关于ηc粒子及其电磁衰变

本文在势模型的框架内估算了ηc粒子的质量、宽度及几种主要电磁衰变道的分支比.指出禁戒型磁跃迁ηc→J/ψγ的相对论修正结果比简单的非相对论估算有可能大一个量级.讨论了北京正负电子对撞机(BEPC)对级联电磁辐射过程ψ′(3686)→γηc→γγ¹P₁,γγJ/ψ,3γ进行测量的可能性.     

J/ψ→γγV(ρ,φ)衰变的实验研究

利用北京谱仪(BES)收集的7.8×10⁶ J/ψ事例,对J/ψ→γγV(ρ,φ)衰变道中的η(1430)共振态进行了分析.从J/ψ→γγρ衰变模式得到其质量及衰变宽度分别为1431±17MeV和88±28MeV,衰变分支比Br(J/ψ→γη(1430))Br(η(1430)→γρ)=(1.1±0.5±0.3)×10^－4;而从J/ψ→γγφ衰变模式得到其质量及衰变宽度分别为1424±15MeV和73±58MeV,衰变分支比Br(J/ψ→γη(1430))Br(η(1430)→γφ)=(2.0±1.0±0.6)×10^－4.     

赝标介子的胶子球分量与它们在J/ψ辐射衰变过程中的产生

本文用微扰论QCD计算了赝标胶子球在J/ψ辐射衰变过程中产生的几率. 指出由于ι(1440)与η、η′的混合, 使η、η′有一个胶子球分量, 这些分量在它们的J/ψ辐射衰变产生中占主导地位. 由此得到的比例Γ(J/ψ→γη′)/Γ(J/ψ→γη)比以前一些理论模型的结果要大, 并且是与实验符合的.     

Charmonium dissociation in collisions with φ mesons in hadronic matter

The φ-charmonium dissociation reactions in hadronic matter are studied.Unpolarised cross sections forφJ/ψ→D_s~-D_s~+,φJ/ψ→D_s~(*-)D_s~+ or D_s~-D_s~(*+),φJ/ψ→D_s~(*-)D_s~(*+),φψ'→D_s~-D_s~+,φψ'→D_s~(*-)D_s~+ or D_s~-D_s~(*+),φψ'→D_s~(*-)D_s~(*+),φχ_c→D_s~-D_s~+,φχ_c→D_s~(*-)D_s~+ or D_s~-D_s~(*+) and φχ_c→D_s~(*-)D_s~(*+) are calculated in the Born approximation,in the quark-interchange mechanism and with a temperature-dependent quark potential.The potential leads to remarkable temperature dependence of the cross sections.With the cross sections and the φ distribution function we calculate the dissociation rates of the charmonia in interactions with the φ meson in hadronic matter.The dependence of the rates on temperature and charmonium momentum is relevant to the influence of φ mesons on charmonium suppression.     

η、η′和ι的夸克和胶子内容、双光子衰变和J/ψ辐射衰变产生

本文引进q_iq_i→q_jq_j以及q_iq_i→(gg)湮没项^[1],并考虑了对湮没项的SU(3)破坏效应^[2],讨论了η、η′和ι的混合,得到了它们的有声有色和胶子内容.与此同时,引入EPCAC(扩充的部分守恒赝矢流)假设^[3],考察了η、η′和ι的双光子衰变.本文还计算了衰变宽度比R₁=Γ(J/ψ→γη′)/Γ(J/ψ→γη)以及R₂=Γ(J/ψ→γη′)/Γ(J/ψ→γι),指出了实验结果对纯胶子球质量值的限制.     

在BEPCⅡ/BESⅢ上寻找胶子球的Monte Carlo研究

在即将建造的BEPCⅡ BESⅢ上利用MonteCarlo模拟研究了J ψ→γX→γηη′(η′→γρ0 ,ρ0 →π+ π-,η→γγ)过程.研究显示BESⅢ的良好性能和大统计量的J ψ事例样本为寻找胶子球态的一些候选者并确认其存在提供了可能.基于所研究的衰变道,为BESⅢ电磁量能器晶体BGO和CsI的选择及磁场强度的选择提供了数据.     

J/ψ衰变中赝标量介子混合的研究

利用PDG-2000公布的J/ψ→VP,γP各个衰变道分支比的世界平均值,对赝标量介子混合重新做了分析.如果η和η′中不含有胶子成分,则得到它们的混合角θ_P=(－19.18±0.91)°.对J/ψ衰变中DOZI的贡献、SU(3)破坏以及矢量介子的混合也做了讨论和分析.     

B→Kη′中双胶子聚合机制的进一步研究

双胶子聚合机制可能解释B→Kη′反常大的分支比.然而由于我们对η′犂犂有效顶点知之甚少,微扰QCD的理论计算存在很大的不确定性.本文尝试了几种不同的η′犂犂形状因子,并将数值结果和实验相比较.我们发现,虽然我们对η′犂犂形状因子了解得很少,但是如果B→Kη′衰变中双胶子聚合机制确实很重要的话,B→K^*η′的分支比将为10^－5量级,这可以被将来的实验检验.     

J/φ强子衰变过程的角分布螺旋度形式

本文给出了e~+e~-→J/φ→V+X,V→P_1P_2和e~+e~-→J/φ→V+X,X→P_4P_5过程的角分布螺旋度形式.为e~+e~-实验数据分析提供了理论公式.     

Exclusive γ(*)γ processes

A short review of experimental and theoretical results on the large angle cross sections"γγ→two mesons"and the form factors γ*γ→P = {π,η,η′} is given.     

赝标介子η,η′和非(qq)介子的混合研究

利用包含η,η′的一些辐射跃迁和它们的双光子衰变过程和某些J/ψ→P+V(赝标介子和矢量介子)电磁过程的最新实验数据,对赝标介子η,η’和非(q,q)同位旋标量味单态(如ι/η(1440)的混合问题进行了研究.用最小二乘法拟合两种方案的混合参数,发现若仅考虑η和η′的混合,则拟合结果不够好.若考虑η,η’和此非(qq)介子(以后用ι表示)的混合,则拟合结果比较好.其结果表明η′必混有少量非(qq)成份,而ι中也混有一定的(qq)成份.     

Relativistic correction to gluon fragmentation function into pseudoscalar quarkonium

Inspired by the recent measurements of the ηc meson production at LHC experiments, we investigate the relativistic correction effect for the fragmentation functions of gluon/charm quark fragmenting into η_c, which constitute the crucial nonperturbative element for the ηc production at high p_T. Employing three distinct methods,we calculate the next-to-leading-order(NLO) relativistic correction to g →η_c fragmentation function in the NRQCD factorization framework, as well as verifying the existing NLO result for the c →η_c fragmentation function. We also study the evolution behavior of these fragmentation functions with the aid of the DGLAP equation.     

Search for ψ(4S) → ηJ/ψ in B~±→ ηJ/ψK~± and e~+e~-→ ηJ/ψ processes

We search for the ψ(4S) state in the B~±→ηJ/ψK~± and e~+e~-→ηJ/ψ processes based on the Belle measurements with the assumed mass M =(4230±8) MeV/c~2 and width Γ =(38±12) MeV. No significant signal is observed in the ηJ/ψ mass spectra. The 90% confidence level upper limit on the product branching fraction B(B~±→ψ(4S)K~±)B(ψ(4S)→ηJ/ψ) 6.8×10~(-6) is obtained in the B~±→ηJ/ψK~± decays. By assuming the partial width of ψ(4S)→e~+e~-to be 0.63 ke V, a branching fraction limitB(ψ(4S)→ηJ/ψ) 1.3% is obtained at the 90%confidence level in e~+e~-→ηJ/ψ, which is consistent with the theoretical prediction.     

确定ξ(2230)自旋的一种新方法

本文得到了过程e~+e~→J/ψ→γB(J~η)、B(J~η)→P_1P_2的矩的光子角分布,提供了确定ξ(2230)自旋的新途径.     

北京谱仪上J/ψ→γπ0、γη、γη'→3γ衰变道的分支比测量

分析J/ψ衰变终态为三个光子的衰变道,测量得到了衰变道J/ψ→γπ⁰和J/ψ→γη’的分支比分别为Br(J/ψ→γπ⁰)=(4.6±1.1)×10^－5和Br(J/ψ→、η＇)=(4.12±0.82)×10^－3;相对分支比F(J/ψ→γη’)/F(J/ψ→γη)=4.79±0.85,在实验误差范围内与两个理论模型的预言都能一致.     

ηb decay into charmonium in association with cc pair

We calculate the inclusive decay rates of ηb into charmonium via double c~ pairs for S- and P-wave states ηc, J/ψ and XcJ within the framework of non-relativistic QCD （NRQCD） factorization at leading order in αs. Besides calculating the contributions of the color-singlet channels ηb → cc[2s＋1SL^（1）]＋cc, the effects of cc pair in the color-octet configurations are also considered. We find that ηb → cc[3S1^（8）] ＋cc make a small contribution to Br（ηb →J/ψ（ηc）＋cc）. While in the ηb →XcJ ＋cc case, the color octet contributions are significant, for they are of the same a 5 order as the color-singlet processes. We predict Br（ηb →J/ψ（ηc）＋cc） = 2.99（2.75） × 10^-5 Vc for S-wave states J/ψ and ηc, and Br（ηb → XcJ ＋cc） = （4.37, 3.40, 2.83） × 10^-5 （for J = 0,1, 2） for P-wave states XcJ. In the end, we also find Br（ηb → cccc） is almost saturated by ηb decay into charmonium in association with cc pair from the point of view of duality.     

通过J/Ψ→NM衰变研究N~*时的核子极点效应

研究了J／Ψ→pp^-π衰变过程中核子极点图的贡献，特别是由离壳效应带来的贡献．发现衰变宽度对形状因子是敏感的．在通过用J／Ψ→pp^-π衰变研究N^*时，核子极点图作为背景道的贡献是非常重要的；在通过J／Ψ→pp^-η和pp^-η研究N^*时，核子极点图的贡献可忽略不计；在通过J／Ψ→pp^-ω研究N^*时，核子极点图有明显的贡献． N-pole contributions, especially due to off shell effect, in J/Ψ→ NM decays are carefully studied. It is found that the decay width is sensitive to the form factor. The N pole contribution as a background is important in the J/Ψ→Nπ decay, ignorable in the J/Ψ→Nη and Nη' decays, and sizable in the J/Ψ→Nω decay.     

η_b decay into charmonium in association with c pair

We calculate the inclusive decay rates of ηb into charmonium via double c pairs for S-and P-wave states ηc,J/ψ and χcJ within the framework of non-relativistic QCD(NRQCD) factorization at leading order in αs.Besides calculating the contributions of the color-singlet channels ηb→c[2S+1SL(1)]+c,the effects of c pair in the color-octet configurations are also considered.We find that ηb→c[3S1(8)]+c make a small contribution to Br(ηb→J/ψ(ηc)+c).While in the ηb→χcJ+c case,the color octet contributions are significant,for they are of the same αs4vc5 order as the color-singlet processes.We predict Br(ηb→J/ψ(ηc)+c)=2.99(2.75)×10-5 for S-wave states J/ψ and ηc,and Br(ηb→χcJ+c)=(4.37,3.40,2.83)×10-5(for J =0,1,2) for P-wave states χcJ.In the end,we also find Br(ηb→ cc) is almost saturated by ηb decay into charmonium in association with c pair from the point of view of duality.     

Determination of J/φ Event Number via J/φ→μ+μ- and J/φ→ e+e- at BESIII

The decays of J/φ→μ⁺μ^- and J/φ→ e⁺e^- are studied by Monte-Carlo simulation, based on the Beijing Spectrometer (BES)Ⅲ offline software system. The methods of determination of the J/φ event number via J/φ→μ⁺μ^- and J/φ→ e⁺e^- are presented, respectively. These methods can be used to determine the J/φevent number for the coming BESⅢ J/φ data sample.     

通过J/Ψ→NM衰变研究N~*时的核子极点效应(英文)

研究了J/Ψ→p pπ衰变过程中核子极点图的贡献 ,特别是由离壳效应带来的贡献 .发现衰变宽度对形状因子是敏感的 .在通过用J/Ψ→ p pπ衰变研究N 时 ,核子极点图作为背景道的贡献是非常重要的 ;在通过J/Ψ→ p pη和 p pη研究N 时 ,核子极点图的贡献可忽略不计 ;在通过J/Ψ→p pω研究N 时 ,核子极点图有明显的贡献 .