Scientists are continuously searching for innovative methods to unlock the mysteries of the universe. One common approach involves smashing matter together and examining the resulting wreckage. While these destructive experiments provide valuable insights, they do have their limitations.
A team of nuclear and particle physicists, including two researchers from CERN’s Large Hadron Collider in Switzerland, recently made an astonishing discovery. Buried within previous studies’ data was a groundbreaking experiment waiting to be unraveled.
The scientists detailed their findings in a research paper published in Physical Review Letters. Their method revolves around measuring the wobbling speed of a particle known as the tau, an approach that deviates from conventional techniques. Instead of focusing on head-on collisions, the team analyzes the instances when particles in the accelerator narrowly pass one another. Surprisingly, this alternative method significantly enhances the accuracy of the tau particle’s wobble measurements. This event marks the first time in nearly two decades that scientists have successfully gauged the tau magnetic moment, shedding light on potential fissures within the existing laws of physics.
Q: What is the purpose of measuring the wobble of particles?
A: Measuring the wobble, or magnetic moment, of particles provides valuable insights into the realm of quantum physics.
The building blocks of atoms, electrons, have two heavier counterparts: muons and taus. Among the three, taus are the heaviest and most enigmatic, existing for extremely brief periods.
Interestingly, when electrons, muons, or taus are placed in a magnetic field, they exhibit a wobbling motion, much like a spinning top. This phenomenon is referred to as a particle’s magnetic moment. Through the Standard Model of particle physics, scientists can theoretically predict the speed at which these particles wobble, offering an understanding of how they interact.
Since the 1940s, physicists have been intrigued by the measurement of magnetic moments, as they reveal intriguing effects within the quantum world. According to quantum physics, clouds of particles and antiparticles continuously appear and vanish, subtly influencing the wobbling speed of electrons, muons, and taus in a magnetic field. Precise measurements of this wobble grant physicists the ability to delve into this mysterious cloud and potentially unveil hitherto unknown particles.
Q: What is the Standard Model of particle physics?
A: The Standard Model refers to scientists’ current description of the fundamental laws of nature, which involves the classification and interaction of various particles.
Julian Schwinger, a notable theoretical physicist, first calculated the impact of the quantum cloud on the electron’s magnetic moment in 1948. Since then, experimental physicists have managed to measure the electron’s wobble speed with extraordinary precision, extending up to 13 decimal places.
The sensitivity of a particle’s wobble to new, undiscovered particles depends on its mass. Due to their lightness, electrons possess limited sensitivity to these hypothetical particles. On the other hand, muons and taus are significantly heavier but have much shorter lifespans than electrons. Recently, scientists at Fermilab in Chicago recorded the muon’s magnetic moment to a precision of 10 decimal places. Notably, their findings revealed that the muon wobbles noticeably faster than anticipated by the Standard Model, indicating the potential presence of unknown particles within the muon’s quantum cloud.
Of the three particles, taus are the heaviest, surpassing muons by a factor of 17 and electrons by a staggering 3,500 times. Consequently, they possess heightened sensitivity to undiscovered quantum cloud particles. However, observing taus poses a substantial challenge as they endure for a mere fraction of the time muons exist.
Thus far, the most accurate measurement of the tau’s magnetic moment was conducted in 2004 using a retired electron collider at CERN. Although a significant scientific achievement, this experiment could only measure the tau’s wobble speed up to two decimal places. To fully test the Standard Model, physicists require a measurement that is ten times more precise.
Q: How can the tau wobble be measured more accurately?
A: Instead of colliding two nuclei head-on, taus can be generated through the near miss of two lead ions.
Since the 2004 measurement of the tau’s magnetic moment, scientists have been tirelessly searching for novel approaches to enhance accuracy.
Typically, the Large Hadron Collider smashes the nuclei of two atoms together, earning its title as a “collider.” While these head-on collisions create a flurry of particle debris, including taus, measuring the tau’s magnetic moment under such chaotic conditions proves challenging.
Between 2015 and 2018, an experiment at CERN was specifically designed to investigate exotic hot matter generated by head-on collisions. Interestingly, this experiment inadvertently provided physicists with an opportunity to develop a fresh method for measuring the tau wobble. Instead of colliding nuclei head-on, the researchers observed that taus could be produced when two lead ions narrowly missed each other.
Through this new technique, scientists were able to attain unprecedented accuracy in measuring the tau’s magnetic moment, unraveling the intricacies of the quantum world and potentially uncovering hidden particles concealed within the tau’s quantum cloud.
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