Bounds on gamma from CP violation measurements in B -> pi+ pi- and B -> psi K_S

We study the determination of gamma from CP-violating observables in B -> pi+ pi- and B -> psi K_S. This determination requires theoretical input to one combination of hadronic parameters. We show that a mild assumption about this quantity may allow bounds to be placed on gamma, but we stress the pernicious effects that an eightfold discrete ambiguity has on such an analysis. The bounds are discussed as a function of the direct (C) and interference (S) CP-violating observables obtained from time-dependent B -> pi+ pi- decays, and their behavior in the presence of new physics effects in B-Bbar mixing is studied. (V2: Misprints corrected. Slightly improved discussion.)Comment: 11 pages, RevTex 4, 5 eps figures include

Lepton-Flavour Violation in Ordinary and Supersymmetric Grand Unified Theories

By an explicit calculation we show that in ordinary SU(5) logarithmic divergence in the amplitude of $\mu \to e\gamma$ cancels among diagrams and remaining finite part is suppressed by at least $1/M_{GUT}^2$. In SUSY SU(5), when the effect of flavour changing wave function renormalization is taken into account such logarithmic correction disappears, provided a condition is met among SUSY breaking masses. In SUGRA-inspired SUSY GUT the remaining logarithmic effect is argued not to be taken as a prediction of the theory.Comment: 8 pages, LaTeX209 file, using axodraw.st

Evidence for the formation of two phases during the growth of SrTiO3 on silicon

International audienceEpitaxial SrTiO3 (STO)/Si templates open a unique opportunity for the integration of ferroelectric oxides, such as BaTiO3 on silicon and for the realization of new devices exploiting ferroelectricity. STO itself has been shown as ferroelectric at room temperature when deposited in thin layers on Si, while bulk STO is tetragonal and, thus, ferroelectric below 105 K. Here, we demonstrate the coexistence, at room temperature, of strained cubic and tetragonal phases in thin STO/Si layers. The tetragonal STO phase presents a pronounced tetragonality for thicknesses up to 24 ML. Above this thickness, the strained cubic STO phase starts relaxing while the tetragonal STO phase progressively transits to cubic STO. The origin of the simultaneous formation of these two phases is analyzed and is attributed to oxygen segregation at the early stages of the growth

Genetic assessment of population restorations of the critically endangered Silene hifacensis in the Iberian Peninsula

In order to preserve endangered plant populations and recover their evolutionary potential and ecological behavior, some restoration measures generally involve the reinforcement of the population size in existing natural populations or the reintroduction of new populations. Genetic monitoring of both natural and restored populations can provide an assessment of restoration protocol success in establishing populations that maintain levels of genetic diversity similar to those in natural populations. The highly threatened Spanish species Silene hifacensis (Caryophyllaceae) has only three natural reduced mainland populations in the Iberian Peninsula, following decline and extinction that occurred during the late 20th century. Preterit restoration strategies were essentially based on the implantation of new populations and reinforcement of certain existing populations using transplants mostly cultivated in greenhouses. In the present contribution, levels and patterns of genetic variability within natural and restored populations of Silene hifacensis were assessed using the molecular technique AFLP. Our results pointed out significant genetic diversity differences across the three existing natural populations though their population fragmentation and progressive loss of individuals have not had an impact on the global genetic diversity of this species. For restored populations, their levels of genetic diversity were similar and even higher than in natural populations. As a result, the past restoration protocols were successful in capturing similar and even higher levels of genetic diversity than those observed within natural pools. However, inbreeding processes have been detected for two restored populations. Finally, the main source of plant material for the long-time restored transplants appears to be the natural population of Cova de les Cendres. This study demonstrates, once again, how genetic markers are useful tools to be taken in consideration for endangered plant species conservation plans.Work was supported by the project CONSELLERIATERRITORIO4-06i (Conselleria de Territori i Habitage, Generalitat Valenciana)

Heavy Majorana Neutrinos and Baryogenesis

The scenario of baryogenesis through leptogenesis is reviewed in models involving heavy Majorana neutrinos. The various mechanisms of CP violation occurring in the out-of-equilibrium lepton-number-violating decays of heavy Majorana neutrinos are studied within a resummation approach to unstable-particle mixing. It is explicitly demonstrated how the resummation approach preserves crucial field-theoretic properties such as unitarity and CPT invariance. Predictions of representative scenarios are presented after solving numerically the Boltzmann equations describing the thermodynamic evolution of the Universe. The phenomenological consequences of loop effects of heavy Majorana neutrinos on low-energy observables, such as lepton-flavour and/or lepton-number non-conservation in $\tau$ and $Z$-boson decays and electron electric dipole moment, are discussed.Comment: 48 pages, minor rewording

Supernova Neutrinos and the LSND Evidence for Neutrino Oscillations

The observation of the $\bar{\nu}_e$ energy spectrum from a supernova burst can provide constraints on neutrino oscillations. We derive formulas for adiabatic oscillations of supernova antineutrinos for a variety of 3- and 4-neutrino mixing schemes and mass hierarchies which are consistent with the LSND evidence for $\bar{\nu}_{\mu}\to \bar{\nu}_e$ oscillations. Finally, we explore the constraints on these models and LSND given by the supernova SN1987A $\bar{\nu}_e$'s observed by the Kamiokande-2 and IMB-3 detectors.Comment: 8 pages, 3 figures. Changes with respect to original version: appendix added; minor changes in text, figures, reference

Exploiting the neutronization burst of a galactic supernova

One of the robust features found in simulations of core-collapse supernovae (SNe) is the prompt neutronization burst, i.e. the first $\sim 25$ milliseconds after bounce when the SN emits with very high luminosity mainly $\nu_e$ neutrinos. We examine the dependence of this burst on variations in the input of current SN models and find that recent improvements of the electron capture rates as well as uncertainties in the nuclear equation of state or a variation of the progenitor mass have only little effect on the signature of the neutronization peak in a megaton water Cherenkov detector for different neutrino mixing schemes. We show that exploiting the time-structure of the neutronization peak allows one to identify the case of a normal mass hierarchy and large 13-mixing angle $\theta_{13}$, where the peak is absent. The robustness of the predicted total event number in the neutronization burst makes a measurement of the distance to the SN feasible with a precision of about 5%, even in the likely case that the SN is optically obscured.Comment: 14 pages, 17 eps figures, revtex4 style, minor comments adde

Natural history of Arabidopsis thaliana and oomycete symbioses

Molecular ecology of plant–microbe interactions has immediate significance for filling a gap in knowledge between the laboratory discipline of molecular biology and the largely theoretical discipline of evolutionary ecology. Somewhere in between lies conservation biology, aimed at protection of habitats and the diversity of species housed within them. A seemingly insignificant wildflower called Arabidopsis thaliana has an important contribution to make in this endeavour. It has already transformed botanical research with deepening understanding of molecular processes within the species and across the Plant Kingdom; and has begun to revolutionize plant breeding by providing an invaluable catalogue of gene sequences that can be used to design the most precise molecular markers attainable for marker-assisted selection of valued traits. This review describes how A. thaliana and two of its natural biotrophic parasites could be seminal as a model for exploring the biogeography and molecular ecology of plant–microbe interactions, and specifically, for testing hypotheses proposed from the geographic mosaic theory of co-evolution

Pulsar acceleration by asymmetric emission of sterile neutrinos

A convincing explanation for the observed pulsar large peculiar velocities is still missing. We argue that any viable particle physics solution would most likely involve the resonant production of a non-interacting neutrino $\nu_s$ of mass $m_{\nu_s}\sim 20$--50 keV. We propose a model where anisotropic magnetic field configurations strongly bias the resonant spin flavour precession of tau antineutrinos into $\nu_s$. For internal magnetic fields B_{int} \gsim 10^{15} G a $\bar\nu_\tau$-$\nu_s$ transition magnetic moment of the order of $10^{-12}$ Bohr magnetons is required. The asymmetric emission of $\nu_s$ from the core can produce sizeable natal kicks and account for recoil velocities of several hundred kilometers per second.Comment: 14 pages, AASTEX, 2 figures (uses epsfig). Minor typos corrected. Added acknowledgments to the funding institutes BID and Colciencia

Supernova prompt neutronization neutrinos and neutrino magnetic moments

It is shown that the combined action of spin-flavor conversions of supernova neutrinos due to the interactions of their Majorana-type transition magnetic moments with the supernova magnetic fields and flavor conversions due to the mass mixing can lead to the transformation of \nu_e born in the neutronization process into their antiparticles \bar{\nu}_e. Such an effect would have a clear experimental signature and its observation would be a smoking gun evidence for the neutrino transition magnetic moments. It would also signify the leptonic mixing parameter |U_{e3}| in excess of 10^{-2}.Comment: LaTex, 25 pages, 3 figures. v4: Discussion section expanded, references added. Matches the published versio