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 measurement of low ${\mathit{m}}_{\mathit{tK}\mathit{s}}^{0}$ production in the rapidity range 2.2y2.6 with silicon beams on a lead target. We have selected central events with a cross section of approximately 280 mb and compare with a low kaon ${\mathit{m}}_{\mathit{t}}$ enhancement as reported earlier.

We present H 0 candidate events, where the H 0 is observed through the decay H 0 → Σ − p . These decays are reconstructed in the three TPC modules of E810 while triggering on central Si Pb events at 14.6 × A GeV/c Si beam.

Charged particle multiplicities, inclusive Λ, Λ , and K s o production cross sections and rapidity distributions have been measured for p interactions on targets of C, Cu, and Pb at 5, 7, and 9 GeV/c. Preliminary results are presented.

We report the first observation of Ξ − in heavy ion collisions at the AGS. The lifetime of Ξ − measured agrees very well with the particle data group value. We present the observed Ξ − effective mass spectrum and the rapidity distribution after acceptance correction. In the measured rapidity region (1.4−2.9) for 14.6 GeV/ c Si on Pb, we obtained a yield of 0.25 ± 0.04 Ξ − per central event and a ratio of N ( Ξ − )/ N ( Λ ) = 0.12 ± 0.02 using a fireball + model (a model which includes a fireball plus a term simulating a cascade) for acceptance correction (see text for systematic error). This result is larger than any cascade model prediction so far.

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.

This study examined the susceptibility of a variety of wild-type strains and efflux pump mutants to besifloxacin and the comparator agents sparfloxacin, ciprofloxacin, norfloxacin, moxifloxacin, tetracycline, and ethidium bromide. Organisms tested included Staphylococcus aureus (mepA or norA), Streptococcus pneumoniae (pmrA, patB), Escherichia coli (acrAB::Tn903, tolC::Tn10), Haemophilus influenzae (acrAB) and Pseudomonas aeruginosa (mepAB-oprM, oprM::ΩHg(r) rpsL). The minimal inhibitory concentrations (MIC) of besifloxacin and comparators were also measured in the presence of the efflux pump inhibitors reserpine, carbonyl cyanide mchlorophenyl- hydrazone, or sodium orthovanadate. Overall, very few meaningful changes (>2-fold) in besifloxacin MIC values resulted from the presence of efflux pump mutations or efflux pump inhibitors. In summary, the novel fluoroquinolone besifloxacin is no exception to the observation that newer fluoroquinolones are generally less affected by efflux pump-mediated resistance than older fluoroquinolones.

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.

We present the first measurement at AGS energies of rapidity distributions of K s 0 and Λ production with silicon beams on silicon and lead targets. The measurements cover the rapidity region of 2.0 y K s 0 's and 1.4 y Λ 's.

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. >

I discuss data from E-810 including K 0 and Λ production, the rise in production of negative particles at small m ⊥ , and the rapidity distributions. The data are compared to various models; in particular they do not agree with a model indicating large nuclear transparency.

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.

We present evidence for the existence of two new $I=0$ scalar mesons [${g}_{s}(1240)$ and ${S}^{*\ensuremath{'}}(1730)$] from an amplitude analysis of the reaction ${\ensuremath{\pi}}^{\ensuremath{-}}p\ensuremath{\rightarrow}{K}_{S}^{0}{K}_{S}^{0}n$ at 23 GeV/c. An examination of the mass splittings present shows that neither of these states can be easily assigned to a (near) ideally mixed ${J}^{\mathrm{PC}}={0}^{++}$ nonet. These results are in qualitative agreement with recent theoretical predictions of glucon-glucon bound states.

We have measured the reaction ..pi../sup -/p ..-->.. K/sup +/K/sup -/K/sup +/K/sup -/n at 22.6 GeV/c and defect strong phi signals in the K/sup +/K/sup -/ effective-mass plots. We do not observe the expected Okubo-Zweig-Iizuka--rule suppression of the phiphin final state and conclude that the rule is working poorly in the observed production processes.

We present data on 3652 analyzed events of the reaction π - p → φφn at 22 GeV/ c . A partial wave analysis has been performed on the φφ system. The results are well represented by three resonances all with quantum numbers I G J PC = 0 + 2 ++ . The absence of the Okubo-Zweig-Iizuka suppression observed in this reaction, the selection of only three J PC =2 ++ states ( g T , g T′ , and g T ″ ) which comprise virtually all of the cross section, and the large φφn signal over a very different φK + K - n background are all well explained if these states are produced by 1–3 glueballs (i.e. multigluon resonances).

We observe a K/sup -/..pi../sup +/ state at 1786 +- 8 MeV with a width 95 m* 31 MeV in reaction K/sup -/p ..-->.. K/sup -/..pi../sup +/n at 6 GeV/c, from an experiment carried out at the Brookhaven National Laboratory multiparticle spectrometer.

A coupled channel analysis has been carried out using a new amplitude analysis of the K0sK0s system produced in the reaction π−p→K0sK0sn at 22 GeV/c, which contained about 40 000 new events in the low-t region (|t−tmin

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 /ital K//sub /ital S///sup 0/K/sub S//sup 0//pi//sup 0/ systems, a pure /ital C/=+1 state, has been studied in the reaction /pi//sup /minus//p/r arrow/K/sub S//sup 0/K/sub S//sup 0//pi//sup 0/n at 21.4GeV//ital c/. The /ital K//sub /ital S///sup 0/K/sub S//sup 0//pi//sup 0/ spectrum is significantly different from the /bar /ital KK///pi/ distribution observed in other lower-energy peripheral hadroproduction experiments. In addition to production of the /ital f//sub 1/(1285), evidence for production of the /eta/(1460) (sometimes called the /iota/(1460)) based on mass spectra and a Dalitz-plot spin-parity analysis is reported. The narrower, lower-mass state observed in other /bar /ital KK///pi/ experiments is observed weakly if at all in this experiment. Hadronic production of the /eta/(1460), which is a good glueball candidate because of its presence in /ital J///psi/ radiative decay, suggests possible mixing with the /bar /ital qq// sector.

In a new experiment we have obtained 3006 new events in the reaction π − p → φφ n, approximately doubling the statistics which now total 6658. A refined partial wave analysis of the φφ system again reveals three resonances (g T , g T′ , g T′' ) with I G J PC =0 + 2 ++ . The absence of the OZI suppression, and the observation of only three J PC =2 ++ states (g T , g T′ , g T′' ) which comprise virtually all the cross section are unusual characteristics of the data. The large φφn signal occurs over a mostly structureless and incoherent φK + K − n background. All these unusual characteristics are well explained if these states are produced by 1–3 glueballs (multigluon resonances).

We have performed a partial-wave analysis of the reaction K/sup -/p ..-->.. K/sup 0//sub S/..pi../sup +/..pi../sup -/n at 6 GeV/c. We present the results of the analysis of about 4500 events in the low-t region ( vertical-bart'vertical-bar

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)

A description is given of a TPC system that operates in a relativistic heavy-ion beam and yields good track reconstruction efficiency in very-high-multiplicity events. The mechanical construction of the chamber is discussed. A set of custom hybrid circuits are used to build a very compact, cost-effective electronics system mounted directly on the chamber. Results from running in test beams and from preliminary experimental runs are given.

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.

A description of the software for a FASTBUS based data-acquisition system in use at the Brookhaven National Laboratory Multiparticle Spectrometer is presented. Data reading and formatting is done by the SLAC scanner processors (SSP's) resident in the FASTBUS system. A multiprocess software system on VAX computers is used to communicate with the SSP's, record the data, and monitor on-line the progress of high energy and heavy ion experiments. The structure and the performance of this system are discussed.

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.

We have carried out an amplitude analysis of the K/sup 0//sub S/K/sup 0//sub S/ system produced in the reaction ..pi../sup -/p..-->..K/sup 0//sub S/K/sup 0//sub S/n at 23 GeV/c, based on about 15 000 events in the low-t region (Vertical Bart-t/sub min/Vertical Bar

This Letter carries out a sensitive (approx.5 events/nb) search for narrow p-barp states at the Brookhaven National Laboratory multiparticle spectrometer. No evidence is found for such states in the mass range 1900-2400 MeV/c/sup 2/ in the reaction ..pi../sup -/p..-->..p..pi../sup -/p-barp at 16 GeV/c. In particular, the p-barp states at 2020 and 2200 MeV/c/sup 2/ previously reported in a CERN ..cap omega..-spectrometer experiment are not observed.

A description of this highly integrated drift chamber system is presented. This high resolution and deadtimeless apparatus achieves excellent performance without channel-by-channel parameter corrections. This approach is suited for very large drift chamber systems since it contains an average of less than one active component per channel. In addition to a description of the system, results from beam tests, and actual use in an experiment are discussed.

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.

A search for production of D*/sup -/'s using the decay chain D/sup 0/..pi../sup -/, D/sup 0/..-->..K/sup +/..pi../sup -/, was carried out at the Brookhaven National Laboratory multiparticle spectrometer with a 16-GeV/c ..pi../sup -/ beam and a hydrogen target. At 95% confidence level the upper limits for the product of peripheral production cross section by branching ratio are 2.4 nb for inclusive D*/sup -/ production and 1.3 nb for the exclusive channel ..pi../sup -/p..-->..D*/sup -/..lambda../sub c/.

A fast logic system designed to select predetermined combinations of three hits in three detectors is described. Central to this system is a random access memory IC that was especially designed for this application.

A TPC (time projection chamber) detector system has been developed to function in the very-high-multiplicity environment of relativistic-heavy-ion experiments. A TPC was chosen because it directly gives three-dimensional points on the tracks, which is a very significant help for track-finding. Of prime importance is a combination of high efficiency, low noise, and two track resolution capability. A significant development is a system of hybridized, high-sensitivity, on-chamber digitizing electronics. A description of the TPC modules, the digitizing electronics, and test results is given. >

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.

We study the production of low-mass (pπ+π−) systems at small t (squared four-momentum transfer) in the reaction p+p→p+(pπ+π−) and p+d→d+(pπ+π−) at 28 GeV. Comparisons of these inelastic reactions with elastic pp and pd scattering reveal the “elastic-like” nature of (pπ+π−) production. Our results provide evidence that (pπ+π−) production in pp reactions is dominated by isospin zero exchange.

Measurements are made on 753 four-prong events obtained by exposing a 20- in liquid hydrogen bubble chamber to 2,85-Bev protons. The partial cross sections observed for multiple meson production reactions are: pp +-(p + p yields p+p+ pi /sup +/+ pi /sup -/),2.67 plus or minus 0.13;pn++-,1.15 plus or minus 0.09; pp +- 0, 0.74 + 0.07; d ++-, 0.06 + 0.02; and four or more meson production, 0.04 plus or minus 0.02 mb. Production of two mesons appears to occur mainly in peripheral collisions with relatively little momentum transfer. In cases of three-meson production, however, the protons are typically deflected at large angles and are more strongly degraded in energy. The 3/2, 3/2 pion- nucleon resonance dominates the interaction; there is some indication that one or both of the T =1/2, pion-nucleon resonances also play a part. The resonance in a T = 0, three-pion state appears to be present in the pp +- 0 reaction, Results are compared with the predictions of the isobaric nucleon model and the statistical model. The cross section for the reaction pi /sup O/ + p yields pi /sup +/+ pi /sup -/ + p is derived using an expression from the one-pionmore » exchange mode. (auth)« less

We study the reactions pd→(p s ) pp π − , pp π + π − , pd→(p s ) pp π − π − π + and pp→pp π + π − π + π − at approximately 28 GeV/ c , as examples of one, two, three- and four-pion production, respectively. One-pion production occurs mainly as the fragmentation or excitation of the target neutron into a low-mass (p π − ) cluster. Likewise, the two-pion production is seen to be mainly the production of a low-mass (p π + π − ) cluster recoiling opposite the remaining proton. For three- and four-pion production, clustering of particles is much less obvious; nevertheless, the data may be interpreted as showing that single excitation is still the dominant process as in the Nova model of Jacob and Slansky. The technique for examining cluster production involves examining the distribution of rapidities of final-state particles. However, it must be realized that the reactions studied represent only the lowest multiplicities at 28 GeV/ c and that particle production in general at this momentum cannot be assumed to be represented by the low-multiplicity channels studied here. The production of secondaries as a result of cluster formation is an attractive model but our analysis shows that, except for the lowest multiplicities, it is certainly not a unique description of the data.

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.