Papers by Edgar perez santiago
Journal of High Energy Physics, 2011
A measurement is presented of the charged hadron multiplicity in hadronic PbPb collisions, as a f... more A measurement is presented of the charged hadron multiplicity in hadronic PbPb collisions, as a function of pseudorapidity and centrality, at a collision energy of 2.76 TeV per nucleon pair. The data sample is collected using the CMS detector and a minimum-bias trigger, with the CMS solenoid off. The number of charged hadrons is measured both by counting the number of reconstructed particle hits and by forming hit doublets of pairs of layers in the pixel detector. The two methods give consistent results. The charged hadron multiplicity density, dN ch /dη| η=0 , for head-on collisions is found to be 1612 ± 55, where the uncertainty is dominated by systematic effects. Comparisons of these results to previous measurements and to various models are also presented.
Journal of Arid Environments, 2007
Ethnobotanical and ecological studies were conducted in the village of Santiago Quiotepec, in the... more Ethnobotanical and ecological studies were conducted in the village of Santiago Quiotepec, in the Tehuaca´n-Cuicatla´n Biosphere Reserve, Mexico, in order to analyse the importance of plant resources in peasant subsistence, and the balance between extraction rates and spatial availability of the main plant resources. Maize agriculture is the principal economic activity of local people but annual production (approximately 45 tons) was insufficient to satisfy the local demand (nearly 75 tons). People import most of their food, but complement their economy by commercialization of fruit produced in homegardens and plantations and gathering of plant products from the forests. A total of 252 useful plant species was recorded, most of them used as fodder , medicine (88), food (74), and fuel wood (70). High quantities of plant products were gathered from forests and disturbed vegetation per year. For instance, nearly 800 kg of the traditional greens and 550 kg of cactus fruits were consumed and about 464 tons of fuel wood was extracted for cooking in the whole village yearly. In general, extraction rates of plant resources for household subsistence were low in relation to their spatial availability, and apparently do not endanger useful plants populations. However, if commercialized, the extraction of fuel wood and other resources may lead to local extinction of populations. Local practices for conservation are discussed. r
The p T -differential inclusive production cross section of the prompt charm-strange meson D + s ... more The p T -differential inclusive production cross section of the prompt charm-strange meson D + s in the rapidity range |y| < 0.5 was measured in proton-proton collisions at √ s = 7 TeV at the LHC using the ALICE detector. The analysis was performed on a data sample of 2.98×10 8 events collected with a minimum-bias trigger. The corresponding integrated luminosity is L int = 4.8 nb −1 . Reconstructing the decay D + s → φ π + , with φ → K − K + , and its charge conjugate, about 480 D ± s mesons were counted, after selection cuts, in the transverse momentum range 2 < p T < 12 GeV/c. The results are compared with the prediction of a model based on perturbative QCD. The ratios of the cross sections of four D meson species (namely D 0 , D + , D * + and D + s ) were determined both as a function of p T and integrated over p T after extrapolating to full p T range, together with the strangeness suppression factor in charm fragmentation. The obtained values are found to be compatible within uncertainties with those measured by other experiments in e + e − , ep and pp interactions at various centre-of-mass energies.
In this Letter we report the first results on π ± , K ± , p and p production at mid-rapidity (|y|... more In this Letter we report the first results on π ± , K ± , p and p production at mid-rapidity (|y| < 0.5) in central Pb-Pb collisions at √ s NN = 2.76 TeV, measured by the ALICE experiment at the LHC. The p T distributions and yields are compared to previous results at √ s NN = 200 GeV and expectations from hydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flow velocity with √ s NN , which in hydrodynamic models is expected as a consequence of the increasing particle density. While the K/π ratio is in line with predictions from the thermal model, the p/π ratio is found to be lower by a factor of about 1.5. This deviation from thermal model expectations is still to be understood. π, K, and p production in central Pb-Pb collisions at √ s NN = 2.76 TeV 1
La palabra robot deriva del checo robota que significa trabajador, pero no es eso exactamente lo ... more La palabra robot deriva del checo robota que significa trabajador, pero no es eso exactamente lo que se entiende hoy en día como el significado de esta palabra. Actualmente se define como robot a un manipulador multifuncional, reprogramable, diseñado para mover materiales, piezas, herramientas u otros dispositivos especializados, a través de distintos movimientos, para el desempeño de una variedad de tareas.
Uploads
Papers by Edgar perez santiago