Chuck Bednar for redOrbit.com – @BednarChuck
Ongoing experiments at a particle accelerator at the US Department of Energy’s Brookhaven National Laboratory have produced new evidence for the existence of a phenomenon called a “chiral magnetic wave” travelling through a state of matter created by the collider.
The wave was found “rippling through the soup of quark-gluon plasma” created by a series of “energetic particle smashups” at the facility’s Relativistic Heavy Ion Collider, the Brookhaven team explained in a statement. Its presence was one of the consequences they expected to find in this quark-gluon plasma, which is a state of matter that existed during the early universe.
In quark-gluon plasma, these two the building blocks of protons and neutrons were free prior to becoming inextricably bound within those larger particles, the scientists explained. If confirmed, this discovery would serve as evidence that ongoing collisions of energetic gold ions at the RHIC recreate nucleus-size blobs of the fiery plasma thousands of times each second.
Furthermore, it would serve as circumstantial evidence supporting a separate and long-disputed quantum phenomenon required for the wave’s existence, they added. A new paper detailing the team’s findings can now be viewed online and will be featured in Physical Review Letters.
Explaining chirality and differently-charged particle flow
Hongwei Ke, a postdoctoral fellow at Brookhaven and a member of the STAR collaboration that was responsible for the discovery, explained the researcher team measures the tendency of negatively-charged particles to emerge from collisions around the equator of the plasma involved in the collision, while positively-charged ones are forced to one of the two poles.
This separation occurs due to the influence of magnetic fields found deep within the plasma that alter how differently-charged particles flow. When the gold ions collide, electrons in those atoms are stripped, leaving positively-charged protons in a naked nucleus, Ke explained.
Once the ions collide, the charged matter begins to swirl, generating a powerful magnetic field perpendicular to the circulating mass of matter. Contained within that mass are a vast number of subatomic particles, including early-stage gluons and quarks, that spin while moving through the magnetic field. The direction of their spin relative to their direction of motion is a property called chirality, identified as right-handed for clockwise and left-handed for counterclockwise.
If the numbers of particles and antiparticles differ, the magnetic field will have a different impact on those right- and left-handed particles differently, the study authors noted. This causes them to separate along the field’s axis based on their “chiral charge,” causing a separation that grows and continues building on one another similar to a wave. Ultimately, the phenomenon causes more of the negative particles into the equator and the positively-charged ones to the poles.
Evidence that the chiral magnetic wave exists
In order to detect this phenomenon, the research team measured the collective motion of specific charged particles produced during collisions in the RHIC. They found that the collective flow of the negatively-charged particles outward from the equator was enhanced, while the flow of positive ones was suppressed, causing a higher abundance of these particles at the poles.
The differences in the flow between positive and negative particles increased with the net charge produced in RHIC collisions, which is precisely what the authors expected to find in calculations using the theory that predicted the existence of the chiral magnetic wave. Also, the results were consistent throughout the entire range of energies at which a quark-gluon plasma is believed to be created at RHIC, and this cannot be explained using any other model.
“Seeing evidence for the chiral magnetic wave means the elements required to create the wave must also exist in the quark-gluon plasma,” Aihong Tang, a STAR physicist from Brookhaven Lab, explained in a statement. “One of these is the chiral magnetic effect – the quantum physics phenomenon that causes the electric charge separation along the axis of the magnetic field.”
This phenomenon “has been a hotly debated topic in physics,” Tang continued, adding that the evidence that this wave exists is also evidence that the chiral magnetic effect does as well. This chiral magnetic effect is also related to another intriguing observation is also evidence of a more-localized charge separation within the quark-gluon plasma within the collider.
—–
Follow redOrbit on Twitter, Facebook, Google+, Instagram and Pinterest.
Comments