共查询到20条相似文献,搜索用时 15 毫秒
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The measurements of the ΔI = 1 part of the parity violating nuclear force when combined with information on neutral current couplings from neutrino
scattering and pion production experiments allow an estimate of the isoscalar admixture in the neutral current if it has a
vector axial-vector structure has been shown. 相似文献
3.
We study the parity-violating neutral current effects in muonic atoms which might result from an interference between E1 and E2 amplitudes in 3D → 1S transitions. We conclude that polarization asymmetries may be measurable in heavy atoms (Z ~ 70) exhibiting large nuclear deformations. 相似文献
4.
A microscopic approach to evaluate the contributions of one-pion exchange currents to the inelastic (e,e') scattering form factor of closed shell nuclei is developed. Both seagull and pionic parts of the two-body term are treated on the same footing and their final expressions are simple, clear and physically transparent. Application to the magnetic stretched states 4?(18.98 MeV) of 16O and 14?(6.74 MeV) of 208Pb is done. Agreement with the available experimental data is discussed. It is found that the effect of the meson exchange currents is a smooth but non-negligible enhancement ?15% at the first scattering maximum) at small momentum transfers and an increase by a factor bigger than 1.5 in the region of the second maximum. 相似文献
5.
I. Rotter 《Czechoslovak Journal of Physics》1986,36(8):979-981
A correction to nuclear structure calculations due to the finite lifetime of the excited states of a nucleus entails many-body effects of different nature. The analytical structure, as well as the results of numerical calculations, are given and discussed.Presented at the symposium Mesons and Light Nuclei, Bechyn, Czechoslovakia, May 27–June 1, 1985. 相似文献
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In a large class of gauge theories the trace of the weak neutral axial charge operator over any complete irreducible gauge multiplet is shown to vanish. This implies a relation involving deep inelastic neutrino-induced neutral current parity-violating cross sections which can be used to test the correctness of the Weinberg-Salam gauge multiplet structure of quarks. 相似文献
7.
Defining the ratiosr
p
=σ(vp →vx)/σ(vp →μ
−
x) and
we obtain the bounds 0.28 ⩽r
p
⩽ 0.61 and
using only the parton model and the data of CDHS group with iron target. We also give the complete set of parton-model relations
which would allow the determination of all the neutral-current coupling constants from inclusive cross sections alone. 相似文献
8.
Based upon the experiments on the electric form factor for the deuteron, we use the valon model to determine the valon distribution functions in a six-quark cluster and calculate the ratio of the structure functions of the nucleon bound in a light or intermediate heavy nucleus to the ones bound in the deuteron. 相似文献
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The study of cluster structures in light nuclei is extending to the heavy nuclei in these years. As for the stable N = Z nuclei, from the lighter 8Be, 12C nuclei to the heavier 20Ne and even the 40Ca and 44Ti medium nuclei, the α cluster structures have been well studied and confirmed. In heavy nuclei, due to the dominated mean field, the existence of α cluster structure is not clear as light nuclei but some clues were found for indicating the core+α cluster structure in some nuclei, in particular, the 208Pb+α structure in 212Po. We review some recent progress about the theoretical and experimental explorations of the α-clustering effects in heavy nuclei. We also discuss the possible α cluster structure of heavy nuclei from the view of α decay. 相似文献
11.
S. Willocq P. Marage M. Aderholz P. Allport J. P. Baton M. Berggren E. F. Clayton A. M. Cooper-Sarkar O. Erriquez P. J. W. Faulkner J. Guy P. O. Hulth G. T. Jones M. M. Mobayyen D. R. O. Morrison M. Neveu S. O'Neale J. Sacton R. A. Sansum K. Varvell W. Venus J. Wells W. Wittek 《Zeitschrift fur Physik C Particles and Fields》1992,53(2):207-217
Neutral strange particle production in \(\bar v\) Ne charged current interactions is studied using the bubble chamber BEBC, exposed to the CERN SPS antineutrino wide band beam. From a sample of 1191 neutral strange particles, the inclusive production rates are determined to be (15.7±0.8)% forK 0 mesons, (8.2±0.5)% for Λ, (0.4±0.2)% for \(\bar \Lambda \) and (0.6±0.3)% for Σ0 hyperons. The inclusive production properties ofK 0 mesons and Λ hyperons are investigated. The Λ hyperons are found to be polarized in the production plane. 相似文献
12.
V. F. Dmitriev 《Physics of Atomic Nuclei》2001,64(3):448-453
Nuclear anapole moments and axial neutral currents are calculated for a set of nuclei. The accuracy of the leading approximation is studied in detail. The core polarization renormalizing both the anapole moment and the axial current is treated in the random-phase approximation with effective forces. Parameters of parity-violating nuclear forces are discussed. The experimental value of the anapole moment of the 133Cs nucleus as extracted from data with allowance for axial-current renormalization is found to be κ=0.39±0.06. 相似文献
13.
H.C. Lee 《Nuclear Physics A》1978,294(3):473-491
Expressions are derived for evaluating the integrated inelastic cross section, , for the nuclear scattering of reactor antineutrinos in terms of experimentally determined B(Ml) values and Gamow-Teller matrix elements. These expressions are used to compute for many nuclear transitions. 相似文献
14.
A. J. Silenko 《Physics of Atomic Nuclei》2000,63(2):204-209
Relativistic expressions for the operators of current electric moments caused by electromagnetic spin-orbit interaction are obtained. Formulas for the matrix elements of the current electric moments of nuclei are derived. The contributions of the current electric moments to the quadrupole moment of the deuteron and to its root-mean-square radius are calculated with allowance for relativistic effects. 相似文献
15.
V. V. Ammosov A. G. Denisov G. S. Gapienko V. A. Gapienko V. I. Klyukhin V. I. Koreshev P. V. Pitukhin V. I. Sirotenko Z. U. Usubov V. G. Zaetz A. E. Asratyan A. V. Fedotov P. A. Goritchev S. P. Krutchinin M. A. Kubantsev I. V. Makhlueva V. I. Shekelyan V. G. Shevchenko A. B. Krebs 《Zeitschrift fur Physik C Particles and Fields》1987,36(3):377-381
The cross section of the quasi-elastic reactions \(\bar v_\mu p \to \mu ^ + \Lambda (\Sigma ^0 )\) in the energy range 5–100 GeV is determined from Fermilab 15′ bubble chamber antineutrino data. TheQ 2 analysis of quasi-elastic Λ events yieldsM A=1.0±0.3 GeV/c2 for the axial mass value. With zero µΛ K 0 events observed, the 90% confidence level upper limit \(\sigma (\bar v_\mu p \to \mu ^ + \Lambda {\rm K}^0 )< 2.0 \cdot 10^{ - 40} cm^2 \) is obtained. At the same time, we found that the cross section of reaction \(\bar v_\mu p \to \mu ^ + \Lambda {\rm K}^0 + m\pi ^0 \) is equal to \(\left( {3.9\begin{array}{*{20}c} { + 1.6} \\ { - 1.3} \\ \end{array} } \right) \cdot 10^{ - 40} cm^2 \) . 相似文献
16.
We use a simple renormalization group argument to demonstrate that the large top mass limit of the axial neutral current in QCD is unambiguously determined by the renormalization of the singlet axial current which suggests a natural scheme independent normalization condition for the latter. By calculating the anomalous dimension of the singlet axial current at three-loop level in the
scheme we derive the result for the top quark decoupling from the axial neutral current valid up to (and including) the terms of order
s
2
.Work supported by DFG Grant Nr. Ku 502/3-1 相似文献
17.
We determine nuclear structure functions and quark distributions for 7Li, 11B, 15N and 27Al. For the nucleon bound state we solve the covariant quark–diquark equations in a confining Nambu–Jona-Lasinio model, which yields excellent results for the free nucleon structure functions. The nucleus is described using a relativistic shell model, including mean scalar and vector fields that couple to the quarks in the nucleon. The nuclear structure functions are then obtained as a convolution of the structure function of the bound nucleon with the light-cone nucleon distributions. We find that we are readily able to reproduce the EMC effect in finite nuclei and confirm earlier nuclear matter studies that found a large polarized EMC effect. 相似文献
18.
P. Guichon M. Giffon J. Joseph R. Laverrière C. Samour 《Zeitschrift für Physik A Hadrons and Nuclei》1978,285(2):183-189
A calculation is made of exchange current corrections for partial capture rates of muons in12C,16O,32S and40Ca nuclei. One-pion exchange is taken into account. Adler-Dothan's results are used to obtain the weak pion production amplitude. The nuclear states are described in the Tamm-Dancoff approximation. It is found that the corrections are very erratic and state dependent. A large effect is found for the 0+→0? transitions due to the size of the time part of the axial exchange current. 相似文献
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