A team of theoretical physicists in the Fermilab Lattice and MILC Collaboration has pioneered a new high-precision computation that could significantly advance the indirect search for new physical theories beyond the Standard Model (SM). This preconception of calculation applies to a particularly rare decay of a subatomic particle, the B meson, which sometimes known as “penguin decay” process.
Problems with the Standard Model
On 8 October 2013, the Nobel prize in new physical innovation was awarded jointly to François Englert and Peter Higgs for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles. As scientists at CERN have announced a breakthrough in Higgs boson research, “last missing piece”, that Standard Model was finally completed. The SM of particle physics now accounts for all known subatomic particles and acceptably rationalises their mutual interactions.
It is a highly successful theory, in that its predictions have been verified regularly by numerous experimental measurements. However, despite being the most triumphant theory of particle physics to date, the Standard Model does not always tell the whole story. As there are numerous enigmatic occurrences in the vast cosmos that baffling researches around the globe for decades and they are desperate to unravel physics beyond the SM, a description of particles and their interactions.
The Standard Model is inherently an incomplete mystery. There are fundamental physical phenomena in nature that the SM does not adequately explain.
• Gravity. The Standard Model is widely considered incompatible with the most successful theory of gravity to date, ‘general relativity’. The approach of graviton to the Standard Model does not recreate what is observed experimentally without further modifications.
• Dark Matter. Cosmological observation tells us the Standard Model represents only 5% of the energy presenting in the universe. About 26% should be the dark matter which only interacts weakly with the SM field. Yet, the Standard Model does not supply any fundamental particles or notions that are considered acceptable dark matter candidates.
• Matter-antimatter asymmetry. The SM predicts that matter and antimatter should have been produced in equal amounts if the conditions of the universe involve disproportionate matter relative to antimatter. Yet, there is no mechanism in the SM to sufficiently explain this asymmetry.
“We have reason to believe that there are yet undiscovered subatomic particles that are not part of the SM,” explains Fermilab scientist Ruth Van De Water. “Generally, we expect them to be heavier than any subatomic particles we have found so far. The new particles would be part of a new theory that would look like the SM at low energies. Additionally, the new theory should account for the astronomical observations of dark matter and dark energy. The particle nature of dark matter is a complete mystery.”
B-meson rare Decay
Scientists are taking the initiative in this problem from several directions. Indirect searches focus on the formation of virtual effects on conjectured new heavy particles in the low-energy process. Direct searches look for the production of new heavy particles in high-energy collisions. The application of both indirect and direct searches methods may ultimately provide us with sufficient indication of the underlying theory that could clarify all of these phenomena.
Predicting the fundamental properties of subatomic particles before their experimental discovery has been a big challenge for physicists. Yet, the discovery of many mesons and baryons since the middle of the 20th Century has engaged in a crucial role in understanding the nature of strong interaction. Syracuse University physicist John “Jack” Laiho describes why “penguin decay” might provide powerful probes for new physics. The contributions from the SM are relatively minor, there is a good possibility that the influences of new virtual heavy particles could lead to observations of physic beyond that of the Standard Model in future experiments. However, B-meson rare decay requires high precision in both the experimental measurements and calculations.
The strange and subtle behaviours of particles namely ‘B mesons’, whose properties make them ripe for observing the effects of new physics. Physicists assemble data on rare decay of B mesons to make a precise measurement of how it decays into known particles, searching for the tiny discrepancy that would reveal the influence of the hypothetical heavy elements. Each anomaly signals the existence of the same exotic new matters. Its identities are not yet classified, but candidates include a heavier type of Z boson or a ‘leptoquark’ Most of the variations are just a few standard deviations away from expectations, and far from the five deviations that physicists require to declare the discovery.
The Introduction of Lattice QCD
CDF physicists have previously measured the rate of the matter-antimatter transitions for the B mesons, which compose of a heavy bottom quark bound by the strong nuclear interaction to a strange antiquark. This strong interaction is mediated by particles called gluon, which are hypothetical massless subatomic elements that transmit the force binding quarks together. The complex theory which describes the action of the strong force is Quantum Chromodynamic (QCD), which can be solved analytically at very high energies where the strength of the interaction is quite small. Decay processes that involve a bound state of quarks require contributions from the strong interactions, which are relatively difficult to compute at low energies. The numerical implementation of QCD on space-time lattices (LQCD) is the only first method for calculating the elements of subatomic particles containing quarks with controlled errors. Lattice QCD also plays an important role in advancing our understanding of matter under high temperature and density similar to the conditions in the early stages of the universe.
The property of QCD makes it extremely complex, where the theory is formulated on the four-dimension space-time lattice. It is computationally demanding, requiring the use of large-scale computational resources. “Fortunately, we were able to leverage supercomputing resources across the U.S. for this project,” comments Indiana University physicist Steven Gottlieb. This programme also involves a large effort from Fermilab Lattice and MILC Collaboration to produce precise theoretical calculations of the strong interaction effects during the decaying process of subatomic particles. “We used allocations at Fermilab (provided by the USQCD Collaboration), at the Argonne Leadership Computing Facility, the National Energy Research Scientific Computing Center, the Los Alamos National Laboratory, the National Institute for Computational Science, the Pittsburgh Supercomputer Center, the San Diego Supercomputer Center, and the Texas Advanced Computing Center.”
The recent measurements are compatible with the SM prior predictions, with corresponding uncertainties from theory and experiment. The observations will draw a more in-depth comprehension of the quantum theory field, the strong interaction governing the structure of subatomic matters. Likewise, this decay postulates the great potentiality in the quest of the existence of a new fundamental theory that lies beyond the SM.
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