[en] It may be possible to create hot (tau approx. 100 MeV), dense (about 5 times the normal nuclear density) matter in central collisions of high energy heavy ions. This matter may reach thermal and chemical equilibrium. Theoretical conjectures suggest that the constituent quarks might determine the behavior of such a system. A possible signature of this quark-gluon plasma may be an abrupt change in average pion production per collision as the threshold beam energy is reached. A search for this signature has been made by comparing pion production in central collisions of carbon and lead at beam energies from 1 to 2 GeV/n. The pion production was recorded by a lucite Cherenkov telescope system, a lead glass system and a sodium iodide system. Pion production, as a function of both beam energy and the associated charged particle multiplicity, is presented. There were no abrupt thresholds observed to within the systematic errors. This null result indicates that either the postulated quark-gluon plasma did not occur, or that it did not occur with a significant probability

[en] Neutron energy spectra from the exclusive pion capture reaction Ho(π, γxn)Dy are presented. Neutron time-of-flight data was collected in coincidence with nuclear gamma rays which identified the final nuclear state. Most of the ground state band levels up to 12⁺ in even-even Dy isotopes were included. These correspond to odd neutron multiplicities from 3 to 11. The spectra show significant changes with neutron multiplicity, exhibiting a sharp cut-off at characteristic energies. Structure in the high energy component of the spectra has been resolved for the first time, and its correlation to the population of high-spin states is observed. This discrete component is strongest in coincidence with the 8⁺ → 6⁺ transition in ¹⁶⁰Dy and ¹⁵⁸Dy (neutron multiplicities 5 and 7). The capture reaction preferentially populates the 4⁺ and 6⁺ states in the ground state bands of ¹⁶⁰Dy and ¹⁶²Dy, corresponding to neutron multiplicities 5 and 3

[en] Negative kaons were stopped in liquid hydrogen and liquid deuterium targets to study radiative capture rates. Branching ratios for the radiative kaon capture reactions K^-p→Λγ and K^-p→Σ⁰γ provide information about the quark structure of the Λ(1405). In the reaction K^-d→Λnγ, the shape of the photon spectrum in the endpoint region provides information on the final state Λ-n interaction. Superior photon resolution is needed to distinguish the signal photons from the background of π⁰ decay photons. Such resolution is provided by the B.U. NaI detector, which has a resolution of 1.3% (FWHM) near 300 MeV. A description of the experimental technique and data reduction is presented, along with preliminary branching ratio results

[en] The neutron spectrum resulting from μ^--capture in ¹⁶⁵Ho has been measured with a time-of-flight spectrometer. For the first time a 13 MeV peak, and a break in the slope at 40 MeV is reported. The slope from 20 to 40 MeV is 8.88 +- 1^- MeV. This represents the first measurement of the neutron spectra by a system capable of resolving neutron energies near the muon mass. Neutron spectra from final nuclear states roughly identified by NaI pulse height are presented. A photon spectrum measured by Ge(Li) detectors exhibits neutron multiplicities up to 5 with an intensity greater than expected

[en] We have designed and tested a new high resolution NaI(Tl) total adsorption scintillation counter. The detector is a cylinder composed of a 26.7 cm diameter by 55.9 cm long NaI core with a concentric 10.8 cm thick NaI annulus that is divided into quadrants. The NaI detector is surrounded by a 12.7 cm thick plastic scintillator to veto both cosmic rays and events with significant shower leakage from the NaI. High uniformity of light production and collection throughout the detector is required for superior resolution. The detector has a measured resolution of 1.3% and 1.7% FWHM for 130 MeV photons and 330 MeV electrons, respectively. Computer simulations to account for loss of resolution due to pileup and energy spread of the beam indicate that the ultimate experimental resolutions at these energies are 1.2±0.1% and 1.3±0.1%. The resolutions at these two energies are at least a factor of 2 better than that of any other total adsorption scintillation counter available today. Based on shower simulations, the detector is expected to have a resolution of approximately 1.3% for collimated 130-2000 MeV photons. (orig.)

[en] We report the measurement of the differential scattering cross section for coherent photon scattering (nuclear Compton scattering) from ⁴He at an average energy of 180 MeV. This represents the first direct observation of the coherent process on a complex nucleus above the pion threshold. The results are compared with the predicton of a claculation utilizing the isobar-hole formalism

[en] We have measured the differential cross sections for coherent Compton photon scattering in the reaction ⁴He(γ,γ) ⁴He at laboratory angles of 24⁰, 30⁰, 45⁰, and 60⁰ with an average laboratory photon energy of 320 MeV, at 22⁰ with 358 MeV, and at 30⁰ with 260 MeV. These measurements are the first unambiguous test of the Δ-hole formalism for this reaction near the peak of the cross section for the Δ resonance. The results are compared to theoretical calculations in the isobar-hole model. Agreement is good for data at the energy corresponding to the Δ peak

[en] The neutron spectrum resulting from μ^- capture in ¹⁶⁵Ho has been measured with a time-of-flight spectrometer. The exponential constant between 13 and 50 MeV is 10.5 +- 1 MeV. The intensity of neutrons with energy greater than 40 MeV is 0.019 +- 0.004/μ^--stop. This represents the first measurement of the neutron spectra by a system capable of resolving neutron energies near 100 MeV. Neutron spectra from final nuclear states roughly identified by NaI pulse height are presented. Above 50 MeV, these spectra do not follow a simple exponential decrease. The photon spectrum measured by Ge(Li) detectors exhibits neutron multiplicities up to 5 with an intensity greater than expected. (orig.)

[en] The production of π⁰ mesons in central collisions of ¹²C and ⁴⁰Ar on ²⁰⁸Pb has been examined at a number of energies from 1 to 2.1 GeV/N, as part of the first systematic study as a function of beam energy and charged-particle multiplicity of the rate of neutral-pion production in relativistic heavy-ion collisions. For comparison, corresponding πsup(+-) data acquired with the same detector system have also been presented. The results indicate that, for a given target-projectile combination, both neutral- and charged-pion production increase smoothly by a factor of approximately 2.9 in this energy range. The measurement of charged-particle multiplicity is discussed in order to indicate how the characteristic distributions observed in this study were used to parameterize the experimental results. The average multiplicity of both pions and nucleons projected from these data is found to disagree with statistical models of particle production. The significance of the Nsub(πsup(+-))/Nsub(charge) and Nsub(πsup(+-))/Nsub(π⁰) ratios observed as a function of beam energy and charged-particle multiplicity is discussed in the context of understanding the nature of the collision process. (orig.)

[en] This paper reports on the measurement of the Weak Radiative Decay Λ → n + γ. An enhancement in the region of interest has been seen and all indications are consistent with a branching ratio higher than previously measured