Antiprotons are tiny particles of antimatter. They have a negative charge, and are the nucleus of an Antihydrogen atom. They are not theoretical, as they have been found in scientific studies. When they come in contact with regular protons, each are annihilated and a relatively massive amount of energy is generated.
Actually, antiproton is a subatomic particle of the same mass as a proton but having a negative electric chargeand oppositely directed magnetic moment. It is the proton’s antiparticle. Antiprotons were first produced and identified in 1955 by Emilio Segrè, Owen Chamberlain (for which they received the Nobel Prize for Physics in 1959), and coworkers by bombarding a copper target with high-energy protons from the proton synchrotron at the University of California at Berkeley. Antiprotons were predicted in the early 1930s, but their discovery had to wait for the technology of high-energy particle accelerators to reach the 6 billion electron-volt range. A collision of an antiproton with a proton results in mutual annihilation, but a near miss may produce by charge exchange an antineutron–neutron pair.