We have conducted a search for bound states of a negative pion and a number of neutrons (pineuts) using the E814 spectrometer. A beam of Si28 at a momentum of 14.6A GeV/c was used to bombard targets of Al, Cu, Sn, and Pb. We describe our experimental technique, present measured upper limits for pineut production, and discuss the significance of our results.
AUTHORS NAMED CHARGED- BY PINEUT. Here ALL means the total number of interactions.
The vector analyzing power iT11 and the composite observable τ22=T22+T20/ √6 were measured at 10 incident pion energies between 100 and 294 MeV, in an angular range between 50° and 120°. Two different techniques were applied, the detection of the pion with a magnet spectrometer, and the πd coincidence method with scintillation counters. In the case of the first technique also two different target materials were used. Consistency among all data was obtained. The experimental data are compared to Faddeev calculations from one of us (H.G.). The discrepancies between theory and experiment are discussed, and an outlook for further research is given.
Vector analyzing power iT11 and composite observale TAU22 = T22 + T20/sqrt(6). LiDeut target.
Vector analyzing power iT11 and composite observale TAU22 = T22 + T20/sqrt(6). LiDeut target.
Vector analyzing power iT11 and composite observale TAU22 = T22 + T20/sqrt(6). LiDeut target.
An investigation of the production of neutron-rich isotopes from the fragmentation of Si28 projectiles at plab=14.6 GeV/c per nucleon was performed using the BNL-AGS-E814 spectrometer. We have measured the inclusive production cross sections of neutron-rich fragments (6He, He8, Li8, Li9, Be10, Be11, and B13). We have also measured the transverse momentum distributions for He6 and Li9, and the forward and transverse energy distributions associated with He6 production. The momentum distributions were analyzed in the context of the Goldhaber model. The question of whether the fragments are produced in the decay of the projectile following its electromagnetic excitation was also investigated.
No description provided.
We report on measurements of the differential π±p cross section at pion energies Tπ=32.7, 45.1, and 68.6 MeV. The measurements, covering the angular range 25°≤θlab≤123°, have been carried out at the Paul-Scherrer-Institute (PSI) in Villigen, Switzerland, employing the magnet spectrometer LEPS. The absolute normalization of the π±p cross sections have been achieved by relating them to the electromagnetic cross sections of μ±12C scattering. The results are in agreement with those of our preceding measurements at Tπ=32.2 and 45.1 MeV insofar as they overlap with the region of the Coulomb nuclear interference investigated there. A comparison with the predictions of the Karlsruhe-Helsinki phase shift analysis KH80, which has formed the basis for the determination of the ‘‘experimental’’ σ term, reveals considerable deviations. These are most pronounced for the π+p cross sections at Tπ=32.7 and 45.1 MeV. Single energy partial wave fits result in S-wave contributions, which are about 1° lower in magnitude then those specified by the KH80 solution. The data at 68.6 MeV are in good agreement with the phase shift analysis.
Statistical and systematic errors are addet in quadrature.
Statistical and systematic errors are addet in quadrature.
Statistical and systematic errors are addet in quadrature.
We have measured a complete isotope distribution of projectile-like nuclear-charge pickup products, formed by bombarding a Al17 target with 790A MeV Xe129 ions. The shape of the cross-section distribution indicates a dominant influence of evaporation processes during the formation of the final cesium fragments observed, thus masking to a large extent the primary processes involved in the charge exchange. We can show, however, that an intranuclear-cascade-plus-evaporation calculation can reproduce the observed yields, and that the effect of Δ-formation during the first stage of the reaction is visible even in the inclusive cross sections. The same model can explain the strong increase in total charge-pickup cross sections with increasing projectile mass noted previously by other authors. It is therefore not necessary to invoke coherent processes to explain this increase as has been suggested previously.
No description provided.
The values of the pion nucleon (πN) σ term, as determined, on the one hand, from experimental pion nucleon scattering by means of dispersion relations and, on the other hand, from baryon masses by means of chiral perturbation theory, differ by 10 to 15 MeV. The origin of this discrepancy is not yet understood. If the difference between the two values is attributed to the scalar current of strange sea quark pairs within the proton, the contribution to the proton mass would be of the order of 120 MeV. The discrepancy may hint at either theoretical deficiencies or an inadequate πN database. In order to provide reliable experimental data we have measured angular distributions of elastic pion proton scattering at pion energies Tπ=32.2 and 44.6 MeV using the magnet spectrometer LEPS located at the Paul-Scherrer-Institute (PSI) in Villigen, Switzerland. From the data covering the region of the Coulomb nuclear interference, the real parts of the isospin-even forward scattering amplitude ReD+(t=0), have been determined as a function of energy. The results have been compared with the predictions of the Karlsruhe-Helsinki phase shift analysis KH80, revealing discrepancies most pronounced for the π+p data. The experimentally determined values for ReD+(t=0), however, support the KH80 prediction (which is based on πN data available in 1979).
Statistical and systematic errors are addet in quadrature.
Statistical and systematic errors are addet in quadrature.
Strange baryon and in particular multi-strange baryon production is suggested to be a useful probe in the search for quark gluon plasma formation in heavy ion collisions. We have measured the (Ω − + Ω + ) (Ξ − + Ξ + ) production ratio to be 0.8±0.4 at central rapidity and ϱ T > 1.6 GeV/c.
No description provided.
Experimental data on multiplicities and correlations of charged particles of different types produced in collisions of 4.5 A GeV/c carbon-12 with emulsion are reported and discussed. The data are compared with the results of other experiments on nucleus–nucleus and hadron–nucleus collisions. It is found that the particle production mechanism in nucleus–nucleus collisions is almost the same as in hadron–nucleus collisions. It is also observed that the shower particles' multiplicity distributions obey a KNO type scaling law, which supports the aforementioned result.
No description provided.
No description provided.
No description provided.
The abundances of light nuclei probe the later stages of the evolution of a system formed in a relativistic heavy-ion collision. After the system has cooled and expanded, nucleons in close proximity and moving with small relative momenta coalesce to form nuclei. Light nuclei production enables the study of several topics, including the mechanism of composite particle production, freeze-out temperature, size of the interaction region, and entropy of the system. NA44 is the only relativistic heavy-ion experiment to have both deuteron and antideuteron results in both pA and AA collisions and the first CERN experiment to study the physics topics addressed by d and d production.
PRELIMINARY DATA.
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PRELIMINARY DATA FOR CENTRAL EVENTS.
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