301 research outputs found
Combined method to extract spectroscopic information
Spectroscopic factors (SF) play an important role in nuclear physics and
astrophysics. The traditional method of extracting SF from direct transfer
reactions suffers from serious ambiguities. We discuss a modified method which
is based on including the asymptotic normalization coefficient (ANC) of the
overlap functions into the transfer analysis. In the modified method the
contribution of the external part of the reaction amplitude, typically
dominant, is fixed and the SF is determined from fitting the internal part. We
illustrate the modified method with reactions on , and targets at different energies. The
modified method allows one to extract the SF, which do not depend on the shape
of the single-particle nucleon-target interaction, and has the potential of
improving the reliability and accuracy of the structure information. This is
specially important for nuclei on dripline, where not much is known.Comment: accepted in Phys. Rev. C, 4 pages and 2 figure
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
Unitary correlation in nuclear reaction theory
We prove that the amplitudes for the (d,p), (d,pn) and (e,e'p) reactions
determining the asymptotic behavior of the exact scattering wave functions in
the corresponding channels are invariant under unitary correlation operators
while the spectroscopic factors are not. Moreover, the exact reaction
amplitudes are not parametrized in terms of the spectroscopic factors and
cannot provide a tool to determine the spectroscopic factors.Comment: 5 page
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
The Cosmological Lithium Problem Revisited
After a brief review of the cosmological lithium problem, we report a few
recent attempts to find theoretical solutions by our group at Texas A&M
University (Commerce & College Station). We will discuss our studies on the
theoretical description of electron screening, the possible existence of
parallel universes of dark matter, and the use of non-extensive statistics
during the Big Bang nucleosynthesis epoch. Last but not least, we discuss
possible solutions within nuclear physics realm. The impact of recent
measurements of relevant nuclear reaction cross sections for the Big Bang
nucleosynthesis based on indirect methods is also assessed. Although our
attempts may not able to explain the observed discrepancies between theory and
observations, they suggest theoretical developments that can be useful also for
stellar nucleosynthesis.Comment: 10 pages, 4 figures. Plenary talk at the XI Latin American Symposium
on Nuclear Physics and Applications, Medellin, Colombia, 30 November - 4
December 2015. AIP conference proceedings, to be publishe
Cosmological Lithium Problems
We briefly describe the cosmological lithium problems followed by a summary
of our recent theoretical work on the magnitude of the effects of electron
screening, the possible existence of dark matter parallel universes and the use
of non-extensive (Tsallis) statistics during big bang nucleosynthesis.
Solutions within nuclear physics are also discussed and recent measurements of
cross-sections based on indirect experimental techniques are summarized.Comment: 9 pages, 5 figures, IX European Summer School on Experimental Nuclear
Astrophysics, St. Tecla (Catania), Italy, 17-24/Sept/201
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