Search

Results on the measurement of inclusive K s o , Λ and Λ production cross sections and rapidity distributions for antiproton interactions on lead, copper and carbon nuclear targets at beam momenta of 5.2, 7.0 and 8.8 GeV/c are reported. Simulations employing a conventional Intra-nuclear cascade model were able to reproduce the experimental results. Hence, no compelling evidence for the formation of exotic quark-gluon states of matter was found.

We present the results of Λ and K05 production from a Si target with a 14.6 × A GeV c Si beam. The measured rapidity distribution and transverse mass exponential slopes are presented and compared with models. We also present a measurement of Ξ− production from a Pb target with the same beam. The rapidity distribution is measured along with a model comparison. Finally we have searched for strangelets which decay in our TPC volume. From a Monte Carlo study with a plasma production model, we have established a upper limit on a given strangelet production cross section.

The TPC's (Time Projection Chamber) used in E-810 at the AGS (Alternating Gradient Synchroton) were exposed to silicon ion fluxes equivalent to more than 10{sup 7} minimum ionizing particles per second to measure the distortion of the electric field caused by positive ions in the drift region. Results of these tests are presented and the consequences for the TPC based experiment at RHIC (Relativistic Heavy Ion Collider) are discussed.

A large-angle multiplicity detector (LAMD) system has been developed and used in the BNL experiment E854, relating to antiproton-nucleus interactions. The purpose of the BNL experiment E854 was to search for the predicted formation of hot hadronic matter by energetic antiproton absorption on a range of nuclei. This experiment probed the high-temperature-low-density region of the nuclear matter phase diagram. The LAMD system performed well with an energetic antiproton beam. Charged particle multiplicity distributions from p annihilations were measured. The design and performance of the LAMD system are outlined. >

TPCs (time projection chambers) used in E-810 at the AGS (alternating gradient synchrotron) were exposed to fluxes equivalent to more than 10/sup 7/ minimum ionizing particles per second to find if such high fluxes cause high changes or distortions of the electric field. Initial results of these and other tests are presented and the consequences for the RHIC (relativistic heavy ion collider) TPC-based experiments are discussed. Measurements of distortions due to ion loading in the E-810 TPCs have been measured to be small even at very high effective particle fluxes. This results supports the use of TPCs at RHIC, even at the highest planned luminosity. In addition, measurement of two-vertex resolution and reconstruction efficiency at high track density showed that a TPC is an excellent detector for the RHIC. >

A measurement of the transverse momentum spectrum of negatively charged tracks from AGS energy silicon ion collisions is presented. The spectrum has a different shape than that of nucleon-nucleon collisions at approximately the same energy. The transverse mass spectrum is well represented by a sum of two exponentials with different slopes and may be reasonably well accounted for by a model of pion production in interacting nuclear matter that includes resonance production and decay.

The tracking detector of AGS Experiment 810 is a three-piece Time Projection Chamber (TPC) which measures all charged tracks in the forward hemisphere of the nucleon-nucleon center of mass system, i. e. forward of 20 degrees in the lab. Each module of the TPC contains twelve rows of short anode wires which give 3-D space points on each track, but no dE/dx information useable for particle identification. The MPS magnet provides a uniform 5 kG field on the TPC volume. The TPC was operated in a beam of 14.6 × A GeV/c silicon ions at the end of June 1989. This talk reports the results of analysis of the gold and copper target data from that run. The trigger was quite simple, requiring a large pulse height in a Cerenkov counter in the incident beam indicating an incident silicon ion, a small pulse height in a scintillation counter centered on the beam behind the TPC corresponding to less ionization than a surviving carbon ion would produce, and a substantial signal in each of two scintillators located above and below the beam just in front of the TPC. The targets were thin, 0.0076 radiation lengths of gold, 0.0089 radiation lengths of copper, to reduce contamination of the events by electron tracks from converted π0 photons. A cut at multiplicity 50 was used to select more central collisions, yielding 2291 events from the gold sample, 2170 from the copper. This corresponds to cross sections of 0.59 and 0.20 barns, respectively, defining the “central” sample for the charged particle distributions presented here.

We have measured the rapidity distributions for charged particles produced in SiAu collisions at 14.6× A GeV/ c . No evidence is seen for enhanced production of protons at high rapidity as recently postulated based on fits to earlier data.

The reaction $pd\ensuremath{\rightarrow}{p}_{\mathrm{spec}}p{\ensuremath{\pi}}^{\ensuremath{-}}p$ is studied at 19 and 28 GeV/c with data from the Brookhaven National Laboratory 80-in. deuterium-filled bubble chamber. In addition, a separate study is made of the low-momentum pion spectra in selected low-multiplicity events presumed to be associated with either of two isospin-conjugate modes of deuteron fragmentation by a 28-GeV/c beam proton. Our results from these complementary studies are that low-multiplicity channels are dominantly of a diffractive nature; however, significant differences seen in the mass spectra and angular correlations in the slow $p\ensuremath{\pi}$ between the 19- and 28-GeV/c data indicate that asymptotic behavior has not been reached, as least at 19 GeV/c. Neither $s$- nor $t$-channel helicity conservation is seen in the excitation of the target neutron into a low-mass $p{\ensuremath{\pi}}^{\ensuremath{-}}$ system. The ${N}^{*}(1.4)$ of missing-mass experiments is shown to be a superposition of nucleon-pion and nucleon-two-pion states.

Using the multiparticle spectrometer facility (MPS) at BNL, we have set upper limits on the formation of a meson state in the mass range 2.99–3.14 GeV from proton-anti-proton annihilations. The upper limits are, in terms of the cross section integrated over the width, 18 MeV · μb for the final state γ γ , 18 MeV · for K 0 K 0∗ (890) + c.c. , and 2 MeV · μb for KSKL.

The collision of 15 GeV/nucleon sulfur and carbon or oxygen ions with various fixed targets such as carbon, sulfur, and gold is to be observed in the MPS magnetic spectrometer with a time projection chamber (TPC) module. This TPC will be placed just downstream of the target and be able to track approximately 50% of all charged particles. The design and construction of the TPC is proceeding, and prototypes of the TPC readout system have been tested and production devices are to be delivered. A TPC track reconstruction program has been developed. Monte Carlo events have been generated and tracked. The track reconstruction program consists of three parts: a local pattern recognition which associates contiguous readouts on adjacent readout wires to form a single hit; a subroutine which positions the hits into slices in the vertical plane; and the track reconstruction section. (LEW)

We have performed a high-statistics search for narrow meson states (GAMMA< or =30 MeV) produced in ..pi../sup -/p interactions at 16 GeV/c and decaying into pp-bar..pi../sup +/ or ..lambda..p-bar..pi../sup + -/. This is the first systematic search in channels requiring exchange of exotic mesons. The cross section for production of such states is ruled out at the 95% confidence level with upper limits ranging from approx.10 nb at 2.3 GeV to approx.40 nb at 2.8 GeV.

We study the multiplicity distribution of charged particles produced in 28-GeV/c $\mathrm{pd}$ interactions in the BNL 80-inch deuterium bubble chamber. We find that (18.3 \ifmmode\pm\else\textpm\fi{} 2.9)% of the three- and more-prong $\mathrm{pd}$ events result from double scattering in deuterium, a fraction observed to be constant from 28-to-400-GeV/c incident momentum. We extract $\mathrm{pn}$ topological cross sections from the odd-prong $\mathrm{pd}$ data by correcting for the effects of spectator visibility, double scattering, and Glauber screening. We find the dispersion of 28-to-400-GeV/c $\mathrm{pd}$ multiplicity distributions to have the same linear dependence on the mean multiplicity as found for $\mathrm{pp}$ data, while the $\mathrm{pn}$ data exhibit a different dependence. Both the $\mathrm{pd}$ and $\mathrm{pn}$ multiplicity distributions at 28 GeV/c are observed to be inconsistent with Koba-Nielsen-Olesen scaling.

The principal detector for AGS Experiment 810 is a Time Projection Chamber (TPC) in which it is intended to measure momenta and angles of a major fraction of the charged particles from each light ion collision. This report describes the results of a test of a prototype of the TPC in a beam of (14.6 × 16 = 233.6 GeV c ) oxygen ions run in June of this year.

The authors have detected 1203 events of the reaction ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}\ensuremath{\phi}\ensuremath{\phi}n$ at 22 GeV/c, and have performed a partial-wave analysis of the $\ensuremath{\phi}\ensuremath{\phi}$ system. The results are well represented by two resonances, both with quantum numbers ${I}^{G}={0}^{+}$, ${J}^{\mathrm{PC}}={2}^{++}$. The breakdown of the Okubo-Zweig-Iizuka suppression observed in this reaction is naturally explained in the context of QCD if these states are considered to be glueball candidates.

The single-particle inclusive pion spectrum from the reaction p + p → π± + anything at 28.5 GeV is presented in both tabular and graphical form. The data are from exposures in the BNL 203 cm bubble chamber. The emphasis of this paper is on exhibiting the single-particle spectra in sufficient detail so that the data will be useful to those interested in testing models and developing new concepts.

The spectra of pions are studied in the inclusive reactions p + p → π ± + anything in bubble chamber data at 28.5 GeV/ c . Comparisons are made with ISR π + spectra to examine energy dependence.

A study of antiproton-proton collisions at $3.3 \mathrm{and} 3.7 \frac{\mathrm{BeV}}{c}$ indicates that (41\ifmmode\pm\else\textpm\fi{}4)% of the total interaction cross section can be attributed to annihilation into pions. The average pion multiplicity is 6.5\ifmmode\pm\else\textpm\fi{}0.5. The positively charged pions and dipions tend to be emitted backward, while the negatively charged pions and dipions tend to be emitted forward in the center-of-mass system. Although there is a substantial amount of resonance production, especially of $\ensuremath{\rho}$ and of $\ensuremath{\omega}$ mesons, there is no clear evidence for double or associated resonance production in these final states. A search for new resonances as well as for some of the recently discovered mesons proved unsuccessful.

The elastic, the pion-production, and the multipion-annihilation cross sections for antiproton-proton interactions at 3.28 and 3.66 BeV/c incident antiproton momenta have been measured. A comparison of the elastic interactions at 3.28 BeV/c with a purely-absorbing disc optical model gave a best value for the radius of interaction of $1.3 F$. The real part of the forward scattering amplitude has been found to be less than 20% of the imaginary part. A study of the asymmetries in double elastic scatters yielded a value for a polarizing power of the hydrogen consistent with zero when averaged over production angles.

Reactions of the type p + p → Δ++ (1238) + M are studied at 28.5 GeV/c incident momentum. Cross sections of the various channels that constitute M suggest the importance of pion exchange at the Δ++ vertex.