why does matter/energy decay?

Question

When I read about the magnetic colliders they are building, they talk about "crashing" particles together, releasing matter and/or energy that quickly disappears. Why does it disappear?
Is it something like a fish out of water? Fish needs water to live... These particles need something else to exist. Take away what they need; do they dissolve or do they change into something else?

Answer 1

Your intuition is pretty close. Many particles "quickly disappear" in vacuum by decaying into other particles. Such particles have a characteristic half-life. This means they have a 50-50 chance of lasting one half-life. Half the survivors decay after another half-life, and so on. Some particles, like the neutron, are only stable if subjected to extremely high pressures like that found in an atomic nucleus or within a neutron star (hence the name). The fish in water analogy has merit in this case. When one is dislodged from a nucleus, it decays in a few minutes into a proton and an electron. Other particles, like mesons, have an intrinsically short half-life and are actually created out of the vacuum from the energy of the collision itself, and then quickly decay. They can only exist when other particles are colliding with each other at sufficient energy, like in colliding beams or a super-hot plasma.

Answer 2

In particle accelerators, where they accelerate particles to near the speed of light so that they can try and make them collide.

They do this as they hope that fundamental particles eg. quarks and guage bosons will be "free" for a short time untill they dissapear into the surroundings, like if they do not have enough energy to interact, as some particles can only be observed at very very high energies.

One thing about accelerating particles to the speed of light is that there mass will increase, and so detection will be easier.

If you cannot convert "one to the other" then what happens in A-Bombs? and in the Sun?? And E=mc^2?? And Anti-matter --matter collisions??

Answer 3

Matter and energy are both conserved, but you can convert one to the other. The thing which is always maintained or lost but never gained is 'order'. The thermodynamic property called entropy is monotonically decreasing.

Answer 4

No they stick around. They turn to energy (photons) or other particles.