Nuclear Physics (1986) / Chapter Skim
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7 Approaching the Quark-Gluon Plasma
7 Approaching the Quark-Gluon Plasma
Pages 137-149
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From page 137... ...
. As the universe continued to cool, the nucleons themselves coalesced to form light nuclei.
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From page 138... ...
In this state, quarks and gluons are no longer bound inside individual hadrons but are contained inside a much larger volume; this will allow the long-range behavior of QCD, which is at present very poorly understood, to be examined. This chapter deals with the various states of nuclear matter, the values of temperatures or densities that are required for achieving quark Reconfinement (based on present theoretical models)
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From page 139... ...
The shaded band schematically represents the transition region for quark Reconfinement, beyond which lies the quark-gluon plasma. The scope of known nuclear physics is confined almost entirely to nuclei under normal conditions.
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From page 140... ...
We will refer to these phases as hadronic matter (which encompasses normal nuclei) and the quark-gluon plasma, or simply quark matter (on the far side of the diffuse boundary region in which quark deconfinement occurs)
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From page 141... ...
Sophisticated theoretical calculations support these simple estimates and predict the following critical values for the transition to a quarkgluon plasma: a temperature between 140 and 200 MeV and an energy density in excess of 0.5 GeV/fm3. The requirement for much higher bombarding energies than are available with today's heavy-ion accelerators lies in the fact that only with such higher energies will we be able to achieve the extreme temperatures and energy densities needed to Reconfine hadronic matter and produce the plasma.
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From page 142... ...
It triggered an explosion for which the number of particles produced (about 1000, mostly pions) indicates that the energy density in the collision was about 3 GeV/fm3, several times the estimated value required for quark Reconfinement.
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From page 143... ...
The answer depends on whether one tries to maximize the baryon density or to achieve a very-high-energy density in the collision process. To maximize baryon density, the energy should be such that the colliding nuclei stop each other with maximum mutual compression (see Figure 7.2~.
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From page 144... ...
(c) At higher energies, the nuclei are transparent as they interpenetrate, producing, in the central region, a quark-gluon plasma under conditions of extremely high energy density and relatively low baryon density.
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From page 145... ...
Finally, it should not be overlooked that the observation of free quarks or unusual combinations of quarks would surely indicate the formation of the quark-gluon plasma and would initiate the study of quark chemistry. Some of the interactions occurring in a relativistic nuclear collider will spew forth hundreds~ven thousands-of particles in a single event.
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From page 146... ...
(Courtesy of the GSI/LBL Collaboration, Lawrence Berkeley Laboratory.) ADDITIONAL RELATIVISTIC HEAVY-ION PHYSICS Although a major focus of research with the relativistic nuclear collider will be the quark-gluon plasma, there are many other important physics questions that can be investigated with such an accelerator.
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From page 147... ...
or delta matter a sudden burst of pions might be observed, possibly in the form of a pion laser. This and many other ideas about excited hadronic matter are admittedly highly speculative, but they do suggest a stimulating and potentially fruitful experimental research program.
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From page 148... ...
A few final examples-outside the arena of nuclear physics but accessible with a fixed-target relativistic nuclear accelerator are found in atomic physics. By accelerating partially stripped ions to sufficiently high energies, one can selectively remove most or all of the remaining orbital electrons.
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From page 149... ...
Theoretical calculations seem to suggest that, under the right conditions, an x-ray laser action might result from such an interaction. The studies outlined above merely suggest the great potential for scientific gain to be realized from a relativistic nuclear collider beyond its use in producing the quark-gluon plasma.
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