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1.
V. F. Dmitriev 《Physics of Atomic Nuclei》2009,72(7):1165-1167
Using a simple phenomenological parametrization of the reaction amplitude we calculated α-particle spectrumin the reaction p + 11B → α + 8Be* → 3α at the resonance proton energy of 675 keV. The parametrization includes Breit-Wigner factor with an energy-dependent width
for intermediate 8Be* state and the Coulomb and the centrifugal factors in α-particle-emission vertices. The shape of the spectrum consists of a well-defined peak corresponding to emission of the primary
α and a flat shoulder going down to very low energy. We found that below 1.5MeV there are 17.5% of α’s and below 1MeV there are 11% of them.
The text was submitted by the author in English. 相似文献
2.
V. A. Kovalchuk 《Physics of Atomic Nuclei》2007,70(4):722-731
A method for determining the angle γ and the ratio of the amplitudes A
λ(B
− →
K
*−) and A
λ)B
− → D
*0
K
*−), r
Bλ, for all three vector-meson polarization states by using the decays B
∓ → D
*
K
*∓ is proposed. This method relies on the interference between the decays B
− → D
*0
K
*− and B
− →
K
*−, which arises if D
*0 and
decay to D
0/
π
0 and D
0/
γ, whereupon D
0 and
mesons decay to common final hadron states. The doubly Cabibbo-suppressed modes of D
0-meson decay are chosen here to specify such final states.
Original Russian Text ? V.A. Kovalchuk, 2007, published in Yadernaya Fizika, 2007, Vol. 70, No. 4, pp. 754–763. 相似文献
3.
J. Ryckebusch W. Van Nespen 《The European Physical Journal A - Hadrons and Nuclei》2004,20(3):435-441
Differential cross-sections for exclusive 16O(e,epp)14C processes are computed within a distorted-wave framework which includes central short-range correlations and intermediate
excitations. The cross-sections are compared to high-resolution data from the MAMI facility at Mainz for a central energy and momentum transfer of
MeV and
MeV, respectively. A fair agreement between the numerical calculations and data is reached when using spectroscopic information extracted from a 15N
C experiment. The comparison between the calculations and the data provides additional evidence that short-range correlations exclusively affect nucleon pairs with a small center-of-mass momentum residing in a relative S state.Received: 3 September 2003, Revised: 2 December 2003, Published online: 18 June 2004PACS:
24.10.-i Nuclear-reaction models and methods - 21.60.-n Nuclear-structure models and methods - 25.30.Fj Inelastic electron scattering to continuum 相似文献
4.
Dong-Xi Wang Yan-Lin Ye Cheng-Jian Lin Jia-Hao Chen Kai Ma Jia-Xing Han Hui-Ming Jia Lei Yang Li-Sheng Yang Zi-Yao Hu Ying Chen Wei-Liang Pu Gen Li Zhi-Wei Tan Hong-Yu Zhu Tian-Peng Luo Shan-Hao Zhong Da-Hu Huang Jian-Ling Lou Xiao-Fei Yang Qi-Te Li Jin-Yan Xu Zai-Hong Yang Kang Wei 《中国物理C(英文版)》2023,47(1):014001-014001-6
5.
Zhi-Gang Wang 《The European Physical Journal C - Particles and Fields》2008,58(2):245-250
We study the final-state rescattering effects in the decay B
0→η
c
K
*. The numerical results indicate that the corrections are comparable with the contribution from the naive factorizable amplitude,
and the total amplitudes can accommodate the experimental data. 相似文献
6.
K. R. Mikhailov A. V. Stavinsky A. V. Vlassov B. O. Kerbikov R. Lednicky 《Physics of Atomic Nuclei》2009,72(4):668-674
We report preliminary data on proton-lambda correlations at small relative momentum q in the e
3He(4He) → e′pΛX reaction at E
0 = 4.7(4.46) GeV using the CLAS detector at Jefferson Lab. The enhancement of the correlation function at small q was found to be in qualitative agreement with theoretical expectations. The size of emission region about 1.5 fm was estimated
using Lednicky-Lyuboshitz analytical model. The experimental correlation function is comparable with the P-matrix fit of the hyperon-nucleon data. Small-relative-momentum-proton-lambda correlations both for 3He(4He) target and for electroproduction reaction were studied for the first time.
(for CLAS Collaboration)
The text was submitted by the authors in English. 相似文献
7.
The e
+
e
− → π
+
π
−
π
+
π
− cross section is calculated for energies of 0.65 ≤ √s ≤ 1 GeV in the framework of the generalized hidden local symmetry model. The calculations are compared with the data of CMD-2
and BaBaR. It is shown that the inclusion of heavy isovector resonances ρ(1450) and ρ(1700) is necessary for reconciling calculations
with the data. It is found that, at √s ≈ 1 GeV, the contributions of the above resonances are much larger, by a factor of 30, than the ρ(770) one, and amount to
a considerable fraction ∼0.3–0.6 of the latter at √s ∼ m
ρ.
The text was submitted by the authors in English. 相似文献
8.
S. Rai Choudhury A. S. Cornell Naveen Gaur 《The European Physical Journal C - Particles and Fields》2008,58(2):251-259
Flavor changing neutral current (FCNC) decays of the B-meson are a very useful tool for studying possible physics scenarios beyond the standard model (SM), where of the many FCNC
modes radiative, purely leptonic and semi-leptonic decays of the B-meson are relatively clean tests. Within this context, the BELLE collaboration has measured the process B→K
*
γ and also searched for the B→K
1(1270)γ process. Theoretical analyses of these processes are yielding similar values of the relevant form factors. In this work we
have used this upper bound in studying the angular correlations for the related semi-leptonic decay mode B
−→K
1−(1270)(→ρ
0
K
−)ℓ
+
ℓ
−, where we have used the form factors that have already been estimated for the B→K
1(1270)γ mode. Note that the additional form factors that are required were calculated using large energy effective theory (LEET). 相似文献
9.
Using the technique of helicity amplitudes, the electromagnetic process e
+
e
− → μ+μ− is theoretically investigated in the one-photon approximation. The structure of the triplet states of the final (μ+μ−) system is analyzed. It is shown that in the case of unpolarized electron and positron the finalmuons are also unpolarized,
but their spins are strongly correlated. Explicit expressions for the components of the correlation tensor of the final (μ+μ−) system are derived. The formula for the angular correlation at the decays of final muons μ+ and μ−, produced in the process e
+
e
− → μ+μ−, is obtained. It is demonstrated that spin correlations of muons in the process of electron-positron pair annihilation have
the purely quantum character, since one of the incoherence inequalities for the correlation-tensor components is always violated.
The additional contribution of the weak interaction of lepton neutral currents through the virtual Z
0 boson is considered; it is established that, taking into account the weak interaction, the qualitative character of the muon
spin correlations does not change.
The text was submitted by the authors in English. 相似文献
10.
V. V. Varlamov B. S. Ishkhanov V. N. Orlin S. Yu. Troshchiev 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):842-849
The results from experimental and theoretical studies of the total and partial cross sections of photoneutron reactions on
the 197Au isotope were analyzed. The cross sections for reactions σ(γ, nX) = σ(γ, n) + σ(γ, np) + … + σ(γ, 2nX) = σ(γ, 2n) + σ(γ, 2np) + … were evaluated in the energy range 7 ≤ E
γ ≤ 30 MeV using an approach free of the shortcomings of experimental photoneutron multiplicity sorting methods. The total
photoneutron reaction cross sections σexp(γ, xn) = σexp(γ, nX) + 2σexp(γ, 2nX) + … = σexp(γ, n) + σexp(γ, np) + 2σexp(γ, 2n) + 2σexp(γ, 2np) + … were used as the initial experimental data. The contributions from the cross sections σ(γ, nX) and σ(γ, 2nX) to the cross sections σexp(γ, xn) were separated using the multiplicity transition functions F
1
theor = σtheor(γ, 1nX)/σtheor(γ, xn) and F
2
theor = σtheor(γ, 2nX)/σtheor(γ, xn), calculated within an updated version of the pre-equilibrium model of photonuclear reactions. New evaluated data for both
partial reaction cross sections, i.e., σeval (γ, 1nX) = F
1
theorσexp(γ, xn) and σeval(γ, 2nX) = F
2
theorσexp(γ, xn), were obtained. The cross sections σeval(γ, nX) and σeval.(γ, 2nX) evaluated using the theoretically calculated functions F
1,2theor are consistent with the Livermore data, but substantially contradict the Saclay data. 相似文献
11.
The polarization of the recoil proton from the reactionp
0
p has been measured for photon energies between 900–1,350 MeV and pion c.m. angles between 70° and 150°. There are significant deviations from recent analysis. 相似文献
12.
Yu-Ming Wang M. Jamil Aslam Cai-Dian Lü 《The European Physical Journal C - Particles and Fields》2009,59(4):847-860
The exclusive weak decay of Λ
b
→Λ
γ and Λ
b
→Λ
l
+
l
− are investigated in the Appelquist–Cheng–Dobrescu model, which is an extension of the standard model in the presence of universal
extra dimensions. Employing the transition form factors obtained in the light-cone sum rules, we analyze how the invariant-mass
distribution, the forward–backward asymmetry and the polarization asymmetry of the Λ baryon of these decay modes can be used to constrain the only additional free parameter with respect to the standard model,
namely, the radius, R, of the extra dimension. Our results indicate that the Kaluza–Klein modes can lead to approximately 25% suppression of the
branching ratio of Λ
b
→Λ
γ; however, their contributions can bring about 10% enhancement to the decay rate of Λ
b
→Λ
l
+
l
−. It is shown that in the present scenario the zero position of the forward–backward asymmetry of Λ
b
→Λ
μ
+
μ
− is sensitive to the compactification parameter R, while the measurement of polarizations of Λ baryon in the Λ
b
decays are not a useful tool to provide any valuable information for the universal extra-dimension model. 相似文献
13.
Cross-sections of the 238U (n, γ) 239U reaction in the 3.0–7.0 MeV energy region measured by relative activation method
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The reaction cross-sections of 238U (n, γ)239U have been experimentally determined at neutron energies of 6.117 ± 0.119 MeV, 4.626 ± 0.086 MeV, and 3.622 ± 0.348 MeV employing the relative activation approach along with the off-line γ-ray spectroscopy method. The D (d, n)3He reaction was utilized to obtain monoenergetic neutrons of the required energy, and the 197Au (n, γ)198Au reaction cross-sections were adopted as the referential standard to ascertain the neutron capture cross-sections of 238U. Furthermore, the effects of low-energy scattered neutrons, neutron fluence fluctuations, counting of geometric corrections when measuring γ-rays, and neutron and γ-ray self-absorption caused by the sample thickness have been considered and revised in the present work. For a comparison with experimental results, the cross-sections of the 238U (n, γ)239U reaction were calculated theoretically with the original parametric TALYS-1.9 program. The experimental measurements were in contrast to previous experimental results and the evaluation data available for ROSFOND-2010, CENDL-3.2 and ENDF/B-VIII.0. 相似文献
14.
In this study,218Ac and 221Th nuclides were produced via the heavy-ion induced fusion evaporation reaction 40Ar+186W.Their decay properties were studied with the help of the gas-filled recoil spectrometer SHANS and a digital data acquisition system.The cross section ratio between 222Pa and 218Ac was extracted experimentally,withmeasured value 0.69(9).Two new possible α decay branches to 221Th are suggested.The valence neutron configurations for the daughter 217Ra are discussed in terms of the hindrance factors. 相似文献
15.
V. A. Zheltonozhskii A. N. Savrasov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(6):829-832
Isomeric yield ratios of 115m,g
Cd and 120m,g
Sb were measured in the (γ, n) reaction in the near-threshold region at γ-ray energies of 9.6, 9.8, 10.0, and 10.5 MeV. Experimental
values of the isomeric yield ratios were compared with theoretical values calculated using the TALYS-1.0 program package.
The (γ, n) reaction is shown to have a statistical character in the excitation region of residual nuclei 0.3–1.5 MeV. 相似文献
16.
DELPHI Collaboration W. Adam T. Adye E. Agasi I. Ajinenko R. Aleksan G. D. Alekseev P. P. Allport S. Almehed S. J. Alvsvaag et al. 《Zeitschrift fur Physik C Particles and Fields》1995,69(1):561-573
An analysis is presented of inclusiveπ
0 production inZ
0 decays measured with the DELPHI detector. At low energies,π
0 decays are reconstructed by using pairs of converted photons and combinations of converted photons and photons reconstructed
in the barrel electromagnetic calorimeter (HPC). At high energies (up to
) the excellent granularity of the HPC is exploited to search for two-photon substructures in single showers. The inclusive
differential cross section is measured as a function of energy forqq andbb events. The number ofπ
0’s per hadronicZ
0 event isN(π
0)/Z
had
0
=9.2±0.2(stat)±1.0(syst) and forbb events the number ofπ
0’s is N(π
0)/bb=10.1±0.4(stat)±1.1(syst). The ratio of the number ofπ
0’s inbb events to hadronicZ
0 events is less affected by the systematic errors and is found to be 1.09±0.05±0.01. The measuredπ
0 cross sections are compared with the predictions of different parton shower models. For hadronic events, the peak position
in theξ
p=ln(1/xp) distribution isξ*
p
=3.90
−0.14
+0.24
. The average number ofπ
0’s from the decay of primary B hadrons is found to be N(B→π
0
X)/B hadron=2.78±0.15(stat)±0.60(syst). 相似文献
17.
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
18.
H. -J. Behrend L. Criegee J. H. Field G. Franke H. Jung J. Meyer O. Podobrin V. Schr?der G. G. Winter P. J. Bussey et al. 《Zeitschrift fur Physik C Particles and Fields》1991,49(1):43-48
We have studied the 0 production rate in the reaction 3+3– in the energy range 1.6W
7.5 GeV with the CELLO detector at PETRA. Our analysis points to a substantial yield of 00+– events in particular atW
>4.0 GeV. We give cross sections for the 02+2– and 00+– final states and calculate upper limits for the reaction 00 (1700) 00+–.Now at CERN 相似文献
19.
The results of recent experiments performed at KEK, Brookhaven National Laboratory, the Institute for High-Energy Physics
(Protvino), and CERN to study the reaction π
−
p → π
0
π
0
n are analyzed in detail. For S-wave pion-pion scattering in the channel of isospin I=0, new data are obtained for the phase shift δ
0
0
and the inelasticity parameter η
0
0
. Difficulties that arise in using, for the amplitudes of the S and D waves of the final π
0
π
0 system, physical solutions selected on the basis of partial-wave analyses are discussed. It is noteworthy that other solutions
are preferable in principle in the region of the invariant mass m of the π
0
π
0 system above 1 GeV. With the aim of clarifying the situation and further studying the properties of the f
0(980) resonance, it is proposed to perform, in the reaction π
−
p → π
0
π
0
n, an especially careful examination of the m region in the vicinity of the
threshold.
__________
Translated from Yadernaya Fizika, Vol. 67, No. 7, 2004, pp. 1380–1391.
Original Russian Text Copyright ? 2004 by Achasov, Shestakov. 相似文献
20.
The resonance states in 16O+16O, 12C+16O, α+16O and α+12C are described using modified Morse potential proposed earlier whose success has already been demonstrated in the case of
12C+12C system. The general validity of such a potential with long range, shallow depth and repulsive soft core determined from
the resonance data itself is being examined through the present study of the resonances in the above four systems. In each
system, the experimental data of a large number of states have been successfully described with a modified Morse potential.
The success points out a common mechanism of the origin of these states, and reaffirms authentically the diatomic-like rotational
and vibrational picture of the nuclear molecular resonances proposed previously. The close resemblance between the physics
of diatomic molecules and nuclear molecular resonances extending to the level of potential which is Morse type in both the
cases — although belong to two different areas of physics — is further strengthened through the present study.
相似文献