What is the meaning when we say we have found a new particle in particle physics? And what are new forces?

A new force is different from a new particle. A new force may be explained by older [that is known] particles as much as it can be by new particles if necessary. All we would see is a force which was hitherto unknown but its sources were known. Its possible that new forms of fundamental forces do exist, something I had “said” first time in september 2008. It would just mean a new source of energy. The mathematical form of energy dependence on location and the rate at which this location is changing etc is different which is why we would call it a different force than what we have known and hence a new force.

So forces are to be associated with Potential Energy only, and only then they will give us the knowledge: a new or known force. For that one subtracts the energy thats coming from pure motion of an object/system from the total energy. Once that is so, one could see if what we observe is explainable by all the terms the potential energy constitutes of. In other words eg if the potential energy that we see is fitting to the “mass” terms? There could be several mass terms and they each correspond to a particle among many.

Sometimes it happens that all the mass terms are fitted/satisfied when we try to distribute the energy to their sources and it happens that we know all the particles or mass-sources. But sometimes it happens that to satisfyingly explain something that we observe we do not see any mass/particle in our list of known particles which are literally 1000s in number .. [See Lund particle scheme] This is what data-analysis in particle physics is, you distribute the energy you observe in a process to various sources that you know exist. The sources that exist are literally 1000s.

So Physicists through years of data analysis iterate through all these particle’s mass and other properties and see if an energy content is fitting to the one that we would reconstruct from the different masses [or particles ] we know.

When we have run out of everything yet can’t explain some part of the energy we understand that some new particles are to be found which we do not know so far.

So Higgs particle is one such particle. If Higgs were not to be found all the theories we had constructed based on this which were used to explain other energy observations were going to fall apart. These theory and observation [and all the related tools, experiments, methods etc ] are together called Standard Model. And Standard Model would have fallen apart to some extent [not necessarily all: much in the same way your house does not break off because you had a gas-pipe blowing up somewhere, not necessarily]. When Higgs particle was found/confirmed, just today, and there may be more to know about it, such as are there more kinds and so on, it meant all the mass-terms we had for particles that we know or that can be hypothetically known from such are now valid, to the extent that we have based our theories or tools etc on Higgs. And it is said that Higgs is central to the theory/tool/fact-list called Standard Model. Now that we find this new particle and realize that it is that central particle called Higgs our methods have just become confident, far more than if we wouldn’t have found. But not finding it wouldn’t have shattered Physics ro Standard Model. [Standard Model is the detailed and fundamental essence of all of Physics so to say, if something would not work in condense matter physics it would definitely change our understanding about all of Physics and Standard Model, a standard model is a standard consensus, much like a pact that everyone has been expected and/or seen to be obeying.]

So you can find new forces, you can find new particles, you can find new channels or reaction [a particular way to spend some energy] and so on. They are all envisaged really well in Standard Model.

So a particle directly corresponds to a mass [rest mass] and a force directly corresponds to a potential energy. New would be something that we hadn’t known so far. But in Physics Force/Energy and mass are two different variables. [They are equivalents per advance understanding but not equal, you can sit in your office and time passes by which is equivalent to you are sitting in your car and time passes by and they are equivalent sans the speed at which the car is moving and sans the other forms of energy that were dilating/contracting the time but they are not equal. One makes you sit in your house. The other lets you enjoy a pub]

Now that Force corresponds to energy and you want to make it correspond to potential energy only you have to subtract the energy due to motion only and that will for a good deal involve various transformations etc because you want to be very careful about everything. But once you have known the potential energy you have observed is a new form or not it may or may not come from a new particle. So there are two: “possibility”. In general an old force and a new force.  And old particle or new particle. And then the possibilities for a set of observations are a combination of these two or four as you wish.