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1.
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
2.
The two-photon decay widths of scalar mesons σ(600), f
0(980), and a
0(980) are calculated in the framework of the local Nambu-Jona-Lasinio model. The contributions of the quark loops (Hartree-Fock
approximation) and the meson loops (next 1/N
c
approximation, where N
c
is the number of colors) are taken into account. These contributions, as we show, are the values of the same order of magnitude.
For the f
0 decay the K-loop contribution turns out to play the dominant role. The results are in satisfactory agreement with modern experimental
data. 相似文献
3.
L. A. Kondratyuk E. L. Bratkovskaya V. Yu. Grishina M. Büscher W. Cassing H. Str?her 《Physics of Atomic Nuclei》2003,66(1):152-171
We consider near-threshold a
0(980)-meson production in πN and NN collisions. An effective Lagrangian approach with one-pion exchange is applied to analyze different contributions to the
cross section for different isospin channels. The Reggeon exchange mechanism is also evaluated for comparison. The results
from πN reactions are used to calculate the contribution of the a
0 meson to the cross sections and invariant
mass distributions of the reactions
and pp → ppK
+
K
−. It is found that the experimental observation of a
0
+
mesons in the reaction
is much more promising than the observation of a
0
0
mesons in the reaction pp → ppK
+
K
−. Effects of isospin violation in the reactions pN → da
0, pd → 3He(3H)a
0, and dd → 4Hea
0, which are induced by a
0(980)-f
0(980) mixing, are also analyzed.
From Yadernaya Fizika, Vol. 66, No. 1, 2003, pp. 155–174.
Original English Text Copyright ? 2003 by Kondratyuk, Bratkovskaya, Grishina, Büscher, Cassing, Str?her.
This article was submitted by the authors in English. 相似文献
4.
Susana Coito George Rupp Eef van Beveren 《The European Physical Journal C - Particles and Fields》2011,71(10):1762
The nature of the X(3872) enhancement is analyzed in the framework of the Resonance-Spectrum Expansion, by studying it as a regular J
PC
=1++ charmonium state, though strongly influenced and shifted by open-charm decay channels. The observed but Okubo–Zweig–Iizuka-forbidden
ρ
0
J/ψ and ωJ/ψ channels are coupled as well, but effectively smeared out by using complex ρ
0 and ω masses, in order to account for their physical widths, followed by a rigorous algebraic procedure to restore unitarity. A
very delicate interplay between the D
0
D
∗0, ρ
0
J/ψ, and ωJ/ψ channels is observed. The data clearly suggest that the X(3872) is a very narrow axial-vector c[`(c)]c\bar{c} resonance, with a pole at or slightly below the D
0
D
∗0 threshold. 相似文献
5.
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
6.
On the basis of the decay couplings f
0 → ππ, K
, ηη, ηη′ found earlier in the study of analytical (IJ
PC
=00++) amplitude in the mass range 450–1900 MeV, we analyze the quark-gluonium content of the resonances f
0(980), f
0(1300), f
0(1500), and f
0(1750) and the broad state f
0(1420
−70
+150
). The K-matrix technique used in the analysis makes it possible to evaluate the quark-gluonium content both for the states with switched-off
decay channels (bare states, f
0
bare
) and for the real resonances. We observe a significant change in the quark-gluonium composition in the evolution from bare
states to real resonances, which is due to the mixing of states in the transitions f
0(m
1) → real mesons → f
0 (m
2) responsible for the decay processes as well. For f
0(980), the analysis confirmed the dominance of q
component, thus proving the n
/s
composition found in the study of the radiative decays. For the mesons f
0(1300), f
0(1500), and f
0(1750), the hadronic decays do not allow one to determine uniquely the n
, s
, and gluonium components, providing relative percentage only. The analysis shows that the broad state f
0(1420
−70
+150
) can mix with the flavor singlet q
component only, which is consistent with gluonium origin of the broad resonance.
From Yadernaya Fizika, Vol. 66, No. 4, 2003, pp. 772–785.
Original English Text Copyright ? 2003 by Anisovich, Nikonov, Sarantsev.
This article was submitted by the authors in English. 相似文献
7.
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
8.
Junfeng Sun Dongsheng Du Yueling Yang 《The European Physical Journal C - Particles and Fields》2009,60(1):107-117
The B
c
→J/ψ
π, η
c
π decays are studied with the perturbative QCD approach. It is found that the form factors
and
for the B
c
→J/ψ, η
c
transitions and the branching ratios are sensitive to the parameters ω, v, f
J/ψ
and
, where ω and v are the parameters of the charmonium wave functions for a Coulomb potential and the harmonic-oscillator potential, respectively,
and f
J/ψ
and
are the decay constants of the J/ψ and η
c
mesons, respectively. The large branching ratios and the clear signals of the final states make the B
c
→J/ψ
π, η
c
π decays the prospective channels for measurements at the hadron colliders. 相似文献
9.
10.
We use a non-perturbative approach which combines coupled channel Lippmann-Schwinger equations with meson-meson potentials provided by the lowest order chiral Lagrangian. By means of one parameter, a cut off in the momentum of the loop integrals, which results of the order of 1 GeV, we obtain singularities in the S-wave amplitudes corresponding to the σ, f0 and a0 resonances. The ππ → ππ, phase shifts and inelasticities in the T = 0 scalar channel are well reproduced as well as the π0η and mass distributions in the T = 1 channel. Furthermore, the total and partial strong decay widths of the f0 and a0 resonances are properly reproduced. The results seem to indicate that chiral symmetry constraints at low energy and unitarity in coupled channels is the basic information contained in the meson-meson interaction below GeV. 相似文献
11.
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
12.
We reconsider the utility of the radiative decay B→γℓν with an energetic photon in the final state for determining parameters of the B-meson light-cone distribution amplitude. Including 1/m
b
power corrections and radiative corrections at next-to-leading logarithmic order, we perform an improved analysis of the
existing BABAR data. We find a provisional lower limit on the inverse moment of the B meson distribution amplitude, λ
B
, which, due to the inclusion of radiative and power corrections, is significantly lower than the previous result. More data
with large photon energy are, however, required to obtain reliable results, as should become available in the future from
SuperB factories. 相似文献
13.
《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
14.
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
15.
通过显微光致发光技术和显微拉曼(Raman)技术研究了半绝缘GaAs (SI-GaAs)晶体的带边附近的发光. 在光荧光谱中,观察到在高于GaAs带边0.348eV处有一个新的荧光峰. 结合Raman谱指认此发光峰来源于GaAs的E0+Δ0能级的非平衡荧光发射. 同时, 通过研究E0+Δ0能级的偏振、激发光强度依赖关系,以及温度依赖关系说明E0+Δ0能级与带边E0共享了共同的导带位置Γ6,同时这也说明在GaAs中主要是导带的性质决定了材料的光学行为.同时,通过与n-GaAs和δ掺杂GaAs相比较,半绝缘GaAs晶体的E0+Δ0能级的发光峰更能反映GaAs电子能级高临界点E0+Δ0的能量位置和物理性质. 研究结果说明显微光致发光技术是研究半导体材料带边以上能级光学性质的一种非常有力的研究工具.
关键词:
半绝缘GaAs
显微光致发光
自旋轨道分裂 相似文献
16.
In terms of the adiabatic theory of interactions, we consider the results of the theoretical estimation of the rate constants
K
ST
of the nonradiative intersystem crossing conversion S
1(ππ*) ⇝ T
1
S
(ππ*) for nine aromatic molecules containing 10–14 carbon atoms and one or two heavy (many-electron) oxygen or chlorine atoms. 相似文献
17.
Simulation study of χc→J/Ψ+γ detection with J/Ψ→e+e? in pp collisions in the ALICE experiment at LHC
P. González P. Ladrón de Guevara E. López Torres A. Marín E. Serradilla 《The European Physical Journal C - Particles and Fields》2009,61(4):915-903
We present Monte Carlo preliminary results about the feasibility to detect the χ
c
family in p-p collisions at 14 TeV in the ALICE Central Barrel at CERN LHC. The χ
c1 and χ
c2 were forced to decay in the radiative channel J/Ψ+γ→e
+
e
−+γ and were merged with a proton-proton non-biased collision. After Monte Carlo transport and simulation of the detector response,
the e
+, e
− and converted γ were reconstructed and identified in the ALICE ITS, TPC and TRD detectors. Separate signals corresponding to γ from χ
c1 and from χ
c2 were observed. The position and relative weight of the fit to gaussians agreed with the input values within the statistical
limits.
An erratum to this article can be found at 相似文献
18.
Absorption spectra of β -carotene in 31 solvents
are measured in ambient conditions. Solvent effects on the 0--0 band
energy, the bandwidth, and the transition moment of the S0 →
S2 transition are analysed. The discrepancies between published
results of the solvent effects on the 0--0 band energy are
explained by taking into account microscopic solute-solvent
interactions. The contributions of polarity and polarizability of
solvents to 0--0 band energy and bandwidth are quantitatively
distinguished. The 0--0 transition energy of the S2 state at the gas
phase is predicted to locate between 23000 and 23600~cm-1. 相似文献
19.
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
20.
轻标量介子性质研究是当今中高能核物理研究中的热点问题之一,特别是质量低于1 GeV的标量介子f0(980)的内部结构一直存在争议,至今未达成共识。基于前人的研究结果,运用有效拉氏量方法,对f0(980)粒子的光生过程γp→pf0(980)进行了更深入的理论研究。探讨了两种传播子形式下得矢量介子ρ和ω交换的贡献,第一种是选择雷吉传播子,第二种是选择普通费曼传播子。第二种形式的微分散射截面理论结果与现有实验数据符合比第一种形式的结果好。基于此,计算了两种形式的总截面,两种形式给出的理论结果相差很大。另外,给出了γp→pf0(980)→pπ+π-过程的π+π-不变质量分布的理论预言,发现π+π-不变质量分布对于f0(980)于K-K的耦合常数(gf0KK)有很强的依赖关系,不同的gf0KK给出明显不同的π+π-不变质量分布。将来相关实验数据可以验证这些理论预言,并对矢量介子传播子形式和耦合常数gf0KK做出限制,加深人们对f0(980)粒子的认识。We study the scalar meson f0(980) in the γp→pf0(980) reaction within an effective Lagrangian approach. Based on previous studies, we calculate the differential cross sections of this reaction. We take two types of the propagators of vector mesons ρ and ω, one is the Regge form, the other one is the normal Feynman propagator. It is found that our theoretical results for the differential cross sections with the Feynman propagator are in agreement with the current experimental data. For the total cross sections, the results with the two types of propagator are much different. On the other hand, we predict the π+π- invariant mass distribution of the γp→pf0(980)→pπ+π- reaction. We find that the π+π- invariant mass distribution depends sensitively on the value of the coupling constant gf0KK. We hope that the future experiments can test our model calculation and give further constraints on the value of gf0KK and also the nature of f0(980). 相似文献