Is there proof a positron exists?

Positrons were first suggested by Paul Dirac in 1928, and they were observed directly in a cloud chamber by Carl D. Anderson in 1932. It should be noted that Caltech graduate student Chung-Yao Chao is credited with detecting the positron in 1930, but he was unable to explain it. As regards Anderson's experiment, it was fairly simple. Highly energetic cosmic rays passing through the cloud chamber interacted with other atoms in a number of pair production events. These high energy gamma rays were actually "creating" matter from electromagnetic energy. A magnetic field set up in the chamber caused the particle pairs, which are an electron and a positron, to be deflected in opposite directions because of their opposite charges. There was only one explanation for the observed results, and this explanation included the existence of a positron, the antiparticle of the electron. Just as Dirac predicted. Positrons have been seen as products in numerous high energy physics experiments. In addition, they are actually used in medical imaging, and we see this in Positron Emission Tomography (PET scan). Without positrons, PET scans wouldn't be possible. Links are provided below for more information.