A Subatomic Challenge Resolved: Supercomputer Calculations Produce the First Accurate Theoretical View of the Sigma Meson
A Subatomic Challenge Resolved: Supercomputer Calculations Produce the First Accurate Theoretical View of the Sigma Meson
The Science
The quarks and gluons that stick together to form the protons and neutrons of the atomic nucleus can also assemble to form other particles. All particles made up of two or more quarks held together by the strong force are called hadrons. Other than protons and neutrons, hadrons include some relatively long-lived particles such as the low-mass pion. But other hadrons, like the sigma meson, exist only for a fleeting moment before decaying into a pair of pions. Nuclear physicists recently combined modern supercomputer calculations with more traditional theoretical tools to study the sigma meson.
The Impact
Scientists think that the sigma particle plays a significant role in many nuclear physics processes. For instance, it may be part of the interactions between protons and neutrons. The sigma is the lightest unstable particle built from quarks and gluons, and it has an extremely short lifetime that makes it difficult to study reliably even with modern supercomputer simulations. In this study, researchers introduced additional calculation tools that consider fundamental symmetries of nature. This step helps to overcome the challenges of studying sigma particles. The result is the first accurate theoretical view of the sigma as a system of quarks and gluons.
Summary
In this research, nuclear physicists computed the formation of the sigma particle directly from quantum chromodynamics (QCD), the theory that describes quarks and gluons. The lattice approach to QCD uses supercomputers to calculate pion-pion scattering, but this approach sacrifices certain fundamental symmetries. This study reintroduced these symmetries by using traditional mathematical tools. This novel combination led to results for properties of the sigma of unprecedented accuracy. This research was initiated by the Exotic Hadron (ExoHad) Topical Collaboration as a proof of concept. The collaboration’s goal is to bring together theorists specializing in the computational and mathematical techniques needed to solve complicated research problems. The study was enabled by combining efforts with the computing resources from the Scientific Discovery through Advanced Computing (SciDAC) program.
Because pairs of pions are ubiquitous in accelerator experiments, a reliable understanding of the sigma aids research at Thomas Jefferson National Acceleratory Facility’s Continuous Electron Beam Accelerator Facility and other accelerator facilities worldwide. Future calculations will build off this study to explore the distribution of quarks and gluons inside the sigma, providing a complete understanding of the lightest unstable hadron.
Contact
Arkaitz Rodas Bilbao
Thomas Jefferson National Accelerator Facility and Old Dominion University
Funding
This material is based on work supported by the Department of Energy (DOE) Office of Science, Office of Nuclear Physics and the computing resources from the Scientific Discovery through Advanced Computing (SciDAC), as well as the Exascale Computing Project. Computing time was provided under the USQCD Initiative, an ALCC award, and the INCITE program at Oak Ridge National Laboratory. This research is also part of the Blue Waters sustained-petascale computing project, which is supported by the National Science Foundation and the state of Illinois. This research used resources from the National Energy Research Scientific Computing Center (NERSC). The Texas Advanced Computing Center (TACC) at The University of Texas at Austin also provided high performance computing resources.
Publications
Rodas, A., Dudek, J., and Edwards, R.G., Determination of crossing-symmetric pipi scattering amplitudes and the quark mass evolution of the sigma constrained by lattice QCD. Physical Review D 109, 3 (2024). [DOI:10.1103/PhysRevD.109.034513]
Related Links
Pooling Skills to Study a Slippery Particle, Jefferson Lab news release
Highlight Categories
Program: NP
