The Coolest Antiprotons

Earlier techniques cooled antiprotons with cold electrons, but the coldest antiproton temperature recorded with this method was about 100 kelvin. To turn down the heat, Hangst and colleagues used a technique called evaporative cooling, which had previously been used only for neutral atoms. “It’s exactly how your coffee cools itself,” Hangst says. “The steam above your coffee, those molecules are the hottest ones. They can escape from the coffee and carry away energy, so the coffee is absolutely colder.”

Meanwhile, protons are suddenly smaller: The proton shrinks in size

Pohl and his team have a come up with a smaller number by using a cousin of the electron, known as the muon. Muons are about 200 times heavier than electrons, making them more sensitive to the proton’s size. To measure the proton radius using the muon, Pohl and his colleagues fired muons from a particle accelerator at a cloud of hydrogen. Hydrogen nuclei each consist of a single proton, orbited by an electron. Sometimes a muon replaces an electron and orbits around a proton. Using lasers, the team measured relevant muonic energy levels with extremely high accuracy and found that the proton was around 4% smaller than previously thought.

Update (7/9) Chad has posted an excellent summary of the paper

Efficient nano motor cleverly harnesses light

Researchers at Lawrence Berkeley Labs and the University of California have made a new nanoscale motor that can drive a disc 4000 times bigger than itself. It is powered via the so-called “plasmonic effect” and could be used to manipulate ultra-small objects like DNA and for powering nanoelectromechanical machines (NEMS). At merely 100 nm across the motor looks like a tiny windmill, inspiring the researchers to dub it a “light mill”.
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In recent years researchers have discovered that they can increase the interactions between light and matter by taking advantage of the electrons that oscillate collectively at the surface of metals – called “surface plasmons”. Light fields are enhanced when they are resonant with these plasmons – an effect that has already been successfully used in techniques like single-molecule detection and surface-plasmon enhanced Raman spectroscopy (SERS).

Do bosons ever masquerade as fermions?

Bosons can pile on top of one another without limit, all occupying the same quantum state. At low temperatures, this causes such strange phenomena as superconductivity, superfluidity and Bose-Einstein condensation. It also allows photons of the same frequency to form coherent laser beams. Fermions, on the other hand, avoid one another. Electrons around a nucleus stack into shells instead of collapsing into a condensed cloud, giving rise to atoms with a great range of chemical properties.
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“If just one pair of photons out of 10 billion had taken the bait and behaved like fermions, we would have seen it,” English said. “Photons are bosons, at least within our experimental sensitivity.”