Estudo sobre a identificação de hádrons em câmaras de fotoemulsão / Study about hadron identification in emulsion chambers

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

16/04/2012

RESUMO

This work introduces the importance of photoemulsion chambers that remain in use after decades and still offer many advantages for elementary particle physics. We cite OPERA (Oscillation Project with Emulsion-tRacking Apparatus) detector that is the greatest lead photoemulsion chamber detector ever constructed as an example of its application nowadays (nine million nuclear emulsion films). We also introduce the CASTOR detector (Centauro And STrange Objects Research) that is a hadronic and electromagnetic calorimeter of tungsten and quartz developed to improve the performance of CMS (Compact Muon Solenoid) experiment of LHC in its frontal region. One of most important features of Castor is its long dimension in the frontal region, which is suited to study long penetrating hadrons, as they appear in hadron-rich cosmic rays events. These hadrons were identified and called strangelets. The proposal of strangelets is that they were a result of baryon-rich quark matter decay and that they would penetrate great depth in lead and would leave the detector almost unattenuated. We presented the basic concepts of extensive air shower and the photoemulsion chamber technique used for its study. We introduce the use of photoemulsion chambers in mountain experiments and cited the Brasil-Japão Collaboration that detected an exotic event called Centauro for having large cross section. Besides, the absence of neutral pions is a remarkable feature of this type of event. Many other events of this type were detected and its search remains until today. Still talking about atmospheric showers, we cited how the classification of local cascades originated by frontal particles of shower were made in photoemulsion chamber literature. The longitudinal profile (in depth) of each local cascade is used to determine the energy of entering particle and it is also a signal of its nature ¿ if it is a part of electromagnetic component (electron, positron or gamma) or hadronic component. Each local cascade is observed is associated to one of these groups. We present Geant software as the simulation tool of this work. Originally developed at CERN for experiments of high energy physics, presently Geant is used in others fields as medicine and astrophysics. The most recent version of Geant is Geant4 and also includes low energy neutrons (<20 MeV) and ion treatment. For neutron physics, Geant4 has the implementation of very high precision neutron models that include elastic and inelastic collision process, capture and fission. For ion treatment, we have inelastic collisions, radioactive decay and electromagnetic dissociation implemented for simulations. We introduce the CBJ and Pamir detectors geometry implemented with Geant4 resources. The CBJ detector was constructed to study local cascades produced in lead or carbon when an air layer is used as a mean where secondary particles propagates and are separated in distances of micra or greater. The longitudinal profile is always used for the analysis. The Pamir detector, made of only lead and photosensitive films, was constructed to study long penetrating particles and to study the depths that neutrons begins its cascade. The results obtained show that there are hadrons, for instance neutrons, interacting in great depths of lead in cases that it could be misidentified as strangelet. To determine the features of cascades produced this way, we used the hadronic collision treatment recently implemented in Geant4. This is an important result because we showed that there is a probability of false identification of particles

ASSUNTO(S)

geant4 long penetrating hadrons raios cósmicos câmaras de emulsão geant4 hádrons penetrantes cosmic rays emulsion chambers

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