This paper presents evidence of the anomalous interaction mean free path of the relativistic alpha particles emitted from the interaction of 12 C with emulsion nuclei at 4.5 GeV/c per nucleon. The tracks were followed systematically through the stack. The detailed measurements show clearly that the interaction mean free path is anomalously shorter for fewer centimeters after their emission. The results have been compared with other results obtained from both accelerator and cosmic-ray data.PACS numbers: 25.70.Np Evidence for anomalously short interaction mean free paths of projectile fragments of different charges from high-energy ion collisions has been observed in cosmic-ray studies. 1 " 8 This has further been supplemented by the observation in emulsion experiments 9 " 12 of similar effects of projectile fragments from 2.1-GeV/nucleon O 16 beam and 1.88-GeV/c 56 Fe and 40 Ar beams from accelerators.To arrive at any confident conclusion about "anomalons" (projectile fragments with anomalous interaction mean free paths), it is absolutely essential to have good statistics of individual charges which is very difficult for higher Z values. Since it has been known for a long time that the fragmentation of heavy primaries into alpha particles is very common, one can confirm the anomalous behavior by taking large statistics of a (i.e., Z = 2) particles as projectile fragments emitted from emulsion nuclei exposed at accelerators to high-energy heavy-ion beams. Jain et al. u have found that in the case of two heavy-ion beams of 40 Ar and 56 Fe at 2A GeV the interaction mean free paths for alpha particles are the same at all distances from their production points. We present in this paper an investigation on anomalous reaction mean free paths of alpha-particle projectile fragments emitted from 12 Cemulsion interaction at 4.5 GeV/ c per nucleon.Our results based on detailed observation can be summarized as follows: (1) The interaction mean free path is anomalously short for a few centimeters after emission.(2) The interaction mean free paths measured at different path lengths from the points of emission are different. (3) The interaction mean free path shows a definite increase in value with increasing path-length interval. (4) The interaction mean free path of particles emitted from primary interaction stars of n h ^ 8 is shorter than for those emitted from stars of n h > 8 in the path-length interval 0-4 cm.The observations were made in a stack of ten plates of NIKFI-BR-2 nuclear emulsion, of pellicle dimensions 10x20 cm 2 x600 /mm with printed grid. The plates were tangentially irradiated with the 4.5A-GQV/C 12 C beam at the Joint Institute for Nuclear Research, Dubna, U.S.S.R. A total of 1200 relativistic alpha particles emitted from the primary interaction within a small forward cone were followed, using Leitz Ortholux microscopes, by the along-the-track method. Identification of a (i.e., Z = 2) particles was carried out by the gap-density method and by 8-ray count for the identification of charge. All electron track...
This paper presents a detailed comparison of the recent experimental data on mean normalized shower multiplicity in proton–emulsion interactions (22.6–400 GeV/c) with the predictions of current theories of multiparticle production in hadron–nucleus interactions. It has been observed that the data favour both the Fishbane–Trefil two-phase model (TEM) and the Fan diagram dominance model (FDDM) over a wide range of target nuclei, although the agreement with the FDDM seems to be better.
Thallium-doped ionic crystals are important for their application as detectors for ionizing radiations. The T1 atoms are usually incorporated into the crystal during growth from its melt and the product is k n o w n as phosphor. Phosphors can also be made by the process of thermal diffusion of T1 in alkalihalide crystals. Although a lot of work (1, 2) has accumulated on the diffusion phenomenon in solids, limited attention (3) has been applied to diffusion of T1 in alkalihalide crystals.The incorporation of T1 atoms in the KC1 lattice is found to create luminescent centers in the host crystal. For constant external conditions of excess T1 atoms at the crystal surface in equilibrium with an external vapor, the distribution is well described by a complementary error function (4). The luminescence yield u n d e r electron irradiation from successive depths of the activated crystal is related to the T1 penetration into the crystal and can be used to obtain information on the diffusion process in alkalihalide phosphors. If a solid is exposed to a volume of metal vapor having a uniform concentration No atoms per unit volume, these atoms will diffuse into the solid medium following an equation (4) NWhen a KC1 crystal is doped with T1 atoms, it becomes a phosphor. If it is assumed that the luminescence yield is linearly proportional to the concentration of T1 atoms in the host crystal the ratioatoms as a function of the distance x from the surface, t is the period of heat-treatment, and Lo is the yield from the surface. Equation [1] takes the formA n experimental determination of L(x, t)/Lo as a function of x may lead to the evaluation of the diffusion coefficient D. The activation energy of diffusion (E) may also be estimated using an equationExperimental A block of cleaved KC1 <100> crystal (Harshaw Chemical) and properly distilled thallium metal of k n o w n weight were put in a glass tube. The glass tube had two intercommunicating sections separated by a constriction to avoid direct contact between the sample and the metallic T1. The tubes were sealed u n d e r vacuum, heated at diffusion temperatures for a period of 4 hr, and quenched to room temperature. Four such KC1 samples were doped with T1 at four different temperatures, 573 ~ 623 ~ 673 ~ and 723~ The time and other conditions for the doping process were kept the same in all the cases.The doped crystals were inserted into an electron accelerator tube and irradiated with normally incident 5 keV electrons. Beam current was 0.5 ~A cm -2. Key words: potassium chloride, thallium d i f f u s i o n , l u m i n e sc e n c e .The intensity of luminescence was measured by an RCA IP21 photomultiplier. All doped samples showed luminescence spectra under electron irradiation peaking at 3050 and 4750A while no luminescence was detected in the case of pure KC1 crystal. The diffusion of T1 was followed by measuring the intensity of luminescence at the surface of the specimen and at various depths along <100> direction by successive removal of surface layers. Results and Discu...
This paper presents a comparison of the data on the target nucleus excitation dependence of two-particle rapidity correlations among relativistic particles in hadron–nucleus interactions at 400 GeV/c with the additive quark model (AQM) for multiple production of particles off nuclei. The number of grey tracks (ng) has been taken as the parameter characterizing the degree of excitation. The dependence has been found to agree quantitatively with the predictions of the AQM.
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