Fine Structure in the Energy Spectrum of Cosmic Ray Protons at 50 GeV ?

The recently published precise spectrum of cosmic ray protons from the Alpha Magnetic Spectrometer has been examined in some detail from the standpoint of a search for deviations from a smooth, simple, power law. We find a significant excess ($\simeq$ 10% over $\sim$ 0.3 interval in logE) centered on 50 GeV in the published data. It is possible that the 'unfolding technique' adopted by the experimenters causes an overestimate of the excess but it is difficult to reduce it much below about (5 $\pm$ 3)%. We have examined other recent data, too. There is also evidence here, for an excess in the same energy region, although of only (1.6 $\pm$ 0.9)%. A value of (3 $\pm$ 1.5)% would be consistent with all the data. There are hints of similar excesses for heavier nuclei and electrons. Possible explanations are put forward for an excess, should it prove to be genuine.