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Galaxy’s tug changes particles’ ways
Posted: 15 July 2011

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The reasoning behind why different amounts of matter, and associate antimatter, has survived the birth of our Universe may just have been solved by a physicist of the University of Warwick.

The two forms differ in the sense that matter is composed of regular particles, whereas antimatter is made up of antiparticles.

Mark Hadley of the university’s Department of Physics, believes that he has found a testable explanation for what is known as apparent Charge Parity (CP) violation where parity is preserved, but the violation is made all the more of a reasonable explanation for the divide between matter and antimatter. CP violation is  a particle physics theory where the laws of physics are violated if a particle were interchanged with its antiparticle (a particle which has the same mass but opposite charge) in charge conjugation symmetry, and left and right are swapped in what is referred to as (parity symmetry). The violation was uncovered in 1964 via the decays of neutral kaons, a particle understood to contain a strange quark paired with an up or down antiquark, resulting in its discoverers, James Cronin and Val Fitch, obtaining a Nobel Prize in Physics in 1980.

Artist’s impression of the frame dragging effect of a galaxy on a grid with particle decay trails superimposed on top. Image: University of Warwick/Mark A Garlick.

In recent years, experimental observations of kaons and B-mesons (a subatomic particle composed of a bottom quark or bottom antiquark) have illustrated notable differences in how their matter and antimatter versions decay. With this, CP is therefore violated, presenting itself as an awkward anomaly for some scientists but simultaneously revealing itself as useful in attempting to explain why more matter than antimatter appears to have survived the turbulence that was the birth of our Universe.

However, Hadley, whose research paper has been published in Europhysics Letters, believes that while trying to solve this problem, scientists have neglected an important factor; the impact of the rotation of our Galaxy and its influence on how subatomic particles break down. “Nature is fundamentally asymmetric according to the accepted views of particle physics. We watch what elementary particles do and we find that some patterns of interactions and decays exist, but the mirror image pattern is absent and this means that there is a clear left-right asymmetry in weak interactions and a much smaller CP violation in kaon systems,” says Hadley. “These have been measured but never explained.”

“This research suggests that the experimental results in our laboratories are a consequence of galactic rotation twisting our local space-time,” he says. “If that is shown to be correct then nature would be fundamentally symmetric after all. This radical prediction is testable with the data that has already been collected at CERN and BaBar by looking for results that are skewed in the direction that the galaxy rotates.” Although it is considered easy to overlook the bigger picture and neglect the effects of something as large as our Galaxy’s effects on us when we have the Sun close by, Hadley believes that the effect generated by a massive spinning body is highly important.

An artist’s conception of the Milky Way galaxy, whose twisting effect is said to be responsible for the differing ways in which the particles decay. Image: Nick Risinger.

It is this effect that generates a speed and angular momentum that drags the reference frame of local space and time, twisting its shape and generating time dilation effects. Due to its size in comparison to the Earth, the Milky Way galaxy has a tugging effect so strong that it is a million times greater than that caused by the spin of our home planet. The frame dragging of the whole Galaxy, according to Hadley, explains the observations of CP violation in the decay of B mesons; where the key difference between the break-up of matter and antimatter versions of the same particle lies in the variation of the decay rates. The combination of the decay rates combined, however, equal the same total for both matter and antimatter types of the same particle which also retain the same structure, becoming mirror images of each other.

Expecting these particles to begin in this state is one expectation, but how they end up after their decay is quite another and it is the tug of the galactic frame which is held responsible. The twisting causes the different structures in each particle to experience different levels of time dilation and therefore decay in different ways, although overall variation of the varying levels of time dilation evens out when considering particles individually and CP violation disappears conserving parity. A massive advantage to the theory is that it can undergo tests and this up-side has not gone unnoticed – large arrays of data are very real, illustrating apparent CP violation in some decays, which can be re-examined to find a pattern that is aligned with the rotation of the galaxy.

While Hadley’s paper, entitled The asymmetric Kerr metric as a source of CP violation , only explains how galactic frame dragging could explain the experimental observations of CP violation, it provides a lead to scientists who regard the violation theory as a useful tool to explain the separation of matter and antimatter at the birth of our Universe.

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