Sidney H. Kahana

One- and Two-Nucleon Transfer Reactions with Heavy Ions

Most review or summary articles on a rapidly developing subject are out of date even before they are published. There is no reason to suppose the present work will deviate from this rule. A great deal of space will not be used, therefore, justifying our presentation. The importance of heavy-ion induced reactions in the near future of nuclear physics is obvious. Several accelerators have been or are being constructed to investigate the interactions between complex nuclei. We can expect two sorts of physics to be studied, one an extension of what has been done with lighter projectiles and the other essentially new. The direct reactions discussed in the present article would seem to fit into the first category and one may well ask what new information is to be gained by looking at few-nucleon transfer with an oxygen beam rather than a deuteron beam. The reaction mechanism is, we believe, a much simpler one than for lighter projectiles. The basis for such a claim is the essentially semiclassical underpinning of all quasi-elastic heavy-ion-induced processes. This simplicity of mechanism should, in principle, lead to more clearly defined spectroscopy about the target and, uniquely in the case of heavy ions, about the projectile. This article briefly touches on some of the spectroscopic evidence, but more detailed experiments and analysis are needed to establish this point. Our main concern will be with the reaction mechanism and with the tools needed for accurate analysis.

Pentaquark as a kaon-nucleon resonance

Several recent experiments have reported evidence for a narrow feature in the K(+)-neutron system, an apparent resonant state ~ 100 MeV above threshold and with a width < 25 MeV. This state has been labelled as Theta(+) (previously as Z(*)), and because of the implied inclusion of a anti-strange quark, is referred to as a pentaquark, that is, five quarks within a single bag. We present an alternative explanation for such a structure, as a higher angular momentum resonance in the isospin zero K(+) -N system. One might call this an exit channel or a molecular resonance. In a non-relativistic potential model we find a possible candidate for the kaon-nucleon system with relative angular momentum L=3, while L=1 and 2 states possess centrifugal barriers too low to confine the kaon and nucleon in a narrow state at an energy so high above threshold. A rather strong state-dependence in the potential is essential, however, for eliminating an observable L=2 resonance at lower energies.

Standard-model bosons as composite particles.

The Standard model of electro-weak interactions is derived from a Nambu, Jona-Lasinio type four-fermion interaction, which is assumed to result from a more basic theory valid above a very high scale A. The masses of the gauge bosons and the Higgs are then produced by dynamicai symmetry breaking of the Nambu model at an intermediate scale #, and are evolved back to experimental energies via the renormalisation group equations of the Standard model. The weak angle sin2(_w) is predicted to be ] at the scale tr, as in grand unified theories, and is evolved back to the experimental value at scale Mw, thus determining . # ,,_ 10Z3GeV. Predictions for the ratios of the masses of the gauge and the Higgs bosons to the top quark mass, at experimental energies, are also obtained. ,L 1DOE funded Research at CEBAF, 12000 Jefferson Ave., Newport News, Virginia 23606 2Supp°rted in part bY USDOE c°ntract DEAC02-76CH00016 MAS ___ t_(: :? : OISTt:I[BUIiOt; FTHISI]05Ug_NTIN UtJLr[,t_i;_{:_

Top quark and Higgs boson masses in dynamical symmetry breaking

A model for composite electroweak bosons is reexamined to establish approximate ranges for the initial predictions of the top quark and Higgs boson masses. Higher order corrections to this four-fermion theory at a high mass scale, where the theory is matched to the standard model, have little effect, as do wide variations in this scale. However, including all one loop evolution and defining the masses self-consistently, at their respective poles, shifts the top quark and Higgs boson masses somewhat from the earlier calculated positions. These masses exhibit a moderate dependence on the measured strong coupling: for example, with {alpha}{sub {ital S}}({ital m}{sub {ital W}})=0.115(0.125), one finds {ital m}{sub {ital t}}{similar_to}180(185) GeV and {ital m}{sub {ital H}}{similar_to}130(135) GeV.

J/ψ production by charm quark coalescence

The production of pairs in elementary hadron–hadron collisions is introduced in a simulation of relativistic heavy ion collisions. Coalescence of charmed quarks and antiquarks into various charmonium states is performed and the results are compared to PHENIX J/ψ Au+Au data. The χ and ψ bound states must be included as well as the ground state J/ψ, given the appreciable feeding from the excited states down to the J/ψ via gamma decays. Charmonium coalescence is found to take place at relatively late times: generally after c()–medium interactions have ceased. Direct production of charmonia through hadron–hadron interactions, i.e. without explicit presence of charm quarks, occurring only at early times is suppressed by collisions with comoving particles and accounts for some ~5% of the total J/ψ production. Coalescence is especially sensitive to the level of open charm production, scaling naively as . The J/ψ transverse momentum distribution is dependent on the charm quark transverse momentum distribution and early charm quark–medium interaction, thus providing a glimpse of the initial collision history.

Is the QCD Plasma Observable at RHIC with Purely Hadronic Signals

A consistent picture of the Au+Au and D+Au, su2009=u2009200 A GeV measurements at RHIC obtained with the PHENIX, STAR, PHOBOS and BRAHMS detectors was previously developed with the simulation LUCIFER. The approach was modeled on the early production of a fluid of pre‐hadrons after the completion of an initial phase of high energy interactions. A successful description of both measured “jet” suppression and elliptical flow is obtained with a key element being the early production of pre‐mesons which are relatively strongly interacting. The synthesis of these two signals in a common description puts in doubt the likelihood of direct hadronic observation of the colored phase which, for appreciably hard partons, lasts only a short interval ∼tp, while the time for pre‐mesons to hadronise tf is in general considerably longer.

Elliptical flow in relativistic ion collisions at \sqrt{s}= 200 GeV

A consistent picture of the Au + Au and D + Au, A GeV measurements at RHIC obtained with the PHENIX, STAR, PHOBOS and BRAHMS detectors including both the rapidity and transverse momentum spectra was previously developed with the simulation LUCIFER. The approach was modelled on the early production of a fluid of pre-hadrons after the completion of an initial phase of high-energy interactions. The formation of pre-hadrons is discussed here, in a perturbative QCD approach as advocated by Kopeliovich, Nemchik and Schmidt. In the second phase of LUCIFER, a considerably lower energy hadron-like cascade ensues. Since the dominant collisions occurring in this latter phase are meson?meson in character while the initial collisions are between baryons, i.e. both involve hadron-sized interaction cross-sections, there is good reason to suspect that the observed elliptical flow will be produced naturally, and this is indeed found to be the case.

Summary for astrophysics and non-accelerator physics

This year’s Non−Accelerator and Astrophysics session of the 1988 Intersections Conference is reviewed. (AIP)