Search

The total cross section for hadron production by ${e}^{+}{e}^{\ensuremath{-}}$ annihilation has been measured at center-of-mass energies between 2.4 and 5.0 GeV. Aside from the very narrow resonances $\ensuremath{\psi}(3105)$ and $\ensuremath{\psi}(3695)$, the cross section varies between 32 and 17 nb over this region with structure in the vicinity of 4.1 GeV.

A search for cosmic-ray antiprotons was recently performed with the use of a balloon-borne superconducting-magnet spectrometer. A total of 46 antiproton candidates were observed in the rigidity interval from 5.6 to 12.5 GV/c. Of these events 18.3 are expected to be atmospheric and instrumentation background. The p(-)/p ratio is found to be 0.00052 + or - 0.00015. This ratio is consistent with secondary production of antiprotons in the interstellar medium.

The paper reports measurement of the antiproton-to-proton and antihelium-to-helium ratios in the 4-100 GeV/c range. A superconducting magnet spectrophotometer obtained the data during a balloon flight in May 1976. The upper limit value for the antiproton ratio is 0.0005 in the 4.2-12.5 GeV/c range. This value is only slightly higher than the expected value for a leaky box-model and nearly equal to the value expected in the Peter-Westergard model. It is suggested that this upper limit value rules out the closed galaxy model. Upper limit values for the antihelium ratio are 0.000058 in the 4-10 GeV/c range; less than 0.0001 in the 4-33 GeV/c range; and less than 0.01 in the 33-100 GeV/c range. The interpretation of the raw data is explained.

We have observed a very sharp peak in the cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}, {e}^{+}{e}^{\ensuremath{-}}$, and possibly ${\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ at a center-of-mass energy of 3.105\ifmmode\pm\else\textpm\fi{}0.003 GeV. The upper limit to the full width at half-maximum is 1.3 MeV.

We have observed a second sharp peak in the cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons}$ at a center-of-mass energy of 3.695\ifmmode\pm\else\textpm\fi{}0.004 GeV. The upper limit of the full width at half-maximum is 2.7 MeV.

We observe $\ensuremath{\psi}(3684)$ to decay into $\ensuremath{\psi}(3095)$ with a branching ratio of 0.57 \ifmmode\pm\else\textpm\fi{} 0.08. The branching ratio for the particular decay mode $\ensuremath{\psi}(3095)+{\ensuremath{\pi}}^{+}+{\ensuremath{\pi}}^{\ensuremath{-}}$ is measured to be 0.32 \ifmmode\pm\else\textpm\fi{} 0.04. Remaining decays leading to $\ensuremath{\psi}(3095)$ are largely, but not entirely, accounted for by the mode $\ensuremath{\psi}(3095)+{\ensuremath{\pi}}^{0}+{\ensuremath{\pi}}^{0}$ if the two pions in this decay are in a state of zero isospin.

In this presentation I shall assume that everyone is familiar with the existence of two narrow resonances coupling to electrons1,2,3 at masses of 3.1 and 3.7 GeV. Properties of these resonances will be described at length. I shall also discuss upper limits which we can place for the production of other such resonances in the range 3.2 to 5.9 GeV.4 Lastly, I shall discuss some tantalizing structure at 4.1 GeV.5 This talk will concentrate upon the experimental facts, various speculations will be left for other speakers. It should be emphasized that most results described are preliminary and are subject to refinement.

The absolute flux of cosmic-ray electrons has been measured using a balloon-borne superconducting magnet spectrometer. The instrument consisted of a gas Cerenkov detector, a momentum spectrometer, and a lead-scintillator shower counter. The flux of electrons in the interstellar medium was determined by correcting the observed flux for energy loss in the atmosphere and the payload and for solar modulation. The flight was made at an average atmospheric depth of 5.8 g cm/sup -2/, and the solar modulation was taken to be 300 MeV. The flux in the interstellar medium was found to be 367E/sup() -3.15plus-or-minus0.2/ e/sup -/ m/sup -2/ sr/sup -1/ s/sup -1/ GeV/sup -1/ in the energy interval 4.5-63.5 GeV. The uncertainty in the absolute flux is 10%. The result has been validated by the use of data from a second balloon flight, the use of alternate selection criteria, and simultaneous measurement of other absolute fluxes.

Data gathered from a balloon flight of a superconducting-magnet spectrometer have been examined for the presence of cosmic-ray antiprotons. The ratio of antiprotons to protons, p(-)/p, in cosmic rays was found to be (0.03 + or - 3.3) ten-thousandths in the rigidity interval from 4.2 to 12.5 GV. The 95%-confidence-level upper limit for p(-)/p is thus 0.00066. This upper limit is in strong contradiction to the prediction of the closed-galaxy model of Rasmussen and Peters (1975), but is not inconsistent with the prediction of the modified closed-galaxy model of Peters and Westergaard (1977). It is nearly equal to the predictions of conventional propagation models. This result provides an independent confirmation of the absence of primary antimatter in the cosmic rays at a level of approximately a few ten-thousandths.