[en] Preliminary results from a high statistics measurements of the π^- p → n π⁺ π^- reaction on a polarized target at 17.2 GeV show unexpectedly strong nucleon polarization effects. If it is due to the exchange of an additional particle, this object has the quantum number of the A₁. Possibly, it can also be explained (similarity to the helicity one moments in one pion exchange) by final-state interaction. The problem is of particular interest for PI PI scattering as A₁ exchange has been assumed to be absent in all PI PI phase shift analysis. A continuation of the unfinished analysis will hopefully clarify the situation

[en] A new central tracker, with larger angular acceptance, has been installed early 1996 inside the DELPHI detector. The tracker consists of 3 sub-detectors: a Si microstrip barrel detector having 3 layers with Rφ and z read-out, surrounded by a Si macropixel detector, surrounded in turn by a Si ''ministrip'' detector. The overall angular acceptance is 11 < θ < 169 . We shall mostly restrict to the barrel detector and review its design, construction, performances and geometrical alignment. (orig.)

[en] The author presents experimental results on hadronic decays of Ξ _c⁺, Λ _c⁺, and the D mesons, obtained in interactions of 230-GeV mesons (96% π^-, 4% K^-) with copper. (HSI)

[en] Preliminary results from a high statistics measurement (1 M events) of the reaction π^-p → π⁺π^-n on a polarized butanol target at 17.2 GeV show unexpectedly strong polarization effects which must be attributed to amplitudes corresponding to ''A₁'' exchange

[en] The reaction π^-p→K⁺K^-n has been studied on a hydrogen target (27000 events) at 18.4 GeV and on a butanol target (54000 events) at 17.2 GeV. In this paper we study the D wave fitting the superpositions of f(1270)+A₂(1310)+f'(1515) resonances to the t₀⁴ moment. This fit gives very high xi²/ND=60/22 for each sample if the parameters of f'(1515) are fixed at their table values. If these parameters are left free we obtain msub(f')=(1503sub(-7)⁺⁶) MeV, GAMMAsub(f')=(144sub(-17)⁺¹⁹) MeV, and BR(f'→ππ/f'→all)=(3.0+-1.0)%. Fixing the parameters of f'(1515) to their table values we obtain a good fit after the introduction of a fourth tensor meson with m=(1422+-9) MeV and GAMMA=(80+-42) MeV. Such an object does not easily fit into the quark-antiquark scheme. (author)

[en] The silicon strip Microvertex detector of the DELPHI experiment at the CERN LEP collider has been recently upgraded from two coordinates (Rφ only) to three coordinates readout (Rφ and z). The new Microvertex detector consists of 125 952 readout channels, and uses novel techniques to obtain the third coordinate. These include the use of AC coupled double sided silicon detectors with strips orthogonal to each other on opposite sides of the detector wafer. The routing of signals from the z strip to the end of the detector modules is done with a second metal layer on the detector surface, thus keeping the material in the sensitive area to a minimum. Pairs of wafers are daisy chained, with the wafers within each pair flipped with respect to each other in order to minimize the load capacitance on the readout amplifiers. The design of the detector and its various components are described. Results on the performance of the new detector are presented, with special emphasis on alignment, intrinsic precision and impact parameter resolution. The new detector has been taking data since spring of 1994, performing up to design specifications. (orig.)

[en] Results of an analysis of two high statistics samples of p anti-p events (10 k events at psub(Lab)=18.8 GeV and 28 k events at psub(Lab)=18.4 GeV) are presented. The data extend from threshold to 2.8 GeV invariant mass. One pion exchange with absorption modification has been assumed as the production process. The mass spectrum and decay angular distribution can be explained as a superposition of resonating partial waves with l=2,3,4,5. Indications of a spin 6 state at 2.7 GeV are given

[en] Evidence is given for the existence of a spin-5 boson resonance from the analysis of the reaction π^-p → K⁺K^- n at 62 GeV incident momentum. A simplified amplitude analysis with a Breit-Wigner ansatz leads to a mass of 2307 +- 6 MeV and a width of 245 +- 20 MeV. The quantum numbers of the resonance are Jsup(P) = 5^-, C = -1, and very probably Isup(G) = 1⁺. (orig.)

No abstract available

No abstract available