Tagged Questions

2
votes
2answers
107 views

How much energy is carried away by neutrinos in matter-antimatter annihilation?

Some people say that neutrinos carry away most of the energy, some others say just a fraction. So what is the truth ? what is the percentage of energy lost due to neutrinos ?
1
vote
3answers
143 views

Do particle pairs avoid each other? Please end my musings

Can you explain what happens when a particle and its antiparticle are created. Do they whiz away from each other at the speed of light or what? I suppose that they don't because otherwise they would ...
1
vote
2answers
134 views

how do we know that the base of entire universe is the proton (hydrogen) and not the antiproton?

It may be that the base of a part of the world is anti-proton, We've always been on the planet Earth and the Milky Way. how do we know that the base of entire universe is proton (hydrogen atom)?
3
votes
2answers
199 views

Can a neutron be created from pure energy

Is it possible to create a neutron out of pure energy, i.e. not by bringing a bunch of already-existing quarks together? (A quick calculation using E = mc2 shows the energy required would be about 1.5 ...
6
votes
3answers
175 views

supressing certain decay paths and enhancing others with interference

In a scattering reaction, there are many possible final states for the products, each with different production rates. Question: Is there a way in which we could in general supress certain rates ...
2
votes
0answers
146 views

What makes *electric* charge special (wrt. CPT theorem)?

I'm wondering why the 'C' in CPT - charge conjugation - refers specifically to electric charge. Of course you could say that C is just defined as $e^+ \leftrightarrow e^-$... but there has to be ...
0
votes
1answer
45 views

Bigger anti-matter particles

I have learned about the existence of positrons as a decay product from uranium fission - if I'm not mistaken. Is there any evidence for higher 'mass' anti-matter, or is that mere speculation or ...
5
votes
2answers
228 views

How does Annihilation work?

I'm wondering why matter and antimatter actually annihilates if they come into contact. What exactly happens? Is that a known process? Is it just because of their different charges? Then what about ...
0
votes
2answers
1k views

What would happen after the collision matter and the anti-matter [duplicate]

Possible Duplicate: What actually happens when an anti-matter projectile collides with matter? Suppose 1 kg of a stray meteorite anti-matter moves to the earth. What would happen after ...
1
vote
0answers
54 views

Energy efficiency of antimatter producion [duplicate]

Possible Duplicate: Matter - Antimatter Reactory Practicality Certain reactions in particle accelerators lead to production of antimatter, which can then be collected in noticeable ...
1
vote
2answers
116 views

Matter - Antimatter Reactory Practicality

With current technology, would the energy released by a matter-antimatter annihilation be more than the energy needed to created the antimatter in the first place? Would it be worth it? Just curious, ...
1
vote
3answers
154 views

mechanism of annihilation

Can the annihilation of matter and antimatter be explained by the electro-weak interaction? Can pair-production be explained in the same way?
14
votes
4answers
610 views

What is anti-matter?

Matter-- I guess I know what it is ;) somehow, at least intuitively. So, I can feel it in terms of the weight when picking something up. It may be explained by gravity which is itself is defined by ...
3
votes
3answers
148 views

What barriers exist to prevent us from turning a baryon into a anti-baryon?

At present the only way we can produce anti-matter is through high powered collisions. New matter is created from the energy produced in these collisions and some of them are anti-matter particles ...
2
votes
2answers
106 views

Can the charge of particles spontaneously flip from positive to negative or vice versa?

I'm thinking of matter antimatter annihilation, are there reactions where normal matter converts to antimatter?
3
votes
2answers
207 views

Can different species of particles annihilate with other species

Obviously electrons annihilate with positrons, but can a muon annihilate with an positron, or can an anti-taon cancel with a muon? similarly for quarks of different species, e.g. u and anti-strange. ...
2
votes
2answers
537 views

What is the correct term for the “polarity” of matter (matter vs. antimatter)? Are fractional polarities allowed?

What is the correct term for the "polarity" of matter (matter vs. antimatter)? Are neutral polarities allowed? (1,0,-1) Are fractional polarities allowed?
9
votes
2answers
1k views

Do anti-photons exist?

I know what anti-matter is and how when it collides with matter both are annihilated. However, what about anti-photons? Are there such things as anti-photons? I initially thought the idea ...
4
votes
2answers
390 views

Is nature symmetric between particles and antiparticles?

Is nature symmetric with respect to presence of particles? Do we have an antiparticle for every particle thought of? Are there any proven examples where we don't have an antiparticle? And what about ...
7
votes
3answers
843 views

Does a particle annihilate only with its antiparticle? If yes, why?

Or to put the question another way - what is the result of a proton-positron collision, or an up quark-charm antiquark collision, etc.? As far as I know, annihilation happens only between particles of ...
7
votes
3answers
608 views

What actually happens when an anti-matter projectile collides with matter?

I'm trying to understand what would really happen when large quantities (e.g., 10g) of anti-matter collide with matter. The normal response is that they'd annihilate each other and generate an ...
6
votes
4answers
352 views

Matter-Antimatter Asymmetry in Experiments?

As I hope is obvious to everyone reading this, the universe contains more matter than antimatter, presumably because of some slight asymmetry in the amounts of the two generated during the Big Bang. ...
1
vote
4answers
383 views

Is “real” antimatter (odd under C, P, T) unphysical?

A positron is odd under charge conjugation and parity reversal but nevertheless even with respect to time reversal. Is a theoretical positron which would be odd under all three symmetries (C, P, T) ...
14
votes
1answer
422 views

In general what will holding an anti-hydrogen atom for more than a 1/10th of second allow scientists to discover?

In general what will holding an anti-hydrogen atom for more than a 1/10th of second allow scientists to discover? Specifically, given that they can hold one for <1/10th of a second, what would ...
15
votes
8answers
9k views

Is anti-matter matter going backwards in time?

Or: can it be proved that anti-matter definitely is nót matter going backwards in time? From wikipedia: [There is considerable speculation as to why the observable universe is apparently almost ...