On the Generalized Borel Transform and its Application to the Statistical Mechanics of Macromolecules

We present a new integral transform called the Generalized Borel Transform (GBT) and show how to use it to compute some distribution functions used to describe the statistico-mechanical behavior of macromolecules. For this purpose, we choose the Random Flight Model (RFM) of macromolecules and show that the application of the GBT to this model leads to the exact expression of the polymer propagator (two-point correlation function) from which all the statistical properties of the model can be obtained. We also discuss the mathematical simplicity of the GBT and its applicability to polymers with other topologies.Comment: 21 pages, 2 figure

On the propagation of the highest energy cosmic ray nuclei

We study the propagation of ultra-high energy cosmic ray nuclei through the background of cosmic microwave and intergalactic infrared photons, using recent re-estimates for the density of the last ones. We perform a detailed Monte Carlo simulation to follow the disintegration histories of nuclei starting as Fe and reaching the Earth from extragalactic sources. We obtain the maximum energies of the arriving nuclear fragments as well as the mass composition as a function of the distance traveled. Cosmic rays with energies in excess of $2\times 10^{20}$ eV cannot originate from Fe nuclei produced in sources beyond 10 Mpc.Comment: 8 page

On the disintegration of cosmic ray nuclei by solar photons

We discuss in detail the possibility of observing pairs of simultaneous parallel air showers produced by the fragments of cosmic ray nuclei which disintegrated in collisions with solar photons. We consider scenarios with different cosmic ray compositions, exploring the predicted rates for existing and planned detectors and looking for methods to extract information on the initial composition from the characteristics of the signal. In particular, we find that fluorescence detectors, such as HiRes or the Telescope Array, due to their low threshold ($\sim 10^{17}$ eV) and large area ($\sim 10^4 km^2$) may observe several events per year if cosmic rays at those energies are indeed heavy nuclei. The possibility of exploiting the angular orientation of the plane containing the two showers to further constrain the cosmic ray composition is also discussed.Comment: 15 page

The Ideal Mixing Departure in Vector Meson Physics

In this work we study the departure for the ideal $\phi-\omega$ mixing angle in the frame of the Nambu-Jona-Lasinio model. We have shown that in that context, the flavour symmetry breaking is unable to produce the shifting in the mixing angle. We introduce a nonet symmetry breaking in the neutral vector sector to regulate the non-strange content of the $\phi$ meson. The phenomenon is well reproduced by our proposal.Comment: 12 pages incl. 1 figur

The role of heavy quarks in light hadron fragmentation

We investigate the role of heavy quarks in the production of light flavored hadrons and in the determination of the corresponding non perturbative hadronization probabilities. We define a general mass variable flavor number scheme for fragmentation functions that accounts for heavy quark mass effects, and perform a global QCD analysis to an up-to-date data set including very precise Belle and BaBar results. We show that the mass dependent picture provides a much more accurate and consistent description of data.Comment: 5 pages, 3 eps figure

Heavy quark mass effects in parton-to-kaon hadronization probabilities

We examine the relevance of the heavy quarks masses in the perturbative QCD description of hard interactions where charged kaons are produced in the final state. We extract a set of parton-to-kaon hadronization probabilities from a next to leading order QCD global analysis where a general mass variable flavor number scheme accounting for mass effects is implemented. We compare the results with those obtained in the massless approximation and also with those found in the case of final state pions. At variance with the very significant improvement found for the much more precise pion fragmentation phenomenology, the heavy quark mass dependent scheme improves mildly the overall description of current kaon production data. Nevertheless, we find a noticeable reduction in the charm-to-kaon hadronization probability.Fil: Epele, Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: García Canal, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Sassot, Rodolfo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin

Uncertainties in pion and kaon fragmentation functions

We present a detailed assessment of uncertainties in parton-to-pion and parton-to-kaon fragmentation functions obtained in recent global QCD analyses of single-inclusive hadron production data at next-to-leading order accuracy. We use the robust Lagrange multiplier approach for determining uncertainties to validate the applicability of the simpler but approximate Hessian method. Extensive comparisons of the results obtained within both methods are presented for the individual parton-to-pion and kaon fragmentation functions. We provide Hessian eigenvector sets of pion and kaon fragmentation functions that allow one to easily propagate their uncertainties to any observable. Various applications of these sets are presented for pion and kaon production in electron-positron annihilation, lepton-nucleon scattering, and proton-proton collisions.Comment: 12 pages, 11 figure

Emergencies and rescues: The logics of vulnerability and care among drug users in Buenos Aires, Argentina

This article addresses the informal practices of care among drug users from vulnerable populations in Buenos Aires, within a context of economic crisis, criminalization, and marginalization. Based on ethnographic research carried out since 2001, I argue that this set of practices, knowledge, and social networking known locally as "rescuing" seek to minimize bodily harms, harm to relationships, as well as to reduce threats to survival. This analysis shows how this logic of care varies according to the type of substance consumed, gender, socioeconomic status, social capital, access to institutions, family networks, and life trajectories. Finally, the development of this logic of care for drug use based on rescuing practices, allows us to understand the relationships between structural transformations and everyday life through the processes the privatization of care and the politicization of suffering.Fil: Epele, Maria E.. Universidad de Buenos Aires. Facultad de Ciencias Sociales. Instituto de Investigaciones "Gino Germani"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Sobre o Cuidado de Outros em Contextos de Pobreza, Uso de Drogas e Marginalização

A coordenação temporária entre a rápida extensão do consumo de Pasta Base/Paco (PB/Paco) e a extrema crise econômico-política (2001-2002) na Argentina promoveu profundas modificações nas redes sociais, nas características corporais e nos problemas de saúde das populações marginalizadas. Partindo dos resultados da pesquisa etnográfica em três bairros e favelas da área metropolitana de Buenos Aires, analiso neste trabalho as características e as tensões das práticas e dos saberes localmente categorizados como "cuidado de outros", sendo estes outros, usuários/as de drogas em geral e de PB/Paco. Através da análise dos desenvolvimentos em ciências sociais e antropologia sobre a temática do cuidado nas últimas décadas, neste artigo examino os modos com que tais práticas e saberes expressam os conflitos e os encerramentos gerados pelas tensões entre as tradições locais de cuidado e os modos institucionais de abordar o uso problemático de drogas e de tratar seus/suas usuários/as.The temporary relationship between the rapid spread of freebase cocaine/paco (PB/paco) and the extreme political-economic crisis (2001-2002) in Argentina engendered deep changes to the social networks, bodily characteristics and health issues of marginalized populations. The present article is based on ethnographic research that I carried out in three neighborhoods (villas) located in the Metropolitan Area of Buenos Aires. Here, I analyze the characteristics of practices and knowledge locally categorized as "care towards others", specifically drug users and, most specifically, PB/paco users. Taking as my point of departure the problematization of care in the social sciences and anthropology during the last decades, this paper examines the ways in which these practices and knowledge express conflicts and entrapments generated by the tensions between local traditions of care, on the one hand, and institutional strategies orientated to intensive drug use and modes of treating drug users, on the other.Fil: Epele, Maria E.. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Neoliberalismo, vulnerabilidad y sufrimiento social : drogas y pobreza

Fil: Epele, María E. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Instituto de Ciencias Antropológicas; ArgentinaLa emergencia instalada en la sociedad argentina por la acelerada expansión del paco parecería\nconfirmar, por el carácter compulsivo de su consumo y su frecuente asociación con actividades ilegales,\nlos supuestos ideológicos más conservadores de los vínculos entre pobreza y drogas. Este artículo\npretende abrir ciertas preguntas y aportar dimensiones de inteligibilidad sobre las complejas relaciones\nentre droga y pobreza