No abstract

No abstract

No abstract

Using a sample of 3.8 M (2S) events accumulated with the BES detector, the process (2S) → ϩ Ϫ J/ is studied. The angular distributions are compared with the general decay amplitude analysis of Cahn. We find that the dipion system requires some D wave amplitude, as well as S wave. On the other hand, the J/Ϫ(ϩ Ϫ) relative angular momentum is consistent with being pure S wave. The decay distributions have been fit to heavy quarkonium models, including the Novikov-Shifman model. This model, which is written in terms of the parameter , predicts that D wave pions should be present. We determine ϭ0.183 Ϯ0.002Ϯ0.003 based on the joint m Ϫcos * distribution. The fraction of D wave amplitude as a function of m is found to decrease with increasing m , in agreement with the model. We have also fit the Mannel-Yan model, which is another model that allows D wave pions.

No abstract

The decays of the c͑2S͒ into vector plus tensor meson final states have been studied for the first time using the BES detector. We determine upper limits on branching fractions for c͑2S͒ decays into vf 2 , ra 2 , K ‫0ء‬ K ‫0ء‬ 2 1 c.c., and ff 0 2 ͑1525͒ that are, in each case, significantly smaller than the corresponding branching fractions for the J͞c meson, scaled according to the expectations of perturbative QCD.[S0031-9007(98)07836-3]

BES data on J/ψ → γ(K + K − π + π − ) are presented. The K * K * contribution peaks strongly near threshold. It is fitted with a broad 0 −+ resonance with mass M = 1800 ± 100 MeV, width Γ = 500 ± 200 MeV. A broad 2 ++ resonance peaking at 2020 MeV is also required with width ∼ 500 MeV. There is further evidence for a 2 −+ component peaking at 2.55 GeV. The non-K * K * contribution is close to phase space; it peaks at 2.6 GeV and is very different from K * K * .PACS numbers: 14.40. Cs, 12.39.Mk, 13.25.Jx, 13.40.Hq Typeset using REVT E X [4]. There, we also find a broad 2 The analysis in this paper uses 7.8 × 10 6 J/ψ triggers collected by the Beijing Spectrometer(BES). This detector has been described in detail in Ref [12]. Here we describe briefly those detector elements crucial to this measurement. Tracking is provided by a 10 superlayer main drift chamber (MDC). Each superlayer contains four layers of sense wires measuring both the position and the ionization energy loss (dE/dx) of charged particles.The momentum resolution is σ P /P = 1.7% A positive identification of at least one K ± and one π ± is required using time of flight and/or dE/dx. If two tracks are ambiguous, both alternative identifications are tried. Events are fitted kinematically to the 4C hypothesis J/ψ → γ(, requiring a confidence level > 5%. If there is more than one photon, the fit is repeated using all permutations.Events with two or more photons are also fitted to J/ψ → γγKThose giving a better fit than to γ(K + K − π + π − ) are rejected, as are events fitting the final stateNext, we require | U miss |=| E miss − P miss |< 0.12 GeV/c 2 , so as to reject the events with multi-photons or more or less than two charged kaons; here, E miss and P miss are, respectively, the missing energy and missing momentum of all charged particles; they are calculated by assuming the charged particles are(GeV/c) 2 is required in order to remove the background J/ψ → π 0

We have measured the radiative decays φ → ηγ , φ → η ′ γ selecting π + π − γ γ γ final state in a sample of ∼5×10 7 φ-mesons produced at the Frascati φ-factory DAΦNE. We obtain Γ(φ → η ′ γ )/Γ(φ → ηγ ) = (4.70 ± 0.47 ± 0.31) × 10 −3 . From this result we derive new accurate values for the branching ratio BR(φ → η ′ γ ) = (6.10 ± 0.61 ± 0.43) × 10 −5 and the mixing angle of pseudoscalar mesons in the flavour basis ϕ P = (41.8 +1.9 −1.6 ) • .