Chapter 422 Achievements of CERN
As a large-scale conference.
The press conference process of Kamiokande Laboratory is actually very complicated.
In addition to introductions, questions and other sessions.
It also has many modules such as video recording, member personal speeches, and guest evaluations.
At least in terms of the process time, it is far more than an hour.
But for Lucas et al.
After Atsushi Suzuki introduced the relevant data, they were almost confident and could return their attention to the CERN site.
This is also the reason why Kamiokande held the press conference only one hour in advance:
The first hour is for professionals, and the latter part is mainly for non-professional media and on-site guests.
And now.
It's CERN's turn to take over.
CERN press conference scene.
It took about ten minutes after the key information of Kamiokande was released.
A little old man with a bloated figure, obvious nasolabial folds, sparse hair on his forehead, and a completely bald head appeared on the side of the podium.
The little old man held a stack of documents in his hands, declined the support of the staff, and walked step by step to the speaking platform at the center of the podium.
Throughout his march, everyone in the audience stopped talking.
The reason for this approach is that the CERN press conference is about to begin, and many media people have begun to prepare to record the content, and have no time to talk nonsense.
The second, more important reason.
It's because the little old man's identity is too special.
He is the famous Carlo Rubbia.
That's right.
He is the discoverer of W and Z bosons.
Carlo Rubbia was born in 1934. As of now, he is 88 years old.
He is a world-famous particle physicist and inventor, and the former director of CERN. He won the Nobel Prize together with Simon van der Meer in 1984 for the discovery of W and Z bosons.
In fact, talking about the Nobel Prize alone, there are not many members of CERN who have won this honor in the history.
But in terms of importance.
Carlo Rubbia's achievements deserve to be ranked first.
In a sense.
Carlo Rubbia's initial award consolidated the structure of the physics community in the past forty years and prevented one company across the sea from becoming dominant.
Otherwise, the current field of microscopic particles is basically all decided by the other side of the sea.
Carlo Rubbia is now 88 years old, and his co-winner Simon van der Meer passed away 11 years ago.
But this little old man is still somewhat lively.
Even last year, there was gossip about him playing a 1v3 team with three maids.
Carlo Rubbia's appearance can also be regarded as CERN's response to the Kamiokande probe carrying out Atsuto Suzuki:
than age.
Carlo Rubbia is older than Atsuto Suzuki.
than status.
He is still taller than Atsuto Suzuki.
Than honor.
Carlo Rubbia can crush Atsushi Suzuki with just one Nobel Prize.
Neon tens of thousands of kilometers away.
Atsushi Suzuki, who had retreated to the audience, apparently realized the implication of CERN's move, and suddenly coughed violently several times.
This time I was angry.
However, he did not rest there, but locked his eyes tightly on Carlo Rubbia on the screen.
He wants to see what results CERN can produce this time.
After arriving at the ceremony stage.
Carlo Rubbia first looked around, moved his round belly twice on the edge of the stage, and then said:
"Dear colleagues and journalists, I am very happy to meet you here today. My name is Carlo Rubbia."
No nationality was mentioned, no position was introduced.
Just a simple sentence: I am Carlo Rubbia. This is the confidence of a Nobel Prize-level boss.
Or on the other hand
He is indeed qualified to introduce himself in this way.
Sure enough.
As soon as Carlo Rubbia finished speaking, there was a burst of warm applause from the audience.
More than ten seconds later.
The applause died down.
Carlo Rubbia picked up the water glass and took a sip of Laoshan White Flower Snake Grass Water. This was a drink he liked during his tenure at China University of Mineral Resources. It tasted quite good.
Then he put down the water glass, picked up the document and shook it a few times, with a trace of emotion on his face:
"Ten years ago in June, in this same conference room, I also chaired the meeting and released the results related to the Higgs particle."
"That is a day that is enough or has already been recorded in history, because we discovered the 'God' particle, and since then we have discovered the mystery of the mass medium."
"But for humans, that's not enough, far from enough."
"The God particle represents light, and wherever there is light in the world, there is also darkness - in our entire universe, darkness even occupies the majority."
"So we have been looking for particles that represent darkness, and just a month ago, we made a huge breakthrough."
Finished.
Carlo Rubbia gestured to the side.
soon.
A slideshow appeared on the big screen behind him.
"Everyone knows."
Carlo Rubbia stretched out his left hand, pointed at the big screen and said:
"For a long time in the past, because neutrinos were assumed to have no mass, the physics community generally believed that there were no right-handed neutrinos."
"But with the discovery of neutrino oscillations, neutrinos were confirmed to have mass."
"So the existence or not of the right-hand neutrino has become confusing again."
Hear this.
Many physics experts in the audience nodded in unison.
As Carlo Rubbia said.
In the Standard Model, neutrinos were long assumed to have no mass.
Because the basic requirements for the electroweak part of the standard model are the gauge symmetry and Lorentz gauge invariance of SU(2)L×U(1)Y.
Therefore, in addition to being massless, neutrinos are also believed to have no right-handed neutrinos and only a Higgs doublet.
The so-called right-handed neutrino belongs to the category of chirality, which is an inherent attribute of a particle and is also a property that can be said to involve the ‘truth of the world’.
It can be called the most refined level that can be studied at present.
What is chirality?
Its English word is called chirality, and the meaning of this term is related to the matrix γ5, which is anti-transmuted with all Dirac matrices, one is the chirality of the spinor.
When the particle mass approaches 0 and the velocity approaches the speed of light, chirality approaches helicity.
Because the quantity momentum contains velocity, it changes with the observer's reference frame. Further, define the positive and antiparticle conjugate operators C^.
If you apply the chiral operator to the positive and antiparticles, you will find an interesting phenomenon:
The antiparticle of a left-handed fermion is right-handed and vice versa.
To explain it in human terms
Everyone has a left hand and a right hand, right?
When you put your two palms together, this state is called Ψ(x), which will satisfy the Dirac equation - you can imagine that there is a gesture lock in front of you that needs to be opened by putting your hands together.
On this basis.
A fundamental particle without mass does not have chirality, which means that it can be understood that the palms cannot be separated, and the only state of it is to put the palms together.
As for elementary particles with mass, they can be separated into left and right hands.
The left-hand ones are left-handed particles.
The ones on the right hand are right-handed particles.
That is, massless particles do not have left and right palms, only closed palms.
Particles with mass can be joined together or divided into left and right hands.
This is the popular explanation of chirality, which is conceptually less precise but easy to understand.
Of course.
In fact, there is another issue of helicity here. This concept is more complicated and unnecessary, so I won’t go into details here.
all in all.
When neutrinos are considered to have no mass, they are naturally inseparable into left and right hands, that is, there are no right-handed neutrinos.
But with the discovery of neutrino oscillations, this situation has exceeded the theoretical scope of Standard Model.
Neutrino oscillation shows that in addition to interaction states, neutrinos also have mass eigenstates.
What really participates in the weak interaction and oscillation process is the interacting state, which is essentially the superposition of mass states.
Two different states need to be connected by a 3×3 unitary matrix.
That is the famous Pontecorvo-Maki-Nakagawa-Sakata matrix, which is also the PMNS matrix.
So this way.
Neutrinos should theoretically have chirality.
That is to say, the palms can be separated, and there should be right-hand neutrinos.
And in the field of dark matter research.
Right-handed neutrinos are possible.
One of the sterile neutrino candidates.
Think of this.
Lucas in the audience couldn't help but reveal a hint of expectation in his eyes.
Are the properties of the right-handed neutrinos discovered by CERN this time related to sterile neutrinos?
Just listen to Carlo Rubbia on the stage say again:
"In the standard model, since the mass of neutrinos is zero, the helicity and chirality of neutrinos are equivalent. So far, only neutrinos with left-handed helicity have been detected."
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"But after adding the non-zero mass term of neutrinos, helicity and chirality are no longer equivalent, and the new neutrino field that appears in the Lagrangian is chirallyright-handed."
"So this time, our bubble chamber constructed a bubble chamber that can superimpose the three known flavor eigenstates."
"That is, the flavor eigenstates of e, μ, and τ are linearly independent."
"Then a 96-meter-long experimental device contained the world's most powerful tritium source and a giant spectrometer, and conducted an extremely delicate experiment."
"The final result. Please look at the big screen."
After Carlo Rubbia finished speaking, he stepped aside and fully displayed the content on the big screen to everyone.
The participants in the audience, whether they really understood or pretended to understand, stretched their necks.
Lucas, who was sitting at the front, had an unobstructed view, so he could easily see the data on the screen.
After a few seconds.
Lucas's pupils shrank after seeing the content clearly, and he turned to look at Lars:
"God. Lars, your neutrino has a mass of 4.7eV? Oh my god."
Lars smiled slightly when he heard this, with a hint of pride on his face.
In 2018.
ESA's Planck satellite project once gave the sum of the three mass states of neutrinos within the framework of the PMNS matrix:
0.12eV.
This value is about 6 orders of magnitude smaller than the electron mass, and is currently recognized as an authoritative value - provided that the cosmological model is introduced.
Then in 2019.
The KATRIN laboratory has locked the upper mass limit of neutrinos to 0.8eV without relying on specific cosmological models or understanding the nature of neutrinos.
At first glance, the 4.7eV measured by CERN seems nothing special, right?
Big mistake.
Be it Planck or KATRIN laboratory.
What they calculate is the precision of neutrinos.
It's like we discovered dust in the air through sunlight, so we want to measure the size of the dust.
At the beginning, the equipment was not very accurate, only a meter stick.
So we can only estimate that a piece of dust is about 1 mm.
Then there was a 15 centimeter scale, and after calculation, it was found that the particles were smaller than 1 millimeter.
Then other more sophisticated equipment comes on the scene.
The mass of neutrinos is like dust. As the measurement accuracy increases, its true mass continues to shrink.
Until now.
The mass of neutrinos has been reduced to less than 1 eV.
No one knows whether it is 0.012eV or 0.0012eV or smaller, but it will never be above 1eV - just like a centimeter of dust does not exist in reality, that thing is called a stone.
Of course.
The premise of the above sentence is that the equipment level is high enough and there is no error.
The result was unexpected.
This time, CERN actually discovered a neutrino with a mass of 4.7eV?
This is no longer a matter of 'precision or imprecision', but a matter of 'existence or non-existence'.
This way.
This points to three possibilities:
Either there is something wrong with CERN's equipment and there are errors in the results.
Either CERN is lying and bragging in order to make big news.
or
That giant neutrino is definitely not the type that has been discovered.
The first possibility can be ruled out first.
CERN is one of the most powerful scientific research institutions in the world and a European scientific research fortress that concentrates the power of European scientific research.
Almost all the instruments used by the entire organization are embargoed treasures, and there is absolutely no possibility of errors in accuracy.
As for lying
That's even more nonsense.
This principle is the same as Gauss's claim to have discovered Pluto in the 1850 copy - there will inevitably be a large number of colleagues to recheck it afterwards, and there is no point in lying.
Therefore, the remaining possibility at this time is the latter possibility
Think of this.
Lucas suddenly realized something and asked Lars again:
"Lars, could it be that the neutrinos you discovered conform to the seesaw mechanism?"
Lars nodded and gave his friend a thumbs up:
"It's true that he was a top student back then. Yes, the neutrino we discovered this time has a Majorana mass term."
Lucas' pupils suddenly shrank.
seesaw mechanism.
Can be translated as a seesaw mechanism.
This is a very subtle or elegant model in the study of right-handed neutrinos.
This mechanism can be generally understood as the left and right hands, which were originally supposed to be of similar size and mass, have become two different situations: one is larger and the other is smaller.
It perfectly balances the Higgs mechanism, the mass term of gauge particles, and the Dirac mass term.
That is to say, the Lagrangian quantity contains both the left-hand doublet of the Higgs mechanism and the coupling term of the Higgs doublet plus the right-hand charged lepton, as well as the Majorana coupling of the right-hand neutrino itself.
This balanced model also has a very cool name:
NMSL.
20 years ago.
CERN's official tweet released a related small result, and then someone left a message below [NMSL? 】, then the official pushed back with a yes
The account that left the message is still Chinese, so there is reason to suspect that the other party did it on purpose.
all in all.
A neutrino that conforms to the seesaw mechanism and has a mass much higher than that of ordinary neutrinos
Then it must be a right-handed neutrino. (End of chapter)