ALICE is one of four large experiments at the CERN Large Hadron Collider, specially designed to study particle production in ultra-relativistic heavy-ion collisions. Located 52 meters underground ...with 28 meters of overburden rock, it has also been used to detect muons produced by cosmic-ray interactions in the upper atmosphere. The large size and excellent tracking capability of the ALICE Time Projection Chamber are exploited to study the muonic component of extensive air showers. We present the multiplicity distribution of these atmospheric muons and its comparison with Monte Carlo simulations. The latest version of the QGSJET hadronic interaction model was used to simulate the development of the resulting air showers. High multiplicity events containing more than 100 reconstructed muons were also studied. Similar events have been studied in previous underground experiments such as ALEPH and DELPHI at LEP without satisfactory explanations for the frequency of the highest multiplicity events. We demonstrate that the high muon-multiplicity events observed in ALICE stem from primary cosmic rays with energies above 1016 eV and that the frequency of these events can be successfully described by assuming a heavy mass composition of primary cosmic rays in this energy range.
The proton-proton collisions have been extensively used as a baseline reference for nucleus-nucleus collisions. In this work, Monte Carlo simulations of inelastic head-on pp interactions at $\sqrt s ...= 6 - 25\,{\rm{GeV}}$ were performed to study the possibilities of the Multi–Purpose Detector (MPD) to register data from small systems at the energy range of NICA. For that purpose the Monte Carlo models EPOS 1.99 and UrQMD 3.4 were used as event generators to analyse the charge particle yield from pp collisions in the framework of MpdRoot. The production of protons, pions and kaons from pp collisions was studied through their mean multiplicity, rapidity spectra and particle ratios as function of the collision energy. The yield of Λ hyperons was also estimated by means of pure Monte Carlo and the reconstruction of the simulated data in MPD. The comparison with recent data from NA61/SHINE experiment is presented.
Data on hadron multiplicities from inelastic proton-proton interactions in the energy range of the NICA collider have been compiled. The compilation includes recent results from the NA61/SHINE and ...NA49 experiments at the CERN SPS accelerator. New parameterizations for excitation functions of mean multiplicities
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,
,
,
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are obtained in the region of collision energies
GeV. The energy dependence of the particle yields, as well as variation of rapidity and transverse momentum distributions are discussed. A standalone algorithm for hadron phase space generation in
collisions is suggested and compared to model predictions using an example of the PHQMD generator. The investigation has been performed at the Laboratory of High Energy Physics, JINR.
The south region of Sao Paulo city hosts the Guarapiranga dam, responsible for water supply to 25% of the city population. Their surroundings have been subject to intense and irregular occupation by ...people from very low socioeconomics classes. Measurements undertaken on sediment and particulate materials in the dam revealed concentrations of lead, copper, zinc and cadmium above internationally accepted limits. Epidemiological and toxicological studies undertaken by the World Health Organization in individuals exhibiting lead concentrations in blood, near or below the maximum recommended (10 µg dl
−
1
), surprisingly revealed that toxic effects are more intense in individuals belonging to low socioeconomics classes. Motivated by these facts, we aimed at the investigation of chronic incorporation of lead, as well as the use of our BIOKINETICS code, which is based on an accepted ICRP biokinetics model for lead, in order to extrapolate the results from teeth to other organs. The focus of our data taking was children from poor families, living in a small, restrict and allegedly contaminated area in São Paulo city. Thus, a total of 74 human teeth were collected. The average concentration of lead in teeth of children 5 to 10 years old was determined by means of a high-resolution inductively coupled plasma mass spectrometer (ICP-MS). For standardization of the measurements, an animal bone certified material (H-Animal Bone), from the International Atomic Energy Agency, was analyzed. The amount of lead in children living in the surroundings of the dam, was approximately 40% higher than those from the control region, and the average lead concentration was equal to 1.3 μg g
−
1
approximately. Grouping the results in terms of gender, tooth type and condition, it was concluded that a carious molar of boys is a much more efficient contamination pathway for lead, resulting in concentrations 70% higher than in the control region. We also inferred the average concentrations of lead in other organs of these children, by making use of our BIOKINETIC code.
Proton induced non-elastic nuclear reactions play an important role in the dose distribution of clinically used proton beams as they deposit dose of high biological effectiveness both within the ...primary beam path as well as outside the beam to untargeted tissues. Non-elastic nuclear reactions can be evaluated using transport codes based on the Monte Carlo method. In this work, we have utilized the Los Alamos code MCNPX and the CERN GEANT4 toolkit, which are currently the most widely used Monte Carlo programs for proton radiation transport simulations in medical physics, to study the contribution of non-elastic nuclear interactions to the absorbed dose of proton beams in the therapeutic energy range. The impact of different available theoretical models to address the nuclear reaction process was investigated. The contribution of secondary particles from non-elastic nuclear reactions was calculated in three materials relevant in radiotherapy applications: water, PMMA and A150. The results evidence that there are differences in the calculated contribution of the secondary particles heavier than protons to the absorbed dose, with different approaches to model the nuclear reactions. The MCNPX calculation give rise to a larger contribution of d, t, a 3 He to the total dose compared to the GEANT4 physical models chosen in this work.
Groups of Wistar rats were fed with ration doped with uranyl nitrate at concentration A ranging from 0.5 to 100 ppm, starting after the weaning period and lasting until the postpuberty period when ...the animals were sacrificed. Uranium in the ashes of bones was determined by neutron activation analysis. It was found that the uranium concentration in the bones, as a function of A, exhibits a change in its slope at ∼20 ppm—a probable consequence of the malfunctioning of kidneys. The uranium transfer coefficient was obtained and an analytical expression was fitted into the data, thus allowing extrapolation down to low doses. Internal and localized doses were calculated. Absorbed doses exceeded the critical dose, even for the lowest uranium dosage.
Se describe el estado actual de un estudio sobre las posibildades del uso del CN-85, detector de nitrato de celulosa de 100 µm de grosor (manufacturado por Kodak-Pathé de Francia), para realizar ...dosimetría neutrónica. El detector fue utilizado sin convertidores n-p adicionales. Las posibilidades de detección del CN-85 fueron analizadas mediante el conteo automático en un procesador de imágenes. Se determinaron las condiciones óptimas para el revelado químico. En el presente trabajo se investiga, además, la relación de la densidad de trazas y sus parámetros geométricos con las características de la radiación neutrónica. Se demuestra que la dependencia de la densidad de trazas con el tiempo de irradiación se ajusta a una expresión matemática específica. Con el propósito de determinar el rango energético de detección de neutrones en el detector CN-85, y dada la ausencia de fuentes de neutrones monoenergéticas, fueron construidos histogramas de distribución de diámetros de las trazas, parámetro inversamente proporcional a la energía incidente en el detector. De acuerdo con los resultados obtenidos se observan algunas modificaciones en el espectro de energías que es capaz de registrar el detector cuando varía la geometría de la instalación. Se muestran figuras y gráficos que describen los comportamientos antes mencionados.
Se describe el estado actual de un estudio sobre las posibildades del uso del CN-85, detector de nitrato de celulosa de 100 µm de grosor (manufacturado por Kodak-Pathé de Francia), para realizar ...dosimetría neutrónica. El detector fue utilizado sin convertidores n-p adicionales. Las posibilidades de detección del CN-85 fueron analizadas mediante el conteo automático en un procesador de imágenes. Se determinaron las condiciones óptimas para el revelado químico. En el presente trabajo se investiga, además, la relación de la densidad de trazas y sus parámetros geométricos con las características de la radiación neutrónica. Se demuestra que la dependencia de la densidad de trazas con el tiempo de irradiación se ajusta a una expresión matemática específica. Con el propósito de determinar el rango energético de detección de neutrones en el detector CN-85, y dada la ausencia de fuentes de neutrones monoenergéticas, fueron construidos histogramas de distribución de diámetros de las trazas, parámetro inversamente proporcional a la energía incidente en el detector. De acuerdo con los resultados obtenidos se observan algunas modificaciones en el espectro de energías que es capaz de registrar el detector cuando varía la geometría de la instalación. Se muestran figuras y gráficos que describen los comportamientos antes mencionados.
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