The researchers discovered a new particle that is a magnetic relative of the Higgs boson. While the discovery of the Higgs boson required the enormous accelerating power of the Large Hadron Collider (LHC) particles, this never-before-seen particle – dubbed the axial Higgs boson – was found using an experiment that would fit the plane of a small kitchen.
In addition to being the first in its own right, this magnetic cousin of the Higgs boson – the particle responsible for granting their mass to other particles – could be a candidate for dark matter, which represents 85% t of the total mass of the universe but is revealed only through gravity.
“When my student showed me the data, I thought she was wrong,” Kenneth Burch, a physics professor at Boston College and lead researcher on the team that made the discovery, told Live Science. “It’s not every day that you find a new particle on the table.”
The Higgs axial boson differs from the Higgs boson, which was first detected by the ATLAS And CMS detectors at the LHC a decade ago in 2012, because it has a magnetic moment, magnetic force, or orientation that creates a magnetic field. As such, it takes a more complex theory to describe it than its mass-granting non-magnetic cousin.
In the standard model of particle physics, particles emerge from different fields that permeate the universe, and some of these particles shape the fundamental forces of the universe. For example, photons mediate electromagnetism and heavy particles known as W and Z bosons mediate the weak nuclear force, which governs nuclear decay at subatomic levels. When the universe was young and hot, however, electromagnetism and weak force were one thing, and all of these particles were nearly identical. As the universe cools, the electroweak force splits, causing the W and Z bosons to gain mass and behave very differently from photons, a process that physicists have called “symmetry breaking.” But how exactly did these weak force mediating particles become so heavy?
It turns out that these particles interacted with a separate field, known as the Higgs field. The perturbations in that field gave rise to the Higgs boson and lent their weight to the W and Z bosons.
The Higgs boson is produced in nature whenever such a symmetry is broken,. “however, typically only one symmetry is broken at a time, and so the Higgs is simply described by its energy,” Burch said.
The theory behind the axial Higgs boson is more complicated.
“In the case of the axial Higgs boson, it appears that multiple symmetries are broken together, leading to a new form of the theory and a Higgs mode [the specific oscillations of a quantum field like the Higgs field] which requires multiple parameters to describe it: in particular, energy and magnetic moment, “said Burch.
Burch, who along with colleagues described Higgs’ new magnetic cousin in a study published Wednesday (June 8) in the journal Nature, explained that the original Higgs boson does not directly couple with light, which means it must be created by destroying other particles along with huge magnets and high-powered lasers, while also cooling the samples to extremely low temperatures. It is the decay of those original particles into others that fleetingly emerge from existence that reveals the presence of the Higgs.
The axial Higgs boson, on the other hand, arose when quantum materials at room temperature mimicked a specific set of oscillations, called the axial Higgs mode. The researchers then used light scattering to observe the particle.
“We found the axial Higgs boson using a tabletop optics experiment that sits on a roughly 1 x 1 meter table focusing on a material with a unique combination of properties,” continued Burch. “In particular we used rare earth Tritelluride (RTe3) [a quantum material with a highly 2D crystal structure]. The electrons in RTe3 self-organize into a wave in which the charge density is periodically increased or decreased. “
The size of these charge density waves, which emerge above ambient temperature, can be modulated over time, producing the axial Higgs mode.
In the new study, the team created the axial Higgs mode by sending laser light of one color into the RTe3 crystal. The light diffused and changed to a lower frequency color in a process known as Raman scattering, and the energy lost during the color change created the axial Higgs mode. The team then rotated the crystal and found that the axial Higgs mode also controls the angular momentum of electrons, or the speed at which they move in a circle, in the material meaning that this mode must also be magnetic.
“Initially we were simply studying the light scattering properties of this material. By carefully examining the symmetry of the response, how it differed as we rotated the sample, we discovered anomalous changes that were the first hints of something new, “Burch explained.” As such, it is the first magnetic Higgs to be discovered and indicates that the Collective behavior of electrons in RTe3 is unlike any state previously seen in nature. “
Particle physicists had previously predicted an axial Higgs mode and even used it to explain dark matter, but this is the first time it has been observed. This is also the first time that scientists have observed a state with multiple broken symmetries.
Symmetry breaking occurs when a symmetrical system that appears the same in all directions becomes asymmetrical. University of Oregon suggests thinking of this as a spinning coin that has two possible states. The coin eventually falls on the face of the head or tail thereby releasing energy and becoming asymmetrical.
The fact that this double symmetry breaking is still in tune with current theories of physics is exciting, because it could be a way to create previously invisible particles that could explain dark matter.
“The basic idea is that to explain dark matter you need a theory that is consistent with experiments on existing particles, but which produces new particles that have not yet been seen,” Burch said.
Adding this further symmetry breaking via axial Higgs mode is one way to do it, he said. Although predicted by physicists, the observation of the axial Higgs boson came as a surprise to the team, who spent a year trying to verify their results, Burch said.
Originally published in Live Science.