Lifeboat Foundation: Safeguarding Humanity
Toggle light / dark theme

Blog

Category: particle physics

Earlier ultra-relativistic freeze-out could revive a decades-old theory for dark matter

A new theory for the origins of dark matter suggests that fast-moving, neutrino-like dark particles could have decoupled from Standard Model particles far earlier than previous theories had suggested.

Through new research published in Physical Review Letters, a team led by Stephen Henrich and Keith Olive at the University of Minnesota proposes that this “ultra-relativistic freeze-out” mechanism could have produced dark matter particles which are almost undetectable, but still compatible with the observed history of the universe.

Despite comprising some 85% of the universe’s total mass, dark matter has never been seen to interact with regular matter except via gravity, making its origins one of the most enduring mysteries in cosmology.

CERN’s ATLAS detects evidence for decay of Higgs boson into muon–antimuon pair

Although its existence had been theorized for decades, the Higgs boson was finally observed to exist in 2012 at the Large Hadron Collider (LHC) at CERN. Since then, it has continued to be heavily studied at the LHC. Now, a new study from the researchers at CERN combines the last two runs of ATLAS—one of the two general-purpose detectors at the LHC—to lay out evidence that the Higgs boson can decay into a muon–antimuon pair.

The study, published in Physical Review Letters, reports a significance of 3.4 standard deviations of excess signal over background, when the two runs are combined—higher than previous evidence from the Compact Muon Solenoid (CMS) of 3.0 standard deviations.

A solid-state quantum processor based on nuclear spins

Quantum computers, systems that process information leveraging quantum mechanical effects, have the potential of outperforming classical systems on some tasks. Instead of storing information as bits, like classical computers, they rely on so-called qubits, units of information that can simultaneously exist in superpositions of 0 and 1.

Researchers at University Paris-Saclay, the Chinese University of Hong Kong and other institutes have developed a new quantum computing platform that utilizes the intrinsic angular momentum (i.e., spin) of nuclei in tungsten-183 (183 W) atoms as qubits.

Their proposed system, introduced in a paper published in Nature Physics, was found to achieve long coherence times and is compatible with existing superconductor-based quantum information processing platforms.

LHC data confirm validity of new model of hadron production—and test foundations of quantum mechanics

A boiling sea of quarks and gluons, including virtual ones—this is how we can imagine the main phase of high-energy proton collisions. It would seem that particles here have significantly more opportunities to evolve than when less numerous and much “better-behaved” secondary particles spread out from the collision point. However, data from the LHC accelerator prove that reality works differently, in a manner that is better described by an improved model of proton collisions.

A lot happens during high-energy proton-proton collisions. Protons are hadrons, i.e. clusters of partons—quarks and the gluons that bind them together. When protons collide with each other at sufficiently high energies, their quarks and gluons (including the virtual ones, which appear momentarily during interactions) enter into various complex interactions.

Only when they “cool down” do the quarks stick together to form new hadrons, which scatter from the collision area and are recorded in detectors. Intuition therefore suggests that the entropy of the produced hadrons—a quantity describing the number of states in which the particle system can find itself—should be different from that in the parton phase of the collision, when there are many interacting quarks and gluons, and the interactions appear at first glance to be as chaotic as they are dynamic.

CMS gets acquainted with a family of all-charm tetraquarks

Upon close inspection, the tetraquark family members are consistent with tightly bound diquark pairs

The CMS Collaboration has identified three extremely rare same-flavor teraquark states and determined, based on their spin-parity configuration, that they are consistent with a diquark-antidiquark model.

In recent years, a long-standing orthodoxy that all strongly interacting particles (hadrons) are either pairs (mesons) or triplets (baryons) of quarks (q) has been fundamentally overturned. Rapid progress has been made in identifying a plethora of candidates for “exotic hadrons”, including tetraquarks (qq̅qq̅) and pentaquarks (qqqqq̅), now recognized within the scientific community.

X-ray imaging reveals how silicon anodes maintain contact in all-solid-state batteries

All-solid-state batteries (ASSBs) using silicon (Si) anodes are among the most promising candidates for high-energy and long-lasting power sources, particularly for electric vehicles. Si can store more lithium than conventional graphite, but its volume expands by roughly 410% during charging. This swelling generates mechanical stress that cracks particles and weakens their contact with the solid electrolyte, disrupting the flow of ions and reducing efficiency.

To address this, a research group led by Professor Yuki Orikasa from the College of Life Sciences, Ritsumeikan University, along with Ms. Mao Matsumoto, a graduate student at the Graduate School of Life Sciences, Ritsumeikan University (at the time), and Dr. Akihisa Takeuchi from the Japan Synchrotron Radiation Research Institute, used operando synchrotron X-ray tomography with nanometer resolution to observe what happens inside these batteries as they charge and discharge in real time.

Their paper is published in ACS Nano.

Scientists rule out fourth neutrino in particle physics mystery

Scientists have taken a major step toward solving a long-standing mystery in particle physics, by finding no sign of the particle many hoped would explain it.

An international collaboration of scientists, including from The University of Manchester, working on the MicroBooNE experiment at the U.S. Department of Energy’s Fermi National Accelerator Laboratory announced that they have found no evidence for a fourth type of neutrino, known as a sterile neutrino.

For decades, physics experiments have observed neutrinos—sub-atomic particles that are all around us—behaving in a way that doesn’t fit the Standard Model of particle physics. One of the most promising explanations was the existence of a sterile neutrino, named because they are predicted not to interact with matter at all, whereas other neutrinos can. This means they could pass through the universe almost undetected.

Deciphering the heavyweights of the tetraquark world

The CMS collaboration reports the first measurement of the quantum properties of a family of tetraquarks that was recently discovered at the LHC.

To date, the Large Hadron Collider (LHC) at CERN has discovered 80 particles. The most famous is the Higgs boson, a crucial ingredient in the fundamental laws of the universe. The rest are particles called hadrons made up of quarks, which allow physicists to investigate the intriguing properties of the strong nuclear force.

Of the hadrons discovered so far, most are familiar sets of two or three quarks (so-called mesons and baryons, respectively). But one of the LHC’s most striking discoveries is the confirmation of exotic hadrons composed of four or five quarks.

Tightening the net around the elusive sterile neutrino

Neutrinos, though nearly invisible, are among the most numerous matter particles in the universe. The Standard Model recognizes three types, but the discovery of neutrino oscillations revealed they have mass and can change identity while propagating.

For decades, puzzling experimental anomalies have suggested the presence of a fourth, “sterile” neutrino, one that interacts even more weakly. Finding it would transform our understanding of particle physics.

New look at hidden structure inside subatomic particles

SUNY Poly Professor of Physics Dr. Amir Fariborz recently published a paper in Physical Review D titled “Spinless glueballs in generalized linear sigma model.” The work takes on a central challenge in modern physics: understanding how the strongest force in nature shapes the inner structure of matter, and how it may produce an unusual form of matter made entirely from the carriers of that force.

Here’s the quick background. Everything is made of atoms. Atoms have a nucleus made of protons and neutrons, and those are made of even smaller pieces called quarks. Quarks are held together by gluons, which carry the strong interaction described by quantum chromodynamics (QCD).

Composite subatomic particles—hadrons—are built from quarks and gluons. Hadrons fall into two main groups: mesons and baryons. QCD does a great job explaining what happens when particles collide at very high energies, but at lower energies it becomes much harder to calculate, so researchers use well-tested models that still follow QCD’s rules.

/* */