Waves & Packets
Jul. 7, 2012

Discovery of Higgs-like particle opens new questions
Waves and Packets
This week, the ATLAS and CMS teams reported the discovery of what very well may be the long sought-after Higgs boson. But like all great discoveries there are many profound questions remaining that can actually be simply stated. Rolf Heuer, CERN's director-general, laid it out simply by saying, "Which Higgs?" Both Joe Incandela and Fabiola Gianotti talked about the need for more data. Yale University's Keith Baker points out that there is not yet enough data to determine the intrinsic spin and parity of whatever particle may be attributed to this excess. Also the gamma-gamma Higgs decay channel can have heavy states contributing to the process that signals new physics beyond even the Higgs itself.

But the "which Higgs" question raises the possibility of multiple Higgs, and that would be an extremely interesting result for theorists like Maryland's Jim Gates. Supersymmetry, which Gates first discussed in his 1977 Ph.D. thesis, demands multiple Higgs particles and their superpartners. On the NSBP blog Vector, several physicists discuss this new discovery, implications for SUSY and what comes next.More

Strands of dark matter that join galaxies and bind universe made 'visible'
Nature News
A giant string of invisible dark matter joining together two clusters of galaxies has been discovered, marking the first time [a dark matter filament] has been convincingly detected from its gravitational lensing effect. This discovery could eventually help astrophysicists to understand the structure of the universe and identify what makes up the mysterious invisible substance known as dark matter. The filament, discovered by an international team of astrophysicists, and reported in Nature, connects two huge clusters called Abell 222 and Abell 223, about 2.7 billion light-years away from Earth. The discovery follows from observations using the XMM-Newton spacecraft along with interpretations from the standard model of cosmology, which suggests that visible stars and galaxies trace a pattern across the sky that was originally etched out by dark matter.More

Particle physicists discover new Ξb baryon
American Physical Society
The CMS team is also celebrating the observation of a different new particle that they conclude is the Ξ b *0. The discovery is reported in Physical Review Letters. This particle is amongst a group of baryons, each of which comprises one strange quark, one b quark (meaning bottom or beauty), and a third quark. When the third member of the trio is an up or down quark, the particle is known as a Ξb baryon. The states of this group are predicted from the quark model along with their approximate masses, but the Ξ b *0 had not been experimentally seen. The Tevatron observed particle decays consistent with some of these states, but a full accounting was not available until enough data was collected by CMS. Larry Gladney, of the University of Pennsylvania, remarked to Waves and Packets that this result is important in that it verifies that the quark model extends to the b quark in all its particulars, and that measurements on these states agrees with calculations using lattice QCD.More

Researchers switch magnetic state and electric resistance of a single molecule on and off
Karlsruhe Institute of Technology
Researchers from France, Germany and Japan have developed a magnetic memory with one bit per molecule, and where the magnetic states can be exquisitely controlled by an electric field. As magnetic crystal memories decrease in size they become susceptible to superparamagnetic effect meaning that magnetic states can be changed simply through thermal fluctuations. When that happens, information can be lost. In the current work, reported in Nature Communications, the researchers placed a single magnetic iron atom in the center of an organic molecule consisting of 51 atoms. The organic shell protected the information stored in the central atom. Then by an electric field provided by the STM tip, the metal-organic molecule could be switched reliably between a conductive, magnetic state and a low-conductive, nonmagnetic state. This result opens up many possibilities as well as questions about how nature, including natural biological systems, might use electrical signals to control magnetic spin state and vice versa. More

The shape of superheavy nuclei
American Physical Society
The view of the nucleus as a sphere with various competing forces amongst the nucleons leads to a stability barrier where elements above Z=104 should not exist. However, some elements beyond this limit — known as "superheavy" — do, in fact, exist, albeit with very short lifetimes. These nuclei achieve their relative stability through a variety of effects, including departure from sphericity, pairing up of nucleons, and quantum-mechanical shell effects, in which large numbers of nucleons form into energetically favorable structures within the nucleus. To elucidate what some of these effects may be a team of physicists has reported the gamma-spectrum of the nucleus 256Rutherfordium (Z=104). This is the heaviest nucleus for which such spectra have been measured to date. In their results, which are reported in Physical Review Letters, they found a rapid increase of the moment of inertia in the nucleus (indicating a departure from spherical shape) at the upper end of the gamma-ray spectrum and the highest spins, an effect they attributed to a pair of nucleons breaking apart under the stress of rotation. This result opens up new challenges for describing nuclear shell-correction energy and describing how kinematic and dynamic moments of inertia are sensitive to the underlying single-particle shell structure.More

Physicists take 1st photo of a single atom's shadow
R&D Magazine
An international research team has been able to photograph the shadow of a single atom for the first time. In achieving this feat they may have reached the extreme limit of atomic microscopy. In experiments reported in Nature Communications, the team trapped single atomic ions of ytterbium and exposed them to 369.5 nm light. Under this light the atom's shadow was cast onto a detector, and a digital camera was then able to capture the image. Such experiments help confirm our understanding of atomic physics and may be useful for quantum computing. But this work is also important for its tests of the limits of microscopy, especially in correlating light absorption and image contrast. In biological microscopy, for instance, scientists want to use as much light as they can to see the structures, but too much UV or X-ray light will destroy the sample. These new results allow predictions of how much light is needed to observe processes within cells, under optimum microscopy conditions, without crossing the threshold and destroying them.More

New result helps cement brown dwarfs' 'failed star' status
Ars Technica
Brown dwarfs are chemically similar to stars, but are not massive enough to trigger nuclear fusion in their cores. However, the similarity in composition begs the question: Do they form the same way as stars? A new study published in Science argues that at least some brown dwarfs form from hydrogen cores, similar to protostars, but much less massive. This means that brown dwarfs and stars may fall along the same continuum in terms of how they begin, helping to clarify formation models and providing hints about the population of brown dwarfs in the galaxy.More

Maxwell's demon goes quantum, can do work, write and erase data
Ars Technica
A Maxwell demon is a hypothetical device that could recover useful work from entropic fluctuations. No such device has ever been constructed for a variety of reasons. But in a paper in the Proceedings of the National Academy of Sciences, theorists at the University of Maryland have proposed a quantum mechanical Maxwell-demonic device that would extract usable energy from thermal fluctuations, store information about its actions and then erase the memory. In principle, this demon could be used to control feedback, create nanoscale devices and perform other functions in contexts where thermal fluctuations are significant. Their hypothetical quantum system is described by three states and one bit variable. In the absence of interactions the system transitions between states randomly. But when coupled to a mass-loaded thermal bath and an information bit stream, directional biases resulted. The directional biases created feedback to the thermal bath which could then do work on the masses, and conditions on the information stream, i.e., what states can accept what information, created the ability for the system to act as "Landauer eraser," and the model offers a simple paradigm for investigating the thermodynamics of information processing by small systems. More

Photonics in automobiles: An Indian perspective
Optics and Photonics News
Traffic accidents kill more people than most diseases — and the roads in India are among the most dangerous in the world. CMOS-based vision sensors could help save lives by extending drivers' sight far beyond their mirrors and headlights, enabling them to react more quickly to potential hazards. The industry is moving towards technologies that provide panoramic vision and/or three-dimensional imaging, along with night vision ability and enhanced signal processing in order to allow for intelligent decisions with sensors.More

The curious case of disappearing dust
Astronomers are perplexed by the case of "first you see it, now you don't" when it comes to dust around the star, TYC 8241 2652. In an account reported in Nature, astronomers report that the dust had been present around the star since at least 1983 (no one had observed the star in the infrared before then), and it continued to glow brightly in the infrared for 25 years. In 2009, it started to dim. By 2010, the dust emission was gone; the astronomers observed the star twice that year from the Gemini Observatory in Chile, six months apart. An infrared image obtained by the Gemini telescope as recently as May 1 of this year confirmed that the warm dust has now been gone for 2 1/2 years. TYC 8241 2652 is believed to be a young analog of our sun that only a few years ago displayed all of the characteristics of hosting a solar system in the making. When the dust was first observed it was thought that planets were forming. But now the dust is gone and there are no compelling explanations as to where it went.

"The most commonly accepted time scale for the removal of this much dust is in the hundreds of thousands of years, sometimes millions," said study co-author Inseok Song. "What we saw was far more rapid and has never been observed or even predicted. It tells us that we have a lot more to learn about planet formation."More

Is there a link between lithium abundance, galactic chemical evolution and exoplanets?
Researchers have acquired spectra of the metallicity, temperature, surface gravity, mass and lithium abundance of 671 stars, plus added several hundred more to their dataset from prior reports, to address three questions about galactic and stellar evolution: (1) How is lithium depleted inside stars and how does the level of depletion depend on stellar characteristics? (2) How has the abundance of lithium changed over the history of the galaxy? and (3) How do planets influence the lithium abundance of their host stars? Lithium is a useful tool for constraining the ages and evolutionary history of stars since the element in primordial astronomers know how much lithium a star had when it formed. Current measurements indicate how much lithium has been lost, primarily through surface depletion. They found that 898 of their stars belong to the thin disk, 144 are part of the thick disk and 43 are halo stars. There is a slight hint that planets might affect the lithium abundance of stars within a narrow range of temperatures 5820-6190K. But more research is required before astronomers can provide further comments on the relationship between planets and lithium abundance in that narrow temperature window.More

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