Pions From and about Heavy Ions

Abstract

When nuclei collide at energies in the center-of-mass system that exceed the rest mass energy of the pion of 140 MeV, it is energetically possible to produce a pion. I recall from a dozon years ago a flurry of excitement over the possibility that pions might be observable from heavy ion linear accelerators and cyclotrons at the modest heavy ion energies then available. I was working at the old Yale Heavy Ion Accelerator at the time, and on a visit to the University of Maryland it was suggested to me that we ought to look for pions with the 400 MeV argon ion beams at the Yale HIA. Though it sounded unlikely that all the nucleons could somehow concentrate their energy into producing a pion, it was argued that there was a coherence effect among the various nucleon-nucleon collisions that would greatly enhance pion production. The skeptics argued that if this coherence worked as advertised, the best way of making pions would be to drop an elephant into a pit—total energy well above threshold and a tremendous number of nucleons to act coherently.KeywordsBlast WaveNeutron DensityMass SingularityProjectile FragmentCoulomb EffectThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.