Symmetry-preserving contact interaction model for heavy-light mesons

We use a symmetry-preserving regularization method of ultraviolet divergences in a vector-vector contact interac- tion model for low-energy QCD. The contact interaction is a representation of nonperturbative kernels used Dyson-Schwinger and Bethe-Salpeter equations. The regularization method is based on a subtraction scheme that avoids standard steps in the evaluation of divergent integrals that invariably lead to symmetry violation. Aiming at the study of heavy-light mesons, we have implemented the method to the pseudoscalar pion and Kaon mesons. We have solved the Dyson-Schwinger equation for the u, d and s quark propagators, and obtained the bound-state Bethe-Salpeter amplitudes in a way that the Ward-Green-Takahashi identities reflecting global symmetries of the model are satisfied for arbitrary routing of the momenta running in loop integrals

The Precision Determination of Invisible-Particle Masses at the LHC

We develop techniques to determine the mass scale of invisible particles pair-produced at hadron colliders. We employ the constrained mass variable m_2C, which provides an event-by-event lower-bound to the mass scale given a mass difference. We complement this variable with a new variable m_2C,UB which provides an additional upper bound to the mass scale, and demonstrate its utility with a realistic case study of a supersymmetry model. These variables together effectively quantify the `kink' in the function Max m_T2 which has been proposed as a mass-determination technique for collider-produced dark matter. An important advantage of the m_2C method is that it does not rely simply on the position at the endpoint, but it uses the additional information contained in events which lie far from the endpoint. We found the mass by comparing the HERWIG generated m_2C distribution to ideal distributions for different masses. We find that for the case studied, with 100 fb^-1 of integrated luminosity (about 400 signal events), the invisible particle's mass can be measured to a precision of 4.1 GeV. We conclude that this technique's precision and accuracy is as good as, if not better than, the best known techniques for invisible-particle mass-determination at hadron colliders.Comment: 20 pages, 11 figures, minor correction

Damages caused by cotton rat, Sigmodon hispidus zanjonensis, on sugar cane in San Pedrosula, Honduras

Technical assistance was given to Compañía Azucarera Hondureña, S.A. (Agro-Industrial Co.), Honduras, Central America, to determine if a campaign against noxious rodents to agriculture crops was needed. Several trappings were carried out at different places using snap traps to determine the population structure of rodents associated with the crop, and live traps to determine the index or density of the Sigmodon hispidus rat population, which was identified as being responsible for the damage to sugarcane. Results were 43.24% adult males, 14.86% young males, 31.41% adult females, and 10.47% young females. Of the adult females captured, 54.83% were pregnant with an average of 3 to 4 embryos per rat. A control demonstration combat was carried out at one of the experimental stations with a bait prepared with 2% zinc phosphide in a place where it had been previously determined there was a population of 39 rats per hectare. After such control, the population was reduced to 18 rats per hectare, which represents an efficiency of 53.85%. An evaluation of damages was also measured at different places to determine the degree of loss caused by the rats, which proved to be 22.79% damage. The size of the sample was estimated in 3 samples per hectare, with a level of confidence of 95%

DIRK Schemes with High Weak Stage Order

Runge-Kutta time-stepping methods in general suffer from order reduction: the observed order of convergence may be less than the formal order when applied to certain stiff problems. Order reduction can be avoided by using methods with high stage order. However, diagonally-implicit Runge-Kutta (DIRK) schemes are limited to low stage order. In this paper we explore a weak stage order criterion, which for initial boundary value problems also serves to avoid order reduction, and which is compatible with a DIRK structure. We provide specific DIRK schemes of weak stage order up to 3, and demonstrate their performance in various examples.Comment: 10 pages, 5 figure

Any-order propagation of the nonlinear Schroedinger equation

We derive an exact propagation scheme for nonlinear Schroedinger equations. This scheme is entirely analogous to the propagation of linear Schroedinger equations. We accomplish this by defining a special operator whose algebraic properties ensure the correct propagation. As applications, we provide a simple proof of a recent conjecture regarding higher-order integrators for the Gross-Pitaevskii equation, extend it to multi-component equations, and to a new class of integrators.Comment: 10 pages, no figures, submitted to Phys. Rev.

AVALIANDO JULGAMENTOS NÃO VERBAIS DE IGUALDADE/DIFERENÇA ENTRE ESTÍMULOS AUDITIVOS EM INDIVÍDUOS COM DEFICIÊNCIAS INTELECTUAIS: UMA INVESTIGAÇÃO METODOLÓGICA

This methodological paper reports an initial attempt to evaluate the feasibility and utility of a nonverbal task for assessing generalized same/different judgments of auditory stimuli in individuals with intellectual disabilities. Study 1 asked whether participants could readily acquire a baseline of auditory same/different, go-left/go-right performance with minimal prompting. Sample stimuli consisted of pairs of successively presented sine-wave tones. If the tones were identical, selections of a visual stimulus on the left side of the computer screen were reinforced. If the tones were different, selections of a visual stimulus on the right side of the computer screen were reinforced. Two of five participants readily acquired the task, generalized performance to other stimuli, and completed a rudimentary protocol for examining auditory discriminations that are potentially more difficult than those used to establish the initial task. In Study 2, two participants who could not perform the “go-left/go-right” task with tone stimuli, but could do so with spoken-word stimuli, successfully transferred control by spoken words to tones via an auditory superimposition-and-fading procedure. The findings support the feasibility of using the task as a general-purpose auditory discrimination assessment.Keywords: auditory discrimination, go-left/go-right, intellectual disabilities, matching to sample, superimposition and fading.O presente artigo metodológico relata uma tentativa inicial de avaliar a viabilidade e a utilidade de uma tarefa não verbal para avaliar o julgamento generalizado de igualdade/diferença entre estímulos auditivos em indivíduos com deficiências intelectuais. O Estudo 1 investigou se os participantes poderiam prontamente adquirir uma linha de base de desempenho discriminativo de igualdade/diferença, em tarefa de “go-left/go-right” (responder à esquerda/responder à direita) com ajuda mínima. Os estímulos-modelo consistiam em pares de sons de frequência única apresentados sucessivamente. Se os sons fossem idênticos, seleções de um estímulo visual no lado esquerdo da tela do computador eram reforçadas. Se os sons fossem diferentes, seleções de um estímulo visual no lado direito da tela do computador eram reforçadas. Dois dos cinco participantes aprenderam prontamente a tarefa, generalizaram o desempenho para outros estímulos e completaram um protocolo rudimentar para avaliar discriminações auditivas que são potencialmente mais difíceis do que aquelas usadas para estabelecer a tarefa inicial. No Estudo 2, dois participantes que não puderam desempenhar a tarefa “go-left/go-right” com os sons de única frequência, mas puderam fazê-lo com palavras faladas como estímulos, transferiram com sucesso o controle das palavras faladas para os sons via um procedimento de esmaecimento e sobreposição de estímulos auditivos. Os achados apoiam a viabilidade de se usar a tarefa como uma avaliação de discriminação auditiva em geral. Palavras-chave: discriminação auditiva, procedimento de resposta à esquerda/resposta à direita, deficiência intelectual, emparelhamento ao modelo, sobreposição e esmaecimento

List Coloring in the Absence of Two Subgraphs

list assignment of a graph G = (V;E) is a function L that assigns a list L(u) of so-called admissible colors to each u 2 V . The List Coloring problem is that of testing whether a given graph G = (V;E) has a coloring c that respects a given list assignment L, i.e., whether G has a mapping c : V ! f1; 2; : : :g such that (i) c(u) 6= c(v) whenever uv 2 E and (ii) c(u) 2 L(u) for all u 2 V . If a graph G has no induced subgraph isomorphic to some graph of a pair fH1;H2g, then G is called (H1;H2)-free. We completely characterize the complexity of List Coloring for (H1;H2)-free graphs