Higgs field is a fundamental field of crucial importance, that gives mass to the other elementary subatomic particles and whose quantum excitation gives rise to the Higgs Bosons.
In 1964 a physicist by the name of Peter Higgs took some ideas that were floating around at that time, incorporated his own ideas and proposed that there is an Energy Field that permeated in the Universe. This energy field is now called the Higgs field.
The reason why he came up with this hypothetical field is that nobody understood why some subatomic particles had a great deal of mass and some had no mass at all. The energy field that Higgs proposed would interact with the subatomic particles and give them their mass.
Before entering deeply into the Higgs bosons, we need to first know the Higgs field works:
So what exactly is a field (no i donot that place where you grow your crops !!! ) ???
Let us analyze the concept of a field with the help of a room :
Imagine you have a completely empty room with a window. Let’s say you measure the temperature of the room. You will find different values of temperature in the room at each point. Slightly cooler near the window and slightly warmer in the middle of the room.
The list of these different values of temperature will be then called the temperature field of that room.
If there is no object/system in the room the field will sit there undisturbed in its place. As you bring some object or any system that interacts with the environment then the field will definitely also affect the object/system.
For example, if you bring an ice cube, it will eventually melt into water due to the surrounding temperature difference and we can clearly see how the temperature field of the room plays a key role in this.
Similarly, if we keep a candle in the room the surrounding air molecules around it will get heated up, thereby increasing the temperature of that region of the room.
It’s the same thing with an electric field.
Imagine an electric field existing between, two plates. If we keep an electron inside the field it will accelerate towards the positive plate whereas a neutron will sit there not interacting much with the field. So in each of the cases, we can see that the field effects the object that sits inside it.
The question that now arises is what did Peter Higgs think when he created what is now known as the Higgs boson back in 1964.
Well, he was trying to understand the question as to why and how do elementary particles have mass? And from where did they get their mass?
Now if you are thinking why the mass is written in terms of energy, then that’s because of E = mc2 , which shows for a small mass we have a lot of energy. It is expressed in energy forms since it’s much easier to interpret than writing in decimal terms of 10^-27.
Way back in the 60’s and 70’s the mathematical equations devised were very accurate in predicting the forces :
1.the gravitational forces
3. and the strong and weak nuclear force.
We have also written down equations that describe the particles of matter on which those forces act like the electron, neutrinos and the quarks.
The thing about this is, those equations have a fantastic amount of symmetry!
By symmetry I mean, it’s the same about all its axis of rotation. Just like a sphere. No matter in whichever axis you rotate it, it will still be the same from all the directions you look at. Similarly, the equations themselves are very symmetric, meaning no matter whichever direction you approach it, I will give you the same results. Nature also prefers symmetry. So the basic equations had a basic symmetry built in it.
The problem was if you wanted to give mass to the matter and even some of the force-carrying particles the entire symmetry of the equation broke up.
The mathematical term which gives mass looks like:
And this exact term was ruining the symmetry. And without symmetry, the equation was inconsistent and didn’t work any longer. So the mathematical puzzle was to give mass to the particle but not break the symmetry.
The idea of Peter Higgs and various others was to introduce a new term :
One that didn’t look quite like a mass term at first, one that was completely symmetric and when you brought this new term in the equation, the equation beautifully maintained the symmetry.
So assume this Ф term was re-written as,
Where m is just a number and if we multiply it through,
And that m is the constant value of the field that is permeating space. So the permeating field in the mathematical disguise gives rise to the mass of the particle!!
Now, let’s try to visualize and try to understand the mechanism of the Higgs field with the help of the two analogies:
1. crowded room
Let’s assume that there was an important meeting of all the physicist and now that the meeting is over , they are all chilling and chit-chatting in a room. Now if I enter the room, I could just simply walk through the room easily without facing much resistance, because obviously, no one would give me any importance(which is really really sad!! 😔as they don’t know me!)
Now imagine a situation where Peter Higgs himself walks into the room…
Obviously, he would not only get bombarded with questions but also so many people would crowd around him, just to get a glimpse of him, or to even talk to him once. He will immediately steal all the attention in the room. So clearly since we would be interacting so much it would be really difficult for him to walk out of the room.
So the crowd here represents the Higgs field and I and Peter Higgs represent the particles respectively
2. A swimming pool
A man will face more resistance than a fish.
So naturally, the man being more bigger and wider than a fish it will interact much more with the water than the fish will. So it will face more resistance.
And more the resistance one faces moving an object that means the object has more mass.
So mass is basically the amount of resistance one has to face while displacing an object from one place to the other.
So the argument is that all the Higgs field exists in all points in space throughout the universe. It is whats called a scalar field and the idea is that particles which have mass interact with that field more than the particles having less mass. particles with no mass don’t interact at all.
The lightest subatomic particle is an electron and the heaviest if the top quark which weighs as an entire gold atom about 350,000 times more than the electron.
The top quark Is not so heavy because it’s bigger. NO, in fact, the top quark has the same size as that of an electron. The top quark is heavier than an electron is because it interacts more with the Higgs field.
Actually, if the Higgs field didn’t exist neither of the subatomic particles would have mass at all.
Higgs bosons are the smallest bits of the Higgs field.
If we are immersed in the water we know its everywhere. Water is a continuous medium and it has no pores or discontinuity. We also know water is made up of molecules of water. If you hold these two ideas, i.e the realization that water contains countless individual molecules, you can now begin to appreciate the Higgs bosons.
The Higgs field that gives subatomic particles their mass is made up of individual particles called the Higgs bosons just water is made up of individual molecules of H20.
Just as in our room which has the temperature field, we can denote that in one axis called the temp axis.
We can say that at any point in the room you would have a number on the temperature scale which would represent the point of the temperature at that point in the room.
Well, the Higgs field is more complicated than that, it has as it were 2 dimensions
Now, where is the state of lowest energy?
As we know everything in the universe always likes to go to its lowest energy state. So similarly according to this graph, all the particles with the lowest energy states eventually occupy the lowest point of the two curves as in the graph.
So any particle belonging to this circle has the lowest energy and in theory is mass-less.
But some particles oscillate around in this section which is almost has a gutter-like shape.
The interaction of the particles with the field causes this oscillation which gives the particle its mass.
So you get the point right?
Mass is just a consequence of a particle interacting more with the field. So massive particles are massive because they interact more with the Higgs field and mass-less particles are those which doesn’t interact at all, like photons and hence have much less mass to almost no mass.
A field is mediated by the gauge bosons,
Repelling of two electrons.
Takes place by the communication of a gauge boson i.e a photon is responsible for the exchange of information between the electrons that cause them to repel.
And similarly, in the Higgs field, this is mediated by the Higgs bosons.
So now the question is how do we find the Higgs bosons? We cant simply photograph it!!
you cant even directly detect it, as you don’t know what exactly are you looking for?!
But as per as the theoretical and experimental pieces of evidence are concerned Higgs boson is predicted to have a hefty mass and it will, therefore, decay into other particles. It is these particles that we are looking for.
So basically you are looking for interactions which generate more of one type of particle than you are expecting, which will give you a hint that the Higgs boson has decayed into those particles.
We can measure the mass of the particles without knowing anything about the Higgs bosons at all. Like we have been doing that for so long now.
If we assume that the mass of the fermions and bosons are both caused due to the interaction with the Higgs field we can use that theory to predict how often the Higgs bosons will decay into those particles.
And the prediction is shown here in this graph:
So the black circle is the actual measurement and the black verticle line is the uncertainty on the measurement and as long as the black line crosses the prediction or at least comes very close, and you can call that an agreement.
As we can see muon agrees with the theory although the practical uncertainty is very big.
What about the tau lepton which has a mass of 1.8billion electron volts. how do Higgs bosons decay into tau leptons?
We see that the measurement agrees with the prediction pretty well.
Same goes with the bottom quark as we can see.
Now when we add the heavyweight top quark, we can see a pretty good agreement.
W boson has a mass of 80 billion electron volts and we see that it plots right on the line.
And finally, the z bosons plots exactly in the line with 91 billion electron volts. We see that this also agrees with the prediction.
So we are actually predicting for more of W bosons, z bosons, and top quarks than we usually get.
In LHC two protons are accelerated nearly at the speed of light and are made to collide together resulting in a cataclysmic collision with all sorts of particles being produced. And what scientists are looking for is evidence of a Higgs boson or in other words, they are probably looking for bottom quarks and w bosons then they might expect usually.
Let me tell you it is not at all as glamorous as you might think! The Higgs boson doesn’t come up to the sensors and say hello!!!
What is typically likely to happen is you will have a graph showing a distribution of emitted particles and what you are looking for is that bleep at the side of the graph which suggests that we have slightly more than we were expecting and that is the evidence that the Higgs bosons are actually existing.
The Higgs field DOES NOT explain why a proton has mass or why I and you have mass. Those are two quite different things.
If we imagine a proton for example:
It has 2 up quarks and 1 down quark. As we saw earlier in the chart that each up quark has 2 MeV of mass and each down quark has 4 Mev of mass, so the total mass of the proton should be 8 Mev. Yet the total mass of a proton is 938 MeV.
So how can a proton be that heavy when its constituent particles weigh only a fraction of its actual weight?
And the answer is to do with what is called the quark confinement which is based on Heisenberg’s uncertainty principle. If you take 3 quarks and constrain them to be inside a proton which is no bigger than 10-15 m then they will have a huge amount of energy associated with them, and which by E = mc2 is manifested in mass, so the proton gets its mass and consequently, you and I get our masses from quark confinement.
Recently CERN announced that new results have now confirmed that quarks indeed acquires its mass from the Higgs field. The Higgs field effectively couples to the heaviest particle, the top quark in the standard model. These experiments have been carried with a lot of statistical precision of about 5 sigmas.
And this is really impressive. This has been one of the biggest milestones of CERN lately since it’s a very rare process and in order to discover it many decay channels were put together and involved 100s of people.
The Higgs Boson, which is an quantum excitation of the Higgs Field is the last missing piece of the Standard Model which details what the universe is made of and how particles within it interact and how the various sub-atomic particles get their mass from. Without this last piece of the puzzle, it would have been impossible to explain why and how some particles are heavier than others. It is absolutely critically important even in our daily basis, because if an electron would be massless it could not be bound to a proton and you could not have an atom and then all of the stars and the planets and even life could not exist because instead of electrons bound to protons in hydrogen atoms and in larger atoms, it would just wiz off to infinity.
More articles on particle physics will be coming soon.
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