What is the higgs boson? Trapping the God particle
What is the God particle? When was the light that exists in our universe born?
How and when was matter born? Follow us, and we’ll tell you the story of the universe,
matter, and energy that we find in the cosmos!
In previous videos on dark matter, dark energy, and cosmic background radiation
we’ ve seen that 95% of the universe is made up of entities that scientists have called "dark":
these are forms of matter and energy that we can’t detect or measure in the current
state of knowledge. We only know that they exist thanks to the indirect effect that they produce
in the universe. These entities are dark matter and dark energy.
Nowadays we can find ordinary energy either in the form of pure energy like light or electromagnetic
radiation in general, either in the form of matter, living matter like mankind,
animals, plants, or "inanimate" objects. In physics ordinary matter is called mass
and is made up of the particles that we all know: protons, neutrons, electrons.
Mass is a form of energy as well, in accordance with Einstein’s famous law E=MC^2.
Today mass and energy are distinct but there was a time, at the dawn of the universe, when
temperature and density were so high that matter and radiation were trapped within a "primordial
broth", fused together, almost indistinguishable, in magma at thermodynamic equilibrium in which the
transformation of matter in energy and the energy in matter continuously took place.
That was the time of the early universe, when the most interesting and mysterious happenings
occured: the birth of matter and of fundamental particles and forces that dominate the universe,
the disappearance of antimatter in favor of matter, the birth of light and many others.
In the video on cosmic background radiation we’ve seen how, by going back in time,
we can go back to the time when the light was born: this is the era of "decoupling",
in which the radiation was freed from the trap of matter and no longer held,
could roam freely through the universe and come down to us today.
That moment occurred about 370ky after the Big Bang,
or, according to current estimates. On the age of the universe, about 13,789,630,000 years ago.
We’re not allowed to “peek" beyond the period of “decoupling”, ‘cause electromagnetic
radiation as said, was trapped in that “primordial broth” and had no way to escape.
We can only reproduce energy, temperature, and density conditions of the early universe,
in particle accelerators, making various types of particles colliding at very high energy,
hoping to detect for a statistically significant number of times,
the presence of physical objects never seen before.
We cannot observe, but we can "listen" to the signals that come from the cosmos,
hoping, for example, to hear one day, gravitational waves caused by events that happened
in the early era, in order to extract precious informations and tear apart the veil of mystery
that hovers over the first universe. Or again, we can study the cosmic background radiation,
hoping one day to recognize hidden traces of events or objects dating back to that period.
Through the contributions of the greatest scientists over the years,
physics of the 20th century has developed a theory: the Standard Model. This theory is the
reference model because it holds and describes all the particles and interactions discovered
so far in our universe and over the years it’s been able to predict many other particles
that had not been discovered yet, proving to be a reliable and consistent theory.
The standard model divides particles into two big groups: fermions and bosons.
Broadly speaking, we can say that fermions are the particles that form the matter we know:
protons, neutrons, and electrons. Bosons, on the other hand, are carrying interaction particles,
and are responsible for the existence of forces, such as nuclear or electromagnetic force.
Up to the 1960s, the Standard Model could not explain what could give mass to the fundamental
known particles. Therefore in 1964, a group of theoretical physicists
tried to answer the question. Francois Englert, Robert Brout,
and Peter Higgs introduced into the Standard Model a theory that explained the origin of mass. They
temporally localized the birth of mass at a precise moment in the history of the universe:
about a hundredth of a billionth of a second after the BIG BANG.
During the very early moments following the Big Bang, in the universe,
elementary particles were massless: they were pure streams of energy that ran at the speed of light.
As the expansion of the universe was proceeding, density and temperature decreased below a certain
key-value and, according to the theory, what is called the "Higgs field" came into action.
The Higgs field can be imagined as a "jelly" which permeates empty space,
while we can visualize particles as marbles moving at the speed of light across the space.
Some marbles have smoother surfaces, some others have rougher surfaces. This “jelly” gives the
vacuum the property of generating friction in the motion of the marbles, to different degrees,
depending on their surface. If it is smooth, the particle passes through the jelly without
feeling friction and remains pure energy. If it’s rougher, it gets slower and heavier.
Through this mechanism, particles gain mass, according to their features.
Brout-Englert-Higgs theory changed the idea of mass: mass becomes a secondary property of the
particle, no longer closely linked to the matter, but rather to its interaction with
the vacuum. Since the vacuum is not actually empty but is permeated by quantum fields,
the Higgs field interacts with particles and can give them mass. It’s counter-intuitive but
void does not indeed exist, it is not empty at all, it is a kind of prologue of matter.
The vacuum virtually holds all the particles that don’t have enough energy to appear,
but providing the right energy, under certain conditions, it may exhibit stunning properties.
A fundamental part of the theory was the presence of a specific particle:
the Higgs boson. A boson that would allow the Higgs mechanism to unfold correctly
and thus give mass to all other particles.
For this reason in mainstream media, Higgs boson has often been called the "God particle" from the
1993 book “The God Particle” by Leon Lederman, although the nickname is strongly disliked
by many physicists, including Higgs himself, who regard it disrespectful towards believers.
In 1964 Higgs boson was theorized only. For several years it was being chased in vain,
by particle accelerators all over the world. As a matter of fact, to reveal it,
a large amount of energy is needed and until a few years ago, no accelerator
still possessed enough energy to discover its existence and detect it incontrovertibly.
In the end, LHC (Large Hadron Collider), the CERN’s particle accelerator has been
turned on in 2008 and managed to recreate in the laboratory the requested energy
and temperature conditions, and in 2012, the Higgs boson was finally experimentally detected.
On July 4, a conference held in the CERN auditorium announced the discovery of a
particle compatible with the Higgs boson. Higgs himself was sitting in the audience,
visibly moved. The intuition he had had in 1964, finally appeared in 2012:
the strength of thought that relying on clues and reason, was able to travel far
into the future, so much so that eyes and hands needed a new century to follow him.
This is the story of an idea that broke-in and changed physics.
Even if LHC is the world’s most powerful particle accelerator as well as the most
complex machine ever built by humanity, it had to work hard to detect Higgs boson.
LHC is located at the CERN in Geneva, between France and Switzerland,
in a region between Geneva Airport and the Jura Mountains, and built inside
a 27 km-long ring-shaped underground tunnel at an average depth of 100m.
The machine accelerates hadron bundles (particles affected by nuclear force) at speeds close
to those of light, in opposite directions, and collides them at four strategic points
of the ring, in which the four main accelerator experiments were installed: ATLAS (A Toroidal LHC
Apparatus), CMS (Compact Muon Solenoid), Lhcb (LHC-beauty) and ALICE (A Large Ion Collider
Experiment). These enormous detectors meticulously analyze the particles and energies that are
created in collisions. To give an idea of the proportions of these mammoth works of human
ingenuity just think that the detector ATLAS is high about a half of the cathedral of Notre
dame de Paris, while CMS contains more iron than the Eiffel Tower and even weighs twice as much.
Higgs boson production in a particle collision is likely to be a very rare event (It occurs
about1 in 10 billion collisions only). Moreover Another issue that has enormously complicated
the "hunting" is the fact that the Higgs boson is not a "stable" particle, once produced, in fact,
it immediately decays, that is, it transforms into other known particles, freeing energy.
Several different modes of decay for Higgs boson, have been assessed and classified,
there is not only one: for example, it can decay into 2 photons or
other particles known as electrons. What at CERN has been done is to analyze
every single collision and to go and see what sort of particle it had produced,
isolating only those events causing decays consistent with Higgs and discarding the others.
Billions of hadrons have been injected into the LHC, producing billions of billions of
collisions. The collisions analysis has requested therefore a stunning computational power.
It was estimated that LHC has produced a mass of data of about 15 million gigabytes each year,
equal to a CD stack of 20 thousand meters, which corresponds to 61 times the height
of the tower Eiﬀel (342 meters). This huge amount of information to analyze required a
global computer infrastructure for fast data exchange, able to help scientists
process them. This infrastructure is called GRID: a planetary network born at CERN which combines
and uses simultaneously the computing power and memory of tens of thousands of calculators
across the world and has been developed to store, process, share and make accessible the data
produced by the LHC accelerator. It is a network of computers spread on a global scale formed
by 11 processing centers that are called main nodes which receive data directly from the LHC
and allocate them extensively to the entire network of minor nodes around the globe.
Will the discovery of the particle of God, change our life? It has already done it! In
order to detect it, in fact, humanity had to build LHC, the greatest engineering and technological
work ever carried out, which required application and development of the most advanced technologies
that enclose broad-spectrum any field of scientific, technical and engineering knowledge.
From superconducting magnets to computing, cryogenics, to vacuum techniques.
All this progress has already been transferred into society in terms of consumer technology:
solar panels, medical diagnostics, nuclear storage processing technologies, and so on...
In particular particle accelerators have plenty of applications in medical therapies and diagnostics.
All the accelerators in the world are based on technologies developed at CERN
or in partner laboratories. Ideas and creativity are the
basis of the progress. Without new ideas, development stagnates. The basic fundamental
research triggers creativity, genius, fantasy because it has no constraints
of profit or delivery of specific products. History shows that the most important progress
of mankind have come directly from fundamental research where mind could travel with fantasy and
unleash the wildest and seemingly counterintuitive insights, considered unthinkable and absurd.
Any other examples? It is enough to consider the fundamental theories of physics:
general relativity and quantum mechanics. Without these abstract, highly counterintuitive,
and sometimes absurd theories, we wouldn’t be able to use for example our precise
geo-localization services, thanks to our modern GPS satellites, or we would never
have developed semiconductors and transistors, and electronics like we know it wouldn’t exist.