Ten years ago, on July 4, 2012, ATLAS and CMS collaborations on the Large Hadron Collider (LHC) announced the discovery of a new particle with characteristics consistent with those of the Higgs boson predicted by the standard physics model of particles. The discovery was a milestone in the history of science and caught the attention of the world. A year later he won the Nobel Prize in Physics for François Englert and Peter Higgs for his prediction made decades earlier, along with the late Robert Brout, of a new fundamental field, known as the Higgs field, which permeates the universe. , manifests as the Higgs boson and gives mass to elementary particles.
“The discovery of the Higgs boson was a milestone in particle physics. It marked both the end of a decade-long exploration journey and the beginning of a new era of studies of this very special particle. said Fabiola Gianotti, CERN’s director general and project leader (“spokesperson”) for the ATLAS experiment. at the time of discovery. “I remember with emotion the day of the announcement, a day of immense joy for the global particle physics community and for all the people who worked tirelessly for decades to make this discovery possible.”
The search for the Higgs boson was an international effort, with the participation of scientists from researchers around the world, including UC Santa Barbara. Physics professors Claudio Campagnari, Joe Incandela, Jeffrey Richman and David Stuart, members of the UCSB High Energy Physics Group, along with their teams of students, postdoctoral fellows and engineers, were among the scientists who introduced the discovery of the Higgs boson. Incandela also served as the project leader for CMS collaboration at the time of the discovery.
In just ten years, physicists have made great strides forward in our understanding of the universe, not only confirming early on that the particle discovered in 2012 is indeed the Higgs boson, but also allowing researchers to begin building an image. of how the widespread presence of a Higgs field across the universe was established a tenth of a billion seconds after the Big Bang.
The new journey so farThe new particle discovered by the international collaborations ATLAS and CMS in 2012 looked very similar to the Higgs boson predicted by the standard model. But was it really that much sought after particle? As soon as the discovery was made, ATLAS and CMS set out to investigate in detail whether the properties of the particle they had discovered actually matched those predicted by the standard model. By using data from the decay, or “disintegration” of the new particle into two photons, the carriers of the electromagnetic force, experiments have shown that the new particle has no intrinsic angular momentum or quantum spin, just like the boson. of Higgs. predicted by the standard model. In contrast, all other known elementary particles have spin: particles of matter, such as the “up” and “down” quarks that form protons and neutrons, and the particles that carry force, such as the W and Z bosons.
By observing that Higgs bosons occur and decay into pairs of W or Z bosons, ATLAS and CMS confirmed that these gain too much through their interactions with the Higgs field, as predicted by the standard model. The strength of these interactions explains the short range of the weak force, which is responsible for a form of radioactivity and initiates the nuclear fusion reaction that feeds the Sun.
Experiments have also shown that the upper quark, lower quark, and lepton tau, which are the heaviest fermions, obtain their mass from their interactions with the Higgs field, again as predicted by the standard model. They did so by observing, in the case of the upper quark, that the Higgs boson occurred together with pairs of upper quarks, and in the cases of the lower quark and tau lepton, the disintegration of the boson into pairs of lower quarks and tau leptons. respectively. . These observations confirmed the existence of an interaction, or force, called the Yukawa interaction, which is part of the Standard Model but is different from all other forces in the Standard Model: it is mediated by the Higgs boson, and its strength is not quantified. that is, it does not come in multiples of a given unit.
ATLAS and CMS measured the mass of the Higgs boson at 125 billion electron volts (GeV), with an impressive accuracy of nearly one per thousand. The mass of the Higgs boson is a fundamental constant of nature that is not predicted by the standard model. In addition, along with the known heaviest elementary particle mass, upper quark, and other parameters, the mass of the Higgs boson can determine the vacuum stability of the universe.
These are just some of the concrete results of ten years of exploration of the Higgs boson at the world’s largest and most powerful collider, the only place in the world where this unique particle can be produced and studied in detail.
“The large data samples provided by the LHC, the exceptional performance of the ATLAS and CMS detectors, and new analysis techniques have allowed both collaborations to extend the sensitivity of their Higgs boson measurements beyond what is he believed it was possible when the experiments were designed “. said ATLAS spokesman Andreas Hoecker.
In addition, since the LHC began colliding protons at record energies in 2010, and thanks to the unprecedented sensitivity and accuracy of the four main experiments, LHC collaborations have uncovered more than 60 composite particles predicted by the LHC. standard model, some of which are exotic. ‘tetraquarks’ and ‘pentaquarks’. Experiments have also revealed a number of intriguing indications of deviations from the standard model that compel further investigation and have studied the quark-gluon plasma that filled the universe in its earliest moments with unprecedented detail. They have also observed many rare particle processes, made increasingly accurate measurements of standard model phenomena, and paved new paths in the search for new particles beyond those predicted by the standard model, including particles that may constitute dark matter. which represents the majority of particles. the mass of the universe.
The results of these searches add important pieces to our understanding of fundamental physics. “Discoveries in particle physics do not have to mean new particles,” said CERN’s Director of Research and Computer Science, Joachim Mnich. “The results of the LHC obtained during a decade of operation of the machine have allowed us to extend a much wider network in our searches, setting strong limits to the possible extensions of the standard model and creating new techniques of search and analysis of data . ”
Surprisingly, all LHC results obtained so far are based on only 5% of the total amount of data the collider will deliver over its lifetime. “With this‘ small ’sample, the LHC has allowed great strides forward in our understanding of elementary particles and their interactions,” said CERN theorist Michelangelo Mangano. “And while all the results obtained so far are consistent with the standard model, there is still a lot of room for new phenomena beyond what this theory predicts.”
“The Higgs boson itself may point to new phenomena, including some that could be responsible for the dark matter in the universe,” CMS spokesman Luca Malgeri said. “ATLAS and CMS are conducting many searches to investigate all forms of unexpected processes involving the Higgs boson.”
The Journey Ahead What remains to be learned about the Higgs field and the Higgs boson ten years later? A lot. Does the Higgs field also give too much to the lighter fermions or could another mechanism be at stake? Is the Higgs boson an elementary or composite particle? Can it interact with dark matter and reveal the nature of this mysterious form of matter? What generates the mass and self-interaction of the Higgs boson? Do you have twins or relatives?
Finding the answers to these and other intriguing questions will not only improve our understanding of the universe on smaller scales, but it can also help unlock some of the greatest mysteries of the universe as a whole, such as how it was like. is. and what might be their final destination. The self-interaction of the Higgs boson, in particular, could contain the keys to a better understanding of the imbalance between matter and antimatter and the stability of the vacuum in the universe.
Since the discovery of the Higgs boson ten years ago, members of the UCSB High Energy Physics group have been busy studying some of the properties of this particle, such as its useful life and its interactions with quarks. superior and delighted. They have also used Higgs bosons as a tool to look for new physical phenomena. The effort at UCSB is extensive, with many postdoctoral, postgraduate, and undergraduate students involved in the effort to build, operate, and update the detector, develop software algorithms, analyze data, and publish data. results. The UCSB effort has been funded throughout the time of the Higgs discovery, and since then, by the U.S. Office of Energy Science and the National Science Foundation.
While the answers to some of the new questions could be provided by data from the LHC’s impending third run or major collider upgrade, the LHC High Brightness, starting in 2029, is believed to be that the answers to other riddles are beyond the reach of the LHC, which requires a future “Higgs factory.” For this reason, CERN and its international partners are investigating the technical and financial viability of a much larger and more powerful machine, the Future Circular Collider, in response to a recommendation made in the latest update of the European Strategy for in Particle Physics.
“High energy colliders remain the most powerful microscope within our reach to explore nature on the smallest scales and …