Search for the Decays D+→φe+ν,D+→φK－π+e+ν,D0→φK－e+νand D0→φK－μ+ν

We report the results of a search for the semileptonic decays D⁺→e⁺ν,D⁺→K^－π⁺e⁺ν,D⁰→K^－e⁺ν and D⁰→K^－μ⁺ν using the BES detector at the BEPC e⁺e^－ Collider. Using a data sample of 22.3pb^－1 collected at the center of mass energy s=4.03GeV, we select 2472±87D 0 tag DX and 7628±149D 0 tag DX singly tagged D events, where the X could be γ, π 0 and/or π^±. Based on the method of "combined D⁺and D⁰ single and double tags", we determine that 2471±218 D⁺X and 7629±251 D⁰ X are contained in the recoil side of the singly tagged neutral and charged D mesons, respectively. No events for the 4 semileptonic decay modes are observed in the recoil side of the tagged D mesons. The 90% confidence level upper limits of B(D⁺→e⁺ν)<1.38%,B(D⁺→K^－π⁺e⁺ν)<2.01%,B(D⁰→K^－e⁺ν)<0.53% and B(D⁰→K^－μ⁺ν)<0.53% are determined from the search for the semileptonic decays of D⁺ and D⁰.     

高能e++e－→e++e－+强子过程中的电弱干涉效应

在这篇文章中, 我们用[2]中的结果讨论了与极化光子结构函数相关的电弱干涉效应, 这个效应提供了对G-W-S(格拉肖-温伯格-萨拉姆)模型作进一步检验的可能并且导致对光子结构函数的更深入的了解.     

ELECTROWEAK INTERFERENCE EFFECTS IN THE HIGH ENERGY e++e－→e++e－+ HADRONS PROCESSES

In this paper we examine the electroweak interference effects related to the polarized photon structure functions making use of the results of the ref.[2]. The effects provide the probability of a further test of the G-W-S model and may lead to a deep understanding to the photon structure functions.     

二价Ba2+、Pb2+和四价Ti4+在硼硅酸盐玻璃系统中对Li+/Na+离子交换的影响

本文讨论了在硼硅酸盐玻璃系统中引入二价Ba²⁺、Pb²⁺和四价Ti⁴⁺后,由于Pb²⁺和Ti⁴⁺配位结构的变化,引起Pb²⁺、Ti⁴⁺场强及其与O^2-离子间距的变化,对Li⁺/Na⁺离子交换产生影响,从而改变折射率差值(ΔN)和折射率分布.     

Analytic Approximation for Process e++e－→τ++τ－ Cross Section Near Threshold

In the structure function approach,we calculate the threshold behaviours for e⁺+e^－→τ⁺+τ^－,which including QED radiative corrections from initial correction,vacuum polarization effect,Coulomb effect and final state correction.This theoretical prediction for threshold behaviours of τ-pair production is useful for BES new measurement of lepton τ mass.     

Event generators for η/η' rare decays into π+π-l+l- and e+e-μ+μ-

Study of the rare and forbidden decays of η/η' offers a sensitive probe to test fundamental symmetries of quantum chromodynamics and search for new physics beyond the Standard Model. To study the rare decays of η/η' to π⁺π^-e⁺e^-, π⁺π^-μ⁺μ^- and e⁺e^-μ⁺μ^- at the BESⅢ detector, we developed several event generators based on the vector meson dominant model with finite-width corrections and the pseudoscalar mesons mixing theory. The various distributions from event generators are in good agreement with the theoretical predictions, which indicates that the event generators work very well after implemention in the BESⅢ Monte Carlo simulation package. In the BESⅢ physics analysis, the performance of the event generators will be improved in accordance with the distributions of different variables of η/η' from data and the improvement on the theoretical calculations.     

D0-MESON DECAYS Γ（D0→K+K-）/Γ（D0→π+π-）

In this paper the nonleptonic D⁰-decays are discussed. Using Gilman and Wise's methods, we derived the effective Hamiltonian for Cabibbo-suppressed nonleptonic D^0*-decays. The rate F(D⁰→K⁺K^-)/Γ(D⁰→π⁺π^-)～1.26 is obtained. Some problems in this method of the calculations are discussed roughly.     

D介子衰变Γ（D0→K+K-）/Γ（D0→π+π-）

考虑强作用修正对D⁰介子衰变的影响,用Gilman和Wise^[1]的方法,导出ΔC=1的等效哈密顿量,算得Γ（D⁰→K⁺K^-）/Γ（D⁰→π⁺π^-）～1.26,简单讨论了这种计算方法中的一些问题。     

YAB晶体中Yb3+到Er3+的能量传递

1.55 μm波段是光通讯的一个重要波段,而且对人眼安全,有高的大气透过率,因此可以广泛应用于通讯和遥感测距等领域。由于Er³⁺离子对商品化的InGaAs激光二极管的抽运波长不能有效吸收,因此一般通过在基质中共掺杂Yb³⁺和Er³⁺离子来获得1.55 μm波段激光输出。采用助熔剂法生长了不同Yb³⁺和Er³⁺掺杂浓度的YAl₃(BO₃)₄(YAB)晶体。运用速率方程模型研究了晶体中Yb³⁺到Er³⁺能量传递过程,得到了根据Yb³⁺离子的荧光寿命计算能量传递系数的简单计算公式。计算了不同掺杂离子浓度的YAB晶体中的能量传递系数等相关参数。结果表明,在YAB晶体中,Yb³⁺到Er³⁺能量传递非常有效,YAB晶体可以作为一种能获得1.55 μm激光输出的良好介质材料。     

Color Rearrangement in e+e－→W+W－→h's Process

The probability of Color Rearrangement at partonic level in e⁺e^－→W⁺W^－→h,s process is studied using the Color Effective Hamiltonian. The comparison between our results and those of Gutafson and Sjostrand et al. is also given. It is found that this probability cannot be neglected, and it is pointed out that to investigate the Color Rearrangements, the hadronization models should be developped and improved.     

A Study of the Processes of e+e－→e+e－,μ+μ－ at Large Angle and Measured Luminosities

Using the BES data collected at √S=4.03GeV.the QED processes of e⁺e^－→e⁺e^－,μ⁺μ^－ have been studied. Our measurements agree with the QED prediction,and luminosities obtained from these two final states are compatible at a level of 4%.The total integrated luminosity of 23.1pb^－1 was given for all data collected at this energy region from the calculation.     

采用Ag+离子与TiF6光学玻璃内的K+或Na+离子交换产生高折射率梯度剖面分布

本文介绍了TiF₆光学玻璃的制作。研究了这种玻璃内的K⁺或Na⁺离子与Ag⁺离子交换。使用双光束干涉法观测了干涉纹、并用电子探针扫描电镜测量了Ag⁺、K⁺和Na⁺离子的浓度分布,还着重研究了离子交换后的玻璃裂纹和着色问题。最后,对结果作了讨论。     

NaYF4∶Eu3+, Tm3+, Yb3+材料中Stokes和反Stokes发光研究

合成了Eu3+,Tm3+和Yb3+掺杂的NaYF₄材料。360 nm光激发呈蓝色发光,峰值位于452 nm,对应Tm3+的1D₂→3F₄跃迁;395 nm光激发呈橙色发光,峰值位于591 nm,对应Eu3+的5D₀→7F₁跃迁;409 nm光激发呈红色发光,峰值位于613 nm,对应Eu3+的5D₀→7F₂跃迁;980 nm光激发呈蓝色和红色发光,发光峰位于474和646 nm。蓝光来源Tm3+的1G₄ →3H₆跃迁,红光来源Tm3+的1G₄→3F₄跃迁。在双对数曲线中,蓝光474 nm和红光646 nm的斜率分别为2.1和2.4,在980 nm光激发下,蓝光和红光发射都是双光子过程。还研究了材料的吸收光谱,并利用X射线衍射,扫描电镜测试了材料的物相结构和微观形貌。结果表明：NaYF₄∶Eu3+, Tm3+, Yb3+材料具有较规则的六方相结构,结晶良好。     

量子色动力学中的e++e-→π+q+q过程

本文利用QCD的渐近自由性质,求出一条腿动量平方固定另一条腿动量平方趋于无穷大时的波函数,并把它应用于计算e⁺+e^-→π+q+（?）过程（其中π介子相对于层子喷注轴有大的横动量）。计算结果表明,这个过程对e⁺+e^-→强子截面的贡献比e⁺+e^-→g+q+（?）过程的贡献小得多。     

水热法合成纳米晶NaYF4 : Er3+,Tm3+,Yb3+ 的上转换发光特性

以EDTA为络合剂,用水热法合成了Er³⁺,Tm³⁺和Yb³⁺共掺杂的NaYF₄纳米晶。XRD和TEM的结果表明:粒径约为30 nm,属于六方晶系。在980 nm半导体激光器激发下,研究了不同Er³⁺离子掺杂浓度对Tm³⁺和Er³⁺离子上转换发光性能的影响,光强与泵浦功率的双对数曲线表明,474,525,539,650 nm的发射均属于双光子过程,408 nm的发射属于三光子过程。讨论了样品的协作敏化和声子辅助共振能量传递的上转换发光机制。     

Er3+单掺及Er3+/Yb3+共掺SiO2-Al2O3-La2O3玻璃光谱性质研究

研究了单掺Er³⁺及Er³⁺/Yb³⁺共掺SiO₂-Al₂O₃-La₂O₃玻璃的光谱性质随稀土离子浓度变化规律,应用McCumber理论计算了玻璃在1.53 μm的发射截面及积分吸收截面.结果表明:在Er³⁺离子掺杂浓度相同时,玻璃在980 nm吸收截面与Yb³⁺掺杂浓度成反比;当样品中Yb³⁺离子掺杂浓度为3.94×10²⁰ cm^-3时,玻璃在1.53 μm的吸收截面和发射截面最大,在1.40～1.60 μm积分吸收截面也最大;Er³⁺/Yb³⁺共掺SiO₂-Al₂O₃-La₂O₃玻璃在1.53 μm的荧光半高宽随Er³⁺掺杂浓度升高而增加,当Er³⁺离子掺杂浓度为2.41×10²⁰ cm^-3时,玻璃的荧光半高宽(FWHM)达到52.5 nm.     

Is JPC=3-+ molecule possible?

The confirmation of charged charmonium-like states indicates that heavy quark molecules should exist.Here we discuss the possibility of a molecule state with J P C= 3-+. In a one-boson-exchange model investigation for the S wave C = + D* ˉD*2states, one finds that the strongest attraction is in the case J = 3 and I = 0 for bothπ and σ exchanges. Numerical analysis indicates that this hadronic bound state might exist if a phenomenological cutoff parameter around 2.3 Ge V(1.5 Ge V) is reasonable with a dipole(monopole) type form factor in the one-pionexchange model. The cutoff for binding solutions may be reduced to a smaller value once the σ exchange contribution is included. If a state around the D* ˉD*2threshold(≈4472 Me V) in the channel J/ψω(P wave) is observed, the heavy quark spin symmetry implies that it is not a cˉc meson and the J P C are likely to be 3-+.     

Fe3+、Ce3+共掺杂γ-LiAlO2的发光性质

采用不同于传统固相反应法的制备方法合成了Fe,Ce 共掺杂γ-LiAlO₂。通过XRD和 SEM分析表明,采用这种方法能够成功获得尺寸小于10 μm的四方相结构γ-LiAlO₂荧光粉。从γ-LiAlO₂ ∶ Fe,Ce 的激发和发射光谱可以看出,通过引入少量的铈离子,我们首先发现了铈离子掺杂对样品的发光效率有明显的影响。并且随着铈离子浓度的增加,其发光效率也出现规律性的变化,而且发射光谱在Ce离子摩尔分数达到1.5%的情况下发光效率最强,当Ce离子摩尔分数达到3％时,发光效率明显下降。这种高效的荧光粉作为转光剂应用于人工植物照明和农用转光膜具有积极的意义。     

Searching for new physics in D0→μ+μ-, e+e-,μ±e干 at BES and/or the super charm-tau factory

In contrast with B⁰-B⁰, B_s-B_s mixing where the standard model (SM) contributions overwhelm that of the new physics beyond standard model (BSM), a measured relatively large D⁰-D⁰ mixing where the SM contribution is negligible, definitely implies the existence of the new physics BSM. It is natural to consider that the rare decays of D meson might be more sensitive to new physics, and the decay mode D⁰→μ⁺μ^- could be an ideal area to search for new physics because it is a flavor changing process. In this work we look for a trace of the new physics BSM in the leptonic decays of D⁰. Concretely we discuss the contributions of unparticle or an extra gauge boson Z' while imposing the constraints set by fitting the D⁰- D⁰ mixing data. We find that the long-distance SM effects for D⁰→l1 still exceed those contributions of the BSM under consideration, but for a double-flavor changing process such as D⁰→μ^±e⁺, the new physics contribution would be significant.     

Er3+/Tm3+共掺碲酸盐玻璃光谱特性及能量传递

采用高温熔融法制备了两系列不同掺杂比的Er³⁺/Tm³⁺共掺的碲酸盐玻璃,测试了样品的吸收光谱和在980 nm LD激发下的发光光谱、上转换发光光谱及发光寿命。讨论了Er³⁺与Tm³⁺掺杂浓度对样品光谱性质的影响,Tm³⁺离子的掺入会减弱Er³⁺的1.53 μm发光强度,但通过共振能量传递可以获得Tm³⁺的1.8 μm发光,并随着Tm³⁺离子浓度的增加而增强。同时表明Tm³⁺离子的增加会减弱Er³⁺离子在528 nm和545 nm附近的上转换绿光强度,而上转换红光出现了先增强后减弱的现象。研究了Er³⁺/Tm³⁺共掺杂碲酸盐玻璃的能量传递机制与传递效率,分析了Tm³⁺/Er³⁺离子掺杂浓度比对上转换发光的影响。