J/φ强子衰变过程的矩分析

本文给出了过程e~++e~-→J/ψ→V+X,V→P_1P_2或P_1P_2P_3和X→PP的角分布螺旋度形式,并在此基础上进行了矩分析,得到了若干关系式,有助于确定玻色共振态X的自旋J_x以及过程J/ψ→V+X的螺旋度振幅之比.     

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.     

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.     

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.     

The X(4140) and X(4160) resonances in the e~+e~-→γJ/ψ? reaction

We investigate the J/Ψ? invariant mass distribution in the e~+e~-→γJ/Ψ? reaction at a center-of-mass energy of ■=4.6 GeV measured by the BESⅢ collaboration,which concluded that no significant signals were observed for e~+e~-→γX(4140) because of the low statistics.We show,however,that the J/Ψ? invariant mass distribution is compatible with the existence of the X(4140) state,appearing as a peak,and a strong cusp structure at the D_s~*■threshold,resulting from the molecular nature of the X(4160) state,which provides a substantial contribution to the reaction.This is consistent with our previous analysis of the B~+→J/Ψ?K~+decay measured by the LHCb collaboration.We strongly suggest further measurements of this process with more statistics to clarify the nature of the X(4140) and X(4160) resonances.     

Perturbative QCD for J/ψ inclusive production via initial state radiation in e~+e~- collisions

The process e+e-→J/ψ+X with the center-of-mass(CM)energy in the range from 3.7 to 10.6 GeV is calculated up to the next-to-leading order(NLO)in quantum chromodynamics(QCD).At 10.6 GeV,the result is consistent with the experimental result from Belle.However,the predictions are much smaller than the background in the measurements at BESIII in the low CM energy range from 3.7 to 4.6 GeV.This indicates that the convergence of the QCD perturbative expansion becomes worse as the CM energy is closer to the inclusive J/ψ production threshold.For a further study of the QCD mechanism of J/ψ production in e~+e~-collisions with different CM energies,the initial state radiation effect of e~+e~-→J/ψ +gg and e~+e~-→J/ψ+cc are calculated in QCD NLO.The results are plotted and the number of events for different CM energy bins are provided for SuperKEKB.This provides a method to precisely test the validity of perturbative predictions for J/ψ production in future measurements.     

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.     

Analytic forms for cross sections of di-lepton production from e~+e~- collisions around the J/ψ resonance

A detailed theoretical derivation of the cross sections of e~+e~-→e~+e~-and e~+e~-→μ+μ-around the J/ψ resonance is reported. The resonance and interference parts of the cross sections, related to J/ψ resonance parameters, are calculated. Higher-order corrections for vacuum polarization and initial-state radiation are considered. An arbitrary upper limit of radiative correction integration is involved. Full and simplified versions of analytic formulae are given with precision at the level of 0.1% and 0.2%, respectively. Moreover, the results obtained in the paper can be applied to the case of the ψ(3686) resonance.     

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.     

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.     

Luminosity measurements for the R scan experiment at BESIII

By analyzing the large-angle Bhabha scattering events e~+e~-→(γ)e~+e~-and diphoton events e~+e~-→(γ)γγ for the data sets collected at center-of-mass(c.m.) energies between 2.2324 and 4.5900 Ge V(131 energy points in total) with the upgraded Beijing Spectrometer(BESIII) at the Beijing Electron-Positron Collider(BEPCII), the integrated luminosities have been measured at the different c.m. energies, individually. The results are important inputs for the R value and J/ψ resonance parameter measurements.     

A discussion on vacuum polarization correction to the cross-section of e~+e~-→γ~*/ψ →μ~+μ~-

Vacuum polarization is a part of the initial-state radiative correction for the cross-section of e~+e~- annihilation processes. In the energy region in the vicinity of narrow resonances J/ψ and ψ(3686), the vacuum polarization contribution from the resonant component has a significant effect on the line-shape of the lepton pair production cross-section. This paper discusses some basic concepts and describes an analytical calculation of the cross-section of e~+e~-→γ*/ψ→μ+μ-considering the single and double vacuum polarization effect of the virtual photon propagator. Moreover, it presents some numerical comparisons with the traditional treatments.     

Hidden-charm Pentaquark Production at e~+e~- Colliders

We study one possible production mechanism for the hidden-charm pentaquark via a color-octet cc pair fragmentation in e~+e~-collision.The pentaquark production at B factory energy is dominated by e~+e~-→ccg→P_c+X,while at Z~0pole energy,there are several partonic processes playing significant role.Our results show that it is possible to search for the direct pentaquark production signal at e~+e~-colliders,which is important to understand the properties of pentaquark.     

Inclusive Cross Section Production of J/ψ in LEP

Cross section production is one of the observable quantities in the hadronic systems. Inclusive cross section production J/ψ may be calculated through the use of the fragmentation c → J/ψ. In this paper we calculate the inclusive cross section production J/ψ about the pole of Z~0 in the e~+e~- annihilation, through the lowest order regim of perturbative of QCD ananlyticaly. The obtained results arrive an excellent agreement with the exprimental data to produce the inclusive cross section production c → J/ψ.     

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.     

The B-L+xY Model and the Higgs-strahlung Processes at a Collider

The gauge extension of the standard model with the U(1)_(B-L+xY) symmetry predicts the existence of a light gauge boson Z' with small couplings to ordinary fermions. We discuss its contributions to the muon anomalous magnetic moment a_μ. Taking account of the constraints on the relevant free parameters, we further calculate the contributions of the light gauge boson Z' to the Higgs-strahlung processes e~+e~-→ ZH and e~+e~-→ Z'H.     

SUSY-QCD Effects in Top Quark Pair Production in Association with a Gluon at the ILC

Given the null results of searches for new physics at the LHC,we investigate the one-loop effects SUSY QCD in the process e~+e~-→tg at the ILC in Minimal Supersymmetric Standard Model(MSSM).We find that the relative SUSY-QCD corrections to the cross section of e~+e~-→ tg can maximally reach 6.5%(3.2%) at the ILC with (1/2)s= 1000 GeV when m__1= 313.4 GeV and m_g =500(1500) GeV.     

Experimental review of e~+e~-→ππh_c

We review the recent BESIII measurement of e~+e~-→ππh_c in which its line shape is studied between the center-of-mass energies of 3.9 to 4.42 Ge V and an iso-vector charmonium-like state Z_c(4020) is observed in the invariant mass of πhc at the BESIII experiment. The charged Z_c(4020)~± is the second observed Z_c state following Z_c(3900), while the Z_c(4020)~0 is the first observed neutral Z_c state. The line shape of σ(e~+e~-→ππh_c) is also reanalyzed in view of searching for the Y state and the existence of the Y(4220) state is confirmed and compared with the previous work of the BESIII experiment.     

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     

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.