For most of us, physics terms such as odderon are – and will always remain – firmly lodged in the science fiction realm. Not so for the scientific community, whose determined members spent nearly half a century searching (without much success) for this mythical particle. Now, a research team including physicists from Hungary and Sweden has discovered the odderon by analysing experimental data from the Large Hadron Collider (LHC) at Switzerland’s European Organization for Nuclear Research, better known as CERN.
Supported by the EU-funded MorePheno project, the physicists have published a paper describing their findings in the ‘The European Physical Journal C’. It all began in 1973, when calculations led to the theory that there might exist a previously unknown subatomic quasiparticle, setting in motion an international hunt for the odderon. As described in an article posted on the ‘SciTechDaily’ website, an odderon is formed “when protons collide in high-energy collisions, and in some cases do not shatter, but bounce off one another and scatter.” To prove the existence of this until now mythical particle, scientists used detailed measurements from high-energy collisions obtained with the LHC, the world’s largest and most powerful particle accelerator.
Evidence of the odderon
In their search for odderons, CERN researchers focused on hadrons, a family of subatomic particles that includes protons and neutrons. Hadrons are composed of two or more quarks that are held – or glued – together by elementary particles called gluons. Whereas previous observations of collisions only involved an even number of gluons exchanged between the protons, finding an odd number – a three-gluon state – would indicate the presence of an odderon.
The scientists conducted extensive analyses of elastic proton-proton (pp) and proton–antiproton (pp¯) collisions at high energies. They studied the scaling properties of data from the ISR and Tevatron colliders, together with data sets provided by the TOTEM Collaboration in a tera-electron-volt (TeV) energy range.
“Rescaling the TOTEM pp data from √s = 7 TeV to 2.76 and 1.96 TeV, and comparing it to data at 1.96 TeV, our results provide an evidence for a t-channel Odderon exchange at TeV energies, with a significance of at least 6.26σ,” the authors explain in the study. “This is a particle physics milestone! It feels fantastic to contribute to an increased understanding of matter; the fundamental building blocks of our world,” reported study co-author Roman Pasechnik of MorePheno project coordinator Lund University, Sweden, in the article.
The MorePheno (Collider Phenomenology and Event Generators) project ran from November 2015 to October 2020. Its aim was to carry out frontline research that would have direct implications for event generators – software libraries generating high-energy particle physics events such as those produced in particle accelerators and collider experiments. Roman Pasechnik’s concluding statement attests to its success: “We worked with some of the world’s best particle physicists. They were astonished when we published our results.”