Waves & Packets
Apr. 27, 2013

LHCb experiment observes new matter-antimatter difference
CERN Press Office
The LHCb collaboration has made the first observation of matter-antimatter asymmetry in the decays of strange B mesons. Matter and antimatter are thought to have existed in equal amounts at the beginning of the universe, but today the universe appears to be composed essentially of matter. By studying subtle differences in the behavior of particle and antiparticles, experiments at the LHC are seeking to cast light on this dominance of matter over antimatter. Neutral B mesons, which include up, down (B0), strange (B0s) and charm types denoting which quark they contain, spontaneously transform into their own antiparticles and back. B mesons decay into kaons and pions. (B0-> K+π- B0s -> K-p+). In results posted on arXiv, LHCb uses proton-proton collision data to show that the CP violation in strange mesons is nearly 0.27 with significance exceeding 5 standard deviations. They also provide the most precise measurement to date of the asymmetry in the down meson decay. Separately, in Physical Review D, the BABAR Collaboration also reported improved measurements of CP-violation parameters in the decays B0π+π-, B0K+π-, and B0π0π0, and of the branching fractions for B0π0π0 and B0K0π0.More

Einstein's gravity theory passes toughest test yet
National Radio Astronomy Observatory
A newly-discovered system containing a pulsar and its white-dwarf companion has put gravitational theories to the most extreme test yet. The two objects orbit each other once every two and a half hours. In such a system, the orbits decay and gravitational waves are emitted, carrying energy from the system. By very precisely measuring the time of arrival of the pulsar's radio pulses over a long period of time (Shapiro delay), astronomers can determine the rate of decay and the amount of gravitational radiation emitted. Astronomers had thought that the extreme conditions of this system, i.e., two very compact objects so close to each other, would provide a scenario where the equations of General Relativity would break down. But observations of this system, carried out via several radio and optical telescopes, produced results consistent with the predictions of Einstein's General Theory of Relativity. The results are reported in Science.More

Atomic magnetometer is most sensitive yet
Physics World
An atomic magnetometer that can detect magnetic fields one hundred billion times smaller than the Earth's and does not require stringent shielding from the Earth's own field has been developed by an international group of researchers. Magnetometers work by detecting how the energy levels of atoms are modified by an external magnetic field, i.e., the Zeeman effect. What’s done in atomic magnetometers is that a laser pumps atoms to specific spin states, and a probe laser measures spin precession, which is proportional to the external magnetic field. This new device, described in Physical Review Letters, improves sensitivity and does away with the need for magnetic shielding by using multi-pass atomic vapor cells. That is, the pulse beam is bounced back in forth several times in the atomic vapor cell to achieve nearly complete spin polarization. The probe beam, which follows within a millisecond, is shot before spin relaxation from the pump sets in, thus increasing sensitivity. With such high sensitivity and without the need for shielding, the new device can be used in various magnetic sensing applications such as measuring biological magnetic fields and land-mine clearance, as well as in geology and fundamental physics experiments.More

Model describing brain as a system close to critical point captures dynamics observed in fMRI experiments
American Physical Society
A new paper in Physical Review Letters shows how cooperative phenomena play a key role in determining brain dynamics, by showing that the brain in its resting state (i.e., when not performing an explicit task) is a system that is at the boundary of an order-disorder phase transition, i.e., at a criticality. Though at criticality, a brain must support a dualism in its dynamics, i.e., it must reliably produce coherent behavior in response to certain stimuli (order). But the brain must also have certain degree of disorder to enable adaptation and learning.

This new work uses existing information on how different cortical areas are connected by an underlying network of so-called fiber tracts. It then uses simple but successful 3-state model where a cortical region is allowed to be either quiescent (unexcited, but excitable), excited, or refractory (recently excited and temporarily not excitable). Transitions from the quiescent to the excited state can be spontaneous, or they can be driven if the signals coming from other excited areas add up to exceed a certain threshold. Once excited, the area remains refractory for a short time before it can get excited again.

Brain function can be followed by detecting associated changes in blood flow, measured as a blood-oxygenation-level dependent MRI signal. For the 3-state model to match the experimental data, the activation threshold had to be set exactly at the level at which their model becomes critical. At criticality, their model predicts a number of statistical properties that are consistent with experiments.More

Researchers at IceCube detect record energy neutrinos
Researchers at IceCube are reporting that they have detected the highest energy neutrinos ever observed. In their paper posted on arXiv, the team describes how in analyzing sensor data over the period 2010 to 2012 they found evidence of two neutrino induced events that were on an order of ten times the energy of any previous event. The two neutrinos recorded at IceCube (dubbed Bert and Ernie) are of particular relevance because the odds are very good that they came from the far reaches of space, rather than as a by-product of a collision between cosmic rays and Earth's atmosphere. Researchers at the IceCube station and elsewhere are hoping that finding neutrinos that originate from outside the solar system will help explain where high energy cosmic rays that reach our planet come from — their source has baffled scientists for nearly a century. If researchers can eventually trace neutrinos back to their source, they might find that doing so also reveals the source of high energy cosmic rays.More

Vaterite: Crystal within a crystal helps resolve an old puzzle
University of Wisconsin
With the help of a solitary sea squirt found in the Mediterranean and Red Seas, scientists have resolved the longstanding puzzle of the crystal structure of vaterite, a form of calcium carbonate that is an enigmatic geologic and biological mineral and whose structure has astrophysical implications. Unlike most minerals, vaterite has defied every effort to resolve its crystal structure, because finding large pure crystals has proven very difficult for over 100 years. But it turns out that Herdmania momus, a solitary sea squirt, and member of a large family of filter-feeding marine invertebrates natively makes large crystals of the material. As reported in Science, using aberration-corrected high-resolution transmission electron microscopy, physicists found that vaterite is actually composed of at least two different crystallographic structures that coexist within a pseudo–single crystal. The major structure exhibits hexagonal symmetry; the minor structure, existing as nanodomains within the major matrix, is still unknown.More

New phase of water could dominate the interiors of Uranus and Neptune
Water has an unusually rich phase diagram, with 15 crystalline phases observed in laboratory experiments and eight additional phases predicted theoretically. One lesser known phase of water is the superionic "ice" phase, where the oxygen atoms occupy fixed lattice positions as in a solid, but the hydrogen atoms migrate through the lattice as in a fluid. Scientists had thought that there was only one phase of superionic ice that exists at pressures in excess of 0.5 Mbar (500,000 times greater than atmospheric pressure) and temperatures of a few thousand Kelvin. But in a in a new study, reported in Physical Review Letters, physicists have discovered a second phase that is more stable than the original. The original phase of superionic ice has a body centered cubic (bcc) structure, and was predicted through ab initio computer simulations in 1999. The new phase, also predicted by ab initio computer simulations, has a face centered cubic (fcc) structure that has a higher density and lower hydrogen mobility than the bcc phase. This difference affects the water's thermal and electrical conductivity. The simulations show that a phase transition between the bcc and fcc phases may exist at pressures of 1.0 ± 0.5 Mbar. The new phase of superionic ice could make up a large component of the interiors of giant icy planets such as Uranus and Neptune. It is possible that the predicted bcc-to-fcc phase transition may explain the planets' unusual magnetic fields. In the future, the researchers plan to investigate the possible existence of a third superionic phase, as well as attempt to detect the predicted transition between the bcc and fcc phases.More

In Memoriam: Edmund C. Zingu
South African Institute of Physics
It is with profound sadness that SAIP informs the global physics community of the death of Professor Edmund C. Zingu. He was the first Black president of SAIP, as well as a world-class researcher, educator and administrator. Professor Zingu was a materials physicist, and with his collaborators at Cornell University invented a new method to study atomic diffusion by transmission electron microscopy. But perhaps his greatest contribution was leading the use of physics a tool of economic development, not only in South Africa but around the world.More

Nigerian physics professor, Fransisca Okeke, wins 2013 L'Oreal UNESCO Women in Science Award
Dr. Francisca Okeke, a Professor of Physics at the University of Nigeria, Nsukka (UNN) has recently received the L'Oreal-UNESCO for Women in Science Award for her contribution to the understanding of "daily variations of the ion currents in the upper atmosphere which may further our understanding of climate change." Professor Okeke was the Dean in the faculty of Physical Sciences at UNN from 2008 – 2010. Other winners of the award include Pratibha Gai, University of York (United Kingdom); Reiko Kuroda, Tokyo University of Science (Japan); Prof Marcia Barbosa, Federal University of Rio Grande do Sul, Porto Alegre (Brazil); and Prof Deborah Jin, National Institute of Standards and Technology, and University of Colorado, Boulder (USA).More

Condensation, atmospheric motion, and cold beer in the summertime
Physics Today
Most of us are familiar with evaporative cooling. We cool our skin by sweating; when our skin is wet, we feel cold standing in the wind. Yet we have little personal experience with the flip side of that energy exchange: the warming that occurs as water vapor condenses to form liquid droplets. It turns out that in sultry weather condensation on the outside of a canned beverage not only makes the can slippery, those drops can provide more heat than the surrounding air, meaning your drink would warm more than twice as much in humid weather compared to in dry heat. In typical hot and humid summer day, heat released by condensation warms the drink by 5-6 degrees Fahrenheit in 5 minutes. A research project conducted by two physics undergraduates shows how the availability of water (relative humidity) and the subsequent latent heat of vaporization plays a major role in keeping a canned drink cool. The beverage's temperature increase is much larger when the air temperature is at 35 °C than 25 °C. At 35 °C and a relative humidity greater than 60 percent, the beverage's temperature rise due to latent heating exceeds that due to heat transfer from dry air. Meterologically this same phenomena is a major avenue for vertical heat between air at Earth's surface and the air aloft. Vapor mixing then leads to horizontal heat transfers from the tropics towards the pole.More

Physics and green beer bottles
Wired Science Blog
Professor Rhett Allain explains why beer in green bottles seems to have an extra taste that maybe is not so great. Green bottles do not block ultraviolet radiation, and UV photoxidation causes chemical changes in the beer. More

National Society of Black Physicists jobs board postings
NASA Postdoctoral Fellowships
Assistant Editor, Physical Review D
Summer Internship
MIT Physics Lecturer/Sr. Lecturer
Martin and Michele Cohen Dean of Science
Visiting Assistant Professor

LHCb experiment observes new matter-antimatter difference
CERN Press Office
The LHCb collaboration has made the  first observation of matter-antimatter asymmetry in the decays of strange B mesons. Matter and antimatter are thought to have existed in equal amounts at the beginning of the universe, but today the universe appears to be composed essentially of matter.More

Why condensed matter physicists should pay attention to atomic physics
American Physical Society
At the APS March meeting in Baltimore, William Phillips of the Joint Quantum Institute described the many ways that trapped atoms are being used to understand the physics of solidsMore

The interesting life of a water molecule caged in a buckyball
American Physical Society
Fullerenes, a carbon allotrope related to graphene and the subject of the 1996 Nobel Prize in Chemistry, are large molecular cages built entirely of carbon atoms.More

Latest research from Reports on Progress in Physics
IOP Publishing
Microlensing detection of extrasolar planets

The electronic properties of bilayer graphene

Information physics fundamentals of nanophotonics

The quark and gluon structure of the proton

Quantum interference and Aharonov–Bohm oscillations in topological insulators

The measurement of surface gravityMore

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Atom lasers: Production, properties and prospects for precision inertial measurement

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Sum rules and scaling in nonlinear optics

Effects of symmetry breaking in finite quantum systems

Stochastic mechano-chemical kinetics of molecular motors: A multidisciplinary enterprise from a physicist’s perspective

Density functionals and model Hamiltonians: Pillars of many-particle physicsMore