Measurement of the charge asymmetry in semileptonic B-s(0) decays

We have performed the first direct measurement of the time-integrated flavor untagged charge asymmetry in semileptonic B-s(0) decays A(SL)(s,unt) by comparing the decay rate of B-s(0) -> mu(+) D-s(-) nu X, where D-s(-) -> phi pi(-) and phi -> K+K-, with the charge-conjugate (B) over bar (0)(s) decay rate. This sample was selected from 1: 3 fb(-1) of data collected by the D0 experiment in run II of the Fermilab Tevatron collider. We obtain A(SL)(s,unt) = [1.23 +/- 0.97(stat) +/- 0.17(syst)] x 10(-2). Assuming that Delta m(s)/(Gamma) over bar (s) >> 1, this result can be translated into a measurement of the CP-violating phase in B-s(0) mixing: Delta Gamma(s)/Delta m(s) tan phi(s) = [2.45 +/- 1.93(stat) +/- 0.35(syst)] x 10(-2).

Miscibility in a degenerate fermionic mixture induced by linear coupling

We consider a one-dimensional mean-field-hydrodynamic model of a two-component degenerate Fermi gas in an external trap, each component representing a spin state of the same atom. We demonstrate that the interconversion between them (linear coupling), imposed by a resonant electromagnetic wave, transforms the immiscible binary gas into a miscible state, if the coupling constant, kappa, exceeds a critical value, kappa(cr). The effect is predicted in a variational approximation, and confirmed by numerical solutions. Unlike the recently studied model of a binary Bose-Einsten condensate with the linear coupling, the components in the immiscible phase of the binary fermion mixture never fill two separated domains with a wall between them, but rather form antilocked (pi-phase-shifted) density waves. Another difference from the bosonic mixture is spontaneous breaking of symmetry between the two components in terms of the numbers of atoms in them, N(1) and N(2). The latter effect is characterized by the parameter nu equivalent to(N(1)-N(2))/(N(1)+N(2)) (only N(1)+N(2) is a conserved quantity), the onset of miscibility at kappa >=kappa(cr) meaning a transition to nu equivalent to 0. At kappa

Conserved currents in gravitational models with quasi-invariant Lagrangians: Application to teleparallel gravity

Conservation laws in gravitational theories with diffeomorphism and local Lorentz symmetry are studied. Main attention is paid to the construction of conserved currents and charges associated with an arbitrary vector field that generates a diffeomorphism on the spacetime. We further generalize previous results for the case of gravitational models described by quasi-invariant Lagrangians, that is, Lagrangians that change by a total derivative under the action of the local Lorentz group. The general formalism is then applied to the teleparallel models, for which the energy and the angular momentum of a Kerr black hole are calculated. The subsequent analysis of the results obtained demonstrates the importance of the choice of the frame.

Lifetime difference and CP-violating phase in the B-s(0) system

From an analysis of the decay B-s(0)-> J/psi phi, we obtain the width difference between the light and heavy mass eigenstates Delta Gamma equivalent to(Gamma(L)-Gamma(H))=0.17 +/- 0.09(stat)+/- 0.02(syst) ps(-1) and the CP-violating phase phi(s)=-0.79 +/- 0.56(stat)(-0.01)(+0.14)(syst). Under the hypothesis of no CP violation (phi(s)equivalent to 0), we obtain 1/Gamma=tau/(B-s(0))=1.52 +/- 0.08(stat)(-0.03)(+0.01)(syst) ps and Delta Gamma=0.12(-0.10)(+0.08)(stat)+/- 0.02(syst) ps(-1). The data sample corresponds to an integrated luminosity of about 1.1 fb(-1) accumulated with the D0 detector at the Fermilab Tevatron collider. This is the first direct measurement of the CP-violating mixing phase in the B-s(0) system.

Search for techniparticles in e plus jets events at D0

We search for the technicolor process p(p) over bar ->rho(T)/omega(T)-> W pi(T) in events containing one electron and two jets, in data corresponding to an integrated luminosity of 390 pb(-1), recorded by the D0 experiment at the Fermilab Tevatron. Technicolor predicts that technipions pi(T) decay dominantly into b(b) over bar, b(c) over bar, or (b) over barc, depending on their charge. In these events b and c quarks are identified by their secondary decay vertices within jets. Two analysis methods based on topological variables are presented. Since no excess above the standard model prediction was found, the result is presented as an exclusion in the pi(T) vs rho(T) mass plane for a given set of model parameters.

Search for pair production of doubly charged Higgs bosons in the H(++)H(--)->mu(+)mu(+)mu(-)mu(-) final state

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Superfluid Bose-Fermi mixture from weak coupling to unitarity

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

Search for Anomalous Wtb Couplings in Single Top Quark Production

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for Resonant Diphoton Production with the D0 Detector

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Relative rates of B meson decays into psi(2S) and J/psi mesons

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for Dark Photons from Supersymmetric Hidden Valleys

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

Stabilization of the electroweak scale in 3-3-1 models

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Signals for new spin-1 resonances in electroweak gauge boson pair production at the LHC

The mechanism of electroweak symmetry breaking ( EWSB) will be directly scrutinized soon at the CERN Large Hadron Collider. We analyze the LHC potential to look for new vector bosons associated with the EWSB sector, presenting a possible model independent approach to search for these new spin-1 resonances. We show that the analyses of the processes pp -> l(+)l(1-)E(T), l +/- jjE(T), l(1 +/-)l(+)l(-)E(T), l(+/-)jjE(T), and l(+)l(-) jj (with l, l' = e or mu and j = jet) have a large reach at the LHC and can lead to the discovery or exclusion of many EWSB scenarios such as Higgsless models.

Combination of Tevatron Searches for the Standard Model Higgs Boson in the W+W- Decay Mode

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Search for the Standard Model Higgs Boson in the ZH -> v(v)over-barb(b)over-bar Channel in 5.2 fb(-1) of p(p)over-bar Collisions at root s=1.96 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)