It could represent a new paradigm for nuclear physics.
There are new experiments underway in the U.S. that hope to test a prevailing hypothesis about protons — one of the building blocks of the Universe. Theory states that protons maintain the same internal structure, no matter where they are located or what they are doing. However, these new tests aim to prove that, under certain conditions, protons can change inside the nucleus of an atom.
If successful, the results could literally lead to a rewrite of nuclear and theoretical physics textbooks. Crazy, right?
“For many scientists, the idea that the internal structure of protons might change under certain circumstances can seem absurd, even sacrilegious,” said one of the researchers, Anthony Thomas, from the University of Adelaide in Australia. “To others like myself, evidence of this internal change is highly sought after and would help to explain some of the inconsistencies in theoretical physics.”
Now, if it turns out that protons do change their structure, it won’t make much difference in the daily lives of you or me. However, it would have profound consequences in the fields of nuclear and theoretical physics.
Protons are one of the smallest building blocks of matter. In fact, they are made up of even smaller particles, known as quarks, which are held together by gluons. Current understanding is that protons that are inside the nuclei of atoms have the exact same structure as protons that are outside.
However, this doesn’t match well with a theory known as quantum chromodynamics — which describes the interactions between quarks and gluons. Based on this theory, protons inside atoms should theoretically undergo changes under certain energy levels.
It used to be impossible to test this idea, however new equipment at the Thomas Jefferson National Accelerator Facility in Virginia has now made it possible.
“By firing a beam of electrons at an atomic nucleus you can measure the difference in energy of the outgoing electrons, representing the changed state,” said Thomas. “We are making some fairly strong predictions about what the outcomes of those tests will show, and we're hopeful of a definitive measurement.”
In preparation for the experiments, the physicists have published some of their predictions as to how and why quarks and gluons feel the presence of nearby nucleons, and as a result, modify their structure.
If the results point to protons changing their structure, it would represent a new paradigm for nuclear physics. “The ramifications for the scientific world are significant,” said Thomas. “This is about as high stakes as it gets in science.”