共查询到20条相似文献,搜索用时 31 毫秒
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A. I. Ahmedov G. V. Fedotovich E. A. Kuraev Z. K. Silagadze 《Physics of Atomic Nuclei》2004,67(5):985-992
We consider the π+π?π0γ final state in electron-positron annihilation at c.m.s. energies not far from the threshold. Both initial-and final-state radiations of the hard photon are considered, but without interference between them. The amplitude for the final-state radiation is obtained by using the effective Wess-Zumino-Witten Lagrangian for pion-photon interactions valid for low energies. In real experiments, energies are never so small that ρ and ω mesons would have a negligible effect. So a phenomenological Breit-Wigner factor is introduced in the final-state radiation amplitude to account for the vector mesons' influence. Using radiative 3π production amplitudes, a Monte Carlo event generator was developed which could be useful in experimental studies. 相似文献
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The Mellin-Barnes representation is used to improve the theoretical estimate of mass corrections to the width of a light pseudoscalar
meson decay into a lepton pair, P → l
+
l
−. The full resummation of the terms ln(m
l
2/Λ2)(m
l
2/Λ2)
n
and (m
l
2/Λ2)
n
to the decay amplitude is performed, where m
l
is the lepton mass and Λ ≈ m
ρ is the characteristic scale of the P → γ*γ* form factor. The total effect of the mass corrections for the e
+
e
− channel is negligible and, for the μ+μ−channel, its order is of a few percent.
The text was submitted by the authors in English. 相似文献
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Let g=vect(M) be the Lie (super)algebra of vector fields on any connected (super)manifold M; let - be the change of parity functor, C
i
and H
i the space of i-chains and i-cohomology. The Nijenhuis bracket makes into a Lie superalgebra that can be interpreted as the centralizer of the exterior differential considered as a vector field on the supermanifold associated with the de Rham bundle on M. A similar bracket introduces structures of DG Lie superalgebra in L
* and for any Lie superalgebra g. We use a Mathematica-based package SuperLie (already proven useful in various problems) to explicitly describe the algebras l
* for some simple finite dimensional Lie superalgebras g and their relatives - the nontrivial central extensions or derivation algebras of the considered simple ones. 相似文献
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Sergey V. Donskov Anatoly K. Likhoded Alexey V. Luchinsky Vladimir D. Samoylenko 《Central European Journal of Physics》2010,8(3):393-399
The decay η′ → ηπ
0
π
0 is studied in the framework of isobar model. It is shown, that good agreement with the experiment is achieved if α
0- and σ-meson contributions are taken into account. The contribution of α
0-meson is dominant, but σ-meson is necessary to reproduce the form of the Dalitz plot. Instead of the usual Breit-Wigner form of σ-meson propagator we use parametrization of the ππ-amplitude, which satisfies analyticity, crossing, unitarity and chirality constraints. This amplitude has a pole in the complex
plane, which corresponds to σ-meson and describe experimental data on ππ-scattering in K
e4 decay. 相似文献
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A precise investigation of radiative pion decay (π+ → e+νγ) in a pion beam from the meson factory of the Paul Scherrer Institute (Switzerland) was performed by the PIBETA Collaboration with the aid of the PIBETA detector. This resulted in finding 41 601 events of radiative pion decay in three kinematical regions. The absolute values of the branching ratio for radiative pion decay were determined in each of these regions. To a precision approximately four times higher than that known previously, the ratio of the axial-vector to the vector form factor was found to be γ ≡ F A /F V = 0.443 (15), the latter being fixed at F V = 0.0259. The number of events found in the kinematical region specified by photon energies of Eγ > 55.6 MeV, positron energies of E e > 20.0 MeV, and angles of θγ, e > 40° between the momenta of the corresponding particles (B region) was 5233. In region B, the measured branching ratio for radiative pion decay, Rπ→evγ(expt) = 11.6(3) × 10?8, proved to be smaller by eight standard deviations than that which follows from the Standard Model, Rπ→evγ (theor) = 14.34(1) × 10?8. 相似文献
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The static spherically symmetric solution for R ± μ
4/R model of f(R) gravity is investigated. We obtain the metric for space-time in the solar system that reduces to the Schwarzschild metric,
when μ tends to zero. For the obtained metric, the deviation from Einstein gravity is very small. This result is different from
the other results have been obtained by equivalence between f(R) gravity and scalar tensor theory. Also it is shown that the vacuum solution in the solar system depends on the shape of
matter distribution which differ from the Einstein’s gravity. 相似文献
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The process γ*γ → σ is investigated in the framework of the SU(2)×SU(2) chiral NJL model. The form factor of the process is derived for arbitrary virtuality of γ* in the Euclidean kinematic domain. The asymptotic behavior of this form factor resembles the asymptotic behavior of the γ*γ → π form factor. 相似文献
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Bastian Kubis Sebastian P. Schneider 《The European Physical Journal C - Particles and Fields》2009,62(3):511-523
Strong final-state interactions create a pronounced cusp in η′→η
π
0
π
0 decays. We adapt and generalize the non-relativistic effective field theory framework developed for the extraction of π
π scattering lengths from K→3π decays to this case. The cusp effect is predicted to have an effect of more than 8% on the decay spectrum below the π
+
π
− threshold. 相似文献
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E. M. Baldin 《Physics of Atomic Nuclei》2009,72(3):495-500
The product of the electron width of the J/ψ meson and the probability for its decay to an electron-positron pair was measured by using data from the KEDR experiment at the VEPP-4M electron-positron collider. The result was Γ ee × Γ ee /Γ = 0.3392 ± 0.0068(stat.) ± 0.0063(syst.) keV. 相似文献
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S. B. Dubovichenko 《Physics of Atomic Nuclei》2012,75(2):173-181
The possibility of describing experimental data on the astrophysical S factor for radiative proton capture on a 13C nucleus at energies in the range 0.03–0.8 MeV is considered within the potential cluster model involving forbidden states.
It is shown that the energy dependence of this astrophysical S factor can be reasonably explained on the basis of the E1 transition to the 3
P
1-wave bound state of the 14N nucleus in the p
13C channel from the 3
S
1 wave of p
13C scattering in the resonance energy region around 0.55 MeV in the laboratory frame. 相似文献
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C. M. Carloni-Calame S. Moretti F. Piccinini D. A. Ross 《The European Physical Journal C - Particles and Fields》2009,62(2):453-364
We compute the full one-loop EW contributions of
entering the electron–positron into two b-quarks and one gluon cross section at the Z peak and LC energies. We include both factorisable and non-factorisable virtual corrections, photon bremsstrahlung but not
the real emission of W
± and Z bosons. Their importance for the measurement of α
S from jet rates and shape variables is explained qualitatively and illustrated quantitatively. Their impact on the forward–backward
asymmetry is also analysed.
Work supported in part by the U.K. Science and Technology Facilities Council (STFC), by the European Union (EU) under contract
MRTN-CT-2006-035505 (HEPTOOLS FP6 RTN) and by the Italian Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR)
under contract 2006020509_004.
An erratum to this article can be found at 相似文献
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C.?M.?Carloni-Calame S.?Moretti F.?Piccinini D.?A.?Ross 《The European Physical Journal C - Particles and Fields》2009,62(2):355-364
We compute the full one-loop EW contributions of \({\mathcal{O}}(\alpha_{\mathrm{S}}\alpha_{\mathrm{EM}}^{3})\) entering the electron–positron into two b-quarks and one gluon cross section at the Z peak and LC energies. We include both factorisable and non-factorisable virtual corrections, photon bremsstrahlung but not the real emission of W ± and Z bosons. Their importance for the measurement of α S from jet rates and shape variables is explained qualitatively and illustrated quantitatively. Their impact on the forward–backward asymmetry is also analysed. 相似文献
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A. I. Golokhvastov 《Physics of Atomic Nuclei》2004,67(12):2227-2244
It is shown that experimental data on the multiparticle production of negatively charged pions in proton-proton interactions at \(\sqrt s \leqslant 30 GeV\) do not involve significant indications of the existence of anycorrela tions between negatively charged pions, apart from those that are associated with momentum conservation and with interference. The multiplicity distributions in rapidity intervals, forward-backward correlations, and two-particle rapidity and transverse-momentum correlations do not contradict the independent production of negatively charged pions. No constraints on the multiplicity distributions of product particles follow from their independent production. 相似文献
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