242 research outputs found
Connection between effective-range expansion and nuclear vertex constant or asymptotic normalization coefficient
Explicit relations between the effective-range expansion and the nuclear
vertex constant or asymptotic normalization coefficient (ANC) for the virtual
decay are derived for an arbitrary orbital momentum together with
the corresponding location condition for the () bound-state energy. They
are valid both for the charged case and for the neutral case. Combining these
relations with the standard effective-range function up to order six makes it
possible to reduce to two the number of free effective-range parameters if an
ANC value is known from experiment. Values for the scattering length, effective
range, and form parameter are determined in this way for the O+,
and He collisions in partial waves where a bound state
exists by using available ANCs deduced from experiments. The resulting
effective-range expansions for these collisions are valid up to energies larger
5 MeV.Comment: 17 pages, 6 figure
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
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
Quantum Monte Carlo calculations of spectroscopic overlaps in nuclei
We present Green's function Monte Carlo calculations of spectroscopic
overlaps for nuclei. The realistic Argonne v18 two-nucleon and
Illinois-7 three-nucleon interactions are used to generate the nuclear states.
The overlap matrix elements are extrapolated from mixed estimates between
variational Monte Carlo and Green's function Monte Carlo wave functions. The
overlap functions are used to obtain spectroscopic factors and asymptotic
normalization coefficients, and they can serve as an input for low-energy
reaction calculations
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
Generalized Faddeev equations in the AGS form for deuteron stripping with explicit inclusion of target excitations and Coulomb interaction
Theoretical description of reactions in general, and the theory for
reactions, in particular, needs to advance into the new century. Here deuteron
stripping processes off a target nucleus consisting of nucleons are
treated within the framework of the few-body integral equations theory. The
generalized Faddeev equations in the AGS form, which take into account the
target excitations, with realistic optical potentials provide the most advanced
and complete description of the deuteron stripping. The main problem in
practical application of such equations is the screening of the Coulomb
potential, which works only for light nuclei. In this paper we present a new
formulation of the Faddeev equations in the AGS form taking into account the
target excitations with explicit inclusion of the Coulomb interaction. By
projecting the -body operators onto target states, matrix three-body
integral equations are derived which allow for the incorporation of the excited
states of the target nucleons. Using the explicit equations for the partial
Coulomb scattering wave functions in the momentum space we present the AGS
equations in the Coulomb distorted wave representation without screening
procedure. We also use the explicit expression for the off-shell two-body
Coulomb scattering -matrix which is needed to calculate the effective
potentials in the AGS equations. The integrals containing the off-shell Coulomb
T-matrix are regularized to make the obtained equations suitable for
calculations. For and nucleon-target nuclear interactions we assume the
separable potentials what significantly simplifies solution of the AGS
equations.Comment: 34 pages, 13 figure
{Once more about astrophysical factor for the reaction
Recently to study the radiative capture process a new measurement of the
dissociation in the field of has been reported in [F.
Hammache {\it et al.} Phys. Rev , 065803 (2010)]. However, the
dominance of the nuclear breakup over the Coulomb one prevented from obtaining
the information about the process from
the breakup data. The astrophysical factor has been calculated
within the two-body potential model with potentials determined from
the fits to the elastic scattering phase shifts. However, the
scattering phase shift itself doesn't provide a unique bound state
potential, which is the most crucial input when calculating the
astrophysical factor at astrophysical energies. In this work we emphasize an
important role of the asymptotic normalization coefficient (ANC) for
, which controls the overall normalization of
the peripheral process and is
determined by the adopted bound state potential. We demonstrate that
the ANC previously determined from the elastic scattering -wave
phase shift in [Blokhintsev {\it et. al} Phys. Rev. {\bf C 48}, 2390 (1993)]
gives , which is at low energies about 38% lower than the one
reported in [F. Hammache {\it et al.} Phys. Rev , 065803 (2010)].
We recalculate also the reaction rates, which are also lower than those
obtained in [F. Hammache {\it et al.} Phys. Rev , 065803 (2010)].Comment: 6 pages and 2 figure
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
A new insight into the observation of spectroscopic strength reduction in atomic nuclei: implication for the physical meaning of spectroscopic factors
Experimental studies of one nucleon knockout from magic nuclei suggest that
their nucleon orbits are not fully occupied. This conflicts a commonly accepted
view of the shell closure associated with such nuclei. The conflict can be
reconciled if the overlap between initial and final nuclear states in a
knockout reaction are calculated by a non-standard method. The method employs
an inhomogeneous equation based on correlation-dependent effective
nucleon-nucleon (NN) interactions and allows the simplest wave functions, in
which all nucleons occupy only the lowest nuclear orbits, to be used. The
method also reproduces the recently established relation between reduction of
spectroscopic strength, observed in knockout reactions on other nuclei, and
nucleon binding energies. The implication of the inhomogeneous equation method
for the physical meaning of spectroscopic factors is discussed.Comment: 4 pages, accepted by Phys. Rev. Let
Asymptotic normalization coefficients of alpha-particle removal from O()
Asymptotic normalization coefficients (ANC) determine the overall
normalization of cross sections of peripheral radiative capture reactions. In a
recent paper [Blokhintsev et al., Eur. Phys. J. A 58, 257 (2022)], we
considered the ANC for the virtual decay O MeV)C(g.s.). In the present paper, which can be regarded as a
continuation of the previous, we treat the ANCs for the vertices
OC(g.s.) corresponding to the other three bound
excited states of O (, , , ). ANCs
() are found by analytic continuation in energy of the
C -wave partial scattering amplitudes, known from the
phase-shift analysis of experimental data, to the pole corresponding to the
O bound state and lying in the unphysical region of negative energies.
To determine , the scattering data are approximated by the sum of
polynomials in energy in the physical region and then extrapolated to the pole.
For a more reliable determination of the ANCs, various forms of functions
expressed in terms of phase shifts were used in analytical approximation and
subsequent extrapolation.Comment: arXiv admin note: substantial text overlap with arXiv:2208.0958
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