Higgs' Boson

The Higgs boson or Higgs particle is a fundamental particle proposed in the Standard Model of particle physics. It receives its name in honor of Peter Higgs, who, along with others, proposed in 1964 what is now called the Higgs mechanism to explain the origin of the mass of elementary particles. The Higgs boson constitutes the quantum of the Higgs field (the smallest possible excitation of this field). According to the proposed model, it does not have spin, electrical charge or color, it is very unstable and it decays rapidly: its half-life is of the order of zeptoseconds. In some variants of the standard model there may be several Higgs bosons.

The existence of the Higgs boson and the associated Higgs field would be the simplest of several Standard Model methods of particle physics that attempt to explain the reason for the existence of mass in elementary particles. This theory suggests that a field permeates all space and that the elementary particles that interact with it acquire mass, while those that do not interact with it do not. In particular, this mechanism accounts for the enormous mass of the W and Z vector bosons, as well as the masslessness of the photons. Both the W and Z particles and the photon are bosons without their own mass. The former show enormous mass because they strongly interact with the Higgs field, and the photon shows no mass because it does not interact with the Higgs field at all.

The Higgs boson has been the subject of a long search in particle physics.

On July 4, 2012, CERN announced the observation of a new particle "consistent with the Higgs boson"; but more time and data would be needed to confirm this. On March 14, 2013, CERN, with twice the data available to it in its discovery announcement in July 2012, found that the new particle resembled even more closely. to the Higgs boson. The way it interacts with other particles and its quantum properties, together with the measured interactions with other particles, strongly indicate that it is a Higgs boson. The question remains whether it is the Higgs boson of the Standard Model or perhaps the lightest of several bosons predicted in some theories that go beyond the Standard Model.

On October 8, 2013, Peter Higgs was awarded, together with François Englert, the Nobel Prize in Physics «for the theoretical discovery of a mechanism that contributes to our understanding of the origin of the mass of subatomic particles, and that It was recently confirmed thanks to the discovery of the predicted fundamental particle by the ATLAS and CMS experiments at CERN's Hadron Collider."

General introduction

Today, virtually all known subatomic phenomena are explained by the Standard Model, a widely accepted theory of elementary particles and the forces between them. However, in the 1960s, when such a model was still being developed, there was an apparent contradiction between two phenomena. On the one hand, the weak nuclear force between subatomic particles could be explained by laws similar to those of electromagnetism (in its quantum version). These laws imply that the particles that act as intermediaries of the interaction, such as the photon in the case of electromagnetism and the W and Z particles in the case of the weak force, must be non-massive. However, based on the experimental data, the W and Z bosons, then only hypothesized, must be massive.

In 1964, three groups of physicists independently published a solution to this problem, which reconciled these laws with the presence of mass. This solution, later called the Higgs mechanism, explains the mass as the result of the interaction of the particles with a field that permeates the vacuum, called the Higgs field. Peter Higgs was alone one of the proponents of such a mechanism. In its simplest version, this mechanism implies that there must be a new particle associated with the vibrations of that field, the Higgs boson.

The standard model was finally constituted using this mechanism. In particular, all the massive particles that make it up interact with this field, and receive their mass from it. Until the 1980s, no experiments using the energy needed to start searching for such a boson could be performed, since the mass it was estimated to have was too high (a few hundred times the mass of a proton)..

The Large Hadron Collider (LHC) at CERN in Geneva, Switzerland, inaugurated in 2008 and whose experiments began in 2010, was built with the main objective of finding it, proving the existence of the Higgs boson and measuring its properties, which that would allow physicists to confirm this cornerstone of modern theory. Previously it was also tried at the LEP (a previous accelerator at CERN) and at the Tevatron (of Fermilab, located near Chicago in the United States).

History

The six authors of the PRL presentations of 1964, who received the Sakurai Prize for their work. From left to right: Kibble, Guralnik, Hagen, Englert, Brout. Right: Higgs

Particle physicists hold that matter is made of fundamental particles whose interactions are mediated by exchange particles known as carrier particles. By the early 1960s, a number of these particles had been discovered or proposed, along with theories suggesting how they were related to each other. However it was known that these theories were incomplete. One omission was that they could not explain the origins of mass as a property of matter. Goldstone's theorem, related to continuous symmetry within some theories, also seemed to rule out many obvious solutions.

The Higgs mechanism is a process by which vector bosons can become mass invariant without explicitly breaking gauge invariance. The proposal for such a spontaneous symmetry breaking mechanism was originally suggested in 1962 by Philip Warren Anderson and, in 1964, developed into a full relativistic model independently and almost simultaneously by three groups of physicists: by François Englert and Robert Brout; The properties of the model were further considered by Guralnik in 1965 and Higgs in 1966. The papers showed that when a gauge theory is combined with an additional field that spontaneously breaks the symmetry of the group, gauge bosons can consistently acquire finite mass. In 1967, Steven Weinberg and Abdus Salam were the first to apply the Higgs mechanism to electroweak symmetry breaking and showed how a Higgs mechanism could be incorporated into Sheldon Glashow's electroweak theory, in what became the Standard Model. of particle physics.

The three papers written in 1964 were recognized as a milestone during the Physical Review Letters 50th anniversary celebration. Its six authors were also honored for their work with the J. J. Sakurai Prize for Theoretical Particle Physics (the In the same year a dispute also arose; in the event of a Nobel Prize, up to 3 scientists would be eligible, with 6 authors credited for the papers.) Two of the three PRL papers (by Higgs and GHK) contained equations for the hypothetical field which would eventually become known as the Higgs field and its hypothetical quantum, the Higgs boson. Higgs's subsequent paper, from 1966, showed the mechanism of boson decay; only a massive boson can decay, and the decays can demonstrate the mechanism.

In the Higgs article the boson is massive, and in a closing sentence Higgs writes that "an essential feature" of the theory "is the prediction of incomplete multiples of scalar and vector bosons". In the GHK paper the boson is massless and decoupled from massive states. In the 2009 and 2011 reviews, Guralnik states that in the GHK model the boson is only in a lower order approximation, but is not subject to any restrictions and acquires mass at higher orders and adds that the GHK paper was the only in showing that there are no massless Goldstone bosons in the model and in giving a full analysis of the general Higgs mechanism.

In addition to explaining how mass is acquired by vector bosons, the Higgs mechanism also predicts the relationship between the masses of W and Z bosons, as well as their couplings with each other and with the standard quark-lepton model. Subsequently, many of these predictions have been verified by precise measurements at the LEP and SLC colliders, overwhelmingly confirming that some kind of Higgs mechanism occurs in nature, but the exact way in which it happens has yet to be discovered. The results of the search for the Higgs boson are expected to provide evidence about how this is done in nature.

Cornering the Higgs boson

Prior to the year 2000, the data collected in the Large Electron-Positron collider (LEP) at CERN for the mass of the Higgs boson of the standard model, had allowed an experimental lower limit of 114.4 GeV/c² with a 95% confidence level (CL). The same experiment has produced a small number of events that could be interpreted as resulting from Higgs bosons with a mass around 115 GeV, just above this cutoff, but the number of events was insufficient to draw any definitive conclusions.

At Fermilab's Tevatron, there were also ongoing experiments looking for the Higgs boson. As of July 2010, the combined data from the CDF and DØ experiments at the Tevatron were sufficient to exclude the Higgs boson in the 158 -175 GeV/c² range to 95%. from CL. Preliminary results from July 2011 extended the excluded region for the 156-177 GeV/c² range to 95% CL.

Data collection and analysis in the search for the Higgs intensified since March 30, 2010, when the LHC began operating at 3.5 TeV. Preliminary results from the LHC ATLAS and CMS experiments, from July 2011, exclude a standard model Higgs boson in the mass range 155-190 GeV/c² and 149-206 GeV/c², respectively, in 95% CL.

As of December 2011 the search had narrowed to approximately the 115–130 GeV region with a specific focus around 125 GeV, where both the ATLAS experiment and CMS independently report excess events, . This meant that, in this energy range, particle patterns compatible with the decay of a Higgs boson were detected in a greater number than expected. The data were insufficient to show whether these excesses were due to background fluctuations (i.e., random chance or other causes), and their statistical significance was not great enough to draw conclusions or even formally count as a "observation". But the fact that two independent experiments had shown excesses around the same mass gave the particle physics community considerable excitement.

On December 22, 2011, the DØ collaboration also reported constraints on the Higgs boson within the Minimally Supersymmetric Standard Model (MSSM), an extension of the Standard Model. Proton-antiproton (pp) collisions with a mass energy of 1.96 TeV had allowed them to set an upper limit for Higgs boson production within MSSM from 90 to 300 GeV and excluding tan β > 20-30 for Higgs boson masses below 180 GeV (tan β is the ratio of the two values of the Higgs doublet vacuum expectation).

For all these reasons, by the end of December 2011, it was expected that the LHC would be able to provide enough data to exclude or confirm the existence of the Higgs boson from the Standard Model by the end of 2012, when the data collection of the LHC would have been examined. 2012 (at energies of 8 TeV).

During the first part of 2012, the two LHC working groups continued updates to the December 2011 tentative data, which were largely being confirmed and further developed. Updates were also available on the group that was analyzing the final data from the Tevatron. All of this went on to highlight and narrow the same 125 GeV region, which was showing interesting features.

On July 2, 2012, the ATLAS collaboration published additional analyzes of their 2011 data, excluding the boson mass ranges from 111.4 GeV to 116.6 GeV, 119.4 GeV to 122.1 GeV, and 129.2 GeV at 541 GeV. They observed an excess of events corresponding to the hypothesized Higgs boson masses of around 126 GeV with a local significance of sigma 2.9. On the same date, the DØ and CDF collaborations announced further analyses, which increased their confidence. The significance of excess energies between 115–140 GeV was quantified as 2.9 standard deviations, corresponding to a 1 in 550 chance of being due to statistical fluctuation. However, this is still far from 5 sigma confidence. Therefore, the results of the LHC experiments are needed to establish a discovery. They exclude the Higgs mass ranges of 100–103 and 147–180 GeV.

A new boson is discovered

In an internal CERN memo dated April 21, 2011, the rumor that LHC physicists had detected the Higgs boson for the first time was contextualized.

The internal note talks about the observation of a resonance at 125 GeV, just the kind of phenomenon one would expect to detect if a Higgs boson had been found in that energy range. However, the large number of observed events, up to thirty times more than those predicted in the standard model of particle physics, surprised the researchers themselves.

At the end of 2011, two of the experiments carried out at the LHC provided clues to the existence of the boson.

On June 22, 2012, CERN announced a seminar covering the provisional conclusions for that same year, Rumors began to spread in the media soon after that this would include a major announcement, but whether this was a stronger signal or a formal discovery was unclear.

On July 4, 2012, CERN presented the preliminary results of the joint analysis of data taken by the LHC in 2011 and 2012 in the presence of several scientists, including Peter Higgs, the theoretician himself. the two main accelerator experiments (ATLAS and CMS). The CMS announced the discovery of a boson with mass 125.3 ± 0.6 GeV/c² at a statistical significance of 4.9 sigma, and the ATLAS of a boson with mass 126.5 GeV/c ² of sigma 5. This meets the formal level needed to announce a new particle that is "consistent with" the Higgs boson.

The study of the properties and characteristics of the new particle needs even more time to be able to confirm if it really is the Higgs boson of the standard model or one of the Higgs bosons that supersymmetric theories predict or if it is a new unknown particle. It is hoped that data collected at CERN's Large Hadron Collider can shed light on the nature of this new boson.

In recent conferences, the data studied shed more light on the nature of the boson and, at least for now, confirm that it is a Higgs boson, although we will have to wait to find out which one it is.

Properties

Summary of interactions between standard model particles.

Many of the properties of the Higgs boson, as described in the Standard Model, are fully determined. As its name indicates, it is a boson, it has spin 0 (what is called a scalar boson). It has no electrical charge or color charge, so it does not interact with the photon or with the gluons. However, it interacts with all the particles in the model that have mass: the quarks, the charged leptons, and the W and Z bosons of the weak interaction. Their coupling constants, which measure how intense each of these interactions is, are known: their value is greater the greater the mass of the corresponding particle. In the original version of the Standard Model, the mass of the neutrinos was not included and, therefore, an interaction between them and the Higgs. Although this could explain the mass of neutrinos, in principle its origin may have a different nature. The Higgs boson is also its own antiparticle.

The standard model does not, however, predict the Higgs mass, which has to be measured experimentally; nor the value of some parameters that depend on it: the coupling constants of the Higgs with itself –which measure how intensely two Higgs bosons interact with each other– or their half-life. To a first approximation, the Higgs mass can take any value. However, the mathematical consistency of the standard model imposes lower bounds between 85 and 130 GeV/c², and upper bounds between 140 and 650 GeV/c². The experiments carried out in the LEP and Tevatron accelerators, and later in the LHC, have set experimental limits for the value of the Higgs mass –always assuming the behavior of the standard model–. In July 2012, the two LHC experiments performing Higgs searches, ATLAS and CMS, presented results excluding mass values outside the interval between 123–130 GeV/c² according to ATLAS, and 122.5–127 GeV/c² according to CMS (both ranges at 95% confidence level). In addition, they announced the discovery of a boson with properties compatible with those of the Higgs, with a mass of approximately 125–126 GeV/c². Its half-life with that mass would be approximately 10⁻²² s, one part in ten thousand trillion of a second.

Alternatives

Since the years the Higgs boson was proposed, there have been many alternative mechanisms. All other alternatives use strongly interacting dynamics to produce an expected value of the vacuum that breaks the electroweak symmetry. A partial list of those alternative mechanisms is:

• Technicolor; it is the kind of model that tries to imitate the dynamics of the strong force as a way to break the electrodebil symmetry.
• The Abbott-Farhi model; the composition of the W and Z vectors.
• Condensados de quarks top.

Literature, fiction and music

• From the publication of the scientific publication book God's particle: if the universe is the answer, what is the question? by Leon Lederman, in popular culture, the Higgs boson is sometimes called "the particle of God"although virtually all scientists, including Peter Higgs, consider it a sensationalist exaggeration. In the movie Angels and Devils, based on the book of the same name (from the author Dan Brown), mentions the Higgs boson in this way.
• In the movie Solaris starring George Clooney and Natascha McElhone is theorized that visitors who materialize the living ocean of the planet would be formed by subatomic particles stabilized by a Higgs field.
• In the science fiction book Flashforwardwritten by Robert J. Sawyer (1999), two scientists unleash a global catastrophe while trying to find Higgs' boson.
• In chapter 21 of the 5th season (The Hawking Excitation) of the series The Big Bang TheorySheldon Cooper thinks he's discovered a proof of the existence of the Higgs boson.
• In the Spanish series The boat, the Great Colisionator of Hadrones (LHC) of the CERN in Geneva, Switzerland causes, after its launch, the sinking of the continents, leaving as unique survivors the crew members of Polar and with a single hope of life that stands in a small piece of land lost on the east face of the planet.
• The Madrid musical group Drove on their album edited in June 2012 and entitled La Voz de la Ciencia dedican un tema al Bosón de Higgs.
• The Galician artist Iván Ferreiro in his latest album published in 2013 and entitled "Val Miñor-Madrid: History and chronology of the world" dedicates a theme to the famous Bosón de Higgs.
• In one of the episodes of The Penguins of Madagascar, reference is made to said Boson. Kowalski, one of the members says that "There is only one like that in the whole universe," and uses it to clone dodos.
• The Australian artist Nick Cave headlines one of his songs Higgs Boson Blues on his album Push the Sky Away2013
• BOSÓN D'HIGGS is a Neopsicodelic Rock band formed in Cuenca-Ecuador in 2014. Currently its members are Esteban Cañizares (Voces, Guitars, Compositions and Vocal Arrangements), Paul Galán (Guitarras, Voces and Arreglos), Fernando Marín (Batteries and Percussions), Danny Galán (Bajo, Voces and Arreglos) and Jorge Pezantes (technicals and arrangements).
• The original German Netflix series Dark uses the Higgs boson as a argumental device that, after its discovery and stabilization, allows the protagonists to travel in time.
• One of the antagonists of the video game The Death Stranding is called Higgs and says it is the divine particle as it is able to control and create entities of another dimension at will, apart from being able to move between that dimension and that which would be ours.
• In the Japanese sleeve series Dr. Stone, mention is made of the Higgs field to explain the operation of the petrifier or "Medusas" devices. It explains that petrification happens when humans come into contact with the waves of these devices capable of modifying the Higgs field.