R.J. Ledoux

Centrality dependence of kaon yields in Si + A and Au + Au collisions at the AGS

Charged kaon production has been measured in Si+Al and Si+Au collisions at 14.6 A GeV/c, and Au+Au collisions at 11.1 A GeV/c by Experiments 859 and 866 (the E--802 Collaboration) at the BNL AGS. Invariant transverse mass spectra and rapidity distributions for both K+ and K- are presented. The centrality dependence of rapidity-integrated kaon yields is studied. Strangeness enhancement is observed as an increase in the slope of the kaon yield with the total number of participants as well as the yield per participant. The enhancement starts with peripheral Si+Al and Si+Au collisions (relative to N+N) and appears to saturate for a moderate number of participating nucleons in Si+Au collisions. It is also observed to increase slowly with centrality in Au+Au collisions, to a level in the most central Au+Au collisions that is greater than that found in central Si+A collisions. The enhancement factor for

Antiproton production in 14.6 AGeVc Si+A collisions

K^+

Production of phi mesons in central 28Si+196Au collisions at 14.6A GeV/c.

production are 3.0 +-0.2(stat.) +-0.4(syst.) and 4.0 +-0.3(stat.) +-0.5(syst.), respectively, for the most central 7% Si+Au collisions and the most central 4% Au+Au collisions relative to N+N at the correponding beam energy.

The Exoscope - A Frame-Based Video/Graphics System for Intraoperative Guidance of Surgical Resection

Abstract Antiproton production cross sections have been measured for minimum bias and central Si+Al and Si+Au collisions at 14.6 A GeV c . The data presented cover the range of transverse momentum from 0.3 to 1.2 GeV c and lab rapidities from 1.1 to 1.7 units. The relative p π − and p K − yields are found to be the smallest for the heaviest system measured, central Si+Au collisions. For these collisions, the p π − ratio, determined from integrated yields for 1.1⩽y⩽1.7, is (0.84±0.07)×10−3. In the same rapidity interval, the average antiproton inverse m⊥ slope is 141±14 MeV for central Si+Al and central Si+Au collisions.

Centrality dependence of K+ and π+ multiplicities from Si + A collisions at 14.6 A GeV/c☆

Production of the {phi} meson in central Si+Au collisions has been measured by E859 at the Brookhaven Alternating Gradient Synchrotron by selecting events with identified K{sup +}K{sup -} pairs. The mass and width of the {phi}, obtained from the invariant mass distribution of kaon pairs, are consistent with those of free f mesons. The transverse mass and rapidity distributions are presented. The inverse slope parameter for an exponential fit to the invariant transverse mass distribution is 179{+-}10{+-}17 MeV.

Rotational band of 12C + 12C gross-structure resonances and its representation by a double-minimum optical potential☆☆☆

A system has been devised to focus a video camera mounted on a CRW stereotactic frame onto the surgical field and to integrate the video picture with a computer-generated three-dimensional view of structures or targets deep within the brain. The surgical resection can then be done with the surgeon looking either at the composite picture on the video/computer monitor (as in almost all endoscopic surgery) or at the surgical field, to perform the resection using the conventional techniques most comfortable to the surgeon and most effective for the resection. The graphics platform on which the Exoscope program is built is the same as used for the RSA X-Knife stereotactic radiosurgery system. The X-Knife graphics program allows the reconstruction of a target mass (such as intracranial tumor) and desired objects (such as surrounding vessels) with accurate registration to stereotactic coordinates derived from the CRW localizing system. By mounting a video system through an externally mounted endoscope on the CRW arc, it is possible to orient the video image with great accuracy to this same stereotactic space. The two images are superimposed on a computer/video console in the operating room. The surgeon visualizes a real-time video image of the operating field upon which is a graphical representation of the computer-generated image of the target mass beneath the surface. In the corners are triplane orthogonal views through the center of target and a view parallel to the trajectory, so the surgeon may gauge his or her progress toward the target.(ABSTRACT TRUNCATED AT 250 WORDS)

Leading particle distributions in 200 GeV/c p+A interactions

Abstract K + and π + multiplicities have been measured in magnetic spectrometer for Si++ Al, Si+ Cu and Si + Au collisions at 14.6 A GeV/ c incident momentum. The multiplicities were obtained for five different windows of forward kinetic energy as detected in a zero degree calorimeter. The K + / π + multiplicity ratio ranges from ≈9% in peripheral interactions to 19% in central Si+Au. The largest K + / π + ratios are observed for those events for each target that leave the least energy in the zero degree calorimeter and the ratio increases with target mass. The observations suggest that multiple interactions are important in the particle production mechanism.

Angular momentum partition as a function of the mass asymmetry in heavy-ion induced fission

Abstract A detailed phase shift analysis of 12 C + 12 C elastic data from E cm = 5.5 to 33 MeV has revealed a pronounced sequence of gross structure resonances. They appear to form a rotational band from l = 0 to at least 16ħ, and are the dominant structural feature of the 12 C + 12 C reaction. The resonances are parametrized by a Breit-Wigner analysis and are simulated by shape-resonances in an optical potential with a secondary minimum at large radius. They are discussed in terms of shape-isometric doorway states in 24 Mg.

Particle production in pA and AA collisions at AGS

Abstract Distributions of the leading positive particle have been measured in collisions of a 200 GeV/ c proton beam with hydrogen, Mg, Ag and Au targets using the FNAL Hybrid Spectrometer. Estimates of the rapidity loss of the projectile have been obtained as a function of the target mass, the multiplicity of negative particles and the number of recoil protons. We obtained a lower limit of the rapidity loss of 2.0±0.2 for central p+Au collisions. The impact parameter dependence of the momenta of the first few leading particles has also been investigated with important implications to estimates of energy densities obtained in central collisions.

Production ofφMesons in CentralS28i+A196uCollisions at14.6AGeV/c

Abstract Gamma ray multiplicities and angular distributions have been measured as functions of the mass asymmetry of the fission fragments for the reactions of 150–210 MeV 137 Cl beams with 107 Ag, and 150–210MeV 32 S beams with 112 Cd. In all reactions, as the mass asymmetry increases the mean total gamma ray multiplicities decreases, the relative width of the multiplicity increases and the gamma ray anisotropy decreases. Thus the more asymmetric the mass splitting, the smaller is the total spin of the fission fragments, and, probably, the total angular momentum of the compound system.