Observation of double ø-meson production in 100 and 175 GeV π−-Be interactions

Inclusive øø production has been studied in π^?-Be interactions for 100 and 175 GeV incident momentum. An upper limit of 72 nb has been set for $\text{σ(π}{}^{\mathrm{?}}\text{Be → η}{}_{\mathrm{<mtext>c</mtext>}}\text{(2980) +}\text{X}\text{)}\text{s}\text{?}\text{BR}\text{(η}{}_{\mathrm{<mtext>c</mtext>}}\text{→ øø) at 175 GeV}$. At both momenta the number of øø events is larger than expected for uncorrelated ø pairs. A narrow width enhancement is observed at M_øø≈2100 MeV with a 4 standard deviation significance.     

Measurement of various decay modes of charmed particlesD 0,D +,D s + andΛ s c

In the CERN NA 32 experiment a high-resolution silicon vertex detector and a purely topological approach have been used to investigate various decays of charmed particles. We observe ～620 fully reconstructed decays ofD ⁰ in 12 channels and determine the branching ratios. For fourD ⁰ decay modes involving a single (unseen) π⁰ the small and narrowD ^*+?D ⁰ mass difference is used to measure their branching ratios. We also observe ～280 fully reconstructedD ⁺ decays in 10 channels, ～90D _s ⁺ decays in 11 channels as well as 160Λ _s ^c and 18 decay channels ofD ⁺. For theD _s ⁺ , we measure the branching fractions within a subset of 16 three- and five-prong decay channels. For theΛ _s ^c , we determine the branching fractions within a sample of 11 three- and five-prong decay channels, nearly all involving a proton.     

Oxidation with sodium peroxide Direct introduction of a γ carbonyl group into α,β unsaturated ketosteroids

Aqueous sodium peroxide oxidises the conjugated Δ⁴-3-ketosteroids $\text{1a}$-$\text{1d}$ to the corresponding Δ⁴-3-4-diones in good yield. Saturated carbonyl and alcohol groups are not affected by the reaction.     

Precise measurement of the pi+-->pi0 e+nu branching ratio

Using a large acceptance calorimeter and a stopped pion beam we have made a precise measurement of the rare pi(+)-->pi(0)e(+)nu (pi(beta)) decay branching ratio. We have evaluated the branching ratio by normalizing the number of observed pi(beta) decays to the number of observed pi(+)-->e(+)nu (pi(e2)) decays. We find the value of Gamma(pi(+)-->pi(0)e(+)nu)/Gamma(total)=[1.036+/-0.004(stat)+/-0.004(syst)+/-0.003(pi(e2))]x10(-8), where the first uncertainty is statistical, the second systematic, and the third is the pi(e2) branching ratio uncertainty. Our result agrees well with the standard model prediction.     

Kinetic energy of π− p-atoms in liquid and gaseous hydrogen

We have measured the Doppler broadening of neutron time-of-flight spectra from the reaction π⁻ p → π⁰ + n in atomic states. From the data, we infer that the kinetic energy distribution of π⁻ p-atoms in liquid and gaseous hydrogen contains discrete ‘high-energy’ components with energies as high as 200 eV attributed to Coulomb de-excitation. In liquid hydrogen, evidence for Coulomb de-excitation transitions with Δn = 2 has been found. This revised version was published online in August 2006 with corrections to the Cover Date.     

Measurement of the masses and lifetimes of the charmed mesonsD 0,D + andD s +

We present the final results on the measurement of the masses and lifetimes of the mesonsD ⁰,D ⁺ andD _s ⁺ in the NA32 experiment at the CERN SPS, using silicon microstrip detectors and charge-coupled devices for vertex reconstruction. We measure the following lifetimes: \(\tau _{D^0 } = 3.88 \pm _{0.21}^{0.23} \cdot 10^{ - 13} s\) using a sample of 479D°→K ^?π⁺π^?π⁺ and 162D°→K ^?π⁺ decays; \(\tau _{D^ + } = 10.5 \pm _{0.72}^{0.77} \cdot 10^{ - 13} s\) with a sample of 317D ⁺→K ^?π⁺π⁺ decays; \(\tau _{D_s^ + } = 4.69 \pm _{0.86}^{1.02} \cdot 10^{ - 13} s\) with a sample of 54D _s ⁺ →K ⁺ K ^?π⁺ decays. We measure the following masses:m _D ⁰=1864.6±0.3±1.0 MeV,m _D ⁺=1870.0±0.5±1.0 MeV and \(m_{D_s^ + } \) =1967.0±1.0±1.0 MeV.     

Study of spin effects in neutron-proton interactions at intermediate energies at PSI

An intensive program of n-p measurement of spin observables in elastic and pion production reactions has been performed at the Paul Scherrer Institute taking advantage of the high intensity polarized neutron beam. In the elastic reaction 16 different spin observables have been measured for kinetic energies from 210 to 590 MeV with the centre of mass angular range from 60 to 180 degrees. This will allow to perform direct reconstruction in the model independent way of the isospin I=0 scattering amplitudes in elastic NN interaction. Three body final state process \(\vec np - pp\pi ^ - \) with polarized neutrons in exclusive experiment has been investigated.