An international team of scientists from RIKEN at Brookhaven National Laboratory (BNL) and elsewhere in the USA, Japan and the UK are testing the Standard Model—the foundation of high-energy physics that unifies three of the four known forces found in nature—by calculating a well-known nuclear decay process (1).
Summarizing the work, Thomas Blum, a member of the team, says: “We want to understand the structure of the particles in the nucleus from the standpoint of the Standard Model, in general, and quantum-chromodynamics (QCD), in particular. QCD is the theoretical basis for the strong force between quarks, the particles that make up neutrons, protons and other particles that are the building blocks of matter in our universe.”
Most of the predictions of the Standard Model, which was developed in the 1960s, can only be tested at high-energy particle accelerators, such as CERN in Switzerland, or the Relativistic Heavy Ion Collider (RHIC) at BNL in the USA. In contrast, beta decay in radioactive nuclei is a well-known process that can be measured, extremely accurately, with a simple experimental set-up. Beta-decay occurs when a neutron emits an electron and a massless particle called a neutrino (Fig. 1). In so doing, the neutron turns into a proton.
Blum and colleagues calculated the part of the decay rate of the neutron that depends on QCD, using a numerical method called ‘lattice gauge theory’ in which each point on a grid corresponds to a point in space–time. By solving the problem on successively finer grids, the calculations approach the true ‘continuum limit’ of the real world. The state-of-the-art calculations were made possible through the use of the QCDOC supercomputers at Columbia University, the RIKEN BNL Research Center, and the University of Edinburgh.
Most implementations of lattice gauge theory correspond to three spatial dimensions and one time dimension, but Blum and his colleagues use a ‘mathematical trick’ called ‘domain wall fermions’. They perform their calculations in four space dimensions—only reducing their answer back to the three-dimensional world at the end. The trick allows the group to capture important physics that most three-dimensional theories cannot.
An important aspect of the work lies in being able to test a sophisticated numerical technique that is consistent with the Standard Model and QCD against a simple result—neutron beta-decay. Confirmation that their results are accurate gives theorists the confidence to pursue increasingly complex problems in particle and nuclear physics.
1. Yamazaki, T., Aoki, Y., Blum, T., Lin, H.W., Lin, M. F., Ohta, S., Sasaki, S., Tweedie, R.J. & Zanotti, J.M. Nucleon axial charge in (2+1)-flavor dynamical-lattice QCD with domain-wall fermions. Physical Review Letters 100, 171602 (2008).
4D imaging with liquid crystal microlenses
20.11.2019 | American Chemical Society
Outback telescope captures Milky Way center, discovers remnants of dead stars
20.11.2019 | International Centre for Radio Astronomy Research
Conventional light microscopes cannot distinguish structures when they are separated by a distance smaller than, roughly, the wavelength of light. Superresolution microscopy, developed since the 1980s, lifts this limitation, using fluorescent moieties. Scientists at the Max Planck Institute for Polymer Research have now discovered that graphene nano-molecules can be used to improve this microscopy technique. These graphene nano-molecules offer a number of substantial advantages over the materials previously used, making superresolution microscopy even more versatile.
Microscopy is an important investigation method, in physics, biology, medicine, and many other sciences. However, it has one disadvantage: its resolution is...
Nanooptical traps are a promising building block for quantum technologies. Austrian and German scientists have now removed an important obstacle to their practical use. They were able to show that a special form of mechanical vibration heats trapped particles in a very short time and knocks them out of the trap.
By controlling individual atoms, quantum properties can be investigated and made usable for technological applications. For about ten years, physicists have...
An international team of scientists, including three researchers from New Jersey Institute of Technology (NJIT), has shed new light on one of the central mysteries of solar physics: how energy from the Sun is transferred to the star's upper atmosphere, heating it to 1 million degrees Fahrenheit and higher in some regions, temperatures that are vastly hotter than the Sun's surface.
With new images from NJIT's Big Bear Solar Observatory (BBSO), the researchers have revealed in groundbreaking, granular detail what appears to be a likely...
The Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM in Dresden has succeeded in using Selective Electron Beam Melting (SEBM) to...
Carbon nanotubes (CNTs) are valuable for a wide variety of applications. Made of graphene sheets rolled into tubes 10,000 times smaller than a human hair, CNTs have an exceptional strength-to-mass ratio and excellent thermal and electrical properties. These features make them ideal for a range of applications, including supercapacitors, interconnects, adhesives, particle trapping and structural color.
New research reveals even more potential for CNTs: as a coating, they can both repel and hold water in place, a useful property for applications like printing,...
15.11.2019 | Event News
15.11.2019 | Event News
05.11.2019 | Event News
20.11.2019 | Life Sciences
20.11.2019 | Physics and Astronomy
20.11.2019 | Health and Medicine