On the Value of R=\Gamma_h/\Gamma_l at LEP

We show that the present experimental LEP average R=\Gamma_h/\Gamma_l= 20.795 +- 0.040 is not unambiguous due to the presence of substantial systematic effects which cannot be interpreted within gaussian statistics. We find by Montecarlo simulation that the C.L. of the original LEP sample is only 3.8 \cdot 10^{-4}. We suggest that a reliable extimate of the true R-value is 20.60< R < 20.98 which produces only a very poor determination of the strong coupling constant at the Z mass scale, 0.10< \alpha_s(M_z)< 0.15.Comment: 4 pages, LaTeX; Postscript file, compressed and uuencoded, availabl

Monitoring of hadrontherapy treatments by means of charged particle detection

The interaction of the incoming beam radiation with the patient body in hadrontherapy treatments produces secondary charged and neutral particles, whose detection can be used for monitoring purposes and to perform an on-line check of beam particle range. In the context of ion-therapy with active scanning, charged particles are potentially attractive since they can be easily tracked with a high efficiency, in presence of a relatively low background contamination. In order to verify the possibility of exploiting this approach for in-beam monitoring in ion-therapy, and to guide the design of specific detectors, both simulations and experimental tests are being performed with ion beams impinging on simple homogeneous tissue-like targets (PMMA). From these studies, a resolution of the order of few millimeters on the single track has been proven to be sufficient to exploit charged particle tracking for monitoring purposes, preserving the precision achievable on longitudinal shape. The results obtained so far show that the measurement of charged particles can be successfully implemented in a technology capable of monitoring both the dose profile and the position of the Bragg peak inside the target and finally lead to the design of a novel profile detector. Crucial aspects to be considered are the detector positioning, to be optimized in order to maximize the available statistics, and the capability of accounting for the multiple scattering interactions undergone by the charged fragments along their exit path from the patient body. The experimental results collected up to now are also valuable for the validation of Monte Carlo simulation software tools and their implementation in Treatment Planning Software packages

Central America in the global accumulation of capital: From commercial integration sustained in the appropriation of land rent to the regional fragmentation of the working class

La región centroamericana ha atravesado una profunda metamorfosis a partir de la década de 1980. Su papel en la división internacional del trabajo ha dejado de girar en torno a la exportación de mercancías agrarias, pasando a constituirse como una región proveedora de fuerza de trabajo abaratada para actividades industriales y de servicios destinadas al mercado mundial. Esta nueva especificidad de la región muestra, sin embargo, diferencias entre sus países integrantes y límites cada vez más explícitos en algunos de ellos. Siguiendo el enfoque propio de la crítica de la economía política marxiana, en este artículo nos proponemos contribuir a la explicación del origen de esta metamorfosis común, de la diferenciación entre los procesos de acumulación nacionales y, con ello, del devenir de la población obrera de estos paísesThe Central American region has undergone a profound metamorphosis since the 1980s. Its role in the international division of labour no longer revolves around the export of agrarian commodities, but rather around the provision of cheap labour for industrial and service activities destined for the global market. This new specificity of the region shows, however, differences among its constituting countries and increasingly explicit limits in some of them. Following the approach of the Marxian critique of political economy, this article aims to contribute to the explanation of the origin of this common metamorphosis, the differentiation among national processes of accumulation, and thus of the future of the working population of these countries.Fil: Tortós, José Enrique. Universidad de Costa Rica; Costa RicaFil: Ferroni, Felix Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto de Altos Estudios Sociales. Centro de Estudios Económicos del Desarrollo; ArgentinaFil: Cazón, Fernando Javier. Universidad de Buenos Aires. Facultad de Ciencias Sociales. Carrera de Sociología; ArgentinaFil: Weksler, Guido Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Instituto de Investigaciones Económicas. Centro de Estudios sobre Población, Empleo y Desarrollo; Argentin

Central America in the global accumulation of capital: From commercial integration sustained in the appropriation of land rent to the regional fragmentation of the working class

La región centroamericana ha atravesado una profunda metamorfosis a partir de la década de 1980. Su papel en la división internacional del trabajo ha dejado de girar en torno a la exportación de mercancías agrarias, pasando a constituirse como una región proveedora de fuerza de trabajo abaratada para actividades industriales y de servicios destinadas al mercado mundial. Esta nueva especificidad de la región muestra, sin embargo, diferencias entre sus países integrantes y límites cada vez más explícitos en algunos de ellos. Siguiendo el enfoque propio de la crítica de la economía política marxiana, en este artículo nos proponemos contribuir a la explicación del origen de esta metamorfosis común, de la diferenciación entre los procesos de acumulación nacionales y, con ello, del devenir de la población obrera de estos paísesThe Central American region has undergone a profound metamorphosis since the 1980s. Its role in the international division of labour no longer revolves around the export of agrarian commodities, but rather around the provision of cheap labour for industrial and service activities destined for the global market. This new specificity of the region shows, however, differences among its constituting countries and increasingly explicit limits in some of them. Following the approach of the Marxian critique of political economy, this article aims to contribute to the explanation of the origin of this common metamorphosis, the differentiation among national processes of accumulation, and thus of the future of the working population of these countries.Fil: Tortós, José Enrique. Universidad de Costa Rica; Costa RicaFil: Ferroni, Felix Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín. Instituto de Altos Estudios Sociales. Centro de Estudios Económicos del Desarrollo; ArgentinaFil: Cazón, Fernando Javier. Universidad de Buenos Aires. Facultad de Ciencias Sociales. Carrera de Sociología; ArgentinaFil: Weksler, Guido Ezequiel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Económicas. Instituto de Investigaciones Económicas. Centro de Estudios sobre Población, Empleo y Desarrollo; Argentin

Charged particle's flux measurement from PMMA irradiated by 80 MeV/u carbon ion beam

Hadrontherapy is an emerging technique in cancer therapy that uses beams of charged particles. To meet the improved capability of hadrontherapy in matching the dose release with the cancer position, new dose monitoring techniques need to be developed and introduced into clinical use. The measurement of the fluxes of the secondary particles produced by the hadron beam is of fundamental importance in the design of any dose monitoring device and is eagerly needed to tune Monte Carlo simulations. We report the measurements done with charged secondary particles produced from the interaction of a 80 MeV/u fully stripped carbon ion beam at the INFN Laboratori Nazionali del Sud, Catania, with a Poly-methyl methacrylate target. Charged secondary particles, produced at 90$\degree$ with respect to the beam axis, have been tracked with a drift chamber, while their energy and time of flight has been measured by means of a LYSO scintillator. Secondary protons have been identified exploiting the energy and time of flight information, and their emission region has been reconstructed backtracking from the drift chamber to the target. Moreover a position scan of the target indicates that the reconstructed emission region follows the movement of the expected Bragg peak position. Exploting the reconstruction of the emission region, an accuracy on the Bragg peak determination in the submillimeter range has been obtained. The measured differential production rate for protons produced with $E^{\rm Prod}_{\rm kin} >$ 83 MeV and emitted at 90$\degree$ with respect to the beam line is: $dN_{\rm P}/(dN_{\rm C}d\Omega)(E^{\rm Prod}_{\rm kin} > 83 {\rm ~MeV}, \theta=90\degree)= (2.69\pm 0.08_{\rm stat} \pm 0.12_{\rm sys})\times 10^{-4} sr^{-1}$.Comment: 13 pages, 9 figure

Measurement of charged particle yields from therapeutic beams in view of the design of an innovative hadrontherapy dose monitor

Particle Therapy (PT) is an emerging technique, which makes use of charged particles to efficiently cure different kinds of solid tumors. The high precision in the hadrons dose deposition requires an accurate monitoring to prevent the risk of under-dosage of the cancer region or of over-dosage of healthy tissues. Monitoring techniques are currently being developed and are based on the detection of particles produced by the beam interaction into the target, in particular: charged particles, result of target and/or projectile fragmentation, prompt photons coming from nucleus de-excitation and back-to-back γ s, produced in the positron annihilation from β + emitters created in the beam interaction with the target. It has been showed that the hadron beam dose release peak can be spatially correlated with the emission pattern of these secondary particles. Here we report about secondary particles production (charged fragments and prompt γ s) performed at different beam and energies that have a particular relevance for PT applications: 12C beam of 80 MeV/u at LNS, 12C beam 220 MeV/u at GSI, and 12C, 4He, 16O beams with energy in the 50–300 MeV/u range at HIT. Finally, a project for a multimodal dose-monitor device exploiting the prompt photons and charged particles emission will be presented