that these differences in rates should not exceed a few tenths of a percent. For $\Lambda_b$ semileptonic decay, however, the inclusive rate is predicted to be about 13% greater than that of the nonstrange $B$ mesons. This value, representing a considerable departure from a calculation using a heavy quark expansion, is close to the corresponding experimental ratio $\Gamma(\Lambda_b)/ \bar \Gamma(B) = 1.13 \pm 0.03$ of total decay rates.Comment: 12 pages, no figures. References adde

The Attractive Universe Theory (AUT): A New approach to electricity and gravity amalgamation.

Attractive Universe Theory presents an approach to electric and gravitational forces as the display of a unique fundamental attraction. One of the main predictions is that a number of physical processes might demonstrate anisotropy. It is supposed, in particular, that gravitational constant (big G) can depend on how the gravitationally interacting masses are oriented with respect to the system of fixed stars. It is proposed that degree of CP symmetry also could depend on the orientation to the fixed stars. Another prediction is that the gravitational constant in a given location depends on the state of surrounding matter of the universe, and thus depends on location and time. This in turn should lead to a change in the method of calculating the age of the universe as well as to the conclusion that there is no such thing as unstoppable gravitation collapse

The Contribution of Bc Mesons to the Search for B->tau nu Decays at LEP

We study the contribution of B_c mesons to the search for B->tau nu decays. We find that at LEP the contributions from B_u and B_c mesons can be comparable. This observation can have a relevant impact on the extraction of constraints on new physics (such as charged-Higgs contributions) from current LEP limits on B->tau nu final states. Inclusion of the B_c contribution can reduce the current L3 limit on Tan(beta)/M_H from 0.38/GeV (90%CL) down to 0.27/GeV (90%CL).Comment: 8 pages, Latex, epsfig, 1 figur

Discovering hidden sectors with mono-photon Z' searches

In many theories of physics beyond the Standard Model, from extra dimensions to Hidden Valleys and models of dark matter, Z' bosons mediate between Standard Model particles and hidden sector states. We study the feasibility of observing such hidden states through an invisibly decaying Z' at the LHC. We focus on the process pp -> \gamma Z' -> \gamma X X*, where X is any neutral, (quasi-) stable particle, whether a Standard Model (SM) neutrino or a new state. This complements a previous study using pp -> Z Z' -> l+ l- X X*. Only the Z' mass and two effective charges are needed to describe this process. If the Z' decays invisibly only to Standard Model neutrinos, then these charges are predicted by observation of the Z' through the Drell-Yan process, allowing discrimination between Z' decays to SM neutrinos and invisible decays to new states. We carefully discuss all backgrounds and systematic errors that affect this search. We find that hidden sector decays of a 1 TeV Z' can be observed at 5 sigma significance with 50 fb^{-1} at the LHC. Observation of a 1.5 TeV state requires super-LHC statistics of 1 ab^{-1}. Control of the systematic errors, in particular the parton distribution function uncertainty of the dominant Z \gamma background, is crucial to maximize the LHC searchComment: 13 pages, 4 figure

Elastic scattering theory and transport in graphene

Electron properties of graphene are described in terms of Dirac fermions. Here we thoroughly outline the elastic scattering theory for the two-dimensional massive Dirac fermions in the presence of an axially symmetric potential. While the massless limit is relevant for pristine graphene, keeping finite mass allows for generalizations onto situations with broken symmetry between the two sublattices, and provides a link to the scattering theory of electrons in a parabolic band. We demonstrate that the Dirac theory requires short-distance regularization for potentials which are more singular than 1/r. The formalism is then applied to scattering off a smooth short-ranged potential. Next we consider the Coulomb potential scattering, where the Dirac theory is consistent for a point scatterer only for the effective impurity strength below 1/2. From the scattering phase shifts we obtain the exact Coulomb transport cross-section in terms of the impurity strength. The results are relevant for transport in graphene in the presence of impurities that do not induce scattering between the Dirac points in the Brillouin zone.Comment: 17 pages, 4 figures. Published versio

The explanation of unexpected temperature dependence of the muon catalysis in solid deuterium

It is shown that due to the smallness of the inelastic cross-section of the $d\mu$-atoms scattering in the crystal lattice at sufficiently low temperatures the $dd\mu$-mesomolecules formation from the upper state of the hyperfine structure $d\mu (F=3/2)$ starts earlier than the mesoatoms thermolization. It explains an approximate constancy of the $dd\mu$-mesomolecule formation rate in solid deuterium.Comment: 6 pages, 2 jpeg-figure

Gravitational Waves in Relativistic Theory of Gravitation

It is shown that, in the framework of Relativistic Theory of Gravitation with massive graviton, gravitational waves, due to the causality condition, do not bear negative energy flows.Comment: 4 page

Bc spectroscopy in a quantum-chromodynamic potential model

We have investigated $B_c$ spectroscopy with the use of a quantum-chromodynamic potential model which was recently used by us for the light-heavy quarkonia. We give our predictions for the energy levels and the $E$1 transition widths. We also find, rather surprisingly, that although $B_c$ is not a light-heavy system, the heavy quark effective theory with the inclusion of the $m_b^{-1}$ and $m_b^{-1}\ln m_b$ corrections is as successful for $B_c$ as it is for $B$ and $B_s$.Comment: 10 page ReVTeX pape

Quadrupolar contact terms and Hyperfine Structure

In the interaction of two electric quadrupoles, there is at short distances a contact term proportional to the second derivative of a delta function. This contact term contributes to the hyperfine splitting of bound states of two particles with spin one or higher-for example the bound states of Omega minus and a nucleus of spin one.The contact hyperfine splitting occurs in states with orbital angular momentum one(p-wave), in contrast to the Fermi contact interaction which is in s-states.We find that these contact splittings will be observable with Omega minus atoms and help measure the quadrupole moment and charge radius of the hyperon.Comment: 19 pages; two sentences deleted from first versio

Light Cone Sum Rules for gamma* N -> Delta Transition Form Factors

A theoretical framework is suggested for the calculation of gamma* N -> Delta transition form factors using the light-cone sum rule approach. Leading-order sum rules are derived and compared with the existing experimental data. We find that the transition form factors in a several GeV region are dominated by the ``soft'' contributions that can be thought of as overlap integrals of the valence components of the hadron wave functions. The ``minus'' components of the quark fields contribute significantly to the result, which can be reinterpreted as large contributions of the quark orbital angular momentumComment: 38 pages, 10 figures; some typos fixed and references added, to appear in Phys. Rev.