Theoretical framework enables more accurate estimation of elementary particle properties

March 20, 2015, RIKEN
The latest experimental measurements of the properties of muons using particle accelerators yield results that differ from those predicted by the standard model of physics. Credit: © -Dant-/iStock/Thinkstock

The 'standard model' of physics is currently our best description of elementary particles and their interactions. Yet experimental results sometimes differ from the model's predictions, tantalizingly suggesting that more remains to be discovered. A theoretical framework developed by an international research team that includes scientists from RIKEN has now closed the gap between predicted and experimentally measured values of the properties of the elementary particle known as the muon.

The carries the same electric charge as an electron but is 200 times more massive. Another important property is its magnetic dipole moment, which makes the particle behave like a tiny magnet. In classical physics, the strength of the muon magnet is exactly 2 Bohr magnetons—the fundamental unit of magnetism. According to , however, the muon emits and absorbs many different elementary particles. "Each particle species adds a small additional contribution to the muon's ," says Taku Izubuchi, part of the research team and a member of the RIKEN Brookhaven National Laboratory Research Center in the United States.

Several research groups have measured the magnetic strength of a muon using particle accelerators. The most recent of these experimental measurements have found that the magnetic strength is significantly higher than that predicted by theory. Exploring this anomalous muon magnetic moment could help scientists understand the limitations of the standard model. Improved experimental facilities are currently being built in the United States and are planned for Japan, but more accurate and reliable theoretical predictions are also required.

Izubuchi and his co-workers developed a theoretical approach that estimates the more accurately by considering the contribution of elementary particles called quarks.

While the contributions of particles such as electrons and photons are described by quantum electrodynamics, the forces between quarks are described using a theory known as quantum chromodynamics. "We have been studying how to reliably compute the quantum chromodynamics contribution using a large-scale numerical computation method called lattice quantum chromodynamics," explains Izubuchi.

The researchers show that their approach can give realistic solutions with systematically reduced errors using only modest computing resources. The initial results raise the hope that a more complete calculation may be possible in the future.

"Our calculation is just a beginning," says Izubuchi. "Yet our method of using lattice quantum chromodynamics and quantum electrodynamics is a promising way to provide the theoretical value with enough accuracy to confront the near-future experiment with greater accuracy."

Explore further: 10-year study reveals incredible level of accuracy to estimate intrinsic magnetic properties of two subatomic particles

More information: Blum, T., Chowdhury, S., Hayakawa, M. & Izubuchi, T. Hadronic light-by-light scattering contribution to the muon anomalous magnetic moment from lattice QCD. Physical Review Letters 114, 012001 (2015). DOI: 10.1103/PhysRevLett.114.012001

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5 / 5 (2) Mar 20, 2015
not falsifiable.

It doesn't have to be; it's not a theory. It's a method of calculation to get more accurate results from the existing theories.
not rated yet Mar 21, 2015
The resolution of the Proton Radius Puzzle is the diffraction pattern, giving another wavelength in case of muonic hydrogen oscillation for the proton than it is in case of normal hydrogen because of the different mass rate.
not rated yet Mar 23, 2015
It is a deep intellectual error to think that, at the very starting point of matter, its elementary building blocks would have such a complex structure as the standard model gives them. The complexity of the structure of elementary particles from the standard model is highly unrealistic and artificial. The quark model of elementary particles has no reductive power. It appeals to 60 primary elements or key states: 36 different quarks (6 families of tri-chromatic quarks and antiquarks), and 24 different gluons (8 tri-chromatic types). Thus, it has no horizon of being unitary, moreover being conceptually quite puzzling. Frank Wilczek, Nobel laureate, 2004, said: "from the perspective of QCD, the foundations of nuclear physics appear distinctly unsound".
not rated yet Mar 23, 2015
Higher the complexity of fundamentals and of descriptive mathematics, lower the probability of coincidence with physical reality, and farther from its reliable description. In our opinion, quarks, with their colours, fractional charges, counterfeit masses, and the eight types of gluons, are the equivalent of the epicycles, the deferents, the equant and the circular orbits of the Ptolemaic system. As long as the quark model will remain an enforced mainstream model, ahead standpoints will be inhibited. The official symptomatic omission of straightforward deductions challenging the Standard Model, is an inappropriate, counterproductive strategy.
not rated yet Mar 23, 2015
Many theoretical physicists are much satisfied with the Standard Model. However, at long run so much complacency is not advisable. What they have really proved in excellence is their expertise in adjusting data. Though, math, which is certainly a key tool in physics, is however a human development (and perhaps of some civilized sympathetic aliens too!). As such, it can serve as well to describe physical reality as to falsify it. Nature does not know about math, it is just due to physical interactions. In its endless chores it makes no calculation, it only interacts, otherwise it would be as clumsy as we are, and most of the time would be wrong or not know what to do, just like us. In our opinion this tendency to equate mathematics with physical reality is a subtle form of animism, but this is another story. Certainly, physical laws do not depend on our math to know how to operate, and when we change them they do not vary accordingly in order to please us.

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