共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
The process of baryon production in Kp collisions at high energies is considered in the framework of the quark-gluon string model. The contribution of the string-junction
mechanism to the strange-baryon production is analyzed. The results of numerical calculations are in reasonable agreement
with the data on inclusive spectra of p, Λ,
and on the
/Λ asymmetry. The predictions for inclusive spectra and production asymmetry of Ξ and Ω baryons are presented.
The text was submitted by the authors in English. 相似文献
3.
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
4.
Zhi-Gang Wang 《The European Physical Journal C - Particles and Fields》2008,57(4):711-718
We calculate the strong coupling constant g
ΔN
π
and study the strong decay Δ++→p
π with light-cone QCD sum rules. The numerical value of the strong coupling constant g
ΔN
π
is consistent with the experimental data. The small discrepancy may be due to the failure to take into account perturbative
corrections. 相似文献
5.
6.
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
7.
Lamia Benhabib 《The European Physical Journal C - Particles and Fields》2009,62(1):197-201
In ultra-relativistic Heavy-Ion Collisions (HIC), the properties of the quark gluon plasma (QGP) can be explored, in particular,
via measurements of neutral pions. The π
0 is an important probe for both proton and heavy ion physics. In the former case, π
0 production provides an important mean of testing pQCD as well as useful data to constrain current and future theoretical
models. In the latter case, π
0 measurements will serve as a baseline for exploring the nature of the HIC hard scattering. In the ALICE experiment, π
0 mesons are identified as they decay into two photons (π
0→γ
γ) using the high-resolution photon spectrometer (PHOS). PHOS will measure π
0 transverse momentum over a wide range, from hundreds of MeV/c to several tens of GeV/c. An estimation of π
0 production cross-section in proton–proton collisions is calculated in a next-to-leading order (NLO) approximation and first
presented. The π
0 geometrical acceptance and the identification efficiency along with the analysis on the invariant mass are the two important
correction factors for obtaining a realistic π
0 spectrum discussed in this paper. 相似文献
8.
9.
V. A. Tryasuchev 《Physics of Atomic Nuclei》2011,74(1):103-109
On the basis of the dynamical model for meson photoproduction on nucleons, it is shown that only eight broad resonances (of
width in excess of 120 MeV), of which two belong to the class of missing resonances, are required for reproducing experimental
data from the threshold for the reaction γp → ηp to the photon energy of 3 GeV. 相似文献
10.
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
11.
L. I. Govor A. M. Demidov V. A. Kurkin I. V. Mikhailov 《Physics of Atomic Nuclei》2010,73(7):1101-1105
The results obtained by studying the angular distributions of gamma rays with respect to the neutron-beam axis in the reaction
178Hf(n, n′γ) involving the deexcitation of the K
π
= 0+ rotational bands of 178Hf are presented.New information about themultipole-mixing parameter δ in gamma transitions from the levels of these bands is obtained. The K
π
= 04+ band is constructed anew. The relationship between the parameter δ for the (2+0
n
−2+01) gamma transition and the energy gap Δ
n
= E
lev(2+0
n
) − E
lev(0+0
n
), on one hand, and the quasiparticle structure of the rotational band, on the other hand, is discussed for 178Hf on the basis of the quasiparticle-phonon model. 相似文献
12.
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
13.
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
14.
S. Faller A. Khodjamirian Ch. Klein Th. Mannel 《The European Physical Journal C - Particles and Fields》2009,60(4):603-615
We derive new QCD sum rules for B→D and B→D
* form factors. The underlying correlation functions are expanded near the light-cone in terms of B-meson distribution amplitudes defined in HQET, whereas the c-quark mass is kept finite. The leading-order contributions of two- and three-particle distribution amplitudes are taken into
account. From the resulting light-cone sum rules we calculate all B→D
(*) form factors in the region of small momentum transfer (maximal recoil). In the infinite heavy-quark mass limit the sum rules
reduce to a single expression for the Isgur–Wise function. We compare our predictions with the form factors extracted from
experimental B→(*)
l
ν
l
decay rates fitted to dispersive parameterizations. 相似文献
15.
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
16.
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
17.
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
18.
Nguyen Thi Thu Huong Ha Huy Bang Nguyen Chinh Cuong Dao Thi Le Thuy 《International Journal of Theoretical Physics》2007,46(1):39-48
We discuss the pair production of scalar quarks in e
+
e
− annihilation within the MSSM with complex parameters. We calculate the SUSY-QCD corrections to the cross section and show that the effect of the CP phases of these complex parameters on the cross section can be quite strong in a large
region of the MSSM parameter space. This could have important implications for squarks searches and the MSSM parameter determination
in future collider experiments.
PACS number(s): 14.80. Ly, 12.60. Jv, 13.10. + q, 13.88. +e. 相似文献
19.
A. Aprahamian 《Physics of Atomic Nuclei》2004,67(9):1750-1755
Low-lying K π = 0+ bands are one of the most fundamental excitation modes in the spectra of deformed nuclei; however, very little is known about the nature of these excitations. We report on some new lifetime measurements using the GRID technique at ILL, and high-precision (p, t) reactions to elucidate the character of low-lying K π = 0+ bands in deformed nuclei. We also present results from a recent calculation on the nature of 0+ states using the projected shell model. 相似文献
20.
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