共查询到20条相似文献,搜索用时 40 毫秒
1.
C.A. Gagliardi A. Azhari V. Burjan F. Carstoiu V. Kroha A.M. Mukhamedzhanov A. Sattarov X. Tang L. Trache R.E. Tribble 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):227-232
Peripheral transfer reactions can be used to determine asymptotic normalization coefficients (ANCs). These coefficients, which
specify the normalization of the tail of the nuclear overlap function, determine S-factors for direct capture reactions at astrophysical energies. A variety of proton transfer reactions involving both stable
and radioactive beams have been used to measure ANCs. Tests have demonstrated that ANCs determined from proton transfer reactions
can be used to calculate astrophysical direct capture rates to within 9%. The 10B(7Be, 8B)9Be and 14N(7Be, 8B)13C reactions have been used to measure the ANC appropriate for determining the 7Be(p,γ)8B rate, and the 14N(11C, 12N)13C reaction has been used to measure the ANC required to calculate the 11C(p,γ)12N rate.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
2.
A new analysis of the precise experimental astrophysical S factors for the direct-capture reaction 7Be(p, γ)8B [A.J. Junghans et al., Phys. Rev. C 68, 065803 (2003) and L.T. Baby et al., Phys. Rev. C 67, 065805 (2003)] is carried out on the basis of a modified two-body potential approach in which the direct astrophysical S factor, S
17(E), is expressed in terms of the asymptotic normalization constants for p + 7Be → 8B and two additional conditions are involved to verify the peripheral character of the reaction under consideration. The Woods-Saxon
potential form is used for the bound-(p + 7Be)-state wave function and for p
7Be-scattering wave function. New estimates are obtained for the “indirectly measured” values of the asymptotic normalization
constants (the nuclear vertex constants) for the p + 7Be → 8B and S
17(E) at E ≤ 115 keV, including E = 0. These values of S
17(E) and asymptotic normalization constants have been used for obtaining the indirectly measured values of the s-wave average scattering length and the p-wave effective-range parameters for p
7Be scattering.
The text was submitted by the authors in English. 相似文献
3.
S. V. Artemov S. B. Igamov K. I. Tursunmakhatov R. Yarmukhamedov 《Bulletin of the Russian Academy of Sciences: Physics》2009,73(2):165-170
Experimental astrophysicalS-factors for the direct radiative capture processes d(p,γ)3He and 16O(p,γ)17F are analyzed using the modified two-body potential approach. The values of the asymptotic normalization coefficients (nuclear
vertex constants) are found for the wave functions of the 3He and 17F nuclei in the (d + p) and (16O + p) channels respectively and are then used to extrapolate the astrophysical S-factor to the region of very low energies.
Original Russian Text ? S.V. Artemov, S.B. Igamov, K.I. Tursunmakhatov, R. Yarmukhamedov, 2009, published in Izvestiya Rossiiskoi
Akademii Nauk. Seriya Fizicheskaya, 2009, Vol. 73, No. 2, pp. 176–181. 相似文献
4.
The 3He(4He, γ)7Be and 3H(4He, γ)7Li reactions are studied in an extended two-cluster model which contains α + h/t and 6Li + p/n clusterizations. We show that the inclusion of the 6Li + p/n channels can significantly change the zero-energy reaction cross sections, S(0), and other properties of the 7Be and 7Li nuclei, like the quadrupole moments Q. However, the results agree with the known correlation trend between S(0) and Q. Moreover, we demonstrate that the value of the zero-energy derivatives of the astrophysical S-factors are more uncertain than currently believed.
Received June 17, 1999; revised February 22, 2000; accepted for publication April 17, 2000 相似文献
5.
The phase-shift-analysis data for the 3He4He scattering are analyzed using the effective-range theory, with the Coulomb interaction taken into account. We find both
the renormalized nuclear vertex constants for the vertex 7Be → 3He + 4He in the ground (3/2−) and in the first excited (1/2−) bound states of 7Be, and the corresponding asymptotic normalization constants of the radial wave functions in these states. The results obtained
can be used in an astrophysical S-factor calculation for radiative capture reaction 4He(3He, γ)7Be 相似文献
6.
The calculated rate of events in some of the existing solar neutrino detectors is directly proportional to the rate of the
7Be(p, γ)8B reaction measured in the laboratory at low energies. However, the low-energy cross sections of this reaction are quite uncertain
as various measurements differ from each other by 30–40%. The Coulomb dissociation process which reverses the radiative capture
by the dissociation of 8B in the Coulomb field of a target, provides an alternate way of accessing this reaction. While this method has several advantages
(like large breakup cross sections and flexibility in the kinematics), the difficulties arise from the possible interference
by the nuclear interactions, uncertainties in the contributions of the various multipoles and the higher order effects, which
should be considered carefully. We review the progress made so far in the experimental measurements and theoretical analysis
of the breakup of 8B and discuss the current status of the low-energy cross sections (or the astrophysical S-factor) of the 7Be(p, γ)8B reaction extracted therefrom. The future directions of the experimental and theoretical investigations are also suggested.
Work supported by EPSRC, UK, grant nos J/95867 and L/94574. 相似文献
7.
S. V. Artemov S. B. Igamov Q. I. Tursunmakhatov R. Yarmukhamedov 《Physics of Atomic Nuclei》2012,75(3):291-309
The astrophysical S factors for the radiative-capture reaction 14N(p, γ)15O in the region of ultralow energies were calculated on the basis of the R-matrix approach. The values of the radiative and protonic widths were fitted to new experimental data. The contribution of
direct radiative capture to bound states of the 15O nucleus was determined with the aid of asymptotic normalization coefficients, whose values were refined in the present study
on the basis of the results obtained from an analysis of the reaction 14N(3He, d)15O at three different energies of incident helium ions. A value of S(0) = 1.79 ± 0.31 keV b was obtained for the total astrophysical S factor, and the reaction rate was determined for the process 14N(p, γ)15O. 相似文献
8.
B. Davids S.M. Austin D. Bazin H. Esbensen B.M. Sherrill I.J. Thompson J.A. Tostevin 《The European Physical Journal A - Hadrons and Nuclei》2002,15(1-2):65-68
A kinematically complete measurement was made of the Coulomb dissociation of 8B nuclei on a Pb target at 83 MeV/nucleon. The cross-section was measured at low relative energies in order to infer the astrophysical
S-factor for the 7Be(p,γ)8B reaction. A first-order perturbation theory analysis of the reaction dynamics including E1, E2, and M1 transitions was employed to extract the E1 strength relevant to neutrino-producing reactions in the solar interior. By fitting the measured cross-section from E
rel = 130 keV to 400 keV, we find S
17(0) = 17.8+1.4
-1.2 eV b. Semiclassical 1st-order perturbation theory and fully quantum-mechanical continuum-discretized coupled-channels analyses
yield nearly identical results for the E1 strength relevant to solar-neutrino flux calculations, suggesting that theoretical reaction mechanism uncertainties need
not limit the precision of Coulomb-breakup determinations of the 7Be(p,γ)8B S-factor. A recommended value of S
17(0) based on a weighted average of this and other measurements is presented. This recommendation implies a revised value for
the theoretical flux of 8B solar neutrinos, which is also given.-1
Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002
RID="a"
ID="a"Present address: Kernfysisch Versneller Instituut, Zernikelaan 25, 9747 AA Groningen, The Netherlands; e-mail: davids@kvi.nl 相似文献
9.
V. S. Belyaev A. P. Matafonov S. M. Ribakov V. P. Krainov V. S. Lisitsa V. P. Andrianov G. N. Ignat’ev A. S. Rusetskiy 《Laser Physics》2011,21(8):1398-1403
The experimental results on the initiation of various (γ, n) and (p, n) nuclear reactions in the picosecond laser plasma are presented. It is demonstrated that the following (γ, n) and (p, n) nuclear reactions can be initiated at a laser intensity of 2 × 1018 W/cm2 with the threshold energies of γ-quanta ranging from 1.67 to 7.56 MeV and the threshold energies of protons ranging from 1.88 to 5 MeV: 9Be(γ, n)2α, 181Ta(γ, n)180Ta, 7Li(p, n)7Be, 63Cu(p, n)63Zn, 48Ti(p, n)48V. The method based on the detection of fast neutrons using the 3He counters is employed for the measurement of the number
of the initiated (γ, n) and (p, n) nuclear reactions. The measured yield of the (γ, n) and (p, n) nuclear reactions ranges from 5 × 101 to 105 reactions per laser pulse. 相似文献
10.
S. B. Dubovichenko 《Russian Physics Journal》2011,53(12):1254-1263
The interaction potentials describing some phases of elastic p
7Li scattering for energies up to 0.8 MeV and the ground bound P
0 state of the 8Be nucleus in the p
7Li cluster channel are obtained. The astrophysical S-factor of the p
7Li → 8Beγ radiative capture is considered for the potential cluster model. 相似文献
11.
Yu. V. Orlov L. I. Nikitina 《Bulletin of the Russian Academy of Sciences: Physics》2012,76(4):446-449
We find the vertex constant for the synthesis α + α → 8Be and the corresponding asymptotic normalization coefficient of the Gamov wave function for 8Be in the ground state. We use modern data on the position and width of the narrow resonance of this state as well as the
energy dependence of the αα scattering phase shift in the s-wave known from the literature. The effective-range theory was applied with the Coulomb interaction taken into account. The
parameters of the standard effective-range function expansion up to the member with k
4 (k being the relative momentum) were found. 相似文献
12.
Yong-Yeon Keum 《Pramana》2004,63(6):1151-1170
We discuss applications of the perturbative QCD approach in the exclusive non-leptonic two-bodyB-meson decays. We briefly review its ingredients and some important theoretical issues on the factorization approach. PQCD
results are compatible with present experimental data for charmless B-meson decays. We predict the possibility of large direct
CP asymmetry in B0 → π+π− (23 +7%) and B0 →K
+π− (− 17 ± 5%). We also investigate the branching ratios, CP asymmetry and isospin symmetry breaking in radiativeB →(K*/ρ)γ decays. 相似文献
13.
V. V. Anisovich L. G. Dakhno M. A. Matveev V. A. Nikonov A. V. Sarantsev 《Physics of Atomic Nuclei》2007,70(1):63-92
In the framework of the spectral integral equation, we consider the
states and their radiative transitions. We reconstruct the
interaction on the basis of data for the levels of the bottomonium states with J
PC = 0−+, 1−−, 0++, 1++, 2++ as well as the data for the radiative transitions γ (3S) → γχbJ(2P) and γ(2S) → γχbJ(1P) with J = 0, 1, 2. We calculate bottomonium levels with the radial quantum numbers n ≤ 6, their wave functions, and corresponding radiative transitions. The ratios Br[χbJ(2P) → γγ(2S)]/Br[χbJ(2P) → γγ(1S)] for J = 0, 1, 2 are found to be in agreement with data. We determine the
component of the photon wave function using the data for the e
+
e
− annihilation, e
+
e
− → γ(9460), γ(10 023), γ(10 036), γ(10 580), γ(10 865), γ(11 019), and predict partial widths of the two-photon decays ηb0 → γγ, χb0 → γγ, χb2 → γγ for the radial excitation states below the
threshold (n ≤ 3).
The text was submitted by the authors in English. 相似文献
14.
15.
T. Kikuchi T. Motobayashi N. Iwasa Y. Ando M. Kurokawa S. Moriya H. Murakami T. Nishio J. Ruan S. Shirato S. Shimoura T. Uchibori Y. Yanagisawa T. Kubo H. Sakurai T. Teranishi Y. Watanabe M. Ishihara M. Hirai T. Nakamura S. Kubono M. Gai R.H. France III K.I. Hahn T. Delbar P. Lipnik C. Michotte 《The European Physical Journal A - Hadrons and Nuclei》1998,3(3):213-215
We have measured the dissociation of 8B in the Coulomb field of 208Pb at Ein=51.9 MeV/nucleon and extracted the cross section of the 7Be(p,γ)8B reaction at 0.4 ≤ Erel≤ 3 MeV, which is of importance for the 8B solar-neutrino production rate. The extracted astrophysical S17 factors are consistent with our earlier Coulomb dissociation measurement, and agree with the values deduced from the direct
capture measurements by Filippone et al., Vaughn et al. and Hammache et al. The S factor at zero energy was extracted to be
18.9±1.8 eV-b with the help of theoretical energy-dependence.
Received: 15 August 1998 相似文献
16.
Preliminary data on the reactions e
+
e
−→φ→γ f
0(980)→γπ0π0 together with data on ππ scattering and the reactions J/ψ→φπ+π− and K
−
p→π +π−(Λ,Σ) are analyzed. The analysis shows that the mass of the f
0(980) meson is
= 950 MeV, and BR(φ→γf
0→γπ0π0)≃ 1× 10−4, indicating that the f
0(980) resonance is of a four-quark nature.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 445–449 (10 April 1998) 相似文献
17.
V.D. Efros H. Oberhummer A. Pushkin I.J. Thompson 《The European Physical Journal A - Hadrons and Nuclei》1998,1(4):447-453
A semi–microscopic model for the low–energy photodisintegration of the 9Be nucleus is constructed, and the experimental data are analyzed with its help. The older radioactive isotope data are supported
by this analysis. The theoretical photodisintegration cross section is derived. The astrophysical rates for the reaction α+α+n→9Be+γ and the reverse photodisintegration of 9Be are calculated. The new reaction rate for α+α+n→9Be+γ is compared with previous estimations.
Received: 19 January 1998 相似文献
18.
P. Descouvemont 《The European Physical Journal A - Hadrons and Nuclei》2001,12(4):413-419
The 9Be and 9B nuclei are investigated in a microscopic three-cluster model involving α + α +
n (or α + α +
p) configurations. The 8Be (0
+
, 2
+
) +
n and 5He (3/2
-
, 1/2
-
) + α (or mirror) channels are included by taking account of the unstable nature of 8Be and 5He. Spectroscopic properties of 9Be and 9B are analyzed. We show that the 5He + α configurations cannot be neglected to derive accurate results. The 9Be(γ,αα)n photodisintegration cross-section is shown to be mainly determined by 8Be + n channels at low energies, but 5He + α channels become important beyond E
γ≈ 4 MeV.
Received: 7 September 2001 / Accepted: 19 November 2001 相似文献
19.
We perform a theoretical study based on dispersion relations of the reaction γγ → π
0
π
0 emphasizing the low-energy region. We discuss how the ƒ
0(980) signal emerges in γγ → ππ within the dispersive approach and how this fixes to a large extent the phase of the isoscalar S-wave γγ → ππ amplitude above the threshold. This allows us to make sharper predictions for the cross-section at lower energies and our results could then
be used to distinguish between different ππ isoscalar S-wave parameterizations with the advent of new precise data on ππ → π
0
π
0. We compare our dispersive approach with an updated calculation employing the unitary chiral perturbation theory (U
gC
PT). We also pay special attention to the role played by the σ-resonance in γγ → ππ and calculate its coupling and width to γγ, for which we obtain Γ(σ → γγ) = (1.68 ± 0.15) keV. 相似文献
20.
X.-J. Wang J.-H. Jiang M.-L. Yan 《The European Physical Journal A - Hadrons and Nuclei》2002,14(2):219-224
In terms of effective field theory and mixed-propagator approach, we show that there is a larger hidden effect of isospin
breaking in ρ→πγ decay due to a ω exchange, ρ→ω→πγ. The branching ratio is predicted as B(ρ→πγ) = (11.67±2.0)×10-4, which is much larger than Particle Data Group's datum (6.8±1.7)×10-4 and one of charged mode, B(ρ±→π±γ) = (4.5±0.5)×10-4.
Received: 7 January 2002 / Accepted: 2 April 2002 相似文献