Antiproton

The antiproton, p, (pronounced p-bar) is the <a href="/facts/Antiparticle/7Ic43ThI">antiparticle</a> of the <a href="/facts/Proton/clCjepXP">proton</a>. Antiprotons are stable, but they are typically short-lived, since any collision with a proton will cause both particles to be <a href="/facts/Annihilation/tm55RWnf">annihilated</a> in a burst of energy.
The existence of the antiproton with electric charge of −1 e, opposite to the electric charge of +1 e of the proton, was predicted by <a href="/facts/Paul_Dirac/6bt5yRdk">Paul Dirac</a> in his 1933 Nobel Prize lecture. Dirac received the Nobel Prize for his 1928 publication of his <a href="/facts/Dirac_equation/DzFaXS4p">Dirac equation</a> that predicted the existence of positive and negative solutions to <a href="/facts/Albert_Einstein/CNTet8qu">Einstein</a>'s energy equation (
 
 
 
 E
 =
 m
 
 c
 
 2
 
 
 
 
 {\displaystyle E=mc^{2}}
 
) and the existence of the <a href="/facts/Positron/HgV4zBzA">positron</a>, the <a href="/facts/Antimatter/NvpGDLof">antimatter</a> analog of the <a href="/facts/Electron/L0KBo5cW">electron</a>, with opposite <a href="/facts/Electric_charge/xxsBfmlB">charge</a> and <a href="/facts/Quantum_spin/4Jvp7e8P">spin</a>.
The antiproton was first experimentally confirmed in 1955 at the <a href="/facts/Bevatron/5llUlISh">Bevatron</a> particle accelerator by <a href="/facts/University_of_California,_Berkeley/MXVEjklr">University of California, Berkeley</a> <a href="/facts/Physicist/cQcgvSIm">physicists</a> <a href="/facts/Emilio_Segr%C3%A8/yqe8NKp3">Emilio Segrè</a> and <a href="/facts/Owen_Chamberlain/cGhJpu6J">Owen Chamberlain</a>, for which they were awarded the 1959 <a href="/facts/Nobel_Prize_in_Physics/o6w1nCbr">Nobel Prize in Physics</a>.
In terms of <a href="/facts/Valence_quark/mmaanHvp">valence quarks</a>, an antiproton consists of two <a href="/facts/Up_quark/Aw3Vp3vk">up</a> antiquarks and one <a href="/facts/Down_quark/Nq10ayEE">down</a> antiquark (<a href="/facts/Up_antiquark/Aw3Vp3vk">u</a><a href="/facts/Up_antiquark/Aw3Vp3vk">u</a><a href="/facts/Down_antiquark/Nq10ayEE">d</a>). The properties of the antiproton that have been measured all match the corresponding properties of the proton, with the exception that the antiproton has electric charge and magnetic moment that are the opposites of those in the proton, which is to be expected from the antimatter equivalent of a proton. The questions of how matter is different from antimatter, and the relevance of antimatter in explaining how our universe survived the <a href="/facts/Big_Bang/I5T1vTnv">Big Bang</a>, remain open problems—open, in part, due to the relative scarcity of antimatter in today's universe.

Antiproton open-in-new

Antiproton