Search

Significant differences are observed between forward-produced Δ ++ (1232) and Λ 0 's in pp interactions and their corresponding anti-particles in p p interactions, as expected from quark counting and single q q annihilation. A possible relationship between these results and the p p -pp total cross section difference is discussed.

The Glauber formalism is used to study p- 3 He and p- 3 H elastic scattering. A wave function is chosen with proper symmetry properties and the nucleon-nucleon amplitude scattering is taken to be spin and isospin dependent. Some numerical results are compared with experimental results at 600 MeV, using cross sections calculated with different phase shifts and studying the importance of the different terms in the nucleon-nucleon amplitude and some corrections.

pp and pp elastic scattering differential cross sections are presented for momentum transfer 0.6

An apparatus, used to search for nucleon isobars, x , in π 4 He → π t x or π 4 He → π 3 He x reactions, is described. The nuclear fragment and the scattered fast pion were measured in a recoil spectrometer and a fast-particle spectrometer, respectively. The recoil spectrometer has multiwire proportional chambers (MWPC) for the measurement of direction and semiconductor detectors and scintillation counters for the measurement of energy. The identification of the recoil is accomplished by means of the E , ΔE method. The target is gaseous to allow the measurement of low-energy recoils and it can hold pressures up to 150 atm. The spectrometer for the scattered pion consists of a magnet and MWPC's.

We report Λ 0 -hyperon polarization measurements at the CERN intersecting storage rings from √ s of 31 to 62 GeV. P Λ 0 changes insignificantly, +(0.8±1.7)%, over this range of √ s . However, P Λ 0 is observed to grow with Feynman- x F and with transverse momentum. At an average p t of 1.1 GeV/ c , P Λ 0 depends linearly on x F and approaches −40% at x F =0.8.

We report results of an inclusive measurement of the charmed baryon, Λc, in the forward direction of proton-proton interactions with s =63 GeV . The signal, seen in the final state Λsπ+π+π−, has 6.0 σ significance with about 620 events on a large background and corresponds to a cross section times branching ratio of 2.84±0.50±0.72 μb for Feynman-xF > 0.5 in both hemispheres. Asymmetries are observed in the decay angular distributions which are characteristic of weak decays and have a combined 3.0 σ significance.

D(1285) and E/iota(1422) are observed in the diffractive dissociation process, pp→(pK 0 K +- π ± )p, with √ s =63Gev. The D(1285) is produced with dominant ±1 helicity. Several unusual features of the data suggest that the mesonic states result from gluonic interactions in the collision.

The differential cross-sections for the elastic scattering of protons on deuterium have been measured at 600 MeV in the |t| range between 0.003 and 0.030 (GeV/c)2. The results are analysed by using the Bethe and Glauber formalisms taking into account spin effects in deuterium wave function and nucleon-nucleon amplitudes. The ratio between the real and the imaginary parts of the spin-independent protonneutron amplitude αpn deduced from dispersion calculations and phase shift analysis is compared with experimental results.

In an experiment at the CERN intersecting storage rings with √s = 31 GeV, we have measured αP, the product of asymmetry parameter and polarization, for Λ 0's and Λ0's produced in p p and pp interactions, respectively. The ratio, (αP) Λ /(αP Λ = −1.04±0.29 , is consistent with the value −1, and constitutes the first test of CP invariance in Λ decay.

We study the production of π+'s and protons at 90° with pt>1.15 GeV and their correlations with forward protons. Fewer forward protons are observed for a 90° proton trigger than for a π+ trigger. This is in qualitative agreement with the idea of an effective diquark scattering mechanism. Additionally, we observe that a K+ produced at 90° is correlated with an enhanced forward production of λO.

La section efficace differentielle de diffusion elastique coherente de pions de 1,12 GeV sur4He a ete mesuree avec une cible gazeuse et detection du noyau de recul dans des emulsions nucleaires. Cette methode a ete etendue a l'utilisation de detecteurs a jonction pour etudier les diffusions p - 3He, p-T a 600 MeV.

We describe the use of semiconductor telescopes to detect, to identify and to measure the energy of the recoil nucleus in proton-nucleus coherent interactions at 600 MeV. Preliminary results are obtained using 3 He and 4 He gaseous targets with a pressure of one atmosphere.

Using both recoil and fast-particle spectrometers, the reaction ${\ensuremath{\pi}}^{\ensuremath{-}}+^{4}\mathrm{He}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}+^{3}\mathrm{H}+x$ has been measured for triton momenta in the region 0.24-0.60 GeV/c. The experimental spectra are presented as functions of triton momentum and angle and of mass of the unmeasured object. In the theoretical analysis it is assumed that the final state can be reached via quasielastic scattering from ${N}^{*}^{3}\mathrm{H}$ states and via ${N}^{*}$ productions from the $p^{3}\mathrm{H}$ state of helium. The most credible of three investigated $p^{3}\mathrm{H}$ wave functions requires one percent of ${N}^{*}^{3}\mathrm{H}$ states in the mass range 1.08-1.80 GeV/${\mathit{c}}^{2}$.NUCLEAR REACTIONS $^{4}\mathrm{He}({\ensuremath{\pi}}^{\ensuremath{-}},{\ensuremath{\pi}}^{\ensuremath{-}}x)t$, $E=5$ GeV, ${E}_{t}g10$ MeV measured $\ensuremath{\sigma}({\ensuremath{\theta}}_{t},{m}_{x})$, $\ensuremath{\sigma}({m}_{x},{E}_{t})$, $\ensuremath{\sigma}({m}_{x},{\ensuremath{\theta}}_{t})$; deduced $p\ensuremath{-}t$ wave-$f$, $x\ensuremath{-}t$ prob. $1.1l{m}_{x}l1.8$ GeV. $p({\ensuremath{\pi}}^{\ensuremath{-}},{\ensuremath{\pi}}^{\ensuremath{-}})x$, $E=5$ GeV, measured $\ensuremath{\sigma}({m}_{x})$.

Differential cross sections for the elastic scattering of protons on 2 H, 3 H, 3 He and 4 He have been measured at 600 MeV. Proton-deuterium elastic scattering is investigated in a four-momentum transfer square t -range corresponding to Coulomb-nuclear interference in order to determine the nucleon-nucleon amplitudes at 600 MeV. For the other nuclei, we investigate the t -range corresponding to the first and second maximum, in order to determine the mechanism of the nuclear process. A few physical comments on the results are made.

Measurements are presented of two exclusive diffractive reactions, pp → (Λ 0 φ 0 K + ) p and pp → (Λ 0 Λ 0 p)p , at √ s = 63 GeV . Pronounced correlations with the beam direction are observed (in the rest frame of the forward-going bracketed system) for those outgoing particles which contain the beam valence quarks. In each case there is a forward-Λ0 in correlation with a backward K+ or p, respectively. No such behavior is seen for the particles which do not contain beam valence quarks (φ 0 and Λ 0 , respectively) . Interpreted as examples of pomeron-proton scattering, these results constitute evidence that, for these final states, the pomeron interacts with a single valence quark and apparently back-scatters it. The subsequent hadronization leads to a longitudinal event structure.

Missing mass spectra from the reactions πp → πx and πα → πtx have been measured and found to be significantly different. Neglecting all background processes an analysis with the impulse approximation yields a 0.24 percent presence of the isobar-triton state in helium in the triton momentum range 0.32–0.70 GeV c and the mass range 1.30–1.86 GeV c 2 .

We study the internal structure of a forward-going pπ + π − π + π − system, with invariant mass in the range 2.5-4 GeV, produced through diffractive dissociation of a beam proton at the ISR. The shape of the system, as seen in its center-of-mass, deviates strongly from isotropic phase space and possesses, rather, a longitudinal structure with a major axis along the incoming proton direction. The final state proton momentum is aligned in the direction of the incoming proton, an effect which becomes more pronounced with increasing diffractive mass.

We describe the use of semiconductor telescopes to detect and to identify the recoil nucleus in proton nucleus coherent interactions at 600 MeV. Preliminary results are obtained using 3 He and 4 He gaseous target with a pressure of one atmosphere. We reach a mean precision of 1% on the quadrimomentum transfer of the elastic interaction.

There is a growing interest among nuclear and particle physicists for the application of the detection techniques used in subatomic physics to medical imaging. As well, the code used to simulate the response of these detectors to ionizing particles named GEANT can be applied to simulate medical imaging devices. GEANT allows a complete Monte-Carlo treatment of the attenuation by body parts and of the generation and tracking of optical photons from scintillation inside the crystal. The authors used GEANT to simulate a high resolution gamma camera for small animal imaging. Their study shows a significant correlation between the depth of a source in the body and the energy spectrum of the photons detected in the gamma-camera.