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Category: particle physics – Page 21

Packed particles power up: Physicists discover particles that accelerate when crowded

What if particles don’t slow down in a crowd, but move faster? Physicists from Leiden worked together and discovered a new state of matter, where particles pass on energy through collisions and create more movement when packed closely together.

We all know crowds of people, or cars in a traffic jam—when it gets too crowded, all you can do is stand still. Until now, scientists have mainly studied cases of large groups just like this, which slow down when they get too close to each other.

But what if the opposite happens? What if could start moving more when packed together? That question hadn’t been studied much—until now. Physicists Marine Le Blay, Joshua Saldi and Alexandre Morin from Leiden University do research in the field of active matter physics—they observe and analyze the collective behaviors that emerge when large groups of particles are packed together.

Carl David Anderson

Carl David Anderson was born in New York City, the son of Swedish immigrants. He studied physics and engineering at Caltech (B.S., 1927; Ph. D., 1930). Under the supervision of Robert Millikan, He began investigations into cosmic rays during the course of which he encountered unexpected particle tracks in his (modern versions now commonly referred to as an Anderson) cloud chamber photographs that he correctly interpreted as having been created by a particle with the same mass as the electron, but with opposite electrical charge. This discovery, announced in 1932 and later confirmed by others, validated Paul Dirac’s theoretical prediction of the existence of the positron. Anderson first detected the particles in cosmic rays. He then produced more conclusive proof by shooting gamma rays produced by the natural radioactive nuclide ThC’’ (208 Tl) [ 2 ] into other materials, resulting in the creation of positron-electron pairs. For this work, Anderson shared the 1936 Nobel Prize in Physics with Victor Hess. [ 3 ] Fifty years later, Anderson acknowledged that his discovery was inspired by the work of his Caltech classmate Chung-Yao Chao, whose research formed the foundation from which much of Anderson’s work developed but was not credited at the time. [ 4 ]

Also in 1936, Anderson and his first graduate student, Seth Neddermeyer, discovered a muon (or ‘mu-meson’, as it was known for many years), a subatomic particle 207 times more massive than the electron, but with the same negative electric charge and spin 1/2 as the electron, again in cosmic rays. Anderson and Neddermeyer at first believed that they had seen a pion, a particle which Hideki Yukawa had postulated in his theory of the strong interaction. When it became clear that what Anderson had seen was not the pion, the physicist I. I. Rabi, puzzled as to how the unexpected discovery could fit into any logical scheme of particle physics, quizzically asked “Who ordered that?” (sometimes the story goes that he was dining with colleagues at a Chinese restaurant at the time). The muon was the first of a long list of subatomic particles whose discovery initially baffled theoreticians who could not make the confusing “zoo” fit into some tidy conceptual scheme.

First Quantum Bit Made of Antimatter Captured in Physics Breakthrough

CERN scientists have analyzed a particle of antimatter isolated in an undecided quantum state known as a superposition for the first time.

While the quantum behavior of ordinary matter has been studied extensively and even used as the basis of quantum computers in the form of qubits, the breakthrough goes far beyond technological applications, potentially helping physicists understand why we even exist today.

The team suspended an antiproton – the antimatter counterpart of the proton – in a system of electromagnetic traps, and suppressed environmental interference that would mess with the particle’s delicate quantum state.

First-Ever Images Capture Atoms “Wiggling” in Quantum Materials

Scientists have imaged atomic thermal vibrations for the first time, revealing hidden patterns that could redefine quantum and nano-electronic device design. Scientists studying atomic-level behavior in advanced electronic and quantum devices have successfully captured the first-ever microscopy i

Neutrino masses are not likely to originate from interactions with dark matter, study finds

Neutrinos are fundamental particles characterized by no electric charge and very small masses, which are known to interact with other matter via the weak force or gravity. While these particles have been the focus of numerous research studies, the processes through which they acquire their masses have not yet been elucidated.

One hypothesis is that neutrino masses originate from interactions with ultralight dark matter, a type of dark matter theorized to be made up of particles or fields with extremely small masses below 10 electron volts (eV). Researchers at Shanghai Jiao Tong University and University of Salerno recently set out to test this hypothesis by comparing data collected by the Kamioka Liquid Scintillator Antineutrino Detector (KamLAND) experiment to theoretical predictions.

Their findings, published in a paper in Physical Review Letters, suggest that neutrino masses are not likely to have a dark origin.

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