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Longman Dictionary of Contemporary English
▪ Because the particle and antiparticle in effect cancel each other out, their appearance together does not violate the laws of physics.
▪ From the observed absence of such annihilation radiation we can conclude that our galaxy is made entirely of particles rather than antiparticles.
▪ In the same way that matter is constituted of fundamental particles, antiparticles are the building blocks of antimatter.
▪ The laws of physics seem to be the same for particles and antiparticles.
▪ The reason is that the laws of physics are not quite the same for particles and antiparticles.
▪ Two antiparticles could therefore be drawn together by antigravity, but a particle of matter would be repelled by an antiparticle.

n. (context particle English) A subatomic particle corresponding to another particle with the same mass, spin and mean lifetime but with charge, parity, strangeness and other quantum numbers flipped in sign.


n. a particle that has the same mass as another particle but has opposite values for its other properties; interaction of a particle and its antiparticle results in annihilation and the production of radiant energy


Corresponding to most kinds of particles, there is an associated antimatter antiparticle with the same mass and opposite charge (including electric charge). For example, the antiparticle of the electron is the positively charged positron, which is produced naturally in certain types of radioactive decay.

The laws of nature are very nearly symmetrical with respect to particles and antiparticles. For example, an antiproton and a positron can form an antihydrogen atom, which is believed to have the same properties as a hydrogen atom. This leads to the question of why the formation of matter after the Big Bang resulted in a universe consisting almost entirely of matter, rather than being a half-and-half mixture of matter and antimatter. The discovery of Charge Parity violation helped to shed light on this problem by showing that this symmetry, originally thought to be perfect, was only approximate.

Particle-antiparticle pairs can annihilate each other, producing photons; since the charges of the particle and antiparticle are opposite, total charge is conserved. For example, the positrons produced in natural radioactive decay quickly annihilate themselves with electrons, producing pairs of gamma rays, a process exploited in positron emission tomography.

Antiparticles are produced naturally in beta decay, and in the interaction of cosmic rays in the Earth's atmosphere. Because charge is conserved, it is not possible to create an antiparticle without either destroying a particle of the same charge (as in decay, when a proton (positive charge) is destroyed, a neutron created and a positron (positive charge, antiparticle) is also created and emitted) or by creating a particle of the opposite charge. The latter is seen in many processes in which both a particle and its antiparticle are created simultaneously, as in particle accelerators. This is the inverse of the particle-antiparticle annihilation process.

Although particles and their antiparticles have opposite charges, electrically neutral particles need not be identical to their antiparticles. The neutron, for example, is made out of quarks, the antineutron from antiquarks, and they are distinguishable from one another because neutrons and antineutrons annihilate each other upon contact. However, other neutral particles are their own antiparticles, such as photons, hypothetical gravitons, and some WIMPs.

Usage examples of "antiparticle".

My own belief is that eventually, something like this will change particles into antiparticles and vice versa.

The old murderers learned to tap the zero point field, that all-pervasive sea of energy where particles and antiparticles engage in a continuous dance of creation and annihilation.

Scientists would soon find themselves adrift in a bewildering realm of particles and antiparticles, where things pop in and out of existence in spans of time that make nanoseconds look plodding and uneventful, where everything is strange.

The cube worlds were antiparticles, moving back through time to initiate their own creation.

Holes move, just as moholes seem to move, just as a discrete particle can separate itself from a continuously dense array, leaving behind its antiparticle or hole.

The values for particle and antiparticle cancel, and their bound energy is released in mutual annihilation.

When a particle collides with its antiparticle, they annihilate, leaving only energy.

It comprises time reversal T combined with interchange of antiparticles and particles, called charge conjugation C, and a mirror-reflection or inversion of space, called parity reversal P.

We have evidence from cosmic rays that the same is true for all the matter in our galaxy: there are no antiprotons or antineutrons apart from a small number that are produced as particle/ antiparticle pairs in high-energy collisions.

Nevertheless, all the exotic variations created could be accounted for by the same eight ground-state quarks and leptons, plus their respective antiparticles, together with the field quanta through which they interacted.

It followed that “antitweedles” didn’t necessarily give an antiparticle, and tweedles didn’t always make a particle.

The explanation of how black holes can emit particles and radiation (given in Chapter 7) was that one member of a virtual particle/ antiparticle pair (say, the antiparticle) might fall into the black hole, leaving the other member without a partner with which to annihilate.

It is therefore possible, if a black hole is present, for the virtual particle with negative energy to fall into the black hole and become a real particle or antiparticle.