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.     

Observation of the baryonic flavor-changing neutral current decay Λb(0)→Λμ+μ-

We report the first observation of the baryonic flavor-changing neutral current decay Λ(b)(0)→Λμ(+)μ(-) with 24 signal events and a statistical significance of 5.8 Gaussian standard deviations. This measurement uses a pp collisions data sample corresponding to 6.8 fb(-1) at √s = 1.96 TeV collected by the CDF II detector at the Tevatron collider. The total and differential branching ratios for Λ(b)(0)→Λμ(+)μ(-) are measured. We find B(Λ(b)(0)→Λμ(+)μ(-))=[1.73 ± 0.42(stat) ± (syst)] × 10(-6). We also report the first measurement of the differential branching ratio of B(s)(0)→?μ(+)μ(-), using 49 signal events. In addition, we report branching ratios for B(+)→K(+)μ(+)μ(-), B(0)→K(0)μ(+)μ(-), and B→K(*)(892)μ(+)μ(-) decays.     

First observation of the decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-)

First observations of the Cabibbo-suppressed decays B(0) → D(+)K(-)π(+)π(-) and B(-) → D(0)K(-)π(+)π(-) are reported using 35 pb(-1) of data collected with the LHCb detector. Their branching fractions are measured with respect to the corresponding Cabibbo-favored decays, from which we obtain B(B(0) → D(+)K(-)π(+)π(-))/B(B(0) → D(+)π(-)π(+)π(-))=(5.9±1.1±0.5)×10(-2) and B(B(-) → D(0)K(-)π(+)π(-))/B(B(-) → D(0)π(-)π(+)π(-))=(9.4±1.3±0.9)×10(-2), where the uncertainties are statistical and systematic, respectively. The B(-) → D(0)K(-)π(+)π(-) decay is particularly interesting, as it can be used in a similar way to B(-) → D(0)K(-) to measure the Cabibbo-Kobayashi-Maskawa phase γ.     

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.     

Study of Exclusive Hadronic Decays for D0→Ks0π+π- and D0→Ks0K+K- and Their Resonant Structures

We report the results of an experimental study of the exclusive hadronic decays for D0→K0 sπ+π - and K 0 sK +K - and their resonant structures using BES-Ⅰ detector at the BEPC Collider. Using the data sample of 22.3 pb -1 collected at the center-of-mass energy s=4.03 GeV, we measured the branching fraction for D 0→K 0π +π - to be (5.32±0.53±0.40)%, the branching fractions for the decays D 0→ K *-π +, D 0→K 0ρ 0 and D 0→K 0(π +π -) non-resonant to be (6.05±0.32±0.49)%, (1.17±0.17±0.13)% and (1.35±0.22±0.17)%, respectively. We measured the branching fractions Br(D 0→f) to be (1.04±0.24± 0.16)% for f=K 0K +K -, (1.12±0.34±0.15)% for f=K0, and (0.27±0.13±0.03)% for f=K 0(K+K-)non-.     

Determination of the branching ratio ofρ 0→+μ− in the coherent dissociation π−→μ+μ−π− and π−→π+π−π−

In the diffraction dissociation of π^? into μ⁺μ^?π^? on a Cu nucleus at 50 GeV/c, the cross section \(\sigma _{\mu ^ + \mu ^ - \pi ^ - } \) for the 1⁺S(ρ⁰π) wave was measured. The branching ratio of ρ⁰→μ⁺μ^? could be calculated from the ratio of this and the corresponding cross sections in the diffraction dissociation of π^? into π⁺π^?π^?. The obtained value \(BR_{\rho ^0 \to \mu ^ + \mu ^ - } = (4.6 \pm 0.2_{stat^ \pm } \pm 0.2_{syst} )10^{ - 5} \) is in good agreement with the branching ratio \(BR_{\rho ^0 \to e^ + e^ - } \) , as expected ifeμ universality holds.     

Comments on preliminary data on the reactions e + e −→φ→γ f 0(980)→γπ0π0

Preliminary data on the reactions e ⁺ e ⁻→φ→γ f ₀(980)→γπ⁰π⁰ together with data on ππ scattering and the reactions J/ψ→φπ⁺π⁻ and K ⁻ p→π ⁺π⁻(Λ,Σ) are analyzed. The analysis shows that the mass of the f ₀(980) meson is = 950 MeV, and BR(φ→γf ₀→γπ⁰π⁰)≃ 1× 10⁻⁴, indicating that the f ₀(980) resonance is of a four-quark nature. Pis’ma Zh. éksp. Teor. Fiz. 67, No. 7, 445–449 (10 April 1998)     

QCD因子化方法下(￣Bs)→π+π-中湮没强度的探索

利用QCD因子化方法,并采用具有质量的有效胶子传播子来消除端点发散,计算了纯湮没衰变(￣Bs)→π π-过程的CP平均分支比并对该过程的CP破坏进行了具体研究.结果表明:该过程的CP平均分支比为1.24×10-7,同时企鹅图对该过程起着主要贡献;(￣Bs)→π π-过程中直接CP破坏参数Cππ估算为-0.05,混合CP破坏参数Sππ比较大,可达到0.18.该过程在未来的LHC-b物理实验上是完全有可能被测量到的,通过对该过程的研究能够使我们更好地了解B介子无璨衰变的动力学机制和胶子的性质.     

News on PHOTOS Monte Carlo:γ*→π+π-(γ)and K±→π+π-e±ν(γ)

PHOTOS Monte Carlo is widely used for simulating QED effects in decay of intermediate particles and resonances.It can be easily connected to other main process generators.In this paper we consider decaying processes γ*→π+π-(γ)and K±→π+π-e±ν(γ)in the framework of Scalar QED.These two processes are interesting not only for the technical aspect of PHOTOS Monte Carlo,but also for precision measurement ofαQED(Mz),g-2,as well as ππ scattering lengths.     

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     

A study of the centrally producedK *0 K^{*0} \bar K^{*0} final state in the reactionpp→p f (K + K -π+π-)p s at 300 GeV/c

The reactionpp→p _f (K ⁺ K ^-π⁺π^-)p _s , where theK ⁺ K ^? π⁺π^- system is centrally produced, has been studied at 300 GeV/c. TheK ^*0 \(K^{*0} \bar K^{*0} \) final state has been observed and the cross sections for its central production are found to be the same at 300 and 85 GeV/c. TheK ^*0 \(K^{*0} \bar K^{*0} \) final state appears to be produced as a non-resonant threshold enhancement.     

Search for CP violation in the decays D(0)→K(S)(0)P(0)

We have searched for CP violation in the decays D(0)→K(S)(0)P(0) where P(0) denotes a neutral pseudoscalar meson that is either a π(0), η, or η' using KEKB asymmetric-energy e(+)e(-) collision data corresponding to an integrated luminosity of 791 fb(-1) collected with the Belle detector. No evidence of significant CP violation is observed. We report the most precise CP asymmetry measurement in the decay D(0)→K(S)(0)π(0) to date: A(CP)(D(0)→K(S)(0)π(0))=(-0.28±0.19±0.10)%. We also report the first measurements of CP asymmetries in the decays D(0)→K(S)(0)η and D(0)→K(S)(0)η': A(CP)(D(0)→K(S)(0)η)=(+0.54±0.51±0.16)% and A(CP)(D(0)→K(S)(0)η')=(+0.98±0.67±0.14)%, respectively.     

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.     

Study of ππ final state interactions in ψ(2S)→π+π-J/ψ

The π+π- transition of heavy quarkonia in decay ψ(2S) ψ(2S)→π+π-J/ψ is studied. With the BESII data on the decay ψ(2S)→π+π-J/ψ, we update the values of coupling constants (gi) and chromopolarizability (аψ(2S)J/ψ) in this process.     

Predictions of γ(4S)→h_b(1P,2P)π^+π^- transitions

We study the contributions of intermediate bottomonium-like Zb states and the bottom meson loops in the heavy quark spin flip transitionsγ(4 S)→hb(1 P,2 P)π+π-.Depending on the constructive or destructive interferences between the Zb-exchange and the bottom meson loops mechanisms,we predict two possible branching ratios for each process:BRγ(4 S)→hb(1 P)π+π-≈(1.20.40.8×10^-6)or(0.5-0.20.5×10^-6),and BRγ(4 S)→(2 P)π+π-≈(7.1-1.1+1.7×10^-10)or(2.4-0.10.2×10^-10)).The contribution of the bottom meson loops is found to be considerably larger than that of the Zbexchange in the T(4 S)→hb(1 P)ππtransitions,while its decay rates are not comparable to those of heavy quark spin conservedγ(4 S)→γ(1 S,2 S)ππprocesses.We also predict the contribution of the charm meson loops in the branch fractions ofΨ(3 S,4 S)→hc(1 P)ππ.     

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)%.