An international collaboration of theoretical physicists, including Professor Chris Sachrajda from the University of Southampton, has published a new calculation that bolsters efforts to explain of the predominance of matter over antimatter in the universe.

The collaboration, known as RBC-UKQCD, includes scientists from the Brookhaven National Laboratory, CERN (the European particle physics laboratory), Columbia University, the University of Connecticut, the University of Edinburgh, the Massachusetts Institute of Technology, the University of Regensburg as well as Southampton.

Their results, published this month in the journal Physical Review D, have been highlighted as an Editor's Suggestion.

Professor Sachrajda, of the Southampton High Energy Physics theory group, explains: "Our current understanding is that the universe was created with almost equal amounts of matter and antimatter so that a difference between their interactions is required to have tipped the balance to favour matter over antimatter.

"Such tiny differences, called 'CP-violation', are a natural feature of the Standard Model of Particle Physics, and the aim of this project was to compute their effect in the decays of subatomic particles called kaons into two pions. Understanding these decays quantitatively and comparing the predictions with the experimental measurements made two decades ago at CERN and the Fermi National Accelerator Laboratory gives scientists a way to test our understanding of 'direct CP-violation'."

The results proved to be consistent with experimental measurements, thus significantly constraining models of 'new physics' attempting to explain phenomena such as dark matter which require physics beyond the standard model.

Professor Norman Christ, of Columbia University, says: "Any differences in matter and antimatter that have been observed to date are far too weak to explain the predominance of matter found in our current universe. Finding a significant discrepancy between an experimental observation and predictions based on the Standard Model would potentially point the way to new mechanisms of particle interactions that lie beyond our current understanding and which we hope to find to help to explain this imbalance."

To this end, following this pioneering work, the focus in the next two-to-three years will be to significantly improve the precision of the computations with the potential of revealing any sources of matter/antimatter asymmetry lying beyond the current theory's description of our world.

The final result depends on calculations performed in 2012 and 2015 which constituted the theses of Southampton PhD students Dr Elaine Goode and Dr Tadeusz Janowski.

The two pions into which the kaon decays can be in either of two channels; in one the interactions between the two pions are attractive and in the other repulsive. The earlier calculations were of the decays into the repulsive channel and the 2012 paper won the Kenneth Wilson Lattice Award for 'excellence in Lattice Field Theory'. The present calculation studies the decays into the attractive channel which required very significant additional theoretical and computational developments.

The difficulty of the calculation is due to the quarks, the constituents of the kaon and pions, interacting through the strong nuclear force. These strong interactions cannot be computed analytically and so to conquer the challenge the theorists used lattice Quantum Chromodynamics. This technique 'places' the particles on a space-time lattice of three spatial dimensions plus time.

Nevertheless, the computation required integrating 67 million degrees of freedom, performed using cutting-edge supercomputers, located in the USA, Japan as well as in the UK.

The University of Southampton’s Space Environment Physics (SEP) Group has been unravelling mysteries around space phenomena for over half a century.

The group is behind ground-breaking research into how our solar system works - with the promise of plenty more discoveries in years to come.

Dr Robert Fear, Associate Professor and Head of the SEP Group since 2013, says: "We look at the natural space environment, from the solar wind down to the upper levels of the atmosphere of Earth and other planets."

Key aspects of the SEP Group's work are driven by understanding the fundamental science, especially around the aurora and how the Earth’s magnetosphere behaves.

Dr Daniel Whiter, NERC Independent Research Fellow, specialises in researching the aurora and its effect on our planet. He is also behind the Aurora Zoo citizen science project.

Shockwaves in space are also of interest to the SEP Group. Dr Imogen Gingell, Royal Society University Research Fellow in Space Physics, is conducting research to understand what happens at shockwaves.

"Similar to when a fighter jet goes past there is a sonic boom - the solar wind gets deflected around bodies in the solar system," she says. "The solar wind is going faster than the speed of sound so you get a shockwave, called a bow shock."

Other magnetospheres in the solar system are also explored by the group. Dr Caitriona Jackman, Associate Professor, has explored how the magnetospheres of Mercury, Earth, Jupiter and Saturn work.

The SEP Group is keen to discover the impact of these natural processes on manmade technology, both in space and on the ground. To do this, it needs to understand 'space weather' - the changing environmental conditions in near-Earth space.

"Space weather can have an impact where we have anything long and metal, particularly at high altitudes," Robert explains. "It's an issue in places such as Canada and Scandinavia, where power grids, oil pipelines and rail infrastructure can get damaged by geomagnetic storms, and is recognised as an issue of growing importance in the UK."

Read more in the Summer 2020 edition of Re:action, the University’s research and enterprise magazine.

An international study led by the University of Southampton has demonstrated for the first time how light can be used to glue together negative charges and create a novel form of matter.

The ground-breaking research, led by Physics and Astronomy's Professor Simone De Liberato, opens new possibilities for engineering novel artificial atoms with designer electronic configurations.

Researchers built upon a theoretical prediction from 2019 to fabricate a nanodevice that trapped electrons within nanoscopic wells.

When photons struck the device with a high enough energy they would extract electrons from the wells. The team then enclosed the device between two gold mirrors, dramatically increasing the interaction between light and matter.

The study observed that a negatively-charged electron would remain trapped, bound to the other negatively-charged electrons in a novel electronic configuration like a 'subatomic zip tie' stabilised by the photon.

Scientists have published their findings in the journal Nature Physics.

The technique will be used to broaden the catalogue of materials available to design photonic devices.

Read the full story on the main news page.

Researchers from the University of Southampton are adapting imaging techniques used to study stars and galaxies to create medical camera systems that use lower doses of radiation.

Physics and Astronomy's Professor Tony Bird is working with specialists at University Hospital Southampton and University spin-out company Symetrica to develop the gamma-ray imaging that will improve the effectiveness of nuclear medicine.

Nuclear medicine is a specialised area of radiology that uses very small amounts of radioactive materials to examine organ function and structure using imagery from sensitive gamma-ray detectors.

Professor Bird, of the Southampton Astronomy Group, says: "The imaging systems we are using were developed for gamma-ray astronomy, where we try to study emissions from distant stars and galaxies. Because those emissions are so faint, our imaging systems (called 'coded masks') are designed to catch every gamma ray they can and are much more efficient than current collimators."

The collaboration is funded through the SPace Research and Innovation Network for Technology (SPRINT).

The University has also developed new software that can deal with a moving camera or patient, based on astronomical imaging allowing a telescope to move across the sky while still collecting information.

Read the full story in the latest edition of Re:action, the University's research and enterprise magazine.

Space physicist Dr Daniel Whiter is investigating the impact on our planet of the huge amounts of energy brought into our atmosphere by the aurora borealis, or Northern Lights.

The researcher at the University of Southampton is one year into a five-year fellowship from the Natural Environment Research Council.

The Northern Lights are caused by charged particles from space colliding with gas particles in the Earth’s atmosphere at 40 million miles per hour.

In order to understand how this energy impacts our planet and whether it could even be affecting our climate, Daniel is developing novel techniques to measure the temperature at auroral heights. This has never been done accurately before, as the altitude is too high for weather balloons but too low for spacecraft.

He is using sensitive cameras equipped with colour filters to map atmospheric temperature, similar to a thermal imaging camera. This is combined with radar measurements of the upper atmosphere to estimate the electrical conductivity, before a computer simulation helps understand how different types of aurora are produced, what electric currents they generate, and how the aurora affects the temperature and chemistry of the upper atmosphere.

“The aurora definitely heats the upper atmosphere,” Daniel says. “The Met Office is starting to expand its models to the upper atmosphere, as we are learning that there is more coupling between layers of the atmosphere than previously thought. We don’t know how it influences the Earth’s climate yet, but it’s something we, and the Met Office, want to understand.”

Read the full feature in the Summer 2020 edition of Re:action, the University’s research and enterprise magazine.