共查询到20条相似文献,搜索用时 390 毫秒
1.
D. Babusci H. Czy? F. Gonnella S. Ivashyn M. Mascolo R. Messi D. Moricciani A. Nyffeler G. Venanzoni KLOE-?Collaboration 《The European Physical Journal C - Particles and Fields》2012,72(3):1917
A possibility of KLOE-2 experiment to measure the width
\varGammap0 ?gg\varGamma_{\pi^{0} \to\gamma\gamma} and the π
0
γγ
∗ form factor F(Q
2) at low invariant masses of the virtual photon in the space-like region is considered. This measurement is an important test
of the strong interaction dynamics at low energies. The feasibility is estimated on the basis of a Monte-Carlo simulation.
The expected accuracy for
\varGammap0 ?gg\varGamma_{\pi^{0} \to\gamma\gamma} is at a per cent level, which is better than the current experimental world average and theory. The form factor will be measured
for the first time at Q
2≤0.1 GeV2 in the space-like region. The impact of these measurements on the accuracy of the pion-exchange contribution to the hadronic
light-by-light scattering part of the anomalous magnetic moment of the muon is also discussed. 相似文献
2.
3.
《The European Physical Journal C - Particles and Fields》2008,58(4):531-541
The production of two high-p
T
jets in the interactions of quasi-real photons in e
+
e
− collisions at
from 189 GeV to 209 GeV is studied with data corresponding to an integrated e
+
e
− luminosity of 550 pb−1. The jets reconstructed by the k
⊥
-cluster algorithm are defined within the pseudo-rapidity range −1<η<1 and with jet transverse momentum, p
T
, above 3 GeV/c. The differential di-jet cross-section is measured as a function of the mean transverse momentum
of the jets and is compared to perturbative QCD calculations.
Deceased 相似文献
4.
R. Akers G. Alexander J. Allison K. J. Anderson S. Arcelli A. Astbury D. Axen G. Azuelos J. T. M. Baines A. H. Ball et al. 《Zeitschrift fur Physik C Particles and Fields》1994,61(2):199-208
We present measurements of the hadronic photon structure functionF
2
(x), in twoQ
2 ranges with mean values of 5.9 GeV2 and 14.7 GeV2. The data were taken by the OPAL experiment at LEP, with
close to theZ
0 mass and correspond to an integratede
+
e
– luminosity of 44.8 pb–1. In the context of a QCD-based model we find the quark transverse momentum cutoff separating the vector meson dominance (VMD) and perturbative QCD regions to be 0.27±0.10 GeV. We confirm that there is a significant pointlike component of the photon when the probe photon hasQ
2>4 GeV2. Our measurements extend to lower values ofx than any previous experiment, and no increase ofF
2
(x) is observed. 相似文献
5.
The branching ratios and photon spectra of the rare processes ρ(ω) → π
0
π
0
γ, ρ(ω) → ηπ
0
γ are calculated in the framework of the standard local quark Nambu-Jona-Lasinio model. Three types of diagrams are considered:
the quark box and the pole diagrams with scalar (σ, α
0(980)) and vector (ρ, ω) mesons. The obtained estimates for the widths of the processes ρ(ω) → π
0
π
0
γ are in satisfactory agreement with existing experimental data. Predictions are made for the widths of the processes ρ(ω) → ηπ
0
γ.
The text was submitted by the authors in English. 相似文献
6.
The influence of hydrothermal modification of γ-Al2O3 on the properties of NiMo/γ-Al2O3 catalyst was investigated in this paper. The experimental results showed that the use of the modified γ-Al2O3 in the preparation of the NiMo/γ-Al2O3 catalyst led to the increase of the dispersion of the surface Mo and Ni oxides, favored the formation of the poly-molybdates and promoted the reduction of the active Mo oxides owing to the increase of the surface acidity of the modified γ-Al2O3. Therefore, the NiMo/γ-Al2O3 catalyst supported on the modified γ-Al2O3 exhibited a higher hydrodenitrogenation (HDN) activity than that supported on the untreated γ-Al2O3 in the temperature range of 300-340 °C. 相似文献
7.
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
8.
9.
Current and upcoming experiments should improve the sensitivity to e
α
→e
β
γ decays by an order of magnitude. This paper assumes that one of the τ→e
β
γ decays is observed, and explores the structure and consequences of the required new flavoured couplings. In simple models
(a low-scale seesaw, leptoquarks) it is shown that the dipole vertex function is proportional to a product of flavoured matrices
from the Lagrangian (a “Jarlskog-like” invariant), provided that the loop particles are weakly coupled to the Higgs. Secondly,
if the dipole vertex function has a hierarchical structure, this might imply that only some of the τ→e
β
γ modes can be observed, due to the “approximate zero” implied by the bound on μ→eγ. The assumptions underlying this potential test of a hierarchical structure are discussed. 相似文献
10.
In this note,we discuss the cross-sections of the production of Υ particles in p-p collisions as color excited states in the Han-Nambu model.The results are consistent with present experiments. 相似文献
11.
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
12.
Cross-sections for the 27Al(γ, x)22Na multichannel reaction with the 28.3 MeV difference of reaction thresholds 下载免费PDF全文
O.S. Deiev I.S. Timchenko S.N. Olejnik V.A. Kushnir V.V. Mytrochenko S.A. Perezhogin 《中国物理C(英文版)》2022,46(6):064002-064002-9
The bremsstrahlung flux-averaged cross-sections \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})}\rangle$\end{document} ![]()
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and the cross-sections per equivalent photon \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})_{Q}}\rangle$\end{document} ![]()
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were first measured for the photonuclear multichannel reaction \begin{document}${^{27}{\rm{Al}}}(\gamma,\textit{x})^{22}{\rm{Na}}$\end{document} ![]()
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at end-point bremsstrahlung gamma energies ranging from 35 MeV to 95 MeV. The experiments were performed with the beam from the NSC KIPT electron linear accelerator LUE-40 using the γ-activation technique. The bremsstrahlung quantum flux was calculated with the GEANT4.9.2 program and was also monitored via the \begin{document}$^{100}{\rm{Mo}}(\gamma,{n})^{99}{\rm{Mo}}$\end{document} ![]()
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reaction. The flux-averaged cross-sections were calculated using the partial cross-section \begin{document}$\sigma(E)$\end{document} ![]()
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values computed with the TALYS1.95 code for different level density models. Consideration is given to special features of calculating the cross-sections \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})}\rangle$\end{document} ![]()
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and \begin{document}$\langle{\sigma(E_{{\gamma {\rm{max}}}})_{Q}}\rangle$\end{document} ![]()
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for the case of the final nucleus \begin{document}$^{22}{\rm{Na}}$\end{document} ![]()
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via several partial channels \begin{document}$\textit{x}$\end{document} ![]()
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: \begin{document}${n}\alpha + {dt} + {npt} + 2{n}{^{3}\text{He}} + {n2d} + {2npd} + {2p3n}$\end{document} ![]()
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. 相似文献
13.
The application of a high purity Germanium (HPGe) γ spectrometer in determining the fuel element burnup in a future reactor is studied. The HPGe detector is exposed by a 60Co source with varying irradiation rate from 10× 103m s-1 to 150× 103m s-1 to simulate the input counting rate in real reactor environment. A 137Cs and a 152Eu source are positioned at given distances to generate a certain event rate in the detector with the former being proposed as a labeling nuclide to measure the burnup of a fuel element. It is shown that both the energy resolution slightly increasing with the irradiation rate and the passthrough rate at high irradiation level match the requirement of the real application. The influence of the background is studied in the different parameter sets used in the specially developed procedure of background subtraction. It is demonstrated that with the typical input irradiation rate and 137Cs intensity relevant to a deep burnup situation, the precision of the 137Cs counting rate in the current experiment is consistently below 2.8%, indicating a promising feasibility of utilizing an HPGe detector in the burnup measurement in future bed-like reactors. 相似文献
14.
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
15.
16.
The widths with respect to the radiative decays f
0(980) → ργ and a
0(980) → ωγ were calculated within the local Nambu-Jona-Lasinio model. The contributions of both quark and meson loops were taken into
account. The latter and the former play a dominant role for the radiative decays of, respectively, the f
0(980) and the a
0(980) meson. 相似文献
17.
We summarize the recent effective field theory (EFT) studies of low-energy electroweak reactions of astrophysical interest, relevant to big-bang nucleosynthesis. The zero energy astrophysical S(0) factor for the thermal proton radiative capture by deuteron is calculated with pionless EFT. The astrophysical S(0) factor is accurately determined to be S(0)=0.243 eV·b up to the leading order (LO). At zero energies, magnetic transition M1 gives the dominant contribution. The M1 amplitude is calculated up to the LO. A good, quantitative agreement between theoretical and experimental results is found for all observables. The demonstrations of cutoff independent calculation have also been presented. 相似文献
18.
The angular distribution for the process J/ψ→V1+X,X→γ+V2,V2→2P or 3P(where V1 and V2 stand for the vector mesons,P is the pseudoscalar meson) are presented.They can be used to distinguish the spin of the boson resonance X and determine the space parity in some special cases. 相似文献
19.
20.
This Letter explores single field inflation models with a constant, but arbitrary speed of sound cs, obtained by deforming the kinetic energy terms to a Dirac–Born–Infeld form. Allowing cs<1 provides a simple parametrization of non-Gaussianity. The dependence of inflationary observables on the parameter cs is considered in the leading order slow roll approximation. The results show that in most cases the dependence is actually rather weak for the range of cs allowed by existing bounds on non-Gaussianity. 相似文献