1900: A physics genius wandering around Europe

Chapter 675 The Particle Tower is Finally Completed! The Standard Model Shocks the World! The Great Dao is Sixty-Two! Gravitons Escape One!

Gell-Mann's quark model explained the complex and diverse types of hadrons.

More and more experiments have shown that hadrons, such as protons, do indeed have finer structures.

As a result, the quark theory was gradually accepted and became a consensus.

But soon, the physicists' faith began to rekindle.

For example, the bigwig Glashow said:
"Look, everyone."

There are four types of leptons: electrons and electron neutrinos, muons and muon neutrinos.

"But there are only three types of quarks, and they're not symmetrical!" (Antiquarks don't count.)
There should be four types of quarks!

Glashow even went so far as to name the fourth quark "charm quark c".

The English meaning of 粲 is symmetry.

That is, it is entirely derived from humanity's pursuit of the symmetrical beauty of the universe.

But simply mentioning it is useless; I could also say that the 18th quark, the Dragon Quark, exists.

We need to find evidence.

Because of this pure belief, many physicists embarked on the search for the fourth quark.

In November 1974, a research team led by Chinese-American physicist Samuel Ting officially announced that they had discovered a new particle, named the J particle, in an experiment where protons collided with protons.

Meanwhile, another research team discovered the same particle using electron-positron collisions and named it the Ψ particle.

Therefore, this particle is called the J/Ψ particle.

Research on the J/Ψ particle has revealed that its properties are very peculiar, and its lifespan is quite different from theoretical predictions.

(The lifetime of a particle can be calculated using the uncertainty principle.)
The existing triquark model cannot explain this lifetime problem.

Thus, Glashow's fourth quark came into play.

With the charm quark, the tetraquark model can explain the lifetime of the J/Ψ particle very accurately.

Furthermore, charm quarks can combine with three other types of quarks to form new hadrons.

Physicists can theoretically predict the mass, quantum number, and other properties of these new hadrons.

Then, through particle collider experiments, these new particles can be found.

Finally, we can verify the correctness of the quark model.

This is the important role of particle colliders.

At that time, it was absolutely the most important instrument in the entire field of physics.

The collision experiment can be considered the last feast of physics!

Why did Yang Zhenning later advise against China building another collider?

It's because he felt that all the particles that needed to be predicted had been found, and that no matter how many times they were hit, nothing would come out.

This is the core of that earth-shattering debate.

Come back again.

Samuel Ting was awarded the Nobel Prize in Physics in 1976 for this achievement.

His discovery directly led to the formation of the fourth quark.

At the same time, theoretical physics, with quantum field theory at its core, was also developing rapidly.

Those theoretical experts have theoretically proven that there should be six types of quarks, that is, six flavors of quarks.

Got it!
Theoretical experts can talk the talk, but experimental experts have to walk the walk.

As a result, particle physics has become lively again.

Countless experimental physicists began searching for evidence of the fifth and sixth quarks.

The method is simple: continue searching for new particles.

If a particle is found that cannot be explained by the existing tetraquarks, it means that a fifth quark exists.

In 1977, a research team led by American physicist Lederman discovered a new particle, which they named the Y particle.

The existing tetraquark theory can no longer explain the strange phenomena of the Y particle.

Thus, the fifth quark naturally emerged.

It is the bottom quark B.

Since the fifth quark is the bottom quark, the sixth quark should be symmetrically named the top quark (t).

After the bottom quark was discovered, the top quark was not discovered until 1995, more than 20 years later.

At this point, all six quarks have been found: up, down, odd, charm, bottom, and top.

Then, something interesting happened.

As mentioned earlier, the leading theorists at the time had theoretically predicted six types of quarks.

When the fifth quark, the bottom quark, was discovered, everyone was convinced that the sixth quark must exist.

At this point, another group of physicists studying leptons had a new idea.

"Since there are six types of quarks, there should also be six types of leptons."

"There are only four types of leptons currently known, which means there are two more types."

This shows how much physicists value beauty and symmetry.

Therefore, some people began to search for the fifth and sixth leptons.

Based on the pattern, this should be a pair of particles similar to an electron and an electron neutrino.

In 1979, American physicist Martin Perl discovered a new particle in an electron-positron collision experiment.

He named it the "Taozi" τ particle, and the corresponding neutrino is the "Taozi Neutrino".

At this point, all six types of leptons have been found.

At this moment, particle physics finally revealed its awe-inspiring side.

All matter particles in the entire universe are composed of quarks and leptons.

Physicists have classified quarks and leptons into three generations based on their weight:
First-generation quarks: up quark, down quark; first-generation leptons: electron, electron neutrino.

Second-generation quarks: strange quarks, charm quarks; second-generation leptons: muons, muon neutrinos.

Third-generation quarks: bottom quark, top quark; Third-generation leptons: tau neutrino, tau neutrino.

It can be seen that our material world (referring to the atomic world composed of protons, neutrons, and electrons) is composed of the first generation of elementary particles.

(Although the bottom and top quarks of the charm also make up hadron matter, they decay into top and bottom quarks in a very short time and are not the mainstream of the matter world.)
The only difference between the second and third generations and the first generation is that the mass has increased; there are no other differences.

For example, the mass of a muon is about 200 times that of an electron, and the mass of a tau is about 3000 times that of an electron (very heavy).

Therefore, physicists are very puzzled:
Why are there three versions of the underlying material code of the universe?

"Could it be a bug that the Creator accidentally created during creation?"

In short, no one knows why so far.

Here's one more thing to add.

The "flavor" of quarks refers to the six types of quarks; it is said that quarks have six flavors.

In addition, quarks have a quantum property called color, which can be simply understood as a property similar to electric charge.

Each flavor of quark comes in three different colors.

Therefore, there are a total of 6 * 3 = 18 types of quarks.

Including the corresponding antiquarks, there are a total of 18*2=36 types of quark particles.

There are six types of leptons, plus anti-leptons, making a total of 6*2=12 types.

As mentioned earlier, fermions are the particles that make up matter, while bosons are the particles that transmit the interactions between particles.

Therefore, there are a total of 48 types of fermions in our universe.

These fermions, like the different elements in the periodic table, form everything through various arrangements and combinations.

While everyone was enthusiastically searching for quarks and leptons, research on bosons was also underway.

The bosons that transmit electromagnetic interactions are photons, that goes without saying.

Subsequently, Glashow and others, in their research on the electroweak unification theory, theoretically proposed the W boson and the Z boson.

The W boson is further divided into two types: W+ and W-.

These three bosons are the mediating particles of the weak force. Here's a little-known fact that 99% of people don't know, but you can use it to impress others.

Take electromagnetic force as an example.

We say that two charged particles interact by exchanging photons.

How was this "exchange" accomplished?

Does the process of particle A emitting a real photon towards particle B, and then particle B receiving it, signify completion?

wrong!
What A and B exchanged were not real photons, but virtual photons.

The properties of virtual particles have already been discussed.

Similarly, when Glashow et al. proposed the W boson and the Z boson, these two particles were also considered "virtual particles".

That is, it exists only in theory and in mathematical form, but does not actually exist.

However, surprisingly, in later experiments, the W and Z bosons were found to actually exist in the real world.

Just like virtual photons and real photons.

Is it amazing?

So how do we understand the issue of moving from the abstract to the concrete?

This is how I understand it.

Every particle is excited by a field.

If a particle exists for too short a time when the field excites it, exceeding the detection range, then it is a virtual particle.

Once a certain energy continuously powers this virtual particle, it enters the real world and becomes a real particle.

How do I charge it?
The answer lies in another field!

That is, the turbulence of another field affects the original field.

This is why the W and Z bosons eventually become real particles.

(Of course, the theoretical process is extremely complex and cannot be explained in a simple and easy-to-understand way; the above is just my personal opinion.)
From the perspective of fantasy novels, this means:

"Emperor Ye Tian stirred up the river of time with his invincible fist light, and then pulled out the back of that person who only existed in the illusion."

When physics reaches its limit, it really does feel quite fantastical.

Okay, now you can use this knowledge to show off.

After the discovery of the W/Z boson, the leading researchers of the powerful boson proposed the concept of the gluon.

Gluon is the particle that transmits the strong force. (The difference between gluons and mesons in transmitting the strong force was explained earlier.)
Next, through theory and experiments, physicists identified a total of eight types of gluons.

As mentioned earlier, this is due to the mass problem in the Yang-Mills equations.

There also exists a special type of particle that provides mass to all the other particles.

It is the famous Higgs boson.

At this point, all bosons had been discovered.

分别是：光子（1）、胶子（8）、W玻色子（2）、Z玻色子（1）、希格斯玻色子（1）。共13种。

It is important to note that the Higgs boson, which provides mass to other particles, is itself a massive particle.

Furthermore, photons have no mass, gluons have no mass, but W and Z bosons do have mass.

All bosons are indivisible fundamental particles.

Physicists breathed a sigh of relief.

"The edifice of particle physics has finally been completed!"

The building is called the Standard Model.

The Standard Model contains 48 fermions and 13 bosons, for a total of 61 elementary particles.

It looks like this:

Among them, the six purple particles are six flavor quarks, and the six green particles below are six leptons.

They are all divided into three generations.

The red column on the right consists of gluons, which transmit the strong force; photons, which transmit the electromagnetic force; and W/Z particles, which transmit the weak force.

The last special yellow particle is the Higgs boson.

Each fermion has its own antiparticle, which is not shown in the table.

It can be said that the seemingly ordinary chart above represents the pinnacle of achievement since the birth of physics!

This table can be used to explain any new particles or phenomena that are discovered in the future.

Moreover, using the standard model, many phenomena can be predicted, and these predictions have all been verified through experiments.

That's what makes it great.

However, some of the predictions have not yet come true.

One of the more famous examples is "proton decay".

Most microscopic particles decay, but why is the proton so stable?
According to the Standard Model, protons should also decay, but this has not been observed to date.

According to physicists' predictions, the proton's half-life exceeds an astonishing 1.6 x 10^34 years.

This timescale transcends the significance of the universe's very existence.

Therefore, protons can be considered to exist eternally!

Another eternal particle of matter is the electron.

In short, the birth of the Standard Model was a groundbreaking event in physics!

It includes all matter and interactions in the universe.

"No! No!"

Suddenly, a senior reader jumped in and said:

Where is gravity?

Why is there no gravity in the Standard Model?

Congratulations! You've discovered one of the greatest unsolved mysteries in physics!

"Gravity is incompatible with the other three forces within the framework of the Standard Model!"

Proponents of the Standard Model argue that the table should be missing a 62nd fundamental particle: the graviton.

With it, the standard model is truly complete!

Any breakthroughs related to gravitons in the future will absolutely cause a major earthquake in the physics community.

Unfortunately, so far, no evidence of the existence of gravitons has been found, not even indirect evidence.

Therefore, whenever you see something about finding gravitons on a marketing account, you can silently repeat "S" in your mind.

However, physicists still hope to incorporate gravity into the framework of quantum field theory.

This led to theories such as quantum gravity.

Opponents of the Standard Model argue that gravity cannot be included in it and that a higher-level theory is required.

Thus, string theory came into being.

This theory posits that there are no fundamental particles; all particles are formed by the vibration of individual strings.

Different vibration patterns of a string give rise to different types of particles.

Within this framework, the graviton can be unified with other fundamental particles.

However, so far, there has been no substantial breakthrough in this theory.

Because it is completely impossible to verify theoretically.

Physicists can't even truly "see" quarks, so how can they observe strings, which are even smaller than quarks?

At this moment, Li Qiwei looked at everyone, and the magnificent history of the development of the Standard Model flashed through his mind.

The path he wants to take is the second one: breaking the framework of the standard model!

In a higher dimension, unify the four fundamental forces and all particles, and even all spacetime!
"The Tao gives birth to One, One gives birth to Two, Two gives birth to Three, and Three gives birth to all things!"

"The Taiji gives rise to Yin and Yang, Yin and Yang give rise to the Four Symbols, the Four Symbols give rise to the Eight Trigrams, and the Eight Trigrams determine the universe!"

(Wow! This is so exciting!)
(End of this chapter)