One of the biggest mysteries for researchers and scientists is the formation of the Universe. Recently, the European Organization for Nuclear Research (CERN) has been trying to discover a new particle known as an axion, which can, for the first time, provide information about the events that occurred in the Universe just one second after the Big Bang.
In this article we're going to tell you everything there is to know about the axion, the particle that could explain the Big Bang.
Axions and dark matter
Initially suggested in the 1970s by physicist Roberto Peccei and his colleague Helen Quinn, the axion is an elementary particle that arises from a theoretical framework intended to address a problem within quantum chromodynamics (QCD), the theory that describes the interactions between quarks and gluons. This problem pertains to the "parity conservation problem," which states that specific properties must remain unaffected by nuclear interactions. The introduction of the axion serves as a mechanism to restore this symmetry.
Among the most notable characteristics of the axion is its potential role as a component of dark matter, which makes up approximately 27% of the total mass of the universe . Dark matter emits neither light nor radioactivity, rendering it invisible and observable only through its gravitational influence. If axions are proven to exist, they could be abundant throughout the universe, thus providing an explanation for the elusive nature of dark matter as extremely light and difficult-to-detect particles.
The Big Bang and axionic particles
The primordial explosion known as the Big Bang, which initiated the formation of the universe, is an event examined by numerous cosmological models and theories. It is believed that immediately after the Big Bang, a variety of particles and radiation emerged. If axions exist, they may have been generated in substantial quantities during this early phase, playing a role in the evolution of the universe.
The study of axions is important not only for understanding dark matter, but also for improving our understanding of the universe during its formative stages . Since the Big Bang produced a vast array of particles, the possible existence of axions could provide insights into the historical organization of matter and energy.
What information do we have about the history of the Universe?
Currently, analysis of the electromagnetic spectrum of the Cosmic Microwave Background (CMB) has allowed scientists to trace back almost 14 billion years to the time when the Universe had cooled enough for protons and electrons to first combine, resulting in the formation of neutral hydrogen.
The photons detected in observations of the Cosmic Microwave Background (CMB) were emitted 400.000 years after the Big Bang, making it extremely difficult to determine the history of the Universe before this time.
However, a trio of British researchers has proposed a theory suggesting the possible existence of a particle known as the axion, which could have been emitted during the initial second of the Universe's history. Although this particle remains hypothetical, there are numerous reasons to believe that the axion could indeed exist within the Universe.
What exactly is an axion?
Axions are theoretical fundamental particles that, although still hypothetical, may resolve certain complex questions within contemporary particle theories.
The presence of the axion would help address the question of strong CP symmetry, which pertains to the balance between matter and antimatter. In fact, it may provide a natural explanation for the striking similarities in the properties of matter and antimatter, while also offering insights into the predominance of matter over antimatter in the universe.
Axions may provide information about the mysterious "dark matter," which makes up 23% of the Universe. Research indicates that these particles are among the most promising candidates for contributing to the invisible matter, or dark matter, that emerged shortly after the Big Bang.
The axion and its role in the context of dark matter
Considering the possibility that dark matter may consist of axions generated in large quantities after the Big Bang, researchers are working diligently to identify axionic dark matter as soon as possible.
An article published in Physical Review D suggests that the advancement of more sensitive instruments designed to detect dark matter may inadvertently lead to the discovery of another indicator of axions, known as CaB. This term denotes an axion that is analogous to the Cosmic Microwave Background (CMB) and is called the Cosmic Axion Background. However, due to the similarities in properties between CaB and dark matter axions, there is a risk that the CaB signal could be dismissed as noise in experimental settings.
For scientists, the identification of CaB would represent a double discovery . Not only would it validate the existence of the axion, but it would also offer a new relic from the early Universe to the scientific community. The method by which CaB was generated could reveal previously unknown facets of the formation and evolution of the Universe.
Methods for detecting an axion
The experiments conducted by CERN aimed to detect the axion. One experiment designed to identify the axion particle involves using resonant microwave cavities, calibrated for the axion's mass, placed within strong magnetic fields. This methodology is currently used in the ADMX experiment at the University of Washington and has the potential to detect the axion , should dark matter be composed entirely of axions.
An additional method for detecting axions involves the use of helioscopes, specifically designed to identify axions generated within the Sun. This is achieved by employing a powerful magnet paired with X-ray detectors that have exceptionally low background. While no evidence of axions has been found to date, the CAST experiment, which includes contributions from researchers at the University of Zaragoza, has overcome astrophysical limitations and opened up a previously unexplored region for exploration.
