Stochastic variational approach applied to 2, 3 and 4 alpha particles

A stochastic variational method is applied to calculate the binding energies and root-mean-square radii of 2, 3 and 4 alpha particles using an S-wave Ali-Bodmer potential. The results agree with other calculations. We discuss the application of the present method to study the universality in weakly-bound three and four-body systems in the context of ultracold atomic traps.

Pseudoclassical mechanics for the spin-0 and -1 particles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Thermodynamics of quasi-particles at finite chemical potential

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Search for Charged Massive Long-Lived Particles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for heavy stable charged particles in pp collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for new physics with jets and missing transverse momentum in pp collisions at root s=7 TeV

A search for new physics is presented based on an event signature of at least three jets accompanied by large missing transverse momentum, using a data sample corresponding to an integrated luminosity of 36 pb(-1) collected in proton-proton collisions at root s = 7 TeV with the CMS detector at the LHC. No excess of events is observed above the expected standard model backgrounds, which are all estimated from the data. Exclusion limits are presented for the constrained minimal supersymmetric extension of the standard model. Cross section limits are also presented using simplified models with new particles decaying to an undetected particle and one or two jets.

Measurement of jet fragmentation into charged particles in pp and PbPb collisions at root s(NN)=2.76 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Scaling invariance for the escape of particles from a periodically corrugated waveguide

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Recurrence of particles in static and time varying oval billiards

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Scaling investigation for the dynamics of charged particles in an electric field accelerator

Some dynamical properties of an ensemble of trajectories of individual (non-interacting) classical particles of mass m and charge q interacting with a time-dependent electric field and suffering the action of a constant magnetic field are studied. Depending on both the amplitude of oscillation of the electric field and the intensity of the magnetic field, the phase space of the model can either exhibit: (i) regular behavior or (ii) a mixed structure, with periodic islands of regular motion, chaotic seas characterized by positive Lyapunov exponents, and invariant Kolmogorov-Arnold-Moser curves preventing the particle to reach unbounded energy. We define an escape window in the chaotic sea and study the transport properties for chaotic orbits along the phase space by the use of scaling formalism. Our results show that the escape distribution and the survival probability obey homogeneous functions characterized by critical exponents and present universal behavior under appropriate scaling transformations. We show the survival probability decays exponentially for small iterations changing to a slower power law decay for large time, therefore, characterizing clearly the effects of stickiness of the islands and invariant tori. For the range of parameters used, our results show that the crossover from fast to slow decay obeys a power law and the behavior of survival orbits is scaling invariant. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772997]

Elementary particles under the lens of the black holes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Evidence of hetero-epitaxial growth of Pb(Mg1/3Nb2/3)O-3 on the BaTiO3 seed particles of a citrate solution

Citrate solution was employed in preparing Pb(Mg1/3Nb1/3)O-3 (PMN) powder from polymeric precursors. BaTiO3 particles of 600 nm average size were used as seed for growing PMN. X-ray diffraction (XRD) indicated the presence of both, pyrochlore Pb6Nb6MgO22 (P6N) and perovskite phases. Transmission electron microscopy (TEM) observations indicated that only the PMN phase has hetero-epitaxially grown on the BaTiO3 seed particles. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Structural and magnetic transformation of monodispersed iron oxide particles in a reducing atmosphere

Uniform metal iron ellipsoidal particles of around 200 nm in length were obtained by reduction and passivation of alumina-coated alpha-Fe2O3 (hematite) particles under different conditions of temperature and hydrogen flow rate. The monodispersed hematite particles were prepared by the controlled hydrolysis of ferric sulfate and further coated with a homogeneous thin layer of Al2O3 by careful selection of the experimental conditions, mainly pH and aluminum salt concentration. The reduction mechanism of alpha-Fe2O3 into alpha-Fe was followed by x-ray and electron diffraction, and also by the measurements of the irreversible magnetic susceptibility. The transformation was found to be topotactic with the [001] direction of hematite particles, which lies along the long axis of the particles, becoming the [111] direction of magnetite and finally the [111] direction of metal iron. Temperature and hydrogen flow rate during the reduction have been found to be important parameters, which determine not only the degree of reduction but also the crystallite size of the final particles. Magnetic characterization of the samples shows that the only parameters affected by the crystallite size are the saturation magnetization and magnetic time-dependence effect, i.e., activation volume. (C) 2002 American Institute of Physics.

MANY-BODY PROBLEMS WITH COMPOSITE-PARTICLES AND Q-HEISENBERG ALGEBRAS

We propose to employ deformed commutation relations to treat many-body problems of composite particles. The deformation parameter is interpreted as a measure of the effects of the statistics of the internal degrees of freedom of the composite particles. A simple application of the method is made for the case of a gas of composite bosons.

Methods to estimate the number of surface nucleation sites on glass particles

Based on the Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory, we propose two new models to describe the crystallisation kinetics of glass particles and use them to determine the density of nucleation sites, N(s), on glass powders. We tested these models with sintered compacts of diopside glass particles using sinter-crystallisation treatments at 825 degrees C (T(g)similar to 727 degrees C), that covered from null to almost 100% crystallised volume time fraction. We measured and compared the evolution of the crystallised volume fractions by optical microscopy and x-ray diffraction. Then we fit our expressions to experimental data using Ns and R (the average particle radius) as adjustable parameters. For comparison, we also fit to our data existing expressions that describe the crystallised volume fraction in glass powders. We demonstrate that all the methods allow one to estimate N(s) with reasonable accuracy. For our ground and water washed diopside glass powder, N(s) is between 10(10)-10(11) sites.m(-2). The reasonable agreement between experimental and adjusted R confirms the consistency of all five models tested. However, one of our equations does not require taking into account the change of crystallisation mode from 3-dimensional to 1-dimensional, and this is advantageous.