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Proton-induced activation cross sections in the energy range below 1 GeV
No full text(Abridged) Modern studies and industrial applications related to the design, radiation protection, and reliability of nuclear facilities, medical applications, as well as space research and exploration are relying on extensive simulations and modeling. Computer codes realizing semi-classical and quantum molecular dynamics (QMD) approaches are often employed to make up for the lack of accelerator data on many nuclear reactions at intermediate and high energies (>10s of MeV/n) and are in high demand. This contribution focuses on the methodology of generating reliable proton-induced cross sections in the energy range below 1 GeV. We developed a problem-oriented computer framework based on MCNPX and CASCADE/INPE codes to calculate activation cross section data at intermediate and high energies. Goodness of the fits of nucleon-nucleus interaction models to the existing data is evaluated based on elaborated algorithms. The method is based on the analysis of a large set of data and calculated cross sections for different targets and residual nuclei in a wide range of proton energies using numerous criteria. In practice, this could be done by tuning the model parameters and algorithms to fit required experimental data subset, or through achieving unification and consistency of fundamental parameters for all considered reactions. The presented framework is pursuing the latter approach. We use proton-induced reactions on Si and Fe nuclei to illustrate the application of the developed multi-criteria algorithm, where we use all data below 1 GeV available from the EXFOR data library and the IAEA CRP 'Benchmark of Spallation Models.' We show that the analysis of the predictive power of various intermediate and high-energy models based on the multi-criteria algorithm allows more sophisticated selection of appropriate models in a given energy range and residual nuclei domain
Criteria of Fractal Reconstruction and Suppressing Background Events with the SePaC Method
No full textThis work analyzes the method of fractals and various background events (mixed, random,and distributed according to Gauss’s law, as well as by power and exponential laws) in order to search andreconstruct fractal structures. It is shown that some of the background events are reconstucted as fractals.Dimensional distributions of various events are considered. It is found that these distributions for fractals andbackground events are different. Characteristics are proposed that describe the features of fractal structures.They are compared for fractals and background events. Criteria for background suppression are proposed andthe results of their application are presented. It is found that the application of the criteria changes the distribution of background events by dimension, and the use of a combination of criteria suppresses the background
Исследование гелимагнетизма в тонких пленках Dy и Ho методом нейтронной рефлектометрии
No full textПредставлены результаты исследования тонких пленок редкоземельных гелимагнетиков (РЗМ) Dy и Ho методом рефлектометрии поляризованных нейтронов. Было показано, что при росте методом магнетронного напыления редкоземельных структур на подложках сапфира с буферным слоем Nb [11ˉ02] Al2O3||[110]Nb||[0001]R происходит полная релаксация кристаллических решеток Nb и редкоземельной пленки. Было установлено, что ряд магнитных фазовых переходов, характерных для объемных Dy и Ho, не наблюдается в тонких пленках [0001]R толщиной 200 нм или наблюдается в измененном виде. Из данных рефлектометрии поляризованных нейтронов и измерений температурной зависимости намагниченности в плоскости образца были определены отличия в температурах Нееля и Кюри для тонких пленок РЗМ по сравнению с объемными
Рефлектометр поляризованных нейтронов с регистрацией нейтронов и гамма-квантов
No full textМетодом рефлектометрии нейтронов измеряют пространственный профиль потенциала взаимодействия нейтронов со средой. На границе раздела сред потенциал взаимодействия является суммой потенциалов отдельных изотопов. Для определения потенциала взаимодействия нейтронов с отдельными изотопами регистрируют нейтроны и гамма-излучение, испускаемое атомными ядрами элемента. На спектрометре РЕМУР созданы каналы регистрации гамма-квантов и нейтронов, испытавших переворот спина. Приведены результаты тестирования каналов, выполнены модельные расчеты коэффициентов поглощения нейтронов, и обсуждаются перспективы, связанные с регистрацией гамма-квантов и поляризованных нейтронов
Spin and orbital angular momentum separation: Theorem on decomposition
No full textRecently, the problem of spin and orbital angular momentum (AM) separation has widely been discussed. Nowadays, all discussions about the possibility to separate the spin AM from the orbital AM in the gauge invariant manner are based on the ansatz that the gluon field can be presented in form of the decomposition where the physical gluon components are additive to the pure gauge gluon components, i.e. . In the present paper, we show that in the non-Abelian gauge theory this gluon decomposition has a strong mathematical evidence in the frame of the contour gauge conception. In other words, we reformulate the gluon decomposition ansatz as a theorem on decomposition and, then, we use the contour gauge to prove this theorem. In the first time, we also demonstrate that the contour gauge possesses the special kind of residual gauge related to the boundary field configurations and expressed in terms of the pure gauge fields. As a result, the trivial boundary conditions lead to the inference that the decomposition includes the physical gluon configurations only provided the contour gauge condition
On the two-loop divergences in 6D, SYM theory
No full textWe continue studying supersymmetric Yang-Mills (SYM) theory in the harmonic superspace formulation. Using the superfield background field method we explore the two-loop divergencies of the effective action in the gauge multiplet sector. It is explicitly demonstrated that among four two-loop background-field dependent supergraphs contributing to the effective action, only one diverges off shell. It is also shown that the divergences are proportional to the superfield classical equations of motion and hence vanish on shell
Neutrino-Nucleon Cross-Section Model Tuning in GENIE v3
No full textWe summarise the results of a study performed within the GENIE global analysis framework, revisiting the GENIE bare-nucleon cross-section tuning and, in particular, the tuning of a) the inclusive cross-section, b) the cross-section of low-multiplicity inelastic channels (single-pion and double-pion production), and c) the relative contributions of resonance and non-resonance processes to these final states. The same analysis was performed with several different comprehensive cross-section model sets available in GENIE Generator v3. In this work we performed a careful investigation of the observed tensions between exclusive and inclusive data, and installed analysis improvements to handle systematics in historic data. All tuned model configurations discussed in this paper are available through public releases of the GENIE Generator. With this paper we aim to support the consumers of these physics tunes by providing comprehensive summaries of our alternate model constructions, of the relevant datasets and their systematics, and of our tuning procedure and results
Lifetime Measurements in the Even-Even Cd Isotopes
No full textThe heaviest N=Z doubly-magic nucleus, Sn, and the neighboring nuclei offer unique opportunities to investigate the properties of nuclear interaction in extreme conditions. In particular, the Cd isotopes are expected to present features similar to those found in the Sn isotopic chain, since they have only two proton holes in the Z=50 shell. In this manuscript, the lifetime measurements of low-lying states in the even-mass Cd is presented. Thanks to the powerful detection capabilities of AGATA array and VAMOS++ spectrometer, the unusual employment of multi-nucleon transfer reactions permitted to investigate the first 2 and 4 states in all these nuclei, together with various deformed bands in Cd. The results were interpreted in the context of new state-of-the-art beyond-mean-field calculations, using the symmetry-conserving configuration-mixing approach. Despite the similarities in the electromagnetic properties of the low-lying states, there is a fundamental structural difference between the ground-state bands in the Z=48 and Z=50 isotopes. The comparison between experimental and theoretical results revealed a rotational character of the Cd nuclei, which have prolate-deformed ground states with . At this deformation Z=48 becomes a closed-shell configuration, which is favored with respect to the spherical one
Mott dissociation and kaon to pion ratio in the EPNJL model
No full textThe behaviour of pseudoscalar mesons within the SU(3)PNJL-like models is considered for finite T and . We compare the pole approximation (Breit-Wigner) with the Beth-Uhlenbeck approach. We evaluate the ratios along the phase transition line in the T- plane with constant and -dependent pion and strange quark chemical potentials. Using the model, we can show that the splitting of kaon and anti-kaon masses appears as a result of introduction of density and this explains the difference in the ratio and ratio at low and their tendency to the same value at high . A sharp 'horn' effect in the ratio is explained by the enhanced pion production which can be described by occurrence of a nonequilibrium pion chemical potential of the order of the pion mass. We elucidate that the horn effect is not related to the existence of a critical endpoint in the QCD phase diagram