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New antimatter gravity experiments begin at CERN
“ALPHA-g is very similar to the ALPHA experiment, which makes neutral antihydrogen atoms by taking antiprotons from the Antiproton Decelerator (AD) and binding them with positrons from a sodium-22... — New antimatter gravity experiments begin at CERN
ALPHA-g is very similar to the ALPHA experiment, which makes neutral antihydrogen atoms by taking antiprotons from the Antiproton Decelerator (AD) and binding them with positrons from a sodium-22 source. ALPHA then confines the resulting neutral antihydrogen atoms in a magnetic trap and shines laser light or microwaves onto them to measure their internal structure. The ALPHA-g experiment has the same type of apparatus for making and trapping antiatoms, except that it is oriented vertically. With this vertical set-up, researchers can precisely measure the vertical positions at which the antihydrogen atoms annihilate with normal matter once they switch off the trap’s magnetic field and the atoms are under the sole influence of gravity. The values of these positions will allow them to measure the effect of gravity on the antiatoms.
The GBAR experiment, also located in the AD hall, takes a different tack. It plans to use antiprotons supplied by the ELENA deceleration ring and positrons produced by a small linear accelerator to make antihydrogen ions, consisting of one antiproton and two positrons. Next, after trapping the antihydrogen ions and chilling them to an ultralow temperature (about 10 microkelvin), it will use laser light to strip them of one positron, turning them into neutral antiatoms. At this point, the neutral antiatoms will be released from the trap and allowed to fall from a height of 20 centimetres, during which the researchers will monitor their behaviour.

Source: home.cern

physics antimatter

Nanosecond Freezing of Water at High Pressures: Nucleation and Growth near the Metastability Limit
“ The fundamental study of phase transition kinetics has motivated experimental methods toward achieving the largest degree of undercooling possible,... — Nanosecond Freezing of Water at High Pressures: Nucleation and Growth near the Metastability Limit
The fundamental study of phase transition kinetics has motivated experimental methods toward achieving the largest degree of undercooling possible, more recently culminating in the technique of rapid, quasi-isentropic compression. This approach has been demonstrated to freeze water into the high-pressure ice VII phase on nanosecond timescales, with some experiments undergoing heterogeneous nucleation while others, in apparent contradiction, suggest a homogeneous nucleation mode. In this study, we show through a combination of theory, simulation, and analysis of experiments that these seemingly contradictory results are in agreement when viewed from the perspective of classical nucleation theory. We find that, perhaps surprisingly, classical nucleation theory is capable of accurately predicting the solidification kinetics of ice VII formation under an extremely high driving force (|Δμ/kBT|≈1) but only if amended by two important considerations: (i) transient nucleation and (ii) separate liquid and solid temperatures. This is the first demonstration of a model that is able to reproduce the experimentally observed rapid freezing kinetics.

Source: journals.aps.org

physics chemistry

The ANITA Anomalous Events as Signatures of a Beyond Standard Model Particle, and Supporting Observations from IceCube
“ The ANITA collaboration have reported observation of two anomalous events that appear to be εcr≈0.6 EeV cosmic ray showers... — The ANITA Anomalous Events as Signatures of a Beyond Standard Model Particle, and Supporting Observations from IceCube
The ANITA collaboration have reported observation of two anomalous events that appear to be εcr≈0.6 EeV cosmic ray showers emerging from the Earth with exit angles of 27∘ and 35∘, respectively. While EeV-scale upgoing showers have been anticipated as a result of astrophysical tau neutrinos converting to tau leptons during Earth passage, the observed exit angles are much steeper than expected in Standard Model (SM) scenarios. Indeed, under conservative extrapolations of the SM interactions, there is no particle that can propagate through the Earth with probability p>10−6 at these energies and exit angles. We explore here whether “beyond the Standard Model” (BSM) particles are required to explain the ANITA events, if correctly interpreted, and conclude that they are. Seeking confirmation or refutation of the physical phenomenon of sub-EeV Earth-emergent cosmic rays in data from other facilities, we find support for the reality of the ANITA events, and three candidate analog events, among the Extremely High Energy Northern Track neutrinos of the IceCube Neutrino Observatory. Properties of the implied BSM particle are anticipated, at least in part, by those predicted for the “stau” slepton (τ̃ R) in some supersymmetric models of the fundamental interactions, wherein the stau manifests as the next-to-lowest mass supersymmetric partner particle.
and from the paper:
In Sec. V we conclude that, taken together, the ANITA and IceCube anomalous events provide dramatic and highly credible evidence of the first new bona fide BSM phenomenon since the discoveries of neutrino oscillations, dark matter, and dark energy.

Source: arxiv.org

physics

Magnetic Field Record Set With a Bang: 1,200 Tesla
“During 40 microseconds last April, Shojiro Takeyama and his team at the University of Tokyo dumped 3.2 megajoules of energy into a newly built scientific instrument and blew part of it to... — Magnetic Field Record Set With a Bang: 1,200 Tesla
During 40 microseconds last April, Shojiro Takeyama and his team at the University of Tokyo dumped 3.2 megajoules of energy into a newly built scientific instrument and blew part of it to smithereens. The smithereens part was expected; the force of the explosion, not quite. The instrument was designed to generate superstrong magnetic fields for examining semiconductors and other materials at the nanometer scale. Takeyama was expecting about 700 Tesla. He got 1,200 T instead—a world record for indoor fields and about 400 times as strong as a typical medical MRI.
Bigger magnetic fields have been made before, but they aren’t practical or reliably reproducible, because they rely on rather dangerous amounts of TNT. It is not an indoor activity.

Source: spectrum.ieee.org

physics

A complex dynamo inferred from the hemispheric dichotomy of Jupiter’s magnetic field
“ The Juno spacecraft, which is in a polar orbit around Jupiter, is providing direct measurements of the planet’s magnetic field close to its surface1. A recent... — A complex dynamo inferred from the hemispheric dichotomy of Jupiter’s magnetic field
The Juno spacecraft, which is in a polar orbit around Jupiter, is providing direct measurements of the planet’s magnetic field close to its surface¹. A recent analysis of observations of Jupiter’s magnetic field from eight (of the first nine) Juno orbits has provided a spherical-harmonic reference model (JRM09)² of Jupiter’s magnetic field outside the planet. This model is of particular interest for understanding processes in Jupiter’s magnetosphere, but to study the field within the planet and thus the dynamo mechanism that is responsible for generating Jupiter’s main magnetic field, alternative models are preferred. Here we report maps of the magnetic field at a range of depths within Jupiter. We find that Jupiter’s magnetic field is different from all other known planetary magnetic fields. Within Jupiter, most of the flux emerges from the dynamo region in a narrow band in the northern hemisphere, some of which returns through an intense, isolated flux patch near the equator. Elsewhere, the field is much weaker. The non-dipolar part of the field is confined almost entirely to the northern hemisphere, so there the field is strongly non-dipolar and in the southern hemisphere it is predominantly dipolar. We suggest that Jupiter’s dynamo, unlike Earth’s, does not operate in a thick, homogeneous shell, and we propose that this unexpected field morphology arises from radial variations, possibly including layering, in density or electrical conductivity, or both.

Source: nature.com

jupiter juno physics

Get ready for atomic radio
“That’s the basis of the radio detection. Anderson and co create a gas of cesium atoms excited into Rydberg states. They then use a laser tuned to a specific frequency to make the gas transparent.
Finally, they shine a... — Get ready for atomic radio
That’s the basis of the radio detection. Anderson and co create a gas of cesium atoms excited into Rydberg states. They then use a laser tuned to a specific frequency to make the gas transparent.
Finally, they shine a second laser through the gas and measure how much light is absorbed, to see how the transparency varies with ambient radio waves.
The signal from a simple light-sensitive photodiode then reveals the way the radio signals are frequency modulated or amplitude modulated.
And that’s it: an antenna consisting of a cloud of excited cesium atoms, zapped by laser light that flickers in time to any ambient radio waves. They call it atomic radio.
[…]
But perhaps most revolutionary is that the detection does not involve conventional radio circuitry. “The atomic radio wave receiver operates by direct real-time optical detection of the atomic response to AM and FM baseband signals, precluding the need for traditional de-modulation and signal-conditioning electronics,” say Anderson and co.
That means the device should be more or less insensitive to the kind of electromagnetic interference that can render conventional antennas useless.

Source: technologyreview.com

radio physics

Indefinite Causal Order in a Quantum Switch
“ In quantum mechanics events can happen in no definite causal order: in practice this can be verified by measuring a causal witness, in the same way that an entanglement witness verifies entanglement.... — Indefinite Causal Order in a Quantum Switch
In quantum mechanics events can happen in no definite causal order: in practice this can be verified by measuring a causal witness, in the same way that an entanglement witness verifies entanglement. Indefinite causal order can be observed in a quantum switch, where two operations act in a quantum superposition of the two possible orders. Here we realise a photonic quantum switch, where polarisation coherently controls the order of two operations, A^ and B^, on the transverse spatial mode of the photons. Our setup avoids the limitations of earlier implementations: the operations cannot be distinguished by spatial or temporal position. We show that our quantum switch has no definite causal order, by constructing a causal witness and measuring its value to be 18 standard deviations beyond the definite-order bound.

physics quantum physics

Measurements of the gravitational constant using two independent methods
“ The Newtonian gravitational constant, G, is one of the most fundamental constants of nature, but we still do not have an accurate value for it. Despite two centuries of... — Measurements of the gravitational constant using two independent methods
The Newtonian gravitational constant, G, is one of the most fundamental constants of nature, but we still do not have an accurate value for it. Despite two centuries of experimental effort, the value of G remains the least precisely known of the fundamental constants. A discrepancy of up to 0.05 per cent in recent determinations of G suggests that there may be undiscovered systematic errors in the various existing methods. One way to resolve this issue is to measure G using a number of methods that are unlikely to involve the same systematic effects. Here we report two independent determinations of G using torsion pendulum experiments with the time-of-swing method and the angular-acceleration-feedback method. We obtain G values of 6.674184 × 10−11 and 6.674484 × 10−11 cubic metres per kilogram per second squared, with relative standard uncertainties of 11.64 and 11.61 parts per million, respectively. These values have the smallest uncertainties reported until now, and both agree with the latest recommended value within two standard deviations.

Source: nature.com

physics

The Internal Constitution of the Stars, Arthur Eddington - 1920 — The Internal Constitution of the Stars, Arthur Eddington - 1920

astrophysics nuclear energy physics extinction

First Successful Test of Einstein’s General Relativity Near Supermassive Black Hole
“Obscured by thick clouds of absorbing dust, the closest supermassive black hole to the Earth lies 26 000 light-years away at the centre of the Milky Way. This... — First Successful Test of Einstein’s General Relativity Near Supermassive Black Hole
Obscured by thick clouds of absorbing dust, the closest supermassive black hole to the Earth lies 26 000 light-years away at the centre of the Milky Way. This gravitational monster, which has a mass four million times that of the Sun, is surrounded by a small group of stars orbiting around it at high speed. This extreme environment — the strongest gravitational field in our galaxy — makes it the perfect place to explore gravitational physics, and particularly to test Einstein’s general theory of relativity.
New infrared observations from the exquisitely sensitive GRAVITY [1], SINFONI and NACO instruments on ESO’s Very Large Telescope (VLT) have now allowed astronomers to follow one of these stars, called S2, as it passed very close to the black hole during May 2018. At the closest point this star was at a distance of less than 20 billion kilometres from the black hole and moving at a speed in excess of 25 million kilometres per hour — almost three percent of the speed of light [2].
The team compared the position and velocity measurements from GRAVITY and SINFONI respectively, along with previous observations of S2 using other instruments, with the predictions of Newtonian gravity, general relativity and other theories of gravity. The new results are inconsistent with Newtonian predictions and in excellent agreement with the predictions of general relativity.

Source: eso.org

eso astronomy physics astrophysics

First 3D colour X-ray of a human using CERN technology
“What if, instead of a black and white X-ray picture, a doctor of a cancer patient had access to colour images identifying the tissues being scanned? This colour X-ray imaging technique could... — First 3D colour X-ray of a human using CERN technology
What if, instead of a black and white X-ray picture, a doctor of a cancer patient had access to colour images identifying the tissues being scanned? This colour X-ray imaging technique could produce clearer and more accurate pictures and help doctors give their patients more accurate diagnoses.
This is now a reality, thanks to a New-Zealand company that scanned, for the first time, a human body using a breakthrough colour medical scanner based on the Medipix3 technology developed at CERN. Father and son scientists Professors Phil and Anthony Butler from Canterbury and Otago Universities spent a decade building and refining their product.
[…]
Hybrid pixel-detector technology was initially developed to address the needs of particle tracking at the Large Hadron Collider, and successive generations of Medipix chips have demonstrated over 20 years the great potential of the technology outside of high-energy physics.

physics medicine

Neutrinos Linked With Cosmic Source for the First Time
“Last September, a rare guest from far beyond the Milky Way ushered in a new era of astronomy. The visitor, an ultrahigh-energy cosmic neutrino, bumped into ice more than a mile beneath the South... — Neutrinos Linked With Cosmic Source for the First Time
Last September, a rare guest from far beyond the Milky Way ushered in a new era of astronomy. The visitor, an ultrahigh-energy cosmic neutrino, bumped into ice more than a mile beneath the South Pole, where detectors from the IceCube experiment were waiting to catch it. After quickly tracking the direction from where it came, physicists got lucky: Another telescope, this one orbiting Earth, spotted a stream of extremely energetic radiation coming from the same direction.
The twin events could have been a cosmic coincidence. But when physicists looked through their archived data, they found several other neutrinos that appear to have come from the same direction. This supporting evidence has convinced them that they’ve achieved a cosmic first: tracing ultrahigh-energy neutrinos back to their astrophysical source.
That source appears to be a supermassive black hole at the center of a distant galaxy.

Source: quantamagazine.org

physics astrophysics astronomy

Higgs boson observed decaying to b quarks – at last!
“Six years after its discovery, ATLAS has observed about 30% of the Higgs boson decays predicted in the Standard Model. However, the favoured decay of the Higgs boson into a pair of b quarks... — Higgs boson observed decaying to b quarks – at last!
Six years after its discovery, ATLAS has observed about 30% of the Higgs boson decays predicted in the Standard Model. However, the favoured decay of the Higgs boson into a pair of b quarks (H→bb), which is expected to account for almost 60% of all possible decays, had remained elusive up to now. Observing this decay mode and measuring its rate is a mandatory step to confirm (or not…) the mass generation for fermions via Yukawa interactions, as predicted in the Standard Model.
Today, at the 2018 International Conference on High Energy Physics (ICHEP) in Seoul, the ATLAS experiment reported a preliminary result establishing the observation of the Higgs boson decaying into pairs of b quarks, furthermore at a rate consistent with the Standard Model prediction. In the community of particle physics (and beyond), for the detection of a process to be qualified as an “observation”, it is necessary to exclude at a level of one in three million the probability that it arises from a fluctuation of the background that could mimic the process in question.

Source: atlas.cern

physics

Real-Life Schrödinger’s Cats Probe the Boundary of the Quantum World
““Schrödinger’s kittens,” loosely speaking, are objects pitched midway in size between the atomic scale, which quantum mechanics was originally developed to describe, and the cat... — Real-Life Schrödinger’s Cats Probe the Boundary of the Quantum World
“Schrödinger’s kittens,” loosely speaking, are objects pitched midway in size between the atomic scale, which quantum mechanics was originally developed to describe, and the cat that Erwin Schrödinger famously invoked to highlight the apparent absurdity of what that theory appeared to imply. These systems are “mesoscopic” — perhaps around the size of viruses or bacteria, composed of many thousands or even billions of atoms, and thus much larger than the typical scales at which counterintuitive quantum-mechanical properties usually appear. They are designed to probe the question: How big can you get while still preserving those quantum properties?
To judge by the latest results, the answer is: pretty darn big. Two distinct types of experiments — both of them carried out by several groups independently — have shown that vast numbers of atoms can be placed in collective quantum states, where we can’t definitely say that the system has one set of properties or another.

Source: quantamagazine.org

physics

Evidence Found for a New Fundamental Particle
“Physicists are both thrilled and baffled by a new report from a neutrino experiment at Fermi National Accelerator Laboratory near Chicago. The MiniBooNE experiment has detected far more neutrinos of a... — Evidence Found for a New Fundamental Particle
Physicists are both thrilled and baffled by a new report from a neutrino experiment at Fermi National Accelerator Laboratory near Chicago. The MiniBooNE experiment has detected far more neutrinos of a particular type than expected, a finding that is most easily explained by the existence of a new elementary particle: a “sterile” neutrino that’s even stranger and more reclusive than the three known neutrino types. The result appears to confirm the anomalous results of a decades-old experiment that MiniBooNE was built specifically to double-check.
[…]
The existence of a sterile neutrino would revolutionize physics from the smallest to the largest scales. It would finally break the Standard Model of particle physics that has reigned since the 1970s. It would also demand “a new standard model of cosmology,” Dodelson said. “There are other potential cracks in the standard picture,” he added. “The neutrino paradox could point our way to a new, better model.”

Source: quantamagazine.org

physics