摘要:

We discuss the stability of multiply strange baryonic systems, in the context of a mean field approach obtained from an underlying set of phenomenological meson–baryon interactions. The coupling parameters which determine the conventional &sgr;+&ohgr; mean fields (Hartree potentials) seen by various baryon species (N, &Lgr;, &Xgr;) in the many‐body system are constrained by reproducing the trend of observed binding energies of single particle (N, &Lgr;, &Xgr;) states, as well as the energy per particle and density of non‐strange nuclear matter. We also consider additional scalar (&sgr;*) and vector (&fgr;) fields which couple strongly to strange baryons. The couplings of these fields are adjusted to produce strong hyperon‐hyperon interactions, as suggested by the data on &Lgr;&Lgr; hypernuclei. Extrapolating this approach to systems of large strangenessS, we find a broad class of objects composed of neutrons, protons, &Lgr;’s and &Xgr;’s, which are stable against strong decay. In these systems, the presence of filled &Lgr; orbitals blocks the strong decay &Xgr;N → &Lgr;&Lgr;, leading to a strangeness fractionfs=‖ S ‖/A≊1, density &rgr;≊(2−3)&rgr;0, and charge fractionfqin the range −0.1<q/A<0.1, comparable to that of hypothetical stable strange quark matter (‘‘strangelets’’), but with a low binding energy per particleEB/A≊−10 to −20 MeV. Such weakly bound multi‐strange objects can be stable for very largeA, unlike ordinary nuclei, since the Coulomb repulsion generated by the protons is largely cancelled by the presence of a comparable number of &Xgr;’s, leading to a small net charge (positive or negative) of orderA1/3. © 1995American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48708

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This contribution summarizes the experimental situation of strange quark matter searches in heavy ion collisions at Brookhaven’s AGS. In particular, E814, E886, and E878, which have completed their experimental programs, have all set limits on the production of these states. E864, which has just completed its first of four runs, is designed to set limits at the level of about 10−11of the total Au+Au interaction cross section. © 1995American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48691

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have searched for strange matter particles, so‐calledstrangelets, in Pb‐Pb interactions atplab=157.7 GeV/cper nucleon. The NA52 apparatus is also ideally suited to measure production yields and rapidity distribution of &pgr;±, K±, p, p¯, d, d¯, ... near 00production angle. Some preliminary results are shown. © 1995American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48718

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Low‐baryon number lumps of strange quark matter, strangelets, are presently searched for in ultra‐relativistic heavy‐ion experiments at CERN and Brookhaven. This paper gives an overview of the physical properties of strangelets with emphasis on experimental signatures such as mass and charge. Direct solutions of the Dirac equation with MIT bag model boundary conditions are applied and compared to calculations based on a smoothed density of states, as well as to simple mass‐formulae based on the MIT bag. Most strangelet properties can be understood within an approximation including bulk, surface and curvature energy contributions. © 1995American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48699

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

If the strange quark matter hypothesis is true, then a new class of white dwarfs can exist whose nuclear material in their deep interiors can have a density as high as the neutron drip density, a few hundred times the density in maximum‐mass white dwarfs and 4×104the density in dwarfs of mass,M∼0.6M⊙. Their masses fall in the approximate range 10−4to 1M⊙. They are stable against acoustical modes of vibration. A strange quark core stabilizes these stars, which otherwise would have central densities that would place them in the unstable region of the sequence between white dwarfs and neutron stars. © 1995American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48713

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Witten pointed out the enormous astrophysical and cosmological significance of strange quark matter (SQM) made up of roughly equal numbers of up, down, and strange quarks. Here we briefly discussrelatedimplications of stable SQM for large binding energy in four areas ofconsiderableinterest: i) The origin of gamma ray bursters (GRBs); ii) Production of SQM drops in present relativistic, heavy‐ion fixed target experiments at BNL and CERN; iii) Enormous technological implications; iv) Scientific implications. © 1995American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48688

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Silicon microdetectors and in particular the novel silicon pixel detectors open up the way for a comprehensive study of strangeness detection in nucleus‐nucleus collisions. We outline the philosophy behind this approach, describe an application in the pixel‐based heavy‐ion experiment WA97, and give some preliminary results on the performance of four silicon pixels planes in the 1994 Pb beam run of WA97. We conclude with an outlook on some possible future applications of silicon pixels. © 1995American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48717

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Time‐of‐flight (TOF) technique is important tool for the particle identification of charged particles in a few GeV/c momentum region. From the series of R&D studies for the construction of AGS‐E802 TOF, AGS‐E866 TOF, and RHIC‐PHENIX TOF, timing properties of a plastic scintillator with photo multiplier readouts have been investigated. In this article, the key to obtain the high resolution TOF is discussed. Recent progress to improve timing resolution of EM‐calorimeter for hadron identification is also discussed. © 1995American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48689

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Detection of multi‐strange and charm particles requires precise measurements of the secondary vertices close to the interaction point and the decay products of strange and charm particles. This presents an unprecedented challenge for relativistic heavy ion experiments, where multiplicity reaches thousands of final state particles per collision. Development of affordable technology for realizing high spatial resolution and low mass vertex detectors has become the ultimate goal of many R&D projects in major laboratories. In this paper we present preliminary results on silicon drift detectors fabricated for the first time on p‐type silicon substrates. These detectors were designed, fabricated and tested recently at LBL and show very interesting properties which make their use in future experiments very likely. © 1995American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48690

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Neutral strange particle productions,K0s, &Lgr; and &Lgr;¯ inp¯pandp¯Ta were studied at 3 and 4 GeV/c. Enhancement of &Lgr; production were observed both at 3 and at 4 Gev/cinp¯Ta with respect to inp¯pand suppression of &Lgr;¯ production. Results were analyzed based on fire ball model. &Lgr; was found to be emitted from the hot clusters of the equilibrated Boltzmann distribution inp¯Ta.K0swas found to be emitted midway equilibrating hot clusters. © 1995American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.48715

出版商:AIP    

年代:1995

数据来源: AIP