IMAGE: The STAR detector at the U.S. Department of Energy’s Brookhaven National Laboratory scene more
Credit: Brookhaven National Laboratory
UPTON, NY – Physicians investigating gold ion accidents at the Relativistic Heavy Ion Collider (RHIC), a U.S. Department of Energy Science Office user facility for nuclear physics research at the DOE Brookhaven national laboratory, embarks on a journey through DOE nuclear levels. subject – the substance that makes up the nuclei of all visible matter in our universe. A new study of crashes conducted at different energies shows tantalizing signs of a crisis point – a change in the way quarries and gluons, building blocks of proteins and neutrons, change from one stage to another. The findings, just published by RHIC’s STAR Collaboration in the journal Corporate Review Letters, physicists will help map out details of these nuclear phase changes to better understand the evolution of the universe and the conditions in the hearts of neutron stars.
“If we can find this point of urgency, our map of nuclear levels – the nuclear level diagram – may find a place in the textbooks, along with water,” said Bedanga Mohanty of the National Institute of Science and Research. India, one of hundreds of physicists collaborating on research at RHIC using the solemn STAR detector.
As Mohanty said, studying nuclear levels is something like learning about the hard, melt and gaseous water forms, and mapping how the transitions occur according to conditions such as temperature. and weight. But with a nuclear case, you can’t just put a pot on the stove and watch it boil. You need powerful accelerators like RHIC to turn up the heat.
RHIC’s highest impact energy melts a normal nuclear material (atomic nuclei made up of proteins and neutrons) to form an exotic phase called plasma quark-gluon (QGP). Scientists believe that the entire universe existed as QGP a fraction of a second after the Big Bang – before it cooled and the quarries connected together (glued with gluons) to form proteins, neutrons and, finally, the formation of atomic nuclei. But the tiny drops of QGP generated at RHIC measure just 10-13 centimeters across (that’s 0.00000000001 cm) and only last for 10-23 seconds! That makes it very challenging to map the melting and freezing of the business that makes up our world.
“Firmly speaking if we do not recognize the end of the stage or the emergency point, we cannot put this forward. [QGP phase] into the textbooks and say we have a new situation, ”said Nu Xu, a STAR physics expert at DOE’s Lawrence Berkeley national laboratory.
Monitoring phase transition
To monitor the transitions, STAR physicists took advantage of RHIC’s incredible flexibility to strike gold ions (the nucleus of gold atoms) over a wide range of energies.
“RHIC is the only facility that can do this, delivering beams from 200 billion volts of electron (GeV) all the way down to 3 GeV. No one can dream of such a good machine, ”said Xu.
The changes in energy turn the beating temperature up and down and also change a size called bare baryon density which is somewhat similar to pressure. Looking at data collected in the first phase of the RHIC “beam energy scan” from 2010 to 2017, STAR physicists found traces of grains flowing out at each impact energy. They performed a detailed statistical analysis of the net number of proteins extracted. A number of theorists had predicted that this would reflect large event-by-event variables as the crisis point approaches.
The reason for the expected variables comes from a theoretical understanding of the force governing quarries and gluons. This theory, known as quantum chromodynamics, suggests that the transition from normal nuclear matter (hadronic protons and neutrons) to QGP can occur in two different ways. At high temperatures, where proteins and anti-protons are extracted in pairs and the net baryon density is close to zero, physics has evidence that they cross smoothly between phases. It’s as if proteins gradually melt to form QGP, like butter gradually melting on the counter on a warm day. But at lower energies, they anticipate what is called a first-order phase transition – a sudden change as water boils at a set temperature as individual molecules escape from the pot to become the steam. Nuclear theorists predict that, in the QGP-to-hadronic-matter phase shift, net proton production should change dramatically as accidents approach this turning point.
“At high energy, there is only one level. The system is largely unconventional, normal, ”said Xu. “But when we switch from high energy to low energy, you also increase the net density of baryon, and the structure of the business can change as you go through the phase shift range.
“It’s just like riding a plane and getting into trouble,” he said. “You see the variability – boom, boom, boom. Then, when you overcome the temptation – the stage of structural change – you are back to normalcy into the one-stage structure. ”
In RHIC crash data, the symptoms of this disturbance are less pronounced than food and beverages kicking off tray boards in an airplane. STAR physicists had to perform a “higher order correlation function” statistical study of the rotation of grains – looking for more than just the meaning and width of the curve representing the data to things such as asymmetric and so that distribution is slippery.
The oscillations they see in these higher orders, especially the skew (or kurtosis), are a reminder of another notable level change seen when carbon dioxide suddenly becomes apparent. when heated, the scientists say. This “critical opalescence” results from large changes in CO2 density – differences in the density of molecules.
“In our data, the oscillations indicate that something interesting is happening, like the opalescence,” Mohanty said.
But despite the tantalizing recommendations, STAR scientists admit that the range of uncertainty in their measurements remains large. The team hopes to dilute that uncertainty to reduce their emergency point detection by analyzing a second set of measurements made from many other crashes at phase II of the RHIC beam energy scan, from 2019 through 2021.
The entire STAR collaboration involved the analysis, Xu notes, with a special group of physicists – including Xiaofeng Luo (and his student, Yu Zhang), Ashish Pandav, and Toshihiro Nonaka, from China, the India and Japan, respectively – meet weekly with US scientists (across many time zones and virtual networks) to discuss and update the results. The work is also a real collaboration between the experimenters with worldwide nuclear theorists and the acceleration physics at RHIC. The latter group, in the Brookhaven Lab Collider-Accelerator Division, devised methods to run RHIC far below its design energy while also increasing impact rates to allow the collection of the necessary data at impact energy. low.
“We are investigating unregistered land,” Xu said. “This has never been done before. We have made many efforts to control the environment and make corrections, and we are eagerly awaiting the next round of higher statistical data, ”he said.
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This study was supported by the DOE Office of Science, the U.S. National Science Foundation, and a wide range of international funding bodies listed in the paper. RHIC operations are funded by the DOE Office of Science. Data analysis was performed using computing facilities at the RHIC and ATLAS Computing Facility (RACF) at Brookhaven Lab, the National Power Research Scientific Computing Center (NERSC) at Lawrence Berkeley National Laboratory, and through the Open Science consortium Grid.
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 fundamental research in the physical sciences in the United States and is working to address some of the most important challenges of our time. For more information, visit https: /
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