A boiling sea of quarks and gluons, including virtual ones—this is how we can imagine the main phase of high-energy proton collisions. It would seem that particles here have significantly more opportunities to evolve than when less numerous and much “better-behaved” secondary particles spread out from the collision point. However, data from the LHC accelerator prove that reality works differently, in a manner that is better described by an improved model of proton collisions.

A lot happens during high-energy proton-proton collisions. Protons are hadrons, i.e. clusters of partons—quarks and the gluons that bind them together. When protons collide with each other at sufficiently high energies, their quarks and gluons (including the virtual ones, which appear momentarily during interactions) enter into various complex interactions.

Only when they “cool down” do the quarks stick together to form new hadrons, which scatter from the collision area and are recorded in detectors. Intuition therefore suggests that the entropy of the produced hadrons—a quantity describing the number of states in which the particle system can find itself—should be different from that in the parton phase of the collision, when there are many interacting quarks and gluons, and the interactions appear at first glance to be as chaotic as they are dynamic.

The CMS collaboration reports the first measurement of the quantum properties of a family of tetraquarks that was recently discovered at the LHC.

To date, the Large Hadron Collider (LHC) at CERN has discovered 80 particles. The most famous is the Higgs boson, a crucial ingredient in the fundamental laws of the universe. The rest are particles called hadrons made up of quarks, which allow physicists to investigate the intriguing properties of the strong nuclear force.

Of the hadrons discovered so far, most are familiar sets of two or three quarks (so-called mesons and baryons, respectively). But one of the LHC’s most striking discoveries is the confirmation of exotic hadrons composed of four or five quarks.

SUNY Poly Professor of Physics Dr. Amir Fariborz recently published a paper in Physical Review D titled “Spinless glueballs in generalized linear sigma model.” The work takes on a central challenge in modern physics: understanding how the strongest force in nature shapes the inner structure of matter, and how it may produce an unusual form of matter made entirely from the carriers of that force.

Here’s the quick background. Everything is made of atoms. Atoms have a nucleus made of protons and neutrons, and those are made of even smaller pieces called quarks. Quarks are held together by gluons, which carry the strong interaction described by quantum chromodynamics (QCD).

Composite subatomic particles—hadrons—are built from quarks and gluons. Hadrons fall into two main groups: mesons and baryons. QCD does a great job explaining what happens when particles collide at very high energies, but at lower energies it becomes much harder to calculate, so researchers use well-tested models that still follow QCD’s rules.

It is something like the “Holy Grail” of physics: unifying particle physics and gravitation. The world of tiny particles is described extremely well by quantum theory, while the world of gravitation is captured by Einstein’s general theory of relativity. But combining the two has not yet worked—the two leading theories of theoretical physics still do not quite fit together.

There are many ideas for such a unification—with names like string theory, loop quantum gravity, canonical quantum gravity or asymptotically safe gravity. Each of them has its strengths and weaknesses. What has been missing so far, however, are observable predictions for measurable quantities and experimental data that could reveal which of these theories actually describes nature best. A new study from TU Wien published in Physical Review D may now have brought us a small step closer to this ambitious goal.