Cern physicists observe new difference between matter and antimatter

This is a piece from a few weeks ago for Wired – a bit of an exclusive – and either read it here in full or follow this link.Image

Even if the charismatic Professor Tara Shears laughs at the thought of there ever being enough antimatter in the world to make Star Trek’s warp drive a possibility, there is nevertheless something “boldly going” about her as she starts to explain to me the latest antimatter research results to be announced from Cern.

 The results come at the start of the “long shutdown” — two years during which the beam of the Large Hadron Collider is off, allowing it to have a £70m upgrade — and represent a success story for British science. Professor Shears is one of the leading British scientists at Cern and has recently broken new ground by becoming the first female professor of physics at the University of Liverpool.

“We have now had the very first observations of CP (charge parity) violation in Bs mesons,” Professor Shears tells me. “This is very exciting, as we expected to see it from our own predictions — and we did.”

Mesons are subatomic particles composed of one quark and one antiquark.

Observing charge parity (CP) violations, or the slight non-symmetrical behaviour of mesons, “helps us with one of the big mysteries of physics: why is there not more antimatter in the universe?”

According to Shears, CP violations were observed experimentally in kaons (or K mesons) in 1964, even if they had not been predicted. Since then, CP violation has also been seen in another type of meson (B) and looked for in D mesons. Until recently it had not been observed in a fourth similar particle — the Bs meson — owing to the lack of a powerful enough accelerator to create the number of collisions necessary to see CP violations.

“So the LHCb [Large Hadron Collider beauty experiment] saw hints of this non-symmetrical behaviour between B mesons and their antimatter twins in 2011 but there wasn’t enough evidence.”

The LHCb is one of four main experiments sited at the Large Hadron Collider. About 25 percent of the scientists working on the LHCb are from British universities. British universities also built major parts of the vital RICH and VELO particle detectors that make these measurements possible.

“Since then we have completed a massive task of processing over 70 trillion proton collisions from the Collider and the results have now passed our gold standard for accuracy. This means that there is a less than 1 in 1.7m chance that they have got it wrong.”

For Shears the significance of these results is that “while it is verification of the validity of the Standard Model of physics as it was predicted, it has pushed us further in our search for the unexplored beyond it. At the same time as keeping us guessing by not giving us any answers as to what might be out there.”

The Standard Model of physics is the kind of physics that we learned at school: how electromagnetic and subnuclear reactions influence the movement of subatomic particles.

The “new physics” is what might explain the things the Standard Model cannot, such as the nature of dark matter and where all the antimatter went.

After all, “the interesting thing” is that half the universe was made up of antimatter at the time of the Big Bang and that a very small difference in behaviours between means that “there was a tiny amount of matter left over to give us our universe”.

“However,” says Shears, “while these results match our theories and experimental data from different facilities and times, the amount of violations is not sufficient to account for the amount of antimatter required to be at the Big Bang.”

For Professor Shears, who is rapidly becoming the go-to scientist to explain all things Cern it was this desire to find the answers to the big questions in physics that propelled her from the local comprehensive in rural Wiltshire to “the baptism of fire” of being the only girl in her A level physics class at the independent Dauntsey’s School, and from there to study physics at Imperial College London followed by a PhD in particle physics at Cambridge.

She was drawn to particle physics in particular because “you can’t get anything more fundamental than that. If you are really trying to understand something the most natural approach is for me to unwrap it and look at its constituent parts.

However, she says, “I learnt my craft at Cern back in the 1990s”, when she worked on the forerunner to the LHC, the LEP, a particle collider with much lower energy that looked at electrons.

Then in 2000 she won a Royal Society University Research Fellowship and went to work at the Fermilab particle physics facility near Chicago, where she continued to explore her research on high energy particle physics.

Four years later she was back at Cern, joining the LHCb experiment at the Large Hadron Collider particle accelerator, which was investigating differences between matter and antimatter, and testing the Standard Model of particle physics. Her own particular research focuses on exploring electroweak forces.

 “Cern is a wonderful place,” Shears says. “It is great to be able to do some fantastic science in such a great setting where there are so many nationalities (including a North Korean) without politics and with a common aim.”

“Yes, there is competition to get there first, but there is also a need to collaborate because of the hundreds of people needed to run our experiments.”

This sense of collaboration extends to the 650 members of the LHCb experiment who have to approve research before it is published.

“The hundreds of very high achievers at Cern keep trying to come up with cleverer and better ways of doing things. We urge each other on.”

Shears says that “yes, it is male” but that “there are women everywhere”, and the fact that it “really has changed” is noticeable when “you look back at documentaries shot in the 1980s at Cern and you can see how few women there were then.”

“Now there is a higher percentage of women” but it is “still not enough”, she admits.

“However, it was quite a shock to realise that I was the first female professor of physics at Liverpool. I think this is a positive sign that more and more women follow physics, and that times have definitely moved on from the days of gentleman scientists. There are quite a few women in our department and if I can get here, so can they.”

For Professor Spears the application of this antimatter research is not about interstellar space travel. It is about saving lives.

“Warp drives are unfeasible as antimatter is the most expensive substance ever made,” she says. “It takes hundreds of millions of Swiss francs to make a billionth of a gram of antimatter and it would in all likelihood take us until the end of time to make as much antimatter as a banana gives off.”

So while mixing matter and antimatter together may have been a very efficient power source for the Enterprise, in real life “there has to be a cheaper and quicker alternative for space travel”.

However, by harnessing the power of antimatter in a PET (Positron Emission Tomography) scan it shows that this research can be used to save people’s lives as well as search for the origins of the universe as it in effect “shines a torch on their illness as “the patient drinks a radioactive dye that gives off positrons or anti matter electrons that are soaked up disproportionately by tumors.”

For Professor Spears who will likely be appearing on a TV screen new you soon, the results announced today are only the start of the journey “that will see us trying to get more hints about what lies beyond the Standard Model”.

The future of the LHCb after the long shut down is not just take to take data at a higher energy [power output will almost double] but to take more data so we can examine the nature of CP violation in great depth. “And help us get a handle on the new physics.”

“If that does sound very Star Trek it is because, she says, they share “the same very optimistic view of the future”.


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