Thursday, October 28, 2021

Is the Great Neutrino Puzzle Pointing to Multiple Missing Particles?


In 1993, the Liquid Scintillator Neutrino

Detector at Los Alamos National Laboratory

reported a puzzling bounty of neutrino detections.


In 1993, deep underground at Los Alamos National Laboratory in New Mexico, a few flashes of light inside a bus-size tank of oil kicked off a detective story that is yet to reach its conclusion.


The Liquid Scintillator Neutrino Detector (LSND) was searching for bursts of radiation created by neutrinos, the lightest and most elusive of all known elementary particles. “Much to our amazement, that’s what we saw,” said Bill Louis, one of the experiment’s leaders.


The problem was that they saw too many. Theorists had postulated that neutrinos might oscillate between types as they fly along — a hypothesis that explained various astronomical observations. LSND had set out to test this idea by aiming a beam of muon neutrinos, one of the three known types, toward the oil tank, and counting the number of electron neutrinos that arrived there. Yet Louis and his team detected far more electron neutrinos arriving in the tank than the simple theory of neutrino oscillations predicted.


Since then, dozens more neutrino experiments have been built, each grander than the last. In mountains, disused mining caverns and the ice beneath the South Pole, physicists have erected cathedrals to these notoriously slippery particles. But as these experiments probed neutrinos from every angle, they kept yielding conflicting pictures of how the particles behave. “The plot keeps thickening,” said Louis. (Full Story)



Understanding the towering ‘fire clouds’ over forest blazes


Courtesy photo.


Across Northern New Mexico, it’s been a hazy summer and early fall for all to see — and smell. Much of that smoke was blown here by winds from the Bootleg Fire, which raged across south-central Oregon, and the Dixie Fire, which scorched Northern California. As these blazes obliterated hundreds of thousands of acres of forest, the roiling flames launched massive smoke plumes high into the atmosphere.


Typically, the smoke has been lofted to a few miles above ground, and then picked up and carried by wind currents across the country, much like weather fronts that carry moisture and bring rain to blanket New York City and the eastern seaboard in a thick haze.


But the Bootleg Fire also sent up a towering vertical plume lofting smoke to a record-breaking 10 miles. Intensely hot fires from dense fuels, local weather conditions and dry surface and high-altitude atmospheric clouds conspired to cause the plume to rise far above ordinary clouds.


When you see these pyrocumulonimbus, you know you’ve got big trouble below. These clouds are so intense that they modify local weather and create amazing lightning storms that can ignite more fires.


In recent years, megafires and their blanketing haze have become an increasingly familiar sight, along with the towering thunderheads of smoke that form above them. Yet we’re only beginning to learn what causes those awe-inspiring “fire clouds,” what’s in them and what effects they have on weather and climate.


Through a combination of field observations, experimental work in the laboratory and computer modeling at local to global scales, our team at Los Alamos National Laboratory is making progress in understanding the mechanisms and climate impacts of pyrocumulonimbus from recent megafires in British Columbia (2017) and Australia (2019-20). (Full story)




Major US and European labs join forces to tackle climate change



Waste heat from the European Spallation Source will

eventually be connected to the local heating system

rather than being vented into the atmosphere

(courtesy: Perry Nordeng/ESS).


Top physics facilities in Europe and the US have come together to tackle the climate crisis. The labs – including CERN, the European Space Agency, Fermilab and the Los Alamos National Laboratory – have announced that they will step up their scientific collaboration on carbon-neutral energy and climate change as well as share best practices to improve the carbon footprint of big-science facilities.


Large labs demand a huge amount of energy. The CERN particle-physics lab near Geneva, for example, uses 1.3 terawatt hours of electricity annually, which is enough to power 300,000 UK homes for a year. In 2020 the lab released its first public Environment Report that detailed the status of CERN’s environmental footprint. It found that greenhouse-gas emissions emitted by the lab in 2018 was 223,800 tonnes of carbon-dioxide equivalent.


Planned facilities, such as the European Spallation Source that is being constructed in Lund, Sweden, meanwhile, have integrated sustainability into their design such as diverting waste heat into local heating systems instead of it being vented into the atmosphere. (Full story)




New Results from MicroBooNE Provide Clues to Particle Physics Mystery


MicroBooNE detector being lowered into the

experimental facility at Fermilab. Photo Courtesy Fermilab.


New results from a more-than-decade long physics experiment offer insight into unexplained electron-like events found in previous experiments. Results of the MicroBooNE experiment, while not confirming the existence of a proposed new particle, the sterile neutrino, provide a path forward to explore physics beyond the Standard Model, the theory of the fundamental forces of nature and elementary particles.


“The results so far from MicroBooNE make the explanation for the MiniBooNE experiment’s anomalous electron-like events more likely to be physics beyond the Standard Model,” said William Louis, physicist at Los Alamos National Laboratory and a member of the MicroBooNE collaboration. “What exactly the new physics is – that remains to be seen.”


The MicroBooNE experiment at the U.S. Department of Energy’s Fermi National Accelerator Laboratory explores a striking anomaly in particle beam experimentation first uncovered by researchers at Los Alamos National Laboratory. In the 1990s, the Liquid Scintillator Neutrino Detector experiment at the Laboratory saw more electron-like events than expected, compared to Standard Model-based calculations. (Full story)



Also from the Los Alamos Reporter:


Improved DOE Exascale Earth System Model Two Times Faster Than Previous Version


High-resolution E3SM simulation over the Arctic showing

surface ocean currents and temperatures (blue) and

January sea-ice concentration (gray/white).


A new version of the Department of Energy’s Energy Exascale Earth System Model (E3SM) is two times faster than its earlier version released in 2018, allowing for more accurate and timely simulations of the changing climate.


“This version of E3SM is faster and more capable than the first,” said Los Alamos National Laboratory scientist Luke Van Roekel, who co-leads the Water Cycle science campaign for the project.


“From one version to another, earth system models typically become better but also quite a bit slower, so both faster and better is significant. The improved fidelity and increased capability in physics and regional resolution position us to begin answering critical questions related to DOE’s mission.”


Earth system models have weather-scale resolution and use advanced computers to simulate aspects of Earth’s variability and anticipate decadal changes that will critically impact the U.S. energy sector in coming years. These critical factors include regional air/water temperatures, which can strain energy grids; water availability, which affects power plant operations; extreme water-cycle events (floods and droughts), which impact infrastructure and bio-energy; and sea-level rise and coastal flooding, which threaten coastal infrastructure. (Full story)