遍举衰变过程D0→Ks0π+π–和D0→Ks0K+K–及其共振态结构的实验研究

利用北京谱仪(BES–Ⅰ)在北京正负电子对撞机(BEPC)e+e–质心系能量为4.03GeV处采集的积分亮度为22.3pb–1的数据,研究了D0→K0sπ+π–,D0→K0sK+K–的衰变及其末态的共振结构.实验测得D0→K0sπ+π–过程的分支比为(5.32±0.53±0.40)%;D0→K–π+,D0→K0ρ0和D0→K0s(π+π–)non resonance过程的分支比分别为(6.05±0.32±0.49)%,(1.17±0.17±0.13)%和(1.35±0.22±0.17)%;测得D0→K0sK+K–,D0→K0和D0→K0(K+K–)non?的分支比分别为(1.04±0.2?4±0?.16)%,(1.12±0.34±0.15)%和(0.27±0.13±0.03)%.     

Cabbibo Suppressed Semileptonic Decay D0→π－e+ve

The transition rate for the Cabibbo suppressed decay d0→π–e+ν e is calculated. This allows the extractions of the form factor |fπ +(0)| and the CKM matrix element |v cd| using the measured branching ratio.     

e+e-→e+e-π0π0 at DAΦNE

The production of the σ(500) meson in γγ→π⁰π⁰ is studied. In particular, the KLOE data collected during the DAΦNE run at are appropriate to this purpose because of the strong reduction of kaon backgrounds. PACS 12.39.-x     

Search for the rare decays K(L)→π0π0μ+μ- and K(L)→π0π0X0→π0π0μ+μ-

The KTeV E799 experiment has conducted a search for the rare decays, K(L)→π(0)π(0)μ(+)μ(-) and K(L)→π(0)π(0)X(0)→π(0)π(0)μ(+)μ(-), where the X(0) is a possible new neutral boson that was reported by the HyperCP experiment with a mass of (214.3 ± 0.5) MeV/c(2). We find no evidence for either decay. We obtain upper limits of Br(K(L)→π(0)π(0)X(0)→π(0)π(0)μ(+)μ(-)) < 1.0 × 10(-10) and Br(K(L)→π(0)π(0)μ(+)μ(-)) < 9.2 × 10(-11) at the 90% confidence level. This result rules out the pseudoscalar X(0) as an explanation of the HyperCP result under the scenario that the dsX(0) coupling is completely real.     

TheK S 0 →π0 l + l − andK L 0 →π0 l + l − decays in the standard model and the extended Nambu-Jona-Lasinio model

TheK _S ^{0 0} l ⁺ l ^– andK _L ^{0 0} l ⁺ l ^– decays are considered within the framework of the Standard model in the one-photon exchange approximation, i.e.K _S,L ^{0 0}+ *⁰ +l ⁺ l ^–. To evaluate the low-energy matrix elements of theK ⁰(¯K ⁰)⁰+ * transitions, the constituentquark-loop approximation, based on the extended Nambu-Jona-Lasino (NJL) model, is used. The obtained results are compared with other theoretical estimates and the experimental bounds.     

Study of the process e+e-→π+π-π0π0 at energies √s< 1 GeV

In an experiment with the Spherical Neutral Detector at VEPP-2M collider the cross section of the process e+e-→π+π-π0π0 was measured. At energies √s < 920 MeV this cross section was measured for the first time. The energy dependence of the cross section is well discribed by the vector dominance model with contributions from ρ, ρ' ρ", mesons. The decay probability ρ→π+π-π0π0was found to be Bρ = (1.60±0.74±0.18)×10-5. The upper limit for the decay ω→π+π-π0π0 was improved by two orders of magnitude compared to the previous measurements and is Bω < 2 × 10-4 at 90% confidence level.     

Superallowed 0+ → 0+ beta-decay and CKM unitarity

Precise measurements of the ft-values for superallowed nuclear β-decay yield results that support conservation of the weak vector current but violate the unitarity of the Cabibbo-Kobayashi-Maskawa matrix by more than two standard deviations. This apparent violation of the Standard Model has led to considerable theoretical and experimental activity largely focussed on reducing uncertainties in the small correction terms that account for charge-dependent nuclear effects. This activity is outlined and the prospects for future sharpening of the unitarity test are assessed. Received: 21 March 2002 / Accepted: 16 May 2002 / Published online: 31 October 2002 RID="a" ID="a"e-mail: hardy@comp.tamu.edu     

Cabbibo压制半径子衰变过程D0→π－e+ve

计算了Cabibbo压制D0→π－e+ve衰变率.利用计算结果和测得分支比来研究形状因子|fπ +(0)|及CKM矩阵元|v cd|     

Compton scattering on the charged pion and the process γγ→π0π0

The Compton scattering on a charged pion and the process γγ→π⁰π⁰ are studied using the dispersion relations. Unknown parameters of the S-wave ππ interaction and a sum and a difference of the π⁰ meson polarizabilities are found from a fit to the experimental data for the γγ→π⁰π⁰ process. The found parameters of the ππ interaction are used for the calculation of the cross section of the elastic γπ^± scattering. The analysis of the obtained results shows that the experimental data for the elastic γπ^± scattering in the energy region up to 1 GeV together with the data for the γγ→π⁰π⁰ process could be used both for a determination of the pion polarizability values and for study of the S-wave ππ interaction. Received: 20 November 1998 / Revised version: 22 January 1999     

Determination of the branching ratiosΓ(K L→3π0)/Γ(K L→π+ - 0) andΓ(K L→3π0)/Γ(K L→πev)

Improved branching ratios were measured for theK _L3⁰ decay in a neutral beam at the CERN SPS with the NA31 detector:

A test of CPT symmetry in K0 vs (K-)0→π+π-π0 decays

I show that the CP-violating asymmetry in K0 vs K-0→π+π-π0 decays differs from that in KL→π+π-,KL→π0π0 or the semileptonic KL transitions,if there exists CPT violation in K0-K-0 mixing.A delicate measurement of this difference at a super flavor factory(e.g.,the φ factory)will provide us with a robust test of CPT symmetry in the neutral kaon system.     

Formalism of Helicity Coupling Amplitudes for J/ψ→π+π-π0

The formalisms of helicity coupling amplitudes for J/ψ→π^＋π^-π^0 are presented. A detailed discussion is also given on the barrier factor, Breit Wigner, and density matrix. A Monte Carlo simulation of J/ψ→ρ（770）π→π^＋π^-π^0 is carried out. The results show that the p（770） resonance is well reproduced compared with experimental data.     

A test of CPT symmetry in K~0 vs ■~0 →π~+π~-π~0 decays

I show that the CP-violating asymmetry in K0 vs K0 →π+π-π0 decays differs from that in KL →π+π-,KL →π0π0 or the semileptonic KL transitions,if there exists CPT violation in K0-K0 mixing.A delicate measurement of this difference at a super flavor factory(e.g.,the φ factory) will provide us with a robust test of CPT symmetry in the neutral kaon system.