Synopsis: Loopy precision

Third-order corrections to the interquark potential within quantum chromodynamics are computed for the first time.
Synopsis figure
Illustration: A. Smirnov et al., Phys. Rev. Lett (2010)

Quantum chromodynamics (QCD), the relativistic quantum theory that describes the interactions of quarks and gluons to make up hadrons, is a pillar of the standard model of particle physics. Yet it remains a work in progress. This is because, while QCD has obvious similarities to the much simpler quantum theory of electrodynamics that involves electrons interacting through exchanges of photons, gluons carry a color quantum number leading to a marked increase in complexity in the number of fundamental interactions.

The static potential between two heavy quarks is a fundamental quantity in QCD that enters the description of several measurable quantities such as threshold production of quark pairs and quark bound states. Though it is possible to compute this potential using perturbation theory, the complicated interactions amongst quarks and gluons pose a challenge. It took more than twenty years to reliably compute the second-order corrections to the potential after the first-order corrections were first computed in the late 1970s!

Writing in Physical Review Letters, two research groups have independently computed the third-order (three-loop) corrections to the interquark potential. This benchmark calculation was carried out by Alexander Smirnov and Vladimir Smirnov from Moscow State University, Russia, and Matthias Steinhauser from Karlsruhe Institute of Technology, Germany, and independently by Chihaya Anzai and Yukinari Sumino from Tohoku University and Yuichiro Kiyo from KEK, both in Japan. The two calculations agree with each other and provide state of the art results for a building block in many physical quantities, some of which are likely to be measured at a future electron-positron linear collider and the large hadron collider at CERN. The potential is also crucial for comparing perturbation theory with lattice simulations. – Abhishek Agarwal


More Features »


More Announcements »

Subject Areas

Particles and Fields

Previous Synopsis


Quiet cascade

Read More »

Next Synopsis

Related Articles

Viewpoint: Spinning Gluons in the Proton
Particles and Fields

Viewpoint: Spinning Gluons in the Proton

Computer simulations indicate that about 50% of the proton’s spin comes from the spin of the gluons that bind its quark constituents. Read More »

Synopsis: Neutrino Flashes from Exploding Stars

Synopsis: Neutrino Flashes from Exploding Stars

Calculations indicate that neutrino emission from a supernova could be detected on Earth, possibly revealing how the star explodes. Read More »

Synopsis: Model Tries to Solve Five Physics Problems at Once
Particles and Fields

Synopsis: Model Tries to Solve Five Physics Problems at Once

A minimal extension to the standard model of particle physics involves six new particles. Read More »

More Articles