Collider serves up drop of primordial soup – Physics World (2024)

A tiny drop of an exotic ultra-hot “soup” that permeated the universe for an instant immediately after the Big Bang appears to have been created in collisions between gold nuclei and deuterons at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Lab in the US. Evidence that a quark–gluon plasma (QGP) may be generated even in collisions involving very light nuclei such as the deuteron first emerged five years ago from data at the Large Hadron Collider in Geneva. But the new RHIC results push this evidence to record-low collision energies, which should help physicists better understand how a QGP forms and evolves.

A quark–gluon plasma (QGP) occurs at a temperature about 100,000 times that at the centre of the Sun. Protons and neutrons “melt” into an unbounded mass of quarks and their force-carrying particles, gluons. This extreme state of matter is believed to have persisted for only a few milliseconds after the Big Bang but can be created artificially by colliding very heavy nuclei that are travelling near to the speed of light.

The first, albeit indirect, evidence for such collisions was claimed by scientists at CERN in 2000, who smashed high-energy beams of lead ions into fixed targets made of lead or gold. Five years later, physicists working at RHIC also showed that they could create a QGP – in this case by colliding two beams of gold ions head on. However, these results contained a surprise: physicists had expected a QGP to behave like a gas, but instead it appeared to resemble a liquid.

Perfect liquid

Plotting the trajectories of the many thousands of particles created in each collision, the RHIC researchers found that the particles were not emitted in random directions as they would be in a gas. Rather, some of the emissions were correlated, meaning that more particles flew off at a narrow angle to the plane of the collision than were emitted at roughly right angles. This elliptical distribution signified that the particles were moving collectively and in fact “flowing” together like an almost friction-free perfect liquid, according to the researchers.

The latest work shows that this liquid state appears to be created even when heavy nuclei collide with very light nuclei at low energies. The first, unexpected, glimpse of such a small-scale QGP came in 2012 from the analysis of collisions between lead nuclei and protons at CERN’s Large Hadron Collider – events that were intended simply as a control for lead–lead collisions rather than to generate the scalding plasma themselves. That result prompted scientists in RHIC’s PHENIX collaboration to re-analyse data from collisions between gold nuclei and deuterons, particles consisting of one proton and one neutron. As they reported in 2013, they too saw telltale signs of fluid flow. A couple of years later the PHENIX team saw similar behaviour in collisions between nuclei of gold and helium-3.

Now, the PHENIX researchers have returned to gold–deuteron events. But this time they have studied the effect of varying the collision energy to see if the liquid behaviour disappears. Carrying out measurements over five weeks last year, they set the collision energy at four different levels: 200, 62.4, 39 and 19.6GeV. They found very similar correlations at all energies when comparing the trajectories of particles grouped into pairs and into sets of four. At 200GeV, they also looked at six-particle correlations. Their conclusion: liquid flow probably occurs all the way down to at least 20GeV.

Tiny volumes

According to PHENIX deputy spokesperson Julia Velkovska of Vanderbilt University in Tennessee, the droplets they have created this time around are about 100 times smaller than those generated in collisions between large nuclei – occupying the volume of just four protons. Calculations suggest that the plasmas also only last for about a fifth of the time – a fleeting 7×10–24s. “We have found correlations on scales much smaller than previously thought possible,” she says. “That means that as long as we achieve a high-enough energy density, size is not so important. A QGP may still be formed.”

The researchers’ next step is to see whether other expected signatures of a QGP, already verified in collisions with heavier nuclei, are also present in these smaller-scale collisions. One such signature is the abundance and flow pattern of different types of particles emitted in the collisions. Collaboration member Darren McGlinchey of Los Alamos National Laboratory says that abundance data provide information on the temperature of a QGP.

PHENIX colleague Ron Belmont of the University of Colorado says it is still possible that the elliptical emission they have observed is due not to the formation of tiny QGPs but instead down to nuclear properties prior to collision. When accelerated close to light speed, time slows down for the heavy nuclei, which means, according to quantum chromodynamics, that they appear as a dense wall of gluons. The fact that these condensates are thicker in the centre of the nuclei might explain why particles generated in the collisions are not emitted in random directions, he says.

Theoretical predictions

The expected effects of these condensates on the gold–deuteron collisions are still being worked out by theorists, says Velkovska, and as such have not yet been compared to the latest results. In contrast, she notes, predictions from hydrodynamics are in, and, she says, “agree with the data well”.

The results have been posted to the arXiv server (arXiv: 1707.06108 and arXiv: 1708.06983) and have been submitted for publication in Physical Review Letters and Physical Review C.

Collider serves up drop of primordial soup – Physics World (2024)


What is the primordial soup physics? ›

The primordial soup is believed to have contained the building blocks of the first forms of life on earth. According to the primordial soup theory, the primordial soup contained small organic molecules (monomers) and complex organic molecules (polymers) formed from inorganic materials in the primitive atmosphere.

What did the Large Hadron Collider prove? ›

This powerful particle accelerator is known as the Large Hadron Collider. It's where some of modern physics' most significant discoveries have been made, including the 2012 identification of the Higgs boson, the culmination of a 50-year search. The Higgs particle gives mass to all other particles.

What is the cosmic soup theory? ›

Instead, physicists believe, the Universe was filled by a soup of particles. Electrons, particles called baryons, which are ordinary matter particles, and particles of light, called photons, sloshed around together and were coupled to each other, behaving like a fluid — the so-called baryon-photon fluid.

What happened to the superconducting super collider? ›

Cancellation. After $2 billion had been spent ($400 million by the host state of Texas, the rest by the Department of Energy), the House of Representatives rejected funding on October 19, 1993, and Senate negotiators failed to restore it. Following Rep.

How to make primordial soup in real life? ›

Boil some water to mimic evaporation of the early ocean. Add a few gases thought to be present in the early atmosphere. Apply a jolt of electricity to simulate lightning. Let run for a few days—and you're left with a brownish soup of amino acids, the building blocks for everything alive on Earth.

What is Stanley Miller's experiment? ›

In 1953, scientist Stanley Miller performed an experiment that may explain what occurred on primitive Earth billions of years ago. He sent an electrical charge through a flask of a chemical solution of methane, ammonia, hydrogen and water. This created organic compounds including amino acids.

What is the Hadron Collider in layman's terms? ›

The Large Hadron Collider (LHC) is the world's largest and most powerful particle accelerator. It consists of a 27-kilometre ring of superconducting magnets with a number of accelerating structures to boost the energy of the particles along the way.

What is the end goal of the Large Hadron Collider? ›

The LHC's goal is to allow physicists to test the predictions of different theories of particle physics, including measuring the properties of the Higgs boson, searching for the large family of new particles predicted by supersymmetric theories, and studying other unresolved questions in particle physics.

What is the point of the CERN collider? ›

The LHC is designed to help answer such questions. The LHC can reproduce the conditions that existed within a billionth of a second of the Big Bang. The colossal accelerator allows scientists to collide high-energy subatomic particles in a controlled environment and observe the interactions.

Is the primordial soup theory true? ›

Yes and no. The Earth must have had a kind of primordial soup in its oceans and ponds every early in its history. This is a logical result of the ordinary laws of chemistry and can't be denied. But that primordial soup wasn't enough, by itself, to produce life.

What is the big slurp universe theory? ›

Big Slurp. This theory posits that the universe currently exists in a false vacuum and that it could become a true vacuum at any moment. In order to best understand the false vacuum collapse theory, one must first understand the Higgs field which permeates the universe.

Which theory proposed that life started in a primordial soup? ›

Heterotrophic theory

According to the theory, organic compounds essential for life forms were synthesized in the primitive Earth under prebiotic conditions. The mixture of inorganic and organic compounds with water on the primitive Earth became the prebiotic or primordial soup.

How many colliders are there in the world? ›

It is a collider accelerator, which can accelerate two beams of protons to an energy of 6.5 TeV and cause them to collide head-on, creating center-of-mass energies of 13 TeV. There are more than 30,000 accelerators in operation around the world.

Why did they shut down hadron collider? ›

The world's largest and most powerful particle accelerator has restarted after a break of more than three years for maintenance, consolidation and upgrade work.

Is there a hadron collider in the US? ›

On why this collider won't be up and running until 2030

There is a collider at Brookhaven National Lab right now called RHIC, which is a relativistic hadron collider. So there's already a loop there that it was accelerating other types of ions. There was an accelerator infrastructure [already] there.

What is the meaning of the primordial soup? ›

The primordial soup is a generic term that describes the aqueous solution of organic compounds that accumulated in primitive water bodies of the early Earth as a result of endogenous abiotic syntheses and the extraterrestrial delivery by cometary and meteoritic collisions, and from which some have assumed that the ...

What is the primordial soup theory also known as? ›

Heterotrophic theory

According to the theory, organic compounds essential for life forms were synthesized in the primitive Earth under prebiotic conditions. The mixture of inorganic and organic compounds with water on the primitive Earth became the prebiotic or primordial soup.

What is the primordial sandwich theory? ›


What makes primordial soup in Little Alchemy 2? ›

Making the Primordial Soup

The fastest way to make Primordial Soup is by combining Earth and Ocean. Make Ocean by starting with Water combined with Water. Keep combining the new water products with itself or with Water until you get Ocean. Now, combine Earth and Ocean and you'll have the Primordial Soup.


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