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Category: particle physics – Page 114

Synthesizing New 3D Materials by Twisting

Overlapping two 3D lattices with a relative twist opens the door to synthesizing crystals with diverse symmetries that showcase nontrivial band structures and novel properties.

When two identical periodic lattices overlap in space, with one twisted at an angle relative to the other, they form moiré lattices. The best-known examples are formed from stacked and rotated 2D sheets. These structures can possess fascinating properties not seen in their component layers. Twisted bilayer graphene, for example, can exhibit superconductor and Mott insulator behavior [1, 2]. Ce Wang of Tongji University in China and his colleagues now propose how to construct a 3D moiré lattice using two cubic optical lattices hosting ultracold atoms [3]. The researchers mathematically describe how two simple periodic structures, twisted relative to each other, can lead to 3D optical moiré patterns (Fig. 1). The result is a crystal-like structure with emergent properties that differ from those of the underlying simple lattices.

Decoding top quarks with precision: Experiment at Large Hadron Collider reveals how pairs of top quarks are produced

The second ATLAS study, presented recently at the 17th International Workshop on Top Quark Physics, broke new ground by providing the first dedicated ATLAS measurement of how often top-quark pairs are produced along with jets originating from charm quarks (c-jets).

ATLAS physicists analyzed events with one or two leptons (electrons and muons), using a custom flavor-tagging algorithm developed specifically for this study to distinguish c-jets from b-jets and other jets. This algorithm was essential because c-jets are even more challenging to identify than b-jets, as they have shorter lifetimes and produce less distinct signatures in the ATLAS detector.

The study found that most theoretical models provided reasonable agreement with the data, though they generally underpredicted the production rates of c-jets. These results, which for the first time separately determined the cross-sections for single and multiple charm-quark production in top-quark-pair events, highlight the need for refined simulations of these processes to improve future measurements.

CERN Just Found Ultra-Rare Particle, Which Is Creating New Physics

In a particle collider at CERN, a rarely-seen event is bringing us tantalizingly close to the brink of new physics.

From years of running what is known as the NA62 experiment, particle physicist Cristina Lazzeroni of the University of Birmingham in the UK and her colleagues have now established, experimentally observed, and measured the decay of a charged kaon particle into a charged pion and a neutrino-antineutrino pair. The researchers have presented their findings at a CERN seminar.

It’s exciting stuff. The reason the team has been pursuing this very specific kind of decay channel so relentlessly for more than a decade is because it’s what is known as a “golden” channel, meaning not only is it incredibly rare, but also well predicted by the complex mathematics making up the Standard Model of physics.

New light-induced material shows powerful potential for quantum applications

Many scientists are studying different materials for their potential use in quantum technology. One important feature of the atoms in these materials is called spin. Scientists want to control atomic spins to develop new types of materials, known as spintronics. They could be used in advanced technologies like memory devices and quantum sensors for ultraprecise measurements.

In a recent breakthrough, researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and Northern Illinois University discovered that they could use light to detect the in a class of materials called perovskites (specifically in this research methylammonium lead iodide, or MAPbI3). Perovskites have many potential uses, from solar panels to quantum technology.

The work is published in the journal Nature Communications.

First coherent picture of an atomic nucleus made of quarks and gluons

The atomic nucleus is made up of protons and neutrons, particles that exist through the interaction of quarks bonded by gluons. It would seem, therefore, that it should not be difficult to reproduce all the properties of atomic nuclei hitherto observed in nuclear experiments using only quarks and gluons. However, it is only now that physicists, including those from the Institute of Nuclear Physics of the Polish Academy of Sciences in Cracow, have succeeded in doing this.

Hunter’s supermoon, a comet, and Orionids meteors are sharing the sky this week

This week, the October sky is treating us to a brilliant display that you won’t want to miss — the Hunter’s supermoon, a rare comet, and the Orionids meteor shower.

Comet C/2023 A3 Tsuchinshan-ATLAS is a rare comet making its journey past Earth, offering a unique opportunity to witness its tail of icy particles glistening against the dark canvas of space.

In addition, this week features the biggest supermoon of the year, Hunter’s supermoon, which will illuminate the night with a breathtaking orangish glow.

Higgs Particles And Tiny Black Holes Could Have Destroyed Our Universe

Although our universe may seem stable, having existed for a whopping 13.7 billion years, several experiments suggest that it is at risk—walking on the edge of a very dangerous cliff. And it’s all down to the instability of a single fundamental particle: the Higgs boson.

In new research by me and my colleagues, just accepted for publication in Physical Letters B, we show that some models of the early universe, those which involve objects called light primordial black holes, are unlikely to be right because they would have triggered the Higgs boson to end the cosmos by now.

The Higgs boson is responsible for the mass and interactions of all the particles we know of. That’s because particle masses are a consequence of elementary particles interacting with a field, dubbed the Higgs field. Because the Higgs boson exists, we know that the field exists.

Heavy Element Formation Limited in Failed Supernovae

Despite its intensity, the gravitational collapse of certain massive stars does not produce an abundance of heavy elements.

About half of the elements heavier than iron are made by the r, or rapid, process. A nucleus captures neutrons so quickly that radioactive decay is forestalled until the neutron-heavy nucleus finally emits electrons and neutrinos and settles at a new, higher atomic number. Besides normal supernovae and neutron-star mergers, the r process is also suspected to occur in so-called collapsars. These are rapidly rotating massive stars that collapse without producing a regular supernova once they exhaust their fuel. However, simulations by Coleman Dean and Rodrigo Fernández of the University of Alberta, Canada, have now undermined that r-process conjecture [1].

A collapsar’s progenitor is massive enough that it forms a black hole. To shed its prodigious angular momentum, it also forms a thick, unstable accretion disk. During the collapse, nuclei in the stellar envelope break apart, and their protons combine with electrons in the envelope to produce neutrons and neutrinos in large numbers. These neutrons could turn the disk into a favorable, if fleeting, site for the r process to forge and disperse heavy elements—provided that this neutron-rich matter can be ejected.