Supernova explosions, 511 keV photons, gamma ray bursts and mirror matter

There are three astroparticle physics puzzles which fire the imagination: the origin of the ``Great Positron Producer'' in the galactic bulge, the nature of the gamma-ray bursts central engine and the mechanism of supernova explosions. We show that the mirror matter model has the potential to solve all three of these puzzles in one beautifully simple strike.Comment: about 9 page

Semileptonic Bc−→D∗0ℓνB_{c}^{-}\to D^{*0}\ell\nu transition in three--point QCD sum rules and HQET with gluon condensate corrections

Taking into account the gluon condensate contributions, the form factors of the semileptonic $B_c^- \to D^{*0}\ell\nu$ transition with $l=\tau, e$ are calculated in the framework of the three point QCD sum rules. The heavy quark effective theory limit of the form factors are also computed. The relevant total decay width as well as the branching ratio are evaluated and compared with the predictions of the other non-perturbative approaches.Comment: 27 Pages, 4 Figures and 4 Table

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

Analysis of the rare semileptonic B_c \rar P(D,D_s) l^{+}l^{-}/\nu\bar{\nu} decays within QCD sum rules

Considering the gluon condensate corrections, the form factors relevant to the semileptonic rare B_c \rar D,D_s(J^{P}=0^{-}) l^{+}l^{-} with $l=\tau,\mu,e$ and B_c \rar D,D_s(J^{P}=0^{-})\nu\bar{\nu} transitions are calculated in the framework of the three point QCD sum rules. The heavy quark effective theory limit of the form factors are computed. The branching fraction of these decays are also evaluated and compared with the predictions of the relativistic constituent quark model. Analyzing of such type transitions could give useful information about the strong interactions inside the pseudoscalar $D_{s}$ meson and its structure.Comment: 32 Pages, 8 Figures and 6 Table

Two-particle decays of B_c meson into charmonium states

The factorization of hard and soft contributions into the hadronic decays of B_c meson at large recoils is explored in order to evaluate the decay rates into the S, P and D-wave charmonia associated with rho and pi. The constraints of approach applicability and uncertainties of numerical estimates are discussed. The mode with the J/psi in the final state is evaluated taking into account the cascade radiative electromagnetic decays of excited P-wave states, that enlarges the branching ratio by 20-25%.Comment: 13 pages, LaTeX axodraw-style, 1 figure, 2 table

Pertussis infection in fully vaccinated children in day-care centers, Israel.

We tested 46 fully vaccinated children in two day-care centers in Israel who were exposed to a fatal case of pertussis infection. Only two of five children who tested positive for Bordetella pertussis met the World Health Organization's case definition for pertussis. Vaccinated children may be asymptomatic reservoirs for infection

A Review of Rare Pion and Muon Decays

After a decade of no measurements of pion and muon rare decays, PIBETA, a new experimental program is producing its first results. We report on a new experimental study of the pion beta decay, Pi(+) -> Pi(0) e(+) Nu, the Pi(e2 gamma) radiative decay, Pi(+) -> e(+) Nu Gamma, and muon radiative decay, Mu -> e Nu Gamma. The new results represent four- to six-fold improvements in precision over the previous measurements. Excellent agreement with Standard Model predictions is observed in all channels except for one kinematic region of the Pi(e2 gamma) radiative decay involving energetic photons and lower-energy positrons.Comment: 10 pages, 6 figures, 2 tables, invited talk presented at MESON 2004, 8th Int'l. Workshop on Meson Production, Properties and Interaction, Krakow, Poland 4-8 June 200

Graviton mass and total relative density of mass Omega_tot in Universe

It is noticed that the total relative density of mass in the Universe Omega_tot should exceed 1, i.e. Omega_tot=1+f^2/6 according to the field relativistic theory of gravity (RTG), which is free of the cosmological singularity and which provides the Euclidean character for the 3-dimensional space. Here f is the ratio of the graviton mass m_g to the contemporary value of the ``Hubble mass'' m^0_H=\hbar H_0/c^2\simeq 3,8\cdot 10^{-66}h(g) (h=0,71\pm0,07). Applying results of the experimental data processing presented in [1] an upper limit for the graviton mass is established as m_g\leq 3,2\cdot 10^{-66}g at the 95% confidence level.Comment: 8 pages, latex fil

A semiclassical model for orientation effects in electron transfer reactions

An approximate solution to the single-particle Schrödinger equation with an oblate spheroidal potential well of finite depth is presented. The electronic matrix element HBA for thermal electron transfer is calculated using these wave functions, and is compared with values of HBA obtained using the exact solution of the same Schrödinger equation. The present method yields accurate results for HBA, within the oblate spheroidal potential well model, and is useful for examining the orientational effects of the two centers on the rate of electron transfer