Unlocking secrets about the origin of the universe

April 15, 2019

Ever step out at night and stare into all those tiny dots splattered across the sky’s vast canvas? Ever wonder how those stars and everything else came to be?

Everything has its origin, even the universe. And although there are many myths and legends about the universe’s creation, it was Belgian priest, physicist and astronomer Georges Lemaître who in 1927 attempted to explain scientifically how the universe was formed. Lemaître believed that the universe began from a tiny, single point and he postulated that a cataclysmic explosion triggered its expansion through the millennia. As enormous as the universe is today, it’s still expanding.

Lemaître’s original idea also “expanded,” with scientists from around the world adding to this theory, which became known as the Big Bang. Today the Big Bang Theory is well-supported by facts, but what scientists know is like several blindfolded people touching different parts of an elephant. Collectively, they have an idea of what an elephant looks like, but no one person “sees” the exact same elephant.

Through science, we know that the universe was born from an unimaginably hot and dense point. A few microseconds after its birth, while this early version of the universe seethed at temperatures 100,000 times hotter than the center of our Sun, the first building blocks of all matter appeared. These elementary particles, known as quarks and gluons, came together to form a primordial “soup” of quark-gluon plasma.

Plasma came about when quarks, with the gluons acting as “glue,” formed composite particles known as hadrons, but physicists still don’t understand exactly how that worked. It remains a hugely consequential yet obscure process.

The most stable of the hadrons became protons and neutrons, which later grouped with electrons to form atoms. Atoms in turn eventually created all the “star stuff” in the universe today, from the galaxies and stars to the planets and everything else made of matter.

To better understand how the universe was born, some physicists have turned away from telescopes and are instead using high-energy particle accelerators. With the help of experimental facilities such as Switzerland’s CERN Super Proton Synchrotron, Large Hadron Collider and the Relativistic Heavy Ion Collider at Brookhaven National Laboratory in New York, scientists have successfully recreated quark-gluon plasma by slamming together high-energy heavy nuclei.

The research shows that quark-gluon plasma is an extreme state of matter, one that is unbelievably hot and dense. Moreover, such plasma does not last very long—a blink of an eye and it’s long gone.

Eager to learn more, scientists and engineers from more than 70 organizations have come together to develop the tools to unravel the microscopic secrets hidden within quark-gluon plasma. This next-generation effort, sPHENIX, will be located at the Relativistic Heavy Ion Collider. It has but one lofty objective: probe the microscopic structure of quark-gluon plasma.

Los Alamos researchers are contributing to the project by designing an advanced tracking detector based on a new type of sensor system called MAPS, short for Monolithic Active Pixel Sensor. When the collider produces quark-gluon plasma in the sPHENIX experiment in several years, a new tracking detector will be there to capture the first measurements of the plasma’s internal structure using heavy quarks.

The MAPS-based VerTex tracking detector (called MVTX) uses a revolutionary new technology that produces highly detailed images of high-energy heavy-ion collision events that last only a fraction of a second. Physicists first thought quark-gluon plasma was gaseous, but they have since discovered the created plasma is the most perfect liquid form ever detected. The tracking detector has been specifically designed to study this plasma’s pristine liquid state with heavy quarks with unprecedented precision.

Think of quark-gluon plasma as a river of water flowing downhill. Scientists want to study the physical properties of the water, such as the density and viscosity. Previous detector technology used at the Relativistic Heavy Ion Collider was akin to throwing tiny rocks into the river, creating such small ripples that the detectors could barely pick up the details that are important to make the connections between the physical properties and the observations.

With this new tracking detector, the detection is akin to throwing much larger rocks into the river, creating greater ripples that provide much better microscopic details than any other detector system can do.

Scientists will compare measurements taken by the new detector to theoretical models of quark-gluon plasma, creating a better-detailed idea of the plasma’s internal structure and interactions. Eventually, along with other experiments undertaken by sPHENIX, scientists at last may unlock some secrets of how quark-gluon plasma came to be in the early universe and the exact processes of how quarks and gluons subsequently transitioned to the atoms we know today.

The updates that will bring sPHENIX online will also provide the foundation for a future Electron Ion Collider facility, which in 2015 the Department of Energy’s Nuclear Science Advisory Committee named as one of the top priorities for the near future in American nuclear physics. The collider will enable scientists to delve deeper into what makes quarks and gluons tick and discover exactly how they form hadrons through the strong interactions.

The work being performed with the new tracking detector and the other components that make up sPHENIX serves as the opening page in a whole new chapter dedicated to unraveling the mysteries of how the universe first came to be.

Ming Xiong Liu works on projects related to high-energy nuclear and particle physics for the Subatomic Group at Los Alamos National Laboratory. Liu has more than 20 years of experience in designing and carrying out high-energy nuclear and particle physics experiments.