Pion interactions in the X(3872)

We consider pion interactions in an effective field theory of the narrow resonance X(3872), assuming it is a weakly bound molecule of the charm mesons D-0(D) over bar (*0) and D-*0(D) over bar (0). Since the hyperfine splitting of the D-0 and D-*0 is only 7 MeV greater than the neutral pion mass, pions can be produced near threshold and are nonrelativistic. We show that pion exchange can be treated in perturbation theory and calculate the next-to-leading-order correction to the partial decay width Gamma[X -> D-0(D) over bar (0)pi(0)].

Leituras sobre usuário e uso de informação na Ciência da Informação

Considering aspects of international literature in the area of Information Science (IS) regarding need, search, behavior and use of information, this study aims to explore the historical path and interpretations of the concepts of user and use of information, under the support reference of the notions of information system and subject agency. For such, a corpus was formed with 15 literature reviews of the Annual Review of Information Science and Technology - ARIST - which brought a theoretical panorama on the concepts here studied. The analysis of these reviews was tooled with categorizations of the use of information proposed by Rachel Anne Fleming-May, making it possible to situate two initial phases identified, particularized for orbiting a notion of information system, being the first phase characterized by a more static conception of system and the second by a more dynamic meaning. Finally, a third and last phase was found in reading ARIST, which was better visualized after the year 2000. In the first decade of the 21st century, studies started considering, complementarily to previous phases, the agency of subjects from the notions of interaction and context, in actions of use, production and appropriation of information and knowledge.