[show abstract][hide abstract] ABSTRACT: We report on a high-statistics search for the \t1540 resonance in $\Sigma^-$-nucleus collisions at 340 \gevc1 . No evidence for this resonance was found in our data sample which contains 13 millions $K^0_s \to \pi^+\pi^- $ decays above background. For the decay channel $\Theta^+ \to K^0_s p$ and the kinematic range $x_F>$ 0.05 we find the production cross section to be $BR(\Theta^+ \to K^0_s p)\cdot \sigma_0 <$ 1.8 $\mu$b per nucleon at 99% CL.
[show abstract][hide abstract] ABSTRACT: We present the measurement of the lifetime of the we have performed using three independent data samples from two different decay modes. Using a Σ− beam of 340 we have obtained clean signals for the decaying i Ξ−K−π+π+ and Ω−π+π−π+, avoiding topological cuts normally used in charm analysis. The short but measurable lifetime of the is demonstrated by a clear enhancement of the signals at short but finite decay lengths. Using a continuous maximum likelihood method we determined the lifetime to be τωc0 = 55−11+13(stat)−23+18(syst) fs. This makes the the shortest living weakly decaying particle observed so far. The short value of the lifetime comfirms the predicted pattern of the charmed baryon lifetimes and demonstrates that the strong interaction plays a vital role in the lifetimes of charmed hadrons.
[show abstract][hide abstract] ABSTRACT: The design and performances of a new Cherenkov counter for on-line tagging of high energy particles are reported. The counter is equipped with a 6 m focal length spherical mirror and a chromatic corrector. The Cherenkov ring size is reduced by means of a set of two conical mirrors to match the active area of an image intensifier which output is read by a matrix of optical fibres partitioned in pixel, each pixels being coupled to a photomultiplier. Results of tests with π (plus K and) beams are reported and performances of the apparatus are discussed. A spatial resolution of 0.125 mm (20.6 μrad angular) on the Cherenkov radius measurement has been obtained with a 50 μrad divergence 220 GeV pion beam, outlining encouraging prospects for a separation of 270 GeV Σ− and Ξ− hyperons at the 5σ level.
Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 01/1994; · 1.14 Impact Factor
[show abstract][hide abstract] ABSTRACT: Calculations of chromatic corrections and design of chromatic corrections are discussed. Application to the case of the new beam-RICH counter HYPOLIT is described.
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. 01/1994;
[show abstract][hide abstract] ABSTRACT: The reaction (13C, 13N) has been studied at 50 MeV/u on a set of nuclear targets including 12C, 40Ca, 58,60Ni, 90Zr, 120Sn and 208Pb. Excitation of ΔT2 = 1 giant dipole resonance has been observed in light nuclei (A⩽ 60) and corresponding angular distribution have been measured. A broad structure is observed at excitation energy above the GDR in nuclei with A⩾ 60. Angular-distribution measurements of elastic-scattering cross sections are also reported on 12C and 58Ni, as well as excitation of low-lying states in 12B. Microscopic DWBA analysis of the results is presented. Some results on the (13C, 13B) reaction are also presented.
[show abstract][hide abstract] ABSTRACT: The 16O+12C reaction at an incident energy E/A of 38 MeV has been investigated experimentally. Singles energy spectra and the angular distribution of reaction residues having 3
Physical Review C 04/1992; 45(3):1189-1193. · 3.72 Impact Factor
[show abstract][hide abstract] ABSTRACT: The giant quadrupole resonance and the low-lying quadrupole transition have been investigated in 58Ni, 92Mo, 120,124Sn, 140Ce, and 208Pb by inelastic scattering of 108.5 MeV 3He particles at very small angles. Anomalous rise of the giant quadrupole resonance cross section is observed to 0°. Distorted-wave Born approximation calculations are reported. Possible interpretations of the anomalous effect are discussed.
Physical Review C 01/1989; 38(6):2514-2519. · 3.72 Impact Factor
[show abstract][hide abstract] ABSTRACT: An elastic scattering phase shift analysis based on McIntyre parametrization is presented. It has been applied successfully to 1449- and 2400-MeV /sup 12/C beams bombarding /sup 12/C and /sup 208/Pb targets.
Physical Review C 12/1986; 34(5):1988-1990. · 3.72 Impact Factor
[show abstract][hide abstract] ABSTRACT: We present measurements of the inclusive pi+/- momentum distributions and total pion production cross sections for 330, 400, and 500 MeV protons incident on 12C and 238U. The pi+/pi- cross section ratio is seen to increase sharply with decreasing projectile energy for the light nucleus. Comparisons are also presented of the projectile energy systematics of data and intranuclear cascade calculations in the intermediate energy region.
Physical Review C 02/1985; 31(1):292-294. · 3.72 Impact Factor
[show abstract][hide abstract] ABSTRACT: An 86 MeV/nucleon 12C beam has been used to bombard targets of C, Ag and Au. Energy spectra of reaction products with Z = 3−6 and A = 6−12 have been measured at angles between 3° and 20°. A simple fragmentation model, while predicting approximately the gross features of the data, fails to describe the results in detail.
Physics Letters B 01/1981; 105(1):25-29. · 4.57 Impact Factor
[show abstract][hide abstract] ABSTRACT: Elastic scattering cross sections of 86 MeV/N 12C ions on 12C, NATCa, 89Y and 208Pb targets has been measured together with inelastic scattering to the 4.4 MeV state of 12C. There is some indication for giant (quadrupole) resonance excitation in 40Ca. Optical model and DWBA analyses are reported. Nuclear transparency effect is discussed.
[show abstract][hide abstract] ABSTRACT: We report on the observation of a KSp resonance signal at a mass of 1765 ± 5MeV/c
2, with intrinsic width Γ = 108 ± 22MeV/c
2, produced inclusively in Σ--nucleus interactions at 340GeV/c in the hyperon beam experiment WA89 at CERN. The signal was observed in the kinematic region xF>0.7, in this region its production cross section rises approximately linearly with (1-xF), reaching BR(X→KSp)dσ/dxF=(5.2±2.3)μb per nucleon at xF=0.8. The hard xF spectrum suggests the presence of a strong leading particle effect in the production and hence the identification as a Σ*+ state. No corresponding peaks were observed in the K-p and Λπ± mass spectra.
European Physical Journal C 50(3):535-538. · 5.25 Impact Factor