Anti-particles are often made out to be a lot more mystical and mysterious than they actually are, thanks to science fiction, and other fiction such as Dan Brown’s Angels and Demons. I emphasize, fiction.
Every type of particle has an anti-particle. Usually this is a distinct type of particle, but it can happen that the anti-particle and the particle are the same. Only particles satisfying certain conditions (for example, if they are electrically neutral) may be their own antiparticles. The only examples so far from the list of elementary particles are photons, Z particles, gluons and gravitons… and possibly the three neutrinos. Every other particle has a distinct anti-particle, with the same mass but opposite electric charge. [The neutron is an example of an electrically neutral particle that is not its own antiparticle; like the proton, the neutron contains more quarks than anti-quarks, whereas the anti-neutron contains more anti-quarks than quarks.]
For those particles that differ from their anti-particles, the names of the anti-particles are usually pretty obvious (up anti-quark, anti-neutrino, anti-tau) with the exception of the anti-electron, which is usually called the positron.
What made anti-matter so famous and thence so mysterious-sounding? The statement that “matter and anti-matter annihilate into pure energy.” This statement, though it sounds cool, is glib. It isn’t false, but it isn’t true either. The reality is both more complex and less astonishing-sounding. I’ll explain that elsewhere.
Often, to keep things simple and short, physicists drop the “anti” prefix when it is obvious from context. Here are two of many examples:
- Many processes produce a muon and an anti-muon; physicists will sometimes call this a “muon pair”.
- A W particle decaying to an up quark and a down anti-quark may be said to decay “to quarks”.
I mostly try to avoid such shorthand on this site, since it is confusing if you’re not used to it, but it does add to the verbiage. Other common shorthand used by particle physicists can be found here (soon).
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is dark matter linked with anti matter..?? what is the significance of selectron and squark in antiparticle physics.??
1) anti-particles are not mysterious to physicists. Since the 1930s, we make them and use them and measure them (in small quantities, mind you) all the time… we even make beams out of them. Some of them rain down onto earth from outer space on a regular basis. Dan Brown and his books make anti-particles sound very weird and scary, but they are standard stuff, completely understood, and not at all dangerous (in small quantities).
2) dark matter’s nature is unknown. However, it cannot not made from known particles, or from the anti-particles of any known particles. Most known particles are unstable, and those that are stable would not be “dark” (i.e., very difficult to observe). The same is true for their anti-particles. The only known stable particles that are dark, in this sense, are neutrinos, but we know enough about them, and about dark matter, to know that dark matter cannot be made from the known neutrinos, or from the known anti-neutrinos.
We do not know if dark matter is made from one type of particle or many, and we do not know if it contains particles and anti-particles, or just particles, or perhaps particles that are their own anti-particles.
3) the selectron, squark and other superpartners of known particles may not even exist; but if they do, then there must also be anti-selectrons and anti-squarks, which are the anti-particles of the selectrons and squarks, and the superpartners of anti-electrons (also called “positrons”) and of anti-quarks.
I am confused as to why a anti-particle would have the opposite overall charge.. love this site but that is one answer I simply cant find easily on the web.
Because of the way the particle-antiparticle relationship arises in the mathematics, a particle and anti-particle always have the same properties as nothing at all, except energy. So their charges of any type — electric charge, or more exotic charges that arise in other forces — must cancel. Their masses, however, must be equal.
I’ll try to think of a more intuitive answer, but for now this will have to do.