高能正负电子对的湮没与超窄共振ψ粒子的作用

本文给出了R=(σ(e⁺e^-→强子))/(σ(e⁺e^-→μ⁺μ^-))随能量上涨的一个解释。研究了新发现ψ粒子所具有作用的性质,指出其强度f²/(4π)～10^-5—10^-6。求得峰值截面σ₀=(12π)/m_ψ²(Γ(ψ→e⁺e     

K_(L3)介子衰变

本文通过强作用K-π中间态,利用色散关系理论计算了Г(K_(μ3)~+)/Г(K_(3)~+),Г(K_2~0→πμ~+ν)/Г(K_2~0→πe~+ν),{Г(K_2~0→πe~+ν)+Г(K_2~0→πe~-ν)}/Г(K_(3)~+)分支比及K_(μ3)~+衰变中的μ谱,当选择定则|ΔI|=1/2及ΔS=+ΔQ被破坏,并且I_x=1/2及I_x=3/2的振幅f~[(3/2)(1/2)](0)及f~[(3/2)(3/2)](0)不等时,上述分支比与实验能很好符合。在本文的理论中,形式因子不是常数。     

关于πρ(1200MeV/c~2)共振态和SU_3群的27维表示

不久前,由实验发现,在质量m=1200MeV/c~2附近存在一个π~+ρ~0共振态A,其宽度Γ=350MeV/c~2。后来,更细致的实验指出,存在两个π~+ρ~0共振态,一个是A_1(1080MeV/c~2),另一个是A_2(1320MeV/c~2);二者的宽度分别为Γ_1=80±10MeV/c~2和Γ_2=100±10MeV/c~2。本文只考察A_1的分类问题。 由于A_1的宽度较大,而A_1→πρ的衰变动量不太大,因此,A_1→πρ衰变较大的可能是通过S波、P波或D波。这样,A_1的量子数(同位旋T、自旋J、宇称P和G宇称G)只可能是 当S波衰变时,     

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.     

北京谱仪BESIII精确测量Y(4260)粒子

利用北京谱仪BESIII实验采集的约9 fb~(-1)数据样本,BESIII测量了e~+e~-→π~+π~- J/ψ过程的产生截面,并对在该过程中观测到的Y(4260)粒子的质量和宽度做了目前世界上最精确的测量。BESIII的测量给出Y(4260)粒子的质量在4.22 GeV/c~2左右,比之前的测量偏低;宽度约44 MeV,比之前的测量窄很多。相比之前的实验,BESIII对Y(4260)粒子参数的精确测量给解释该粒子的理论模型提供了更强的约束。另外,BESIII实验在4.32 GeV/c~2附近还观测到一个新粒子信号,信号显著性为7.6σ。新粒子的质量和宽度和之前观测到的Y(4360)粒子的质量和宽度在误差范围内吻合,有可能是同一个粒子。     

ι-E疑难和推广的矩分析

本文引进过程e~+e~-→J/ψ→γB,B→P_1P_2P_3的矩的光子角分布来讨论■E疑难,得到了判断J/ψ→γKK_π过程中产生的共振峰是否包含E(1~(++))分量的一个有效判据.     

Production of charmonium（like）states in e^＋e^- interactions

We present a search for new charmonium like states in e~ e~- annihilation using the initial-state radiation and the process e~ e~-→J/ψD~(*)~(*).The analyses are based on a huge data sample recorded near theγ(4S)resonance with the Belle detector at the KEKB e~ e~- asymmetric-energy collider.     

用动量为70亿电子伏/c和80亿电子伏/c的π~-介子产生Ξ~-超子

本文研究了用动量为68亿电子伏/c和80亿电子伏/c的刀π~-介子产生Ξ~-超子,得到了π~-介子的动量为68和80亿电子伏/c的Ξ~-产生的截面(当68亿电子伏/c时σ=3.6_(-2.1)~( 2.5)μδ/N,当80亿电子伏/c时σ=10.6_(-3.2)~( 4.4)μδ/N),Ξ~-的质量(M_Ξ~-=1317.0±2.2兆电子伏)和Ξ的寿命τ_0=3.5_(-1.2)~( 3.4)×10~(-10)秒。     

Study of the rare decay J/ψ→e~+e~-φ

We study the decay process of J/ψ→e~+e~-φ where the relatively clean electromagnetic(EM) transitions appear at leading order at tree level while the hadronic contributions only emerge via hadronic loop transitions. We include the low-lying scalar f_0(980) and pseudoscalar η/η as the dominant contributions in the evaluation of the hadronic loop contributions. It is found that the hadronic effects are negligible compared with the EM contributions.The decay width of J/ψ→e~+e~-φ is determined to be about 2.12 × 10~(-6) ke V if there is no other leading mechanism contributing. This result will be tested by the BESIII experiment with a large J/ψ data sample.     

MIT口袋模型中的π~0→2γ衰变

本文用MIT口袋模型和波包方法计算了π~0→2γ过程的宽度。计算发现m_π→0是一个好的近似。MIT口袋模型给出,Γ(π~0→2γ)∞m_π~3/F_x~2,这种形式与Adler的结果相符合,但数字结果显示。Γ(π~0→2γ)的理论值是实验值的2.7倍,这个差主要来自F_π的理论值与实验值的差。而这个差很强地依赖于MIT口袋模型的方程和边界条件,从而对MI7口袋模型构成了一个检验。     

Rare decays B_(s,d)~O→e~+e~- in a top quark two-Higgs-doublet model

In the framework of T2HDM, we calculated the new physics contributions involving neutral Higgs bosons to the branching ratios of B_(s,d)~0→e~+e~-(e=e,μ) decays. Comparing the theoretical predictions with the experimental upper-limits, we found that (a) The data of Br(B_d~0→e~+e~-)give the upper bound on tanβ: tanβ≤ 22, while Br(B_s~0→e~+e~-)give tanβ≤12 for fixed δ = 0°, m_H+=350 GeV, m_Ho = 160 GeV, m_Ho= 115 GeV and m_Ao=120 GeV; (b) A light neutral Higgs boson mass m_Ho (m_Ao) less than 50 GeV (120 GeV) is excluded by the data of branching ratios for B_(s,d)~0→e~+e~-(e=μ) decays with tanβ=10; (c) The bounds on m_(h~0) and tanβ, or m_(A~0) and tanβ are strongly correlated: a smaller (larger) tanβ means a lighter (heavier) neutral Higgs boson.     

ρ-ω mixing in J/ψ→VP decays

The study of ρ-ω mixing has mainly focused on vector meson decays with isospin I = 1, namely theρ(ω)→π+π- process. In this paper, we present a study of ρ-ω mixing in ρ(ω)→π+π-π0(I = 0) using a flavor parameterization model for the J/ψ→VP process. By fitting a theoretical framework to PDG data, we obtain the SU(3)-breaking effect parameters sV = 0.03±0.12, sP = 0.17±0.17 and the ρ-ω mixing polarization operatorΠρω =(0.006±0.011) GeV2. New values are found for the branching ratios when the mixing effect is incorporated:Br(J/ψ→ωπ0)=(3.64±0.37)×10-4, Br(J/ψ→ωη)=(1.48±0.17)×10-3, Br(J/ψ→ωη)=(1.55±0.56)×10-4, these are different from the corresponding PDG2012 values by 19%, 15% and 15%, respectively.     

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.     

低温氧化物热敏材料电导公式的研究

本文提出了多晶多相A_2、A_3型低温氧化物热敏材料的电导模型,给出了其电导公式。σ=C_0T~(-1)+∑C_ie~(-B_i/T),进一步得到热敏电阻的电阻公式:R~(-1)=A_1e~((-B)_1/T)+A_2e~((-B_2/T))+A_3e~((-B)_3/T)。由三个温度点的电阻值可定出A、B值,初步计算,公式与实验间的偏差不大于3.6×10~(-3)     

过程e~+e~-→J/ψ→γB,B→P_1P_2的角分布和玻色子B的自旋分析

本文给出了过程e~+e~-→J/ψ→γB,B→P_1P_2的螺旋性形式(HF)~[1]和等效相互作用形式(EIF)~[2]之间的关系.在B的不同自旋(J=2,4)下赝标介子的角分布显示,为了确定B的自旋,存在敏感区域和不敏感区域.令人遗憾的是,θ/f_2(1720)和ξ(2230)的数据正好掉入不敏感区域.     

A method for measuring D~* electromagnetic form factors in e~+e~- annihilation

We describe a method for measuring the electromagnetic form factors of the D~* meson at time-like momentum transfer in e~+e~-annihilation.This is to study the joint angular distribution of the e~+e~-→γ~*→D~*+D~*-,D~*~+→D~0π~+,and D~*-→D~0π-processes.The magnitudes and relative phases of the charge,magnetic and quadrupole form factors can be determined.The method can also be applied to other vector particles.     

Exclusive Ω_(ccc)~(++)Ω_(ccc)~(--) Production from Z~0/r~* Decays

Based on the quark model the cross section for the e~+e~-→ Z~0/r~*→Ω_(ccc)~(++)Ω_(ccc)~(--) exclusive process is investigated at the tree level. Compared with the Z~0→Ω~-Ω~+ decay, our result shows that the Z~0 boson favors decaying into charmed baryon pairs. The results are also compared with the calculation of inclusively charmed baryon production.     

Observation of e~+e~-→D_s~+■~((*)0)K~- and study of the P-wave D_s mesons

Studies of e~+e~→D_s~+■~((*)0)K~-and the P-wave charmed-strange mesons are performed based on an e~+e~-collision data sample corresponding to an integrated luminosity of 567 pb~(-1) collected with the BESIII detector at s~(1/2)=4.600 GeV. The processes of e~+e~-→D_s~+■~(*0)K~- and D_s~+■~0K~- are observed for the first time and are found to be dominated by the modes D_s~+D_(s1)(2536)~-and D_s~+D_(s2)~*(2573)~-, respectively. The Born cross sections are measured to be σ~B(e~+e~-→D_s~+■~(*0)K~-) =(10.1±2.3±0.8) pb and σ~B(e~+e~-→D_s~+■~0K~-) =(19.4±2.3± 1.6) pb, and the products of Born cross section and the decay branching fraction are measured to be σ~B(e~+e~-→D_s~+D_(s1)(2536)~-+c.c.)·B(D_(s1)(2536)~-→■~(*0)K~-)=(7.5±1.8±0.7) pb and σ~B(e~+e~-→D_s~+D_(s2)~*(2573)~-+ c.c.)·B(D_(s2)~*(2573)~-→■~0 K~-)=(19.7 ± 2.9 ±2.0) pb. For the D_(s1)(2536)~-and D_(s2)~*(2573)~-mesons, the masses and widths are measured to be M(D_(s1)(2536)~-)=(2537.7±0.5 ±3.1) MeV/c2, Γ(D_(s1)(2536)~-) =(1.7 ±1.2 ±0.6)MeV, and M(D_(s2)~*(2573)~-)=(2570.7±2.0 ±1.7) MeV/c~2, Γ(D_(s2)~*(2573)~-)=(17.2 ±3.6 ±1.1) MeV. The spin-parity of the D_(s2)~*(2573)~-meson is determined to be J~p= 2~+. In addition, the processes e~+e~-→D_s~+■~((*)0)K~-are searched for using the data samples taken at four(two) center-of-mass energies between 4.416(4.527) and 4.575 GeV, and upper limits at the 90% confidence level on the cross sections are determined.     

Measurement of e~+e~-→D■ cross sections at the ψ(3770) resonance

We report new measurements of the cross sections for the production of DD final states at theψ(3770)resonance.Our data sample consists of an integrated luminosity of 2.93 fb~(-1)of e~+e~-annihilation data produced by the BEPCⅡ collider and collected and analyzed with the BESⅢ detector.We exclusively reconstruct three D~0and six D~+hadronic decay modes and use the ratio of the yield of fully reconstructed DD events("double tags")to the yield of all reconstructed D or D mesons("single tags")to determine the number of D~0 D~0and D~+D~-events,benefiting from the cancellation of many systematic uncertainties.Combining these yields with an independent determination of the integrated luminosity of the data sample,we find the cross sections to beσ(e~+e~-→D~0D~0)=(3.615±0.010±0.038)nb andσ(e~+e~-→D~+D~-)=(2.830±0.011±0.026)nb,where the uncertainties are statistical and systematic,respectively.     

SU_3~(1)×Su_3~(2)结构模型下一种可能的介子质量谱和新粒子的产生与衰变

最新的实验表明,在质心系总能量2—7.6GeV之间,在e~ e~-湮灭道中存在两个窄共振J(3.1),'(3.7)和至少两个宽共振'(4.1)和''(4.4)。从实验曲线看,在宽共振区域4.1—4.4GeV内可能还有新的共振存在。实验还发现了C宇称为正的粒子,质量分别为2.8,3.41,3.51,3.53GeV。实验还测定了Г_(→e~ e~-)和Г_(J→e~ e~-)的比值约为1:2。文献