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Category: particle physics – Page 26

Latest Data Rule Out a Leading Explanation of a Neutrino Anomaly

In 2018, results from the MiniBooNE neutrino experiment suggested the exciting possibility that low-energy muon neutrinos quantum-mechanically flip into electron neutrinos more frequently than predicted by the standard model of particle physics. Theorists have sought to explain this anomaly, known as the low-energy excess (LEE), by invoking beyond-standard-model explanations such as the existence of new flavors of neutrinos (see Viewpoint: The Plot Thickens for a Fourth Neutrino). However, there was always the possibility that photon emission attributed to electron-neutrino interactions had been caused by other processes. Now, an analysis of five years of data from MicroBooNE, a follow-up experiment with a different design, has effectively ruled out the electron-neutrino-based interpretation of the LEE [1].

MiniBooNE operated by observing the Cherenkov radiation from fast-moving charged particles generated by neutrino–nucleus interactions in the 800 tonnes of mineral oil that constituted the detector’s sensitive volume. But the experiment could not easily exclude photons from other sources. MicroBooNE has a smaller sensitive volume composed of liquid argon, but it can reconstruct charged particles’ trajectories and energies precisely, allowing it to identify photon origins more reliably. As well as taking advantage of this intrinsic selectivity, the MicroBooNE team took elaborate steps to reduce all sources of uncertainty, both instrumental and theoretical.

The resulting high-quality data show good agreement with the standard-model predictions. By comparing these results with those from MiniBooNE, the researchers were able to exclude the electron-neutrino-based explanation for the apparent LEE at a confidence level of over 99%. While this conclusion might be disappointing for some, it compels scientists to look for new explanations for the MiniBooNE anomaly, the cause of which is still unknown.

Optical resonator enables a new kind of microscope for ultra-sensitive samples

Everyone who ever took a photo knows the problem: if you want a detailed image, you need a lot of light. In microscopy, however, too much light is often harmful to the sample—for example, when imaging sensitive biological structures or investigating quantum particles. The aim is therefore to gather as much information as possible about the object under observation with a given amount of light.

Cost-effective method developed for high-entropy alloy film production

A collaborative research team has developed a novel method for forming high-performance high-entropy alloy (HEA) films on various surfaces without using expensive alloy targets. This was achieved using a proprietary rotating target composed of multiple pure metal segments and pulsed laser deposition (PLD) technology.

This method uniquely enables not only the deposition of metal atoms onto the substrate surface through laser irradiation but also their implantation into the subsurface, forming robust films that integrate with the substrate material.

Traditionally, producing HEA requires expensive pre-made alloy targets. In contrast, the new method uses inexpensive pure metals, significantly reducing costs. The team also demonstrated precise control of film thickness and depth by adjusting the pressure during deposition.

Watching Electron Dynamics Shape Chemical Reactions

Scientists have used ultrashort x-ray pulses to directly observe the motion of electrons driving a chemical reaction.

A chemical reaction occurs when chemical bonds break and new ones form. These bonds hold atoms together within molecules and are governed by the atoms’ outermost electrons. The motion of these so-called valence electrons dictates how a reaction starts and determines its final products. For decades, chemists have envisioned the possibility of watching such electron movement in real time, capturing a movie of valence electrons as bonds break and form. Now Ian Gabalski at Stanford University and his colleagues have brought this dream closer to reality [1]. They have observed valence-electron motion occurring within a few hundred femtoseconds—where one femtosecond is a millionth of a billionth of a second. This feat was accomplished using ultrashort, high-energy x-ray pulses produced at SLAC National Accelerator Laboratory in California. The team’s findings provide an intuitive view of how electron dynamics influence chemical reactions.

Directly observing electron motion during chemical reactions presents two main challenges. First, it requires an imaging technique that can map the spatial distribution of electrons, known as the electron density. This distribution spans only a few tenths of a nanometer, demanding extremely high spatial resolution. Second, the task needs ultrahigh temporal resolution, because electron movement occurs on a timescale of femtoseconds or even attoseconds—thousandths of a femtosecond. Capturing such rapid motion requires the sample to be subjected to light pulses that are short enough to effectively freeze electron dynamics in time, similarly to using a high-speed camera to capture the fluttering wings of a hummingbird.

One atom, endless power: Scientists create a shape-shifting catalyst for green chemistry

A team in Milan has developed a first-of-its-kind single-atom catalyst that acts like a molecular switch, enabling cleaner, more adaptable chemical reactions. Stable, recyclable, and eco-friendly, it marks a major step toward programmable sustainable chemistry.

New AI model advances fusion power research by predicting the success of experiments

Practical fusion power that can provide cheap, clean energy could be a step closer thanks to artificial intelligence. Scientists at Lawrence Livermore National Laboratory have developed a deep learning model that accurately predicted the results of a nuclear fusion experiment conducted in 2022. Accurate predictions can help speed up the design of new experiments and accelerate the quest for this virtually limitless energy source.

In a paper published in Science, researchers describe how their AI model predicted with a probability of 74% that ignition was the likely outcome of a small 2022 fusion experiment at the National Ignition Facility (NIF). This is a significant advance as the model was able to cover more parameters with greater precision than traditional supercomputers.

Currently, nuclear power comes from nuclear fission, which generates energy by splitting atoms. However, it can produce radioactive waste that remains dangerous for thousands of years. Fusion generates energy by fusing atoms, similar to what happens inside the sun. The process is safer and does not produce any long-term radioactive waste. While it is a promising energy source, it is still a long way from being a viable commercial technology.

LHCb collaboration observes ultra-rare baryon decay

Baryons, composite particles made up of three quarks bound together via the so-called strong force, make up the most visible matter and have thus been the focus of numerous physics studies. Studying the rare processes via which unstable baryons decay into other particles could potentially contribute to the discovery of new physics that is not explained by the Standard Model of particle physics.

Theoretical study reveals failure of key quark-gluon plasma probe in low-energy region

According to theoretical predictions, within a millionth of a second after the Big Bang, nucleons had not yet formed, and matter existed as a hot, dense “soup” composed of freely moving quarks and gluons. This state of matter is known as quark-gluon plasma (QGP). Finding definitive evidence for the existence of QGP is crucial for understanding cosmic evolution.

Scientists Flip the Script and Solve a Longstanding Spintronics Challenge

A breakthrough in spintronics reveals that material defects can be harnessed to boost device efficiency, overturning decades of assumptions. Scientists have discovered a way to transform what was once considered a major problem in electronics, material defects, into a powerful quantum-based advan

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