938 research outputs found
Astrophysical factor for the reaction from -matrix analysis and asymptotic normalization coefficient for . Is any fit acceptable?
The reaction provides a path from the CN
cycle to the CNO bi-cycle and CNO tri-cycle. The measured astrophysical factor
for this reaction is dominated by resonant capture through two strong
resonances at and 962 keV and direct capture to
the ground state. Recently, a new measurement of the astrophysical factor for
the reaction has been published [P. J.
LeBlanc {\it et al.}, Phys. Rev. {\bf C 82}, 055804 (2010)]. The analysis has
been done using the -matrix approach with unconstrained variation of all
parameters including the asymptotic normalization coefficient (ANC). The best
fit has been obtained for the square of the ANC fm,
which exceeds the previously measured value by a factor of . Here we
present a new -matrix analysis of the Notre Dame-LUNA data with the fixed
within the experimental uncertainties square of the ANC
fm. Rather than varying the ANC we add the contribution from a
background resonance that effectively takes into account contributions from
higher levels. Altogether we present 8 fits, five unconstrained and three
constrained. In all the fits the ANC is fixed at the previously determined
experimental value fm. For the unconstrained fit with
the boundary condition , where is the energy of the
second level, we get keVb and normalized , i.e. the result which is similar to [P. J. LeBlanc {\it et
al.}, Phys. Rev. {\bf C 82}, 055804 (2010)]. From all our fits we get the range
keVb which overlaps with the result of [P. J.
LeBlanc {\it et al.}, Phys. Rev. {\bf C 82}, 055804 (2010)]. We address also
physical interpretation of the fitting parameters.Comment: Submitted to PR
Coulomb renormalization and ratio of proton and neutron asymptotic normalization coefficients for mirror nuclei
Asymptotic normalization coefficients (ANCs) are fundamental nuclear
constants playing important role in nuclear reactions, nuclear structure and
nuclear astrophysics. In this paper the physical reasons of the Coulomb
renormalization of the ANC are addressed. Using Pinkston-Satchler equation the
ratio for the proton and neutron ANCs of mirror nuclei is obtained in terms of
the Wronskians from the radial overlap functions and regular solutions of the
two-body Schr\"odinger equation with the short-range interaction excluded. This
ratio allows one to use microscopic overlap functions for mirror nuclei in the
internal region, where they are the most accurate, to correctly predict the
ratio of the ANCs for mirror nuclei, which determine the amplitudes of the
tails of the overlap functions. Calculations presented for different nuclei
demonstrate the Coulomb renormalization effects and independence of the ratio
of the nucleon ANCs for mirror nuclei on the channel radius. This ratio is
valid both for bound states and resonances. One of the goals of this paper is
to draw attention on the possibility to use the Coulomb renormalized ANCs
rather than the standard ones especially when the standard ANCs are too large.Comment: 20 pages, 14 figure
Adaptive Finite Element Methods with Inexact Solvers for the Nonlinear Poisson-Boltzmann Equation
In this article we study adaptive finite element methods (AFEM) with inexact
solvers for a class of semilinear elliptic interface problems. We are
particularly interested in nonlinear problems with discontinuous diffusion
coefficients, such as the nonlinear Poisson-Boltzmann equation and its
regularizations. The algorithm we study consists of the standard
SOLVE-ESTIMATE-MARK-REFINE procedure common to many adaptive finite element
algorithms, but where the SOLVE step involves only a full solve on the coarsest
level, and the remaining levels involve only single Newton updates to the
previous approximate solution. We summarize a recently developed AFEM
convergence theory for inexact solvers, and present a sequence of numerical
experiments that give evidence that the theory does in fact predict the
contraction properties of AFEM with inexact solvers. The various routines used
are all designed to maintain a linear-time computational complexity.Comment: Submitted to DD20 Proceeding
Опыт смешанного обучения основам цифровой электроники ГГУ им. Ф. Скорины
The article considers the practical experience of blended learning of students in the basics of digital electronics based on the use of the instrumental distance learning system DL.GSU.BY developed at the FranciskSkorinaGomelStateUniversity. There are described specialized tools for designing, modeling, debugging, and researching digital electronics devices developed specifically for learning the basics of digital electronics.В статье рассматривается практический опыт смешанного обучения студентов основам цифровой электроники на базе использования инструментальной системы дистанционного обучения DL.GSU.BY, разработанной в ГГУ им. Ф. Скорины. Описываются специализированные средства проектирования, моделирования, отладки и исследования устройств цифровой электроники, разработанные специально для обучения основам цифровой электроники
ОБ ОПЫТЕ СМЕШАННОГО ОБУЧЕНИЯ ОСНОВАМ ПРОГРАММИРОВАНИЯ НА ФАКУЛЬТЕТЕ МАТЕМАТИКИ И ТЕХНОЛОГИЙ ПРОГРАММИРОВАНИЯ ГГУ ИМ. Ф. СКОРИНЫ
The article considers the practical experience of mixed teaching first-year students the programming framework on the use of distance learning tool system DL.GSU.BY developed at the GSU. The main factors of increasing the intensity and quality of the learning process are illustrated: the integration of theory and practice, automated personalized learning, automatic knowledge testing, support and encouragement of independent work, automatic permanent visualization of the score sheet.В статье рассматривается практический опыт смешанного обучения первокурсников основам программирования на базе использования инструментальной системы дистанционного обучения DL.GSU.BY, разработанной в ГГУ им. Ф. Скорины. Иллюстрируются основные факторы повышения интенсивности и качества процесса обучения: интеграция теории и практики, автоматизированное персонализированное обучение, автоматическая проверка знаний, поддержка и поощрение самостоятельной работы, автоматическая перманентная визуализация ведомости оценок
Bound, virtual and resonance -matrix poles from the Schr\"odinger equation
A general method, which we call the potential -matrix pole method, is
developed for obtaining the -matrix pole parameters for bound, virtual and
resonant states based on numerical solutions of the Schr\"odinger equation.
This method is well-known for bound states. In this work we generalize it for
resonant and virtual states, although the corresponding solutions increase
exponentially when . Concrete calculations are performed for the
ground and the first excited states of , the resonance
states (, ), low-lying states of and
, and the subthreshold resonances in the proton-proton system. We
also demonstrate that in the case the broad resonances their energy and width
can be found from the fitting of the experimental phase shifts using the
analytical expression for the elastic scattering -matrix. We compare the
-matrix pole and the -matrix for broad resonance in
Comment: 14 pages, 5 figures (figures 3 and 4 consist of two figures each) and
4 table
Electromagnetic form factors in the J/\psi mass region: The case in favor of additional resonances
Using the results of our recent analysis of e^+e^- annihilation, we plot the
curves for the diagonal and transition form factors of light hadrons in the
time-like region up to the production threshold of an open charm quantum
number. The comparison with existing data on the decays of J/\psi into such
hadrons shows that some new resonance structures may be present in the mass
range between 2 GeVand the J/\psi mass. Searching them may help in a better
understanding of the mass spectrum in both the simple and a more sophisticated
quark models, and in revealing the details of the three-gluon mechanism of the
OZI rule breaking in K\bar K channel.Comment: Formulas are added, typo is corrected, the text is rearranged.
Replaced to match the version accepted in Phys Rev
Theory of deuteron stripping. From surface integrals to generalized -matrix approach
There are two main reasons for absence of the practical theory of stripping
to resonance states which could be used by experimental groups: numerical
problem of the convergence of the DWBA matrix element when the full transition
operator is included and it is unclear what spectroscopic information can be
extracted from the analysis of transfer reactions populating the resonance
states. The purpose of this paper is to address both questions. The theory of
the deuteron stripping is developed, which is based on the post continuum
discretized coupled channels (CDCC) formalism going beyond of the DWBA and
surface integral formulation of the reaction theory [A. S. Kadyrov et al., Ann.
Phys. {\bf 324}, 1516 (2009)]. First, the formalism is developed for the DWBA
and then extended to the CDCC formalism, which is ultimate goal of this work.
The CDCC wave function takes into account not only the initial elastic
channel but also its coupling to the deuteron breakup channel
missing in the DWBA. Stripping to both bound states and resonances are
included. The convergence problem for stripping to resonance states is solved
in the post CDCC formalism. The reaction amplitude is parametrized in terms of
the reduced width amplitudes (ANCs), inverse level matrix, boundary condition
and channel radius, that is the same parameters which are used in the
conventional -matrix method. For stripping to resonance states many-level,
one and two-channel cases are considered. The theory provides a consistent tool
to analyze both binary resonant reactions and deuteron stripping in terms of
the same parameters.Comment: 37 page
Experimental study of the decay PHI(1020)--->ETA+GAMMA in multi-photon final state
In the SND experiment at VEPP-2M e^+e^- collider the phi(1020) ---> eta+gamma
---> 3pi^0+gamma decay was studied. The branching ratio B(phi--->eta+gamma) =
(1.246 +- 0.025 +- 0.057)% was measured.Comment: 4 pages, 1 figure, 1 table, Submitted to JETP Let
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