We know very little about the first few microseconds after the Big Bang. We have theories, most of which we’re still double- and triple-checking to see if they actually make scientific sense. The research process can seem tedious at times, but a newcomer from Long Island offers promising advances in our quest to understand how our universe came to be.
In a recent paper for the Journal of High Energy Physics, researchers with the sPHENIX Collaboration announced that it had passed a “standard candle” test with flying colors, correctly catching and measuring the energy level of colliding gold ions traveling close to the speed of light.
The sPHENIX detector is a 1,000-ton, two-story-tall instrument equipped with a powerful camera that catches and measures 15,000 particle collisions per second. It’s the much-awaited upgrade to PHENIX, a now-retired detector at the Brookhaven National Laboratory’s Relativistic Heavy Ion Collider (RHIC).
“This indicates the detector works as it should,” Gunther Roland, a physicist at MIT and the sPHENIX Collaboration, told MIT News. “It’s as if you sent a new telescope up in space after you’ve spent 10 years building it, and it snaps the first picture. It’s not necessarily a picture of something completely new, but it proves that it’s now ready to start doing new science.”
The hot mess of the early universe
Quarks and gluons are fundamental particles that make up protons and neutrons. Usually, these two particles are nearly impossible to pull apart, unless they’re in an environment with extremely high temperatures and pressures—such as the few microseconds immediately after the Big Bang.
Under such conditions, quarks and gluons would have existed separately in a dense, soupy plasma known as the quark-gluon plasma (QGP). The RHIC attempts to replicate these conditions by flinging particles in opposite directions. When some of these particles smash into one another, they release a gigantic load of energy that exists very briefly—for a sextillionth of a second—as QGP.
“You never see the QGP itself—you just see its ashes, so to speak, in the form of the particles that come from its decay,” Roland said. “With sPHENIX, we want to measure these particles to reconstruct the properties of the QGP, which is essentially gone in an instant.”
The ‘Big Bang machine’
Passing the test bodes well for the detector’s future. However, the team wants to put it through a few more quality checks. The sPHENIX detector is like a “giant 3D camera” tracking the number, energy, and paths of particles generated by a single collision, the researchers said.
A schematic of sPHENIX, a detector with precision particle tracking capabilities. Key components include outer and inner hadronic calorimeters, an electromagnetic calorimeter, tracking systems, and a superconducting solenoid magnet. Credit: Brookhaven National Laboratory“sPHENIX takes advantage of developments in detector technology since RHIC switched on 25 years ago to collect data at the fastest possible rate,” Cameron Dean, a postdoctoral student at MIT and a member of the sPHENIX Collaboration, also told MIT News. “This allows us to probe incredibly rare processes for the first time.”
Ironically, the very features that make sPHENIX so impressive are also why it requires a lot of maintenance. But the researchers are hopeful they’re on the right path. As of now, sPHENIX is busy collecting data for RHIC’s 25th and final run, after which the collider’s successor, the Electric-Ion Collider, will take over.
“The fun for sPHENIX is just beginning,” Dean said.
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