Pressure is felt as the force exerted on bodies when they are submerged in a material; you’ve felt it as you dive to the bottom of the pool and when you uncork a bottle. Recently, scientists have measured the pressure within a proton, a particle that comprises the atom.  Protons are made of fundamental particles called ‘quarks’ and ‘gluons‘ which are constantly bumping together creating a pressure inside the proton that other particles can feel when they collide with protons.

Before now, scientists have not had the tools nor methodology to measure the pressure distribution inside a proton. A proton is primarily made of 3 quarks, but these quarks are trapped in a cloud of other very low-energy quarks and gluons. Particle physicists have not yet developed the theoretical tools to calculate exactly what this cloud looks like, and therefore rely on computer simulations and experimental data. Previously, electrons were collided with protons to probe the proton’s internal pressure. However, this picture was incomplete as the analysis neglected the gluons’ effects. Physicists have improved their measurements by simulating protons on supercomputers. They set up many possible configurations of quarks and gluons and average the resulting pressure distributions. This has led to the novel discovery that protons have a large pressure pushing the core out, whereas the edges of the proton are being pulled in.  

Scientists hope to learn more about the structure of the proton by measuring the pressure distribution. Since the theory cannot predict exact quark and gluon configurations, indirect measurements of the structure and components of a proton are necessary to guide theoretical understanding. This might reveal new information about the nature of our universe, increasing our knowledge of fundamental particles and their interactions. As most matter is made of protons, this could lead to new research areas on a macroscopic scale as well.

Managing Correspondant: Cari Cesarotti

Read More/Image Credit: Physicists calculate proton’s pressure distribution for first time