GeV 81.gev.002 Louis J. Sheehan, Esquire

In the third method of search, Fig. 10(c), only a single γ-ray is detected. The presence of a monoenergetic y-ray line would signal a radiative transition directly to a specific intermediate state. In our apparatus, this method is difficult to apply because of the severe background problems, but we were able to identify the direct γ-ray transition to the 3.4 GeV state [17]. A different experimental group working at SPEAR (a collaboration among the Uni- versities of Maryland, Princeton, Pavia, Stanford and UC-San Diego) was able to make use of a more refined detection system to observe several of these radiative transitions and to measure the v’ branching franctions of those states [19]
.
To summarize, these studies have led to the addition of four (the 2800-MeV state is still marginal) new intermediate state, all with charge-conjugation C = + 1, to the original ψ and y’ particles.
6. TOTAL CROSS SECTION AND BROADER STATES
6.1. Total Cross Section
So far our discussion of the process e+e-→hadrons has been concerned largely with the two psi particles, which are created directly in e+e- annihilation, and with the intermediate states, which are not directly created but rather appear only in the decay products of the ψ and y’. It is now time to turn our attention to the larger picture of hadron production to see what else can be learned.
Figure 4 presented the total cross section for e+e-→hadrons over the full range of c.m. energies accessible to SPEAR. This figure was dominated by the ψ and y’ resonance peaks, and very little else about the possible structure of the
cross section outside of these peaks was observable. We now remedy this situation in Fig. 13, which shows the hadron/muon-pair ratio R, with the dominating ψ and w’ resonance peaks removed, including their radiative tails.
8-
6-
B. Richter 297
We can characterize the data in the following way. Below about 3.8 GeV, R lies on a roughly constant plateau at a value of ~2.5; there is a complex transition region between about 3.8 and perhaps 5 GeV in which there is considerable structure; and above about 5.5 GeV, R once again lies on a roughly constant plateau at a value of ~5.2 GeV.
6.2. Broader (Psi?) States
The transition region is shown on a much expanded energy scale in Fig. 14. This figure clearly shows that there seem to be several individual resonant states superposed on the rising background curve that connects the lower and upper plateau regions [20]. One state stands out quite clearly at a mass of 3.95 GeV, and another at about 4.4 GeV. The region near 4.1 GeV is re- markably complex and is probably composed of two or more overlapping states; more data will certainly be required to try to sort this out.