共查询到20条相似文献,搜索用时 31 毫秒
1.
BES Collaboration 《中国物理C(英文版)》2002,26(1):8-16
The decay mode of J/ψ→π03(π+π-) was studied very little before. There are no informations except branching ratios for this channel in PDG book which based on less than 0.2×106J/ψ events of MARKⅠ. Now, BESⅠ has a data sample of 7.8×106J/ψ events, we can make more accurate results than MARKⅠ. Total of 3290±43 J/ψ→π03(π+π-) events including 1275±86 J/ψ→ω2(π+π-) events are selected. J/ψ→π03(π+π-) and J/ψ→ω2(π+π-) events have been generated with MC simulition for calculating events selection efficiency. BESⅠ result is: Br(J/ψ→π03(π+π-))=(2.52±0.06±0.43)% and Br(J/ψ→π03(π+π-))=(1.31±0.09±0.21)%. Meanwhile, we studied the invariant mass of 4π and ωππ to find interesting signals. It seems that there is a peak at about 1.74GeV in the invarianat mass spectrum of 4π, and a enhancement was also found at about 1.9GeV in the invariant mass spectrum of ωππ. It is not clear whether they are from resonances or background. Therefore, more work in detail is still going on. 相似文献
2.
BES Collaboration 《中国物理C(英文版)》1999,23(8):745-752
The decay J/ψ→γπ0π0 is studied with 7.0×106 produced J/ψ events collected by the Bening Spectrometer(BES) with the tugger mode senseuve to both chmped and neutral final state at the Bening Electron-Positron Collider(BEPC), The evidences for the existence of fJ(1710) and E(2230) in this channel are presented, and the corresponding masses as wen asthe product branching ratios are obtained. 相似文献
3.
BES Collaboration 《中国物理C(英文版)》1996,20(2):97-106
Two processes ψ(2S)→π+π-J/ψ,J/ψ→1+1- and J/ψ→anything are carefully studied to get the J/ψ leptonic branching fractions with the ψ(2S)data at BES/BEPC.The results are B(J/ψ→e+e-)=(5.90±0.07±0.16)% and B(J/ψ→μ+μ-)=(5.96 ±0.08±0.16)%,and Be/Bμ is estimated to be 0.990±0.018±0.024.Assuming Be=Bμ,the leptonic branching fraction of the J/ψ is B(J/ψ→1+1-)=(5.93±0.05 ± 0. 16 )%.This result is used to estimate the QCD scale factor ∧(nf/MS) and the strong coupling constant αs. 相似文献
4.
The coupling problem of the three different intermediate processes J/ψ→ωf2(1270),f2→π+π- and J/ψ→b1±(1235)π+,b1±→ωπ± included in the hadronic decay process J/ψ→ωπ+π- is discussed.The consideration of the coupling effect is very important for measuring the parameters of the resonances f2 and b1± and the helicity amplitude ratios of these reactions precisely. 相似文献
5.
The study of Bose-Einstein correlations between two identical particles offers a powerful probe to the space-time evolution of ultrarelativistic nucleus collisions.We calculate the correlation function of π-π- due to the four space-time and four-momentum distributions of π-at freeze-out in hadronic cascade simulation of 28Si(14.6 A GeV/c)+Au reactions.The correlation function calculated by Fourier transformation method,the correlation function resulted from fullcalculation and the corresponding experimental correlation function agree each other very well.The above freeze-out configuration of π- is also used to calculate the root mean square length of π- source.These lengths are compared with the conventional fitted radius parameters of source. 相似文献
6.
We analyze the decay amplitudes of the process a2(1320)→π+π+π- using the tensor analysis method and show how to obtain three body amplitudes. 相似文献
7.
π-核双电荷交换反应的强度与反应过程的两核子转移的核谱振幅直接联系着. 本文讨论了这类反应与它们的核谱因子的关系. 并以26Mg(π+, π-)26Si为例, 用两种核结构讨论了它的激发函数和微分截面. 我们所用的理论方法能够解释实验数据. 相似文献
8.
The structure function of τ→π±2π0v is measured by model independent method. The result is compared with Kuhn-Santamaria model, Isgur-Morningstar-Reader model and Feindt model. Good consistency between data and the three models is shown within the experimental error range. The comparison with the structure function of τ→3π±v measured by OPAL Collaboration also shows there is no obvious difference within 0.52. 相似文献
9.
Based on 58 million J/ψ data collected with the BESII detector at the BEPC, Partial Wave Analysis(PWA) is performed on J/ψ→ppπ0. The new excited baryon N(2065) is confirmed. Clear signals for other N* states are observed and the corresponding masses, widths and spin-parity are also measured. Processes such as J/ψ→ppη,ppη'
are also studied and the branching ratios are measured. 相似文献
are also studied and the branching ratios are measured. 相似文献
10.
The τ polarization asymmetry in τ→a1v→π±π0 π0v decay at Z0 peak is measured using data collected by L3 detector at LEP in 1992 and 1993, Apol=-0.239±0.126±0.100, where the first error is statistical and the second systematic. And the effective electroweak mixing angle sin2θw=0.2197±0.0219 is derived. 相似文献
11.
利用北京谱仪(BES)上取得的ψ(2S)数据,对ψ(2S)→π+π-J/ψ,J/ψ→1+1-和J/ψ→任意末态两个过程进行了细致的研究,得到J/ψ的轻子道衰变分支比为B(J/ψ→e+e-)=(5.90±0.07±0.16)%和B(J/ψ→μ+μ-)=(5.96±0.08±0.16)%,由此给出Be/Bμ的值为0.990±0.018±0.024.假定Be=Bμ,J/ψ的轻子道衰变分支比为B(J/ψ→1+1-)=(5.93±0.05±0.16)%.上述结果可用来估计强相互作用耦合常数αs和QCD减除参数∧. 相似文献
12.
本文用π核散射的微观描述,计算了Tπlab=240、343MeV时π+-16O弹性散射微分截面,定性地符合实验。 相似文献
13.
Using the method of QCD factorization, we calculate the branching ratio and the CP violation for pure annihilation decay BS→π+π- in the Standard Model. Meanwhile, we employ an effective gluon mass resulted in the study of the infrared behaviour of gluon propagators to avoid the soft endpoint divergence. We find that the CP-averaged branching ratio is about 1.24×10-7, and the penguin diagram contributions is dominant in this process. The direct CP violation parameter is about -0.05, while the mixing-induced CP asymmetry is a quite large number of 0.18. Once these quantities can be measured in the future LHC-b experiments, studying such a process will enrich our knowledge on the dynamics of the charmless hadronic decay of B-meson and the property of gluon. 相似文献
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15.
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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本文利用复合粒子量子场论的微扰展开方法计算了双例外原子(π&;#177;μ?)的四体衰变的几率,并与自由μ衰变作了比较。 相似文献
18.
我们在程函扭曲的DWIA框架下,用跃迁密度方法计算了180MeV和230MeV的π在18O上的非弹性散射到2+(1.98MeV)激发态的微分截面,分析了π-对π+的截面比,研究了中子分布半径对微分截面的影响,我们的结果与实验定性符合。 相似文献
19.
本文在π介子的一核子吸收模型下,导出了(π+,d)反应的扭曲波玻恩近似的截面公式,在平面波近似下,对12C(π+,d)10C 反应作了估计.认为,这一类反应对于研究π吸收的过程和原子核的对结构都是值得重视的反应. 相似文献