To answer that, first you have to say what light is. Look into the ocean. The water exists. There are waves on water.The waves occur but the water is that which exist. Suppose you call both wave and water, water, and then ask me whether water exist, how can I answer? So tell me what light is.
Here again the terms "energy" and and "exist" has to be defined. If energy is an object you can simply point to it(or its picture) and say, look this is energy. Can you do that? [Object:A material thing that can be seen and touched, is the definition given in dictionary, but the definition is subjective, hence I'll define it as having shape] But energy is defined(all concepts are) and defined as 'ability to do work' and ability is what something has, not what something is. So the something should be there to posses energy.
Now exist, I once more define it as having physical presence, a statement that CLARIFIES and RESTRICT the meaning of the term. You are unhappy with this definition, you are free to bring your own definition, only one condition, the meaning should be clear(That is the purpose of definition) and should be OBJECTIVE.
When two particles collide, two different particles appear. So what? You provided the mass as number of particles, but mass has no clear definition. What they do in colliders are measuring "the energy" they have to spent in accelerating the particles, so is an indirect measurement. We have really no idea what is inside an atom, or how they behave. Unless we can really see the particles, or find out what from what all these a subatomic 'particles' are made of(the real basic unit) and count the particles, it all as good as guess work.
You are pointing two lasers, aren't you? The lasers are 'something', aren't they? What you got is not particles, but foot prints, which you infer as particles. Suppose you get the foot print that looked like that of the elephant, can you make sure that is made by an elephant. Here again we have a fairly good knowledge about biology, and how each animal can look like, still we may error, then how much is the error were we know near to nothing? We only know matter is made of basic units called atoms. We do not know the structure of an atom, nor we know what is inside an atom, so it is imperative to come up with the basic structure of an atom and the structure of light before discussing, how two laser beams can cause changes in a photo plate.
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