Newswise – UPTON, NY – A new analysis of the STAR collaboration on Relativistic heavy ion accelerator (RHIC), a particle accelerator at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory, provides the first direct evidence of the traces left by what may be the universe’s strongest magnetic fields in “deconfigured” nuclear matter. The evidence comes from measuring the way differently charged particles separate as they emerge from atomic collisions cores in this DOE Office of Science User Facility.

As described in the diary Physical Examination XThe data suggests that strong magnetic fields generated during off-center collisions induce an electric current Quarks and gluons freed or deconsolidated by particle shattering of protons and neutrons. The results offer scientists a new way to study the electrical conductivity of this “quark-gluon plasma” (QGP) to learn more about these fundamental building blocks of nuclear energy cores.

“This is the first measurement of the interaction of the magnetic field with the quark-gluon plasma (QGP),” said Diyu Shen, a STAR physicist from Fudan University in China and leader of the new analysis. In fact, measuring the effects of this interaction provides direct evidence that these strong magnetic fields exist.

Stronger than a neutron star

Scientists have long believed that off-center collisions of heavy atoms can occur cores B. Gold, also called heavy ions, would generate strong magnetic fields. That’s because some of the non-colliding ones are made up of positively charged protons – and neutral neutrons cores would be thrown into a vortex if the ions brush sideways over each other at almost the speed of light.

“These fast-moving positive charges should create a very strong magnetic field, probably 10.”18 Gauss,” said Gang Wang, a STAR physicist at the University of California, Los Angeles. He wrote this down for comparison Neutron starsthe densest objects in the universe, have fields of about 1014 Gauss, while refrigerator magnets produce a field of around 100 Gauss and the protective magnetic field of our home planet is only 0.5 Gauss. “This is probably the strongest magnetic field in our universe.”

However, since things happen very quickly in severe ion collisions, the field doesn’t last long. It dissolves in less than 10-23 Seconds – ten millionths of a billionth of a billionth of a second – which makes observation difficult.

So instead of trying to measure the field directly, STAR scientists looked for evidence of its influence on the particles escaping from the collisions.

“Specifically, we studied the collective motion of charged particles,” said Wang.

Detect deflection

Magnetic fields are known to affect the movement of charged particles and can even induce electromagnetic fields in conductive forms of matter such as metals. That’s the same thing that’s happening here, but on a much smaller scale.

“We wanted to see whether the charged particles produced in off-center heavy ion collisions are deflected in a way that can only be explained by the existence of an electromagnetic field in the tiny QGP particles created in these collisions,” said Aihong Tang, a Brookhaven Lab physicist and member of the STAR collaboration.

The team used STAR’s advanced detector systems to track the collective motion of different pairs of charged particles while excluding the influence of competing non-electromagnetic effects. They were particularly interested in ruling out deflections caused by charged quarks carried along in the collision cores. Fortunately, these “transported quarks” create a deflection pattern opposite to that triggered by the electric current induced by the magnetic field, known as Faraday induction.

A clear signal

“Ultimately, we see a pattern of charge-dependent deflection that can only be triggered by an electromagnetic field in the QGP – a clear sign of Faraday induction,” Tang said.

The scientists saw this strong signal not only in off-center collisions between two pieces of gold cores at high energy – gold-gold at 200 billion electron volts or GeV – but also in off-center collisions of smaller ones cores–Ruthenium-ruthenium and zirconium-zirconium, both at 200 GeV.

“This effect is universal. This happens not only in a large system, but also in a smaller system,” Shen said.

The scientists saw an even stronger signal when they analyzed data from gold-gold collisions at a relatively low energy – 27 GeV. This finding provides further supporting evidence that the particle deflection electromagnetic field was induced by the strong magnetic fields generated by off-center collisions.

This is because Faraday induction occurs when the magnetic field dissipates. This happens more slowly in lower energy collisions.

“This effect is stronger at lower energy because the lifetime of the magnetic field is longer at lower energy; The speed of the nuclear fragments is slower, so the magnetic field and its effects last longer,” Wang said.


Now that scientists have evidence that magnetic fields in the QGP induce an electromagnetic field, they can use the induction to study the conductivity of the QGP.

“This is a fundamental and important property,” Shen said. “We can infer the value of conductivity from our measurement of collective movement. The extent to which the particles are deflected is directly dependent on the strength of the electromagnetic field and the conductivity in the QGP – and no one has ever measured the conductivity of QGP.”

Understanding the fundamental electromagnetic properties of the QGP could provide insights into important questions in physics. On the one hand, the magnetic fields that cause the electromagnetic effects could contribute to an interesting separation of particles according to their “handedness” or chirality.

“This study provides strong evidence for the magnetic field being one of the prerequisites for this.”chiral magnetic effect“‘” Shen said.

The QGP’s magnetic field and electromagnetic properties also play a role in determining the conditions under which it is free and deconcentrated Quarks and gluons fuse together to form composite particles called hadrons – like the protons and neutrons that make up ordinary particles cores.

“We want to design the nuclear ‘phase diagram’ that shows at what temperature the… Quarks and gluons can be considered free and at what temperature they “freeze” and become hadrons. These properties and the basic interactions of Quarks and gluons“Imparted by the strong force are changed under an extreme electromagnetic field,” Wang said. With this new study of the QGP’s electromagnetic properties, he added, “We can study these fundamental properties in a different dimension to provide more information about the strong interaction.”

The scientists emphasized that theorists will look at these results for now to refine their interpretations.

This research was funded by the DOE Office of Science, the US National Science Foundation, and a number of international organizations and agencies identified in the scientific paper. The STAR team used computing resources at the Scientific Data and Computing Center at Brookhaven Lab, the National Energy Research Scientific Computing Center (NERSC) at DOE’s Lawrence Berkeley National Laboratory, and the Open Science Grid consortium.

Brookhaven National Laboratory is supported by the U.S. Department of Energy’s Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information visit

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