The divine particle

After dieting, you step on the scale hoping to see a lower figure than a few months ago; you want to lose weight, which is the result of multiplying your mass by the acceleration of gravity. And what determines the mass? It may seem like a Byzantine question, like that medieval discussion about the sex of angels, but theoretical physicists have been eating this question for half a century. They have finally found an answer: there is a particle, calledHiggs’ Boson, responsible for the value of the mass of the universe. Scientists are so determined to hunt it down that billions of euros are being spent building a device to find it. Never has so much money been invested to find a single particle.Click here and discover the 5 fundamental questions and answers to understand the Higgs boson.

The ins and outs of the atom still keep secrets

But let’s start at the beginning. We all know that matter is made of molecules, and molecules are made of atoms. These, in turn, are organized as a one-hundred-millionth-centimeter cloud of electrons that surrounds a nucleus 100,000 times even smaller. The central heart is a conglomerate of neutrons and protons whose mass is thousands of times greater than that of electrons. Up to this point physicists know why the atom is the way it is, but it resists themunderstand why elementary particles have the masses that they have. There are many and with enormous differences between them; the heaviest, the top quark, is 350,000 times more massive than the electron. The problem is massive. Physicists have developed a theoretical model that describes elementary particles and the interactions between them … but requires that the mass of all be zero. These are the puzzles that theorists love.

The essential ideas are in the fields

In 1964 the British Peter Higgs proposed an elegant solution to this discrepancy. He assumed that the entire universe is occupied by an electromagnetic-like field. The concept of “field”, introduced by the English physicist Michael Faraday in the 19th century, is one of the most important in physics. In the space that surrounds us there is not only matter. If we could get every last speck of dust and the last molecule of air out of a room, we would not be able to say that there is nothing left there. The tangible proof is that if we throw a pear, it will fall to the ground; there is something that makes it fall that we call? gravity ?. More correctly said, there is a gravitational field caused by the planet at our feet. But not only that. If we launch an electron in a straight line and analyze its trajectory, we will notice that something changes its path. That something only influences electrically charged particles; the neutrals don’t even know. Is heelectromagnetic field. Its origin is thesum of earth’s magnetism, the effects of antennas, televisions, house wiring, appliances, etc.Ultimately, a force is nothing other than the effect of a field; and matter has properties – such as mass and charge – that make it sensitive to different fields. Higgs’s proposal was revolutionary: there is a field that fills space, and when particles interact with it, they acquire mass.

The idea collides with intuition. Isn’t mass an intrinsic property of matter? To understand this, we usually use an example: imagine that you are at a party and Jessica Alba enters. Those who are by the door are grouped around it. As she moves through the room, the closest attendees are attracted by the actress, who moves with more difficulty than if she were alone, as everyone tries to capture her attention. This accumulation effect is the Higgs mechanism.

Much more than a number on the scale

This is how mass works, which determines the resistance of a body to change its state of motion, inertia. We notice its effect every day on the bus: when it starts we go backwards and if it brakes we are pushed forward. The more mass we have, the greater that resistance will be and that is why the braking distance of our car with a full boot is longer than if we go empty. As the theorist Brian Greene puts it, “The forces that we all exert thousands of times a day to change the speed of an object fight against the friction of the Higgs ocean.”

There are only four ways to relate

The theory says that this peculiar field fills the universe and adds mass to all the particles that move in it. Determining whether it actually exists leads us to another analogy. If we want to communicate with a friend we can do it in four ways: by voice, by mobile phone, by email or by letter. For each of them there is an object that carries the information: air, microwaves, ADSL cable and paper. With thesubatomic particlessomething similar happens. The relationships that may exist between them are called forces. In nature there are four: gravity, electromagnetic and two nuclear forces; one is the strong one, which holds the nucleus together, and the other is the weak one, responsible for beta radioactive decay.

Well, each of these forms of communication is associated with a particle responsible for transporting the information. In the case ofelectromagnetic, the particle is thephoton; for thegravityis hegraviton; and in thestrong force, thegluón-of Englishglue, glue-. The weak one has three carrier particles, thebosones W +, W- y Zº. Thus, in our empty room, the gravitational field causes the pear and the Earth to exchange gravitons like two children throwing snowballs at each other. The fruit does not notice the electromagnetic field because without net charge it is as if it does not have the tool to collect the photons that reach it.

Responsible for the entire mass of the cosmos

We are now in a position to answer the question of how to prove the existence of the Higgs field: by finding its carrier particle, the Higgs boson. From CERN in Geneva and Fermilab in Chicago, particle physicists have been trying for two decades. The search began in the 1980s, when the so-called standard model of particle physics was established. Theorists had managed to bring order to the complicated subatomic world that was emerging from theparticle accelerators. The crisis of the 1960s had been overcome, when these immense instruments put researchers in a tight spot by producing more and more particles each time they were plugged in. But in 1962 the physicist Murray Gell-Mann came into play and announced a way of grouping them together that he called “the eightfold way”, alluding to Buddhist philosophy. His theory predicted a new particle, W-, which was discovered the following year. Two years later Gell-Mann threw quarks into the elementary particle ring. Physicists were already able to answer the question posed by Greek philosophers more than 2,000 years ago:What is matter made of?

The theoretical framework is thestandard model, which we can summarize like this. There are two main lines ofparticles of matter, quarks and leptons. There are quarks of six flavors and they are grouped into three families of two:up -up anddown -under-;strange -weird- andcharm ?charmed?;bottom -valle- andtop -top-. Leptons can also be of six flavors: the electron and its neutrino; the muon and the muon neutrino, the tau and the tauon neutrino. Leptons can be found alone in nature, while quarks always appear in pairs or trios, and are held together by gluons. They are the bricks with which the rest of the particles are built.

A golden age to solve mysteries

We have the particles explained; it is the turn of the forces. In the late 1970s, Glashow, Salam and Weinberg cherished the dream of theoretical physicists: to bring together the four forces of nature under a single mathematical description. The first and hopeful step of the three scientists was to find a way to describe the electromagnetic and weak forces under the same formulation. Among his predictions were the transmitters of the weak force, the W +, W- and Zº bosons. But if these particles existed, they had to have very high masses, and that placed the standard model at a dangerous point. No one could explain why the photon was massless and the new bosons were tremendously heavy. To solve it, theHiggs field.

The challenge in the 1980s was to find the heaviest quark, thetop, and show that the W +, W- and Zº bosons existed. The machines to detect them had to produce enough energy, which depended on how much their mass was. In the late 1970s the best theoretical estimates pointed to “hundreds of times the mass of the proton.” A not very accurate assessment, but enough for CERN to decide to spend $ 100 million to find it. These were moments of euphoria: it seemed that the Holy Grail of physics was at hand, a final theory that would govern the forces and the forces. particles of the universe. Many had tried since the 1940s, even Einstein. No one had come close to getting it. In January 1983 the Italian Carlo Rubbia, responsible for the search, announced that he had found the two W. Six months later, the Z appeared. Only the quark was missing.top, which fell in 1995 thanks to another big accelerator, the Tevatron at Fermilab, in Chicago. The standard model was complete … except for the Higgs boson. In recent years, in Chicago and Geneva experiments have been carried out to be able to glimpse any trace of its existence. Physicists know that it is difficult because the energy required to see it is beyond their means. They have dedicated themselves to colliding particles in the accelerators to see if the flute would sound, but to find the mother of all masses a bigger machine is needed. In the late 1980s, the Americans designed the SSC, the super collider that was wanted to be built in Texas. In 1987 scientists told the US Congress that it would cost $ 4.4 billion and in 1992 it was going for $ 12 billion. It was too much, considering that the International Space Station (ISS) had a similar cost. For the North American congressmen, the state could not invest in both projects and the SSC was canceled. In Europe, CERN decided to dismantle its accelerator, the LEP, and build another capable of reaching enough energy to see the Higgs, theLarge Hadron Collider (LHC). After several delays, it will be put into operation in the middle of this year and its cost will have been between 3,000 and 6,500 million euros.

The path of theoretical physics depends on the boson

What if he didn’t find her? The elementary particle edifice, which scientists have so carefully constructed over the past half century, would collapse. “The Higgs field, the standard model, and our picture of how God made the universe depends on finding the Higgs boson,” Leon Lederman commented more than a decade ago. The two passions of physicists are at odds. Finding him would imply that they have done a good job and that their ideas on the matter are correct: it would be the demonstration of the power of theory, of pure thought, to understand the world. Not finding it would tell them that they have overlooked something, that their ideas were going well but went wrong, that there are new mysteries to unravel. And for a scientist, good mysteries are the sauce of his life.

Miguel Angel Sabadell

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