thenewenlightenmentage:

Electrons in Concert: A Simple Probe for Collective Motion in Ultracold Plasmas

(PhysOrg.com) — Collective, or coordinated behavior is routine in liquids, where waves can occur as atoms act together. In a milliliter (mL) of liquid water, 10²² molecules bob around, colliding. When a breeze passes by, waves can form across the surface. These waves are not present in the same volume of air, where only 10¹⁹ gas molecules randomly move about.

Do such waves occur in plasmas, the most prevalent state of matter in the universe? Like gases, they are made of particles bumping around in a shapeless glob. However, plasma densities can range from 10²⁶ atom/mL all the way down to much less than 1 atom/mL. Wave-like features that occur even at such miniscule densities are one key feature of plasmas.

Unlike in liquids, these “waves” happen in plasmas because the particles are charged, thus exerting strong forces on each other, even at large distances. But not all seas of charged particles are plasmas. What makes a plasma a plasma is the organized behavior of the charged particles.

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laboratoryequipment:

Proton Beams Create New States of Matter

By focusing proton beams using high-intensity lasers, a team of scientists have discovered a new way to heat material and create new states of matter in the laboratory. Using the Trident sub-picosecond laser at Los Alamos, the team generated and focused a proton beam using a cone-shaped target. The protons were found to have unexpectedly curved trajectories due to the large electric fields in the beam. A sheath electric field also channeled the proton beam through the cone tip, substantially improving the beam focus.

Read more: http://www.laboratoryequipment.com/news-Proton-Beams-Heat-Material-Create-New-States-of-Matter-120611.aspx

New Twist in the Search for Dark Matter

New research using observations from dwarf galaxies has set a lower limit on the mass of dark matter particles. But the results contradict findings from several previous experiments, which observed dark matter particles with masses below this threshold.

Dark matter is an invisible substance found throughout the universe that doesn’t emit any light. Scientists know that if dark matter exists, then so does anti-dark matter, and putting the two together will cause them to annihilate each other and produce gamma radiation.

“We are looking for this byproduct of the annihilation,” said physicist Savvas Koushiappas of Brown University in Providence, Rhode Island, who co-authored one of the papers, which will both be published Dec. 1 in Physical Review Letters.

(via kenobi-wan-obi)

Signal of Destroyed Dark Matter Seen in Space Telescope’s Data

In 2008, the Italian satellite PAMELA picked up an unusual signal: a spike in antimatter particles whizzing through space. The discovery, controversial at the time, hinted that physicists might be coming close to detecting dark matter, an enigmatic substance thought to account for 85% of the matter in the universe. Now, new data from NASA’s Fermi Gamma-ray Space Telescope confirm the spike. Alas, they also undermine its interpretation as a sign of dark energy.

Physicists hope they might use the accumulating data on antimatter to home in on the mass of the weakly interacting massive particle (WIMP), which is thought to be the fundamental dark matter particle. The expected signal would be a steady rise of positrons over a given range of energies, followed by a sudden drop-off. Noting the energy level—physicists measure this in billions of electron volts—at which the positron signal drops off would allow physicists to calculate the WIMP’s mass.

After the excitement generated by the PAMELA result, Stanford University physicists Stefan Funk and Justin Vandenbroucke wanted to zero in on the positron signal. They found a way to do so, using Earth itself as a particle filter. “You can basically look in certain directions from which only electrons or only positrons will get through the Earth’s magnetic field,” Vandenbroucke says.

Funk and Vandenbroucke’s method, which has been submitted to Physical Review Letters, confirmed the Italian result. That is, that the relative abundance of positrons seems to rise from 20 billion to 100 billion electron volts. And for the first time, the researchers showed that the signal continues to get stronger up to 200 billion electron volts. If what they’re seeing are remnants of dark matter deaths, then the mass of the WIMP would have to be at least 100 times that of a proton, which is within many theoretical predictions.

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(via kenobi-wan-obi)