We present a new measurement of the cosmic-ray positron fraction e + =(e + + e ) obtained from the rst balloon ight of the High Energy Antimatter Telescope (HEAT). Using a magnet spectrometer combined with a transition radiation detector, an electromagnetic calorimeter, and time-of-ight counters we have achieved a high degree of background rejection. Our results do not indicate a major contribution to the positron ux from primary sources. In particular, we see no evidence for the signi cant rise in the positron

No abstract

No abstract

No abstract

No abstract