共查询到20条相似文献,搜索用时 15 毫秒
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用BESⅠ的7.8×106J/ψ数据更为精确地测定了J/ψ→π03(π+π-)和J/ψ→ω2(π+π-)的分支比(Br(J/ψ→π03(π+π-))=(2.52±0.06±0.43)%,Br(J/ψ→π03(π+π-))=(1.31±0.09±0.21)%.同时对4π不变质量谱和ωππ不变质量谱进行研究分析,试图观察是否存在有兴趣的信号. 相似文献
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We have analyzed the D^0→π^+π^- decay with α_s corrections in quantum chromodynamic (QCD) factorization and with the soft-gluon corrections in the light cone QCD sum rules. The soft-gluon effects are firstly calculated in the decay channel. The results show that once the factorization contributions, the α_s corrections, and the soft-gluon effects are all considered, we can satisfactorily explain the experimental data in the decay channel. 相似文献
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基于北京谱仪收集的7.0×106有中性触发的J/ψ事例,分析了J/ψ→γπ0π0衰变道.除了在π0π0不变质量谱中看到了众所周知的f2(1270)外,还证实了fJ(1710)和ξ(2230)的存在,同时给出了它们的质量以及相应的衰变分支比. 相似文献
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E. P. Shabalin 《Physics of Atomic Nuclei》2010,73(11):1908-1915
The unitarization of the amplitude for the decay process K
10 → π+π− and allowance for the rescattering of final-state pions in the decay process K
+ → π+π+π− make it possible to evaluate, by using the parameters extracted from data on K → 2π decays, the K
+ → π+π+π− decay width. The result agrees with the experimental width value at a level of a few percent. Allowance for corrections for
higher order terms of the momentum expansion of the amplitude for the decay process K
+ → π+π+π− leads to the slope-parameter value of g
++−th = 0.2182, which agrees with its experimental counterpart, g
++−exp = 0.2154 ± 0.0035. 相似文献
9.
《The European Physical Journal C - Particles and Fields》2007,50(2):329-340
Measured ratios of decay rates for , and are presented. These measurements are based on K± decays collected in a dedicated run in 2003 by the NA48/2 experiment at CERN. The results obtained are and . Using the PDG average for the K±→π±π0 normalisation mode, both values are found to be larger than the current values given by the particle data book and lead to
a larger magnitude of the |Vus| CKM element than previously accepted. When combined with the latest particle data book value of |Vud|, the result is in agreement with unitarity of the CKM matrix. In addition, a new measured value of is compared to the semi-empirical predictions based on the latest form factor measurements.
An erratum to this article can be found at 相似文献
10.
《The European Physical Journal C - Particles and Fields》2007,52(4):1021-1023
In an earlier paper [1], the background for Ke3 was over estimated due to an erroneous calculation of the electron identification efficiency. The correct ratios of the partial
widths involving this channel are and . Assuming the PDG value [2] for the K2π branching ratio, the measured branching fraction of Br (Ke3) continues to exceed the current PDG value [2]. The extracted value of |Vus|f+(0) is in agreement with the CKM unitary prediction; thus, our conclusions in [1] do not change.
The online version of the original article can be found at 相似文献
11.
本文用层子模型研究π0→2γ衰变的常见物理机制。在层子质量很大的假设下,对这些机制的贡献作了估计。 相似文献
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本文提出了ρ0-ω介子混合的一个可能形式,由(ρ0,ω)→π+π-衰变定出其耦合常数,并计算了它对ρ0,ω介子正负电子对衰变率的影响,结果表明其混合效应对ρ0→e+e-增加9.4%,而对ω→e+e-则减少2.6%. 相似文献
13.
基于北京谱仪收集的4.03GeV质心系能量下e+e-对撞数据,分析τ±τ±→e±+π±+nπ0+ν's(n=0,1,2)事例,给出分支比值Br(τ±→π±ντ)=(11.64±0.49+0.76-0.73%,Br(τ±→π±π0ντ)=(24.00±1.34+1.36-1.30%,Br(τ±→π±2π0ντ)=(9.39±1.68+1.69-1.66%. 相似文献
14.
The e
+
e
− → π
+
π
−
π
+
π
− cross section is calculated for energies of 0.65 ≤ √s ≤ 1 GeV in the framework of the generalized hidden local symmetry model. The calculations are compared with the data of CMD-2
and BaBaR. It is shown that the inclusion of heavy isovector resonances ρ(1450) and ρ(1700) is necessary for reconciling calculations
with the data. It is found that, at √s ≈ 1 GeV, the contributions of the above resonances are much larger, by a factor of 30, than the ρ(770) one, and amount to
a considerable fraction ∼0.3–0.6 of the latter at √s ∼ m
ρ.
The text was submitted by the authors in English. 相似文献
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利用色散关系研究了弱电流不守恒情况下的π-→π0+e+ν衰变过程。在对π—π散射相移作了一些假定后,证明了π、π中间态的贡献很小。在N、N中间态项中出现的N、N湮灭矩阵元用Chew-Ball理论及湮灭实验估计,同时出现的核子弱作用形状因子又用色散关系计算,证明了N、N中间态对它的贡献很小,计算了π、π中间态对它的贡献。根据现有N、N湮灭实验估计,π-→π0+e+ν过程的衰变几率<6×10-4秒-1。 相似文献
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DELPHI Collaboration W. Adam T. Adye E. Agasi I. Ajinenko R. Aleksan G. D. Alekseev P. P. Allport S. Almehed S. J. Alvsvaag et al. 《Zeitschrift fur Physik C Particles and Fields》1995,69(1):561-573
An analysis is presented of inclusiveπ
0 production inZ
0 decays measured with the DELPHI detector. At low energies,π
0 decays are reconstructed by using pairs of converted photons and combinations of converted photons and photons reconstructed
in the barrel electromagnetic calorimeter (HPC). At high energies (up to
) the excellent granularity of the HPC is exploited to search for two-photon substructures in single showers. The inclusive
differential cross section is measured as a function of energy forqq andbb events. The number ofπ
0’s per hadronicZ
0 event isN(π
0)/Z
had
0
=9.2±0.2(stat)±1.0(syst) and forbb events the number ofπ
0’s is N(π
0)/bb=10.1±0.4(stat)±1.1(syst). The ratio of the number ofπ
0’s inbb events to hadronicZ
0 events is less affected by the systematic errors and is found to be 1.09±0.05±0.01. The measuredπ
0 cross sections are compared with the predictions of different parton shower models. For hadronic events, the peak position
in theξ
p=ln(1/xp) distribution isξ*
p
=3.90
−0.14
+0.24
. The average number ofπ
0’s from the decay of primary B hadrons is found to be N(B→π
0
X)/B hadron=2.78±0.15(stat)±0.60(syst). 相似文献
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In this article,we calculate the contribution from the nonfactorizable soft hadronic matrix element to the decay B~0→χc1~π~0 with the light-cone quantum chromo-dynamic(QCD) sum rules.The numerical results show that its contribution is rather large and should not be neglected.The total amplitudes lead to a branching fraction which is in agreement with the experimental data marginally. 相似文献
19.
利用QCD因子化方法, 并采用具有质量的有效胶子传播子来消除端点发散, 计算了纯湮没衰变BS→π+π-过程的CP平均分支比并对该过程的CP破坏进行了具体研究. 结果表明: 该过程的CP平均分支比为1.24×10-7, 同时企鹅图对该过程起着主要贡献; BS→π+π-过程中直接CP破坏参数Cππ估算为-0.05, 混合CP破坏参数Sππ比较大,可达到0.18. 该过程在未来的LHC-b物理实验上是完全有可能被测量到的, 通过对该过程的研究能够使我们更好地了解B介子无璨衰变的动力学机制和胶子的性质. 相似文献
20.
The decays η → 3π
0 and η → π
0
π
+
π
− are considered within the isobar model. It is shown that, in order to explain the branching ratio and the shape of the Dalitz
plot for the decay η′ → 3π
0, it is sufficient to take into account the contributions of the σ and a
0 mesons. The inclusion of the σ meson is necessary for reproducing the shape of the distribution over the Dalitz plot. The branching ratio for the decay
η′ → π
0
π
+
π
− is obtained. The predictions for the distributions over the Dalitz plot for this decay are presented. These predictions depend
strongly on model parameters. 相似文献