Is the Photon Really Its Own Antiparticle?

[sreerajt]

Photon's antiparticle!

It's said that photon is an antiparticle of itself. Also there are some particle following this property. How is this happening?

 

[Pengwuino]

It's said that photon is an antiparticle of itself. Also there are some particle following this property. How is this happening?

Who says everything has to have a separate, distinguishable anti-particle? There is no reason to assume such a thing must happen. I don't know any other particles that are their own anti-particles (although there are theories that neutrinos may be their own anti-particles but this has not been experimentally shown and is not currently an accepted idea).

 

[tom.stoer]

the neutral pion π° is its own antiparticle

 

[sreerajt]

i heard that force carrier's have this property.

 

[jtbell]

Not all of them. The W+ and W- are antiparticles.

 

[VreemdeGozer]

A particle that is it's own anti-particle is called a Majorana particle (and is elementary). (http://en.wikipedia.org/wiki/Majorana_particle)

Currently, only Majorana bosons are known to exist, although, the neutrino might be a Majorana fermion.

 

[Meir Achuz]

I have never seen (until now) the term 'Majorana bosons' used, because the Majorana equation applies only to fermions.

 

[thedemon13666]

The photon can not be as it does not self-couple

 

[tom.stoer]

The photon can not be as it does not self-couple

For the classicfication of particles and antiparticles in terms of C, P- and T-symmetry this is irrelevant

 

[sreerajt]

after all what is this c,p,t symmetry means?

 

[tom.stoer]

after all what is this c,p,t symmetry means?

C = Charge conjugation
P = Parity (space inversion)
T = Time inversion

You need them to classify particles and antiparticles mathematically

 

[ofirg]

Hi,

The Z boson and gluon are also there own antiparticle, right?

Ofir

 

[Meir Achuz]

No. A gluon has a color combination, such Red-AntiBlue. Its antiparticle would be
AntiRed-Blue. The Z is its own antiparticle.

 

[ofirg]

Hi,

Thanks for your reply

I agree that a gluon with a specific color combination could have an antiparticle with a different color. However, the resulting color would be a linear combination of the colors of the gluons, with no need for antigluons. I believe that the gluon, as a color octet, is its own antiparticle.

For example, in supersymmetry, there is a hypothetical particle called the gluino. It has the same charges as the gluon but is spin half. It is treated as a majorana fermion, therefore its own antiparticle.

Ofir

 

[sreerajt]

More than mathematics what is this symmetry?

 

[tom.stoer]

what do you mean? which symmetry?

the symmetry of the quarks and gluons is called SU(3); it describes a rotation in a 3-dim. vector complex space; therefore when constructing this SU(3) one finds that there are 8 angles for rotations (instead of 3 as for rotations in a 3-dim. real vector space)

 

[Dickfore]

the higgs boson is its own antiparticle.

 

[tom.stoer]

in the simplest model - and iff it exists ;-)

 

[Dickfore]

yes. i just wanted to point out that whenever your field is real, the antiparticle is the same as the particle.

 

[tom.stoer]

i just wanted to point out that whenever your field is real, the antiparticle is the same as the particle.

Good point; this is due to the fact that for a real scalar field the operator C for charge conjugation reduces obviously to the identity, i.e. C=1

 

[Dickfore]

The photon is in the vector representation, being described by the 4-potential A_\mu(x), but it is still real.

 

[tom.stoer]

yes, but being real is not sufficient as you can see when looking at W^±

 

[Dickfore]

yes, but being real is not sufficient as you can see when looking at W⁺ and W^-

So, does it have to transform according to the trivial representation of the operation \mathit{C}?

 

[tom.stoer]

I would say 'yes'