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Category: particle physics – Page 535

It sounds like the start of a very bad physics riddle: I’m a particle that really isn’t; I vanish before I can even be detected, yet can be seen. I break your understanding of physics but don’t overhaul your knowledge. Who am I?

It’s an odderon, a particle that’s even more odd than its name suggests, and it may have recently been detected at the Large Hadron Collider, the most powerful atom smasher, where particles are zipped at near light speed around a 17-mile-long (27 kilometers) ring near Geneva in Switzerland.

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The most popular contender over the past few decades has been string theory, and the related concepts of superstring theory and M-theory, in which particles are considered as tiny units of one-dimensional string. However, a lesser-known theory has also gained traction; loop quantum gravity (LQG), which attempts to solve the quantum gravity problem by focusing on the very fabric of spacetime, rather than the particles themselves.

In “Quantum Space,” the popular-science writer Jim Baggott lays out the basic principles of LQG for science enthusiasts. The book looks at how loop quantum gravity has emerged by following the work of two of its leading proponents, Carlo Rovelli and Lee Smolin, and assesses where the theory is now, and where it might be going.

Although the concepts are — not surprisingly — mind-boggling, Baggott asks deep questions about the nature of the universe, what space is actually composed of, and the existence of time itself. (The book covers a lot of challenging material, however, and some prior reading may help readers find their way.)

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When a particle is completely isolated from its environment, the laws of quantum physics start to play a crucial role. One important requirement to see quantum effects is to remove all thermal energy from the particle motion, i.e. to cool it as close as possible to absolute zero temperature. Researchers at the University of Vienna, the Austrian Academy of Sciences and the Massachusetts Institute of Technology (MIT) are now one step closer to reaching this goal by demonstrating a new method for cooling levitated nanoparticles. They now publish their results in the renowned journal Physical Review Letters.

Tightly focused can act as optical “tweezers” to trap and manipulate tiny objects, from glass to living cells. The development of this method has earned Arthur Ashkin the last year’s Nobel prize in physics. While most experiments thus far have been carried out in air or liquid, there is an increasing interest for using to trap objects in ultra-high vacuum: such isolated particles not only exhibit unprecedented sensing performance, but can also be used to study fundamental processes of nanoscopic heat engines, or phenomena involving large masses.

A key element in these research efforts is to obtain full control over the particle motion, ideally in a regime where the laws of quantum physics dominate its behavior. Previous attempts to achieve this, have either modulated the optical tweezer itself, or immersed the particle into additional light fields between highly reflecting mirror configurations, i.e. optical cavities.

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Everything you see around you is made up of elementary particles called quarks and leptons, which can combine to form bigger particles such as protons or atoms.

But that doesn’t make them boring – these subatomic particles can also combine in exotic ways we’ve never spotted.

Now CERN’s LHCb collaboration has announced the discovery of a clutch of new particles dubbed “pentaquarks”. The results can help unveil many mysteries of the theory of quarks, a key part of the standard model of particle physics.

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If you throw a ball at a wall, it’s going to bounce back at you – that’s classical physics at work. But of course, the world of quantum physics is much spookier, so if you did the same with a particle, there’s a chance that it will suddenly appear on the other side. This is thanks to a phenomenon known as quantum tunneling, and now a team of physicists has measured just how long that process takes.

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