IceCube detector uses entire Earth to measure interactions of neutrinos

Enlarge / The IceCube facility sits at the South Pole above an array of photodetectors, drawn into the image above. (credit: IceCube Collaboration, U. Wisconsin, NSF ) Neutrinos are one of the most plentiful particles out there, as trillions pass through you every second. But they’re incredibly hard to work with. They’re uncharged, so we can’t control their path or accelerate them. They’re also nearly massless and barely interact with other matter, so they’re hard to detect. All of this means that a lot of the predictions our physics theories make about neutrinos are hard to test. The IceCube detector , located at the South Pole, has now confirmed a part of the Standard Model of physics, which describes the properties of fundamental particles and their interactions. According to the Standard Model, neutrinos should become more likely to interact with other particles as their energy goes up. To test this, the IceCube team used neutrinos thousands of times more energetic than our best particle accelerators can make and used the entire planet as a target. Polar cube IceCube consists of hundreds of detectors buried in the ice under the South Pole. These detectors pick up particles that move through the ice. In some cases, IceCube sees a spray of particles and photons when something slams into one of the atoms in the ice. In other cases, particles simply nudge the atoms, liberating a few photons. There’s no neutrino source pointed at IceCube, though. Instead, it relies on natural sources of neutrinos. Some of these are produced far away in space, and travel great distances to Earth. Others are produced as cosmic rays slam into the atmosphere. Read 9 remaining paragraphs | Comments

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IceCube detector uses entire Earth to measure interactions of neutrinos

Matter-antimatter asymmetry confirmed in baryons

The LHCb detector. (credit: Fermilab ) Everyone, at some point in their lives, wonders why they are here. Existential questions don’t stop at the personal level, though. Why is there a Universe, and why is it filled with matter? The last question is a puzzle that has gainfully occupied the minds of and employed physicists for many years. The time spent pondering such questions has not been wasted, as it turns out, as researchers from the LHCb detector report  that one of the theoretical paths that allows matter to outnumber antimatter is open for business. An overly simple reading of the Standard Model of physics predicts that matter will be produced at the same rate as antimatter. The antimatter and matter should, through simple statistics, collide and wipe each other out, leaving only energy. But that didn’t happen. The substance we label matter was, somehow, produced in greater abundance than antimatter. In the beginnings of the Universe, antimatter was eliminated, leaving only matter. A closer look at the Standard Model reveals that some imbalance is expected. But it also predicts a Universe with much less matter than we observe. And, experimentally, we’ve only observed the relevant matter/antimatter asymmetry for a particular class of particles, called mesons. That notably leaves out the particles that make up the Universe, called baryons. Luckily, baryon asymmetry is exactly what one of the LHC detectors, called LHCb, is designed to investigate. Read 13 remaining paragraphs | Comments

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Matter-antimatter asymmetry confirmed in baryons