Quenching of para-H-2 with an ultracold antihydrogen atom (H)over-bar(1s)

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Stringent limits on top-quark compositeness from t(t)over-bar production at the Tevatron and the LHC

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

Some Comments Regarding the Synthetic (X)over-bar Chart

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

The steady-state behavior of the synthetic and side-sensitive synthetic double sampling (X)over-bar charts

The steady-state average run length is used to measure the performance of the recently proposed synthetic double sampling (X) over bar chart (synthetic DS chart). The overall performance of the DS X chart in signaling process mean shifts of different magnitudes does not improve when it is integrated with the conforming run length chart, except when the integrated charts are designed to offer very high protection against false alarms, and the use of large samples is prohibitive. The synthetic chart signals when a second point falls beyond the control limits, no matter whether one of them falls above the centerline and the other falls below it; with the side-sensitive feature, the synthetic chart does not signal when they fall on opposite sides of the centerline. We also investigated the steady-state average run length of the side-sensitive synthetic DS X chart. With the side-sensitive feature, the overall performance of the synthetic DS X chart improves, but not enough to outperform the non-synthetic DS X chart. Copyright (C) 2014 John Wiley &Sons, Ltd.

Bell inequalities for K-0(K)over-bar(0) pairs from Phi-resonance decays

We analyze the premises of recent propositions to test local realism via the Bell inequalities using neutral kaons from φ resonance decays as entangled Einstein-Podolsky-Rosen pairs. We pay special attention to the derivation of the Bell inequalities, or related expressions, for unstable and oscillating kaon quasispin states and to the possibility of the actual identification of these states through their associated decay modes. We discuss an indirect method to extract probabilities to find these states by combining experimental information with theoretical input. However, we still find inconsistencies in previous derivations of the Bell inequalities. We show that the identification of the quasispin states via their associated decay mode does not allow the free choice to perform different tests on them, a property which is crucial to establish the validity of any Bell inequality in the context of local realism. In view of this we propose a different kind of Bell inequality in which the free choice or adjustability of the experimental setup is guaranteed. We also show that the proposed inequalities are violated by quantum mechanics. ©1999 The American Physical Society.

Influence of a dynamical gluon mass in the pp and (p)over-bar-p forward scattering

We compute the tree level cross section for gluon-gluon elastic scattering taking into account a dynamical gluon mass, and show that this mass scale is a natural regulator for this subprocess cross section. Using an eikonal approach in order to examine the relationship between this gluon-gluon scattering and the elastic pp and (p) over barp channels, we found that the dynamical gluon mass is of the same order of magnitude as the ad hoc infrared mass scale m(0) underlying eikonalized QCD-inspired models. We argue that this correspondence is not an accidental result, and that this dynamical scale indeed represents the onset of nonperturbative contributions to the elastic hadron-hadron scattering. We apply the eikonal model with a dynamical infrared mass scale to obtain predictions for sigma(tot)(pp,(p) over barp), rho(pp,(p) over barp), slope B-pp,B-(p) over barp, and differential elastic scattering cross section d sigma((p) over barp)/dt at Tevatron and CERN-LHC energies.

Search for a nonstandard Higgs boson in diphoton events at p(p)over-bar collisions

We estimate the attainable limits on the coupling of a nonstandard Higgs boson to two photons taking into account the data collected by the Fermilab collaborations on diphoton events. We based our analysis on a general set of dimension-6 effective operators that give rise to anomalous couplings in the bosonic sector of the standard model. If the coefficients of all blind operators have the same magnitude, indirect bounds on the anomalous triple vector-boson couplings can also be inferred, provided there is no large cancellatton in the Higgs-gamma-gamma coupling.

Future e(+)e(-) colliders' sensitivity to Hb(b)over-bar coupling and CP violation

A complete analysis of the sensitivity to new Hbb̄ couplings from the process e+e- → bb̄vv̄ at the next generation of linear colliders was performed. These new couplings were predicted by many extensions of the Standard Model. The results are comparable to the study performed previously where a global fit analysis for L=500 fb-1 and √s=500 GeV resulted in a relative accuracy of 2.2% in the gHbb Yukawa coupling.

Anomalous Higgs boson contribution to e(+)e(-)->b(b)over-bar gamma at CERN LEP 2

We study the effect of anomalous Hγγ and HZγ couplings, described by a general effective Lagrangian, on the process e+e-→bb̄γ at CERN LEP 2 energies. We include the relevant irreducible standard model background to this process, and from the photon energy spectrum, we determine the reach of LEP 2 to unravel the anomalous couplings by analyzing the significance of the signal for a Higgs boson with a mass up to 150 GeV.

Medium effects in the pion-pole mechanism [gamma gamma ->pi(0)->nu(R)(nu)over-bar(L)(nu(L)(nu)over-bar(R))] of neutron star cooling

Nuclear medium effects in the neutrino cooling of neutron stars through the reaction channel γγ→π0 →ν Rν̄L(νLν̄R) are incorporated. Throughout the paper we discuss different possibilities of right-handed neutrinos, massive left-handed neutrinos, and standard massless left-handed neutrinos (reaction is then allowed only with medium modified vertices). It is demonstrated that multiparticle effects suppress the rate of this reaction channel in the dense hadron matter by 6-7 orders of magnitude that does not allow to decrease existing experimental upper limit on the corresponding π0νν̄ coupling. Other possibilities of the manifestation of the given reaction channel in different physical situations, e.g., in the quark color superconducting cores of the most massive neutron stars, are also discussed. We demonstrate that in the color-flavor-locked superconducting phase for temperatures T≲ 0.1-10 MeV (depending on the effective pion mass and the decay width) the process is feasibly the most efficient neutrino cooling process, although the absolute value of the reaction rate is rather small.

Search for a multi-Higgs-boson cascade in W(+)W(-)b(b)over-bar events with the ATLAS detector in pp collisions at root s=8 TeV

A search is presented for new particles in an extension to the Standard Model that includes a heavy Higgs boson (H-0), an intermediate charged Higgs-boson pair (H-+/-), and a light Higgs boson (h(0)). The analysis searches for events involving the production of a single heavy neutral Higgs boson which decays to the charged Higgs boson and a W boson, where the charged Higgs boson subsequently decays into a W boson and the lightest neutral Higgs boson decaying to a bottom-antibottom-quark pair. Such a cascade results in a W-boson pair and a bottom-antibottom-quark pair in the final state. Events with exactly one lepton, missing transverse momentum, and at least four jets are selected from a data sample corresponding to an integrated luminosity of 20.3 fb(-1), collected by the ATLAS detector in proton-proton collisions at root s = 8 TeV at the LHC. The data are found to be consistent with Standard Model predictions, and 95% confidence-level upper limits are set on the product of cross section and branching ratio. These limits range from 0.065 to 43 pb as a function of H-0 and H-+/- masses, with m(h)o fixed at 125 GeV.