Quarks

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.

An unforeseen feature in proton-proton collisions previously observed by the CMS experiment at CERN's Large Hadron Collider (LHC) has now been confirmed by its sister experiment ATLAS.

Author(s): Aapeli Kärkkäinen, Pablo Navarrete, Mika Nurmela, Risto Paatelainen, Kaapo Seppänen, and Aleksi VuorinenA new theoretical framework simplifies the four-loop Feynman diagrams for dense QCD to few infrared-finite integrals, which brings the higher-order calculation of the pressure inside cold and dense quark matter within reach. [Phys. Rev. Lett. 135, 021901] Published Mon Jul 07, 2025

New data from particle collisions at the Relativistic Heavy Ion Collider (RHIC), an "atom smasher" at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, reveals how the primordial soup generated in the most energetic particle collisions "splashes" sideways when it is hit by a jet of energetic particles.

Very soon after the Big Bang, the universe enjoyed a brief phase where quarks and gluons roamed freely, not yet joined up into hadrons such as protons, neutrons and mesons. This state, called a quark-gluon plasma, existed for a brief time until the temperature dropped to about 20 trillion Kelvin, after which this "hadronization" took place.

A team of physicists has embarked on a journey where few others have gone: into the glue that binds atomic nuclei. The resultant measurement, which was extracted from experimental data taken at the U.S. Department of Energy's Thomas Jefferson National Accelerator Facility, is the first of its kind and will help physicists image particles called gluons.

Author(s): Nikhil KarthikA new model of quark–gluon plasma finds that the strong force was more potent in the early Universe than previously thought. [Physics 18, s68] Published Fri May 23, 2025

A new study published in Physical Review D titled, "Extending the Bridge Connecting Chiral Lagrangians and QCD Gaussian Sum-Rules for Low-Energy Hadronic Physics," offers significant advancements in the understanding of the strong nuclear force. This fundamental interaction is responsible for holding protons and neutrons together within atomic nuclei and plays a central role in the formation of matter.

Brookhaven National Laboratory is pushing the boundaries of particle physics.

The CMS collaboration at CERN has observed an unexpected feature in data produced by the Large Hadron Collider (LHC), which could point to the existence of the smallest composite particle yet observed. The result, reported at the Rencontres de Moriond conference in the Italian Alps this week, suggest that top quarks—the heaviest and shortest lived of all the elementary particles—can momentarily pair up with their antimatter counterparts to produce an object called toponium.

In late 2023, Wojciech Brylinski was analyzing data from the NA61/SHINE collaboration at CERN for his thesis when he noticed an unexpected anomaly—a strikingly large imbalance between charged and neutral kaons in argon–scandium collisions. He found that, instead of being produced in roughly equal numbers, charged kaons were produced 18.4% more often than neutral kaons.

Author(s): R. Aaij et al. (LHCb Collaboration)An indication of isospin breaking is seen in certain decay modes of T c s 0 * ( 2870 ) and T c s 1 * ( 2900 ) , which might shed light on the nature of these tetraquark candidates. [Phys. Rev. Lett. 134, 101901] Published Tue Mar 11, 2025

Atomic nuclei exhibit multiple energy scales simultaneously—ranging from hundreds down to fractions of a megaelectronvolt. A new study demonstrates that these drastically different scales can be explained through calculations based on the strong nuclear force. The research also predicts that the atomic nucleus neon-30 exhibits several coexisting shapes.

Researchers have been working for decades to understand the architecture of the subatomic world. One of the knottier questions has been where the proton gets its intrinsic angular momentum, otherwise referred to as its spin.

In the first study of its kind at the Large Hadron Collider (LHC), the CMS collaboration has tested whether top quarks adhere to Einstein's special theory of relativity. The research is published in the journal Physics Letters B.

A new analysis of data from the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) reveals fresh evidence that collisions of even very small nuclei with large ones might create tiny specks of a quark-gluon plasma (QGP). Scientists believe such a substance of free quarks and gluons, the building blocks of protons and neutrons, permeated the universe a fraction of a second after the Big Bang.

A new analysis of data from the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) reveals fresh evidence that collisions of even very small nuclei with large ones might create tiny specks of a quark-gluon plasma (QGP). Scientists believe such a substance of free quarks and gluons, the building blocks of protons and neutrons, permeated the universe a fraction of a second after the Big Bang.

At extremely high densities, quarks are expected to form pairs, as electrons do in a superconductor. This high-density quark behavior is called color superconductivity. The strength of pairing inside a color superconductor is difficult to calculate, but scientists have long known the strength's relationship to the pressure of dense matter. Measuring the size of neutron stars and how they deform during mergers tells us their pressure and confirms that neutron stars are indeed the densest visible matter in the universe.

A unique property of quantum systems is on display in one of the LHC's standard particle production methods.

Queen Mary University of London physicist Professor Chris White, along with his twin brother Professor Martin White from the University of Adelaide, have discovered a surprising connection between the Large Hadron Collider (LHC) and the future of quantum computing.

Neutron stars are so named because in the simplest of models they are made of neutrons. They form when the core of a large star collapses, and the weight of gravity causes atoms to collapse. Electrons are squeezed together with protons so that the core becomes a dense sea of neutrons.

When a massive star dies as a supernova, it can leave behind a pulsar, a rapidly spinning neutron star. The fastest pulsars can spin upwards of 700 times a second, blasting out regular pulses of energy. In a new paper, researchers propose that the fastest-spinning pulsars could contain quark matter in their cores. This would be even denser matter than neutrons and help explain how surprisingly massive neutron stars can spin so rapidly, maybe reaching 1,000 Hz. The post Do the Fastest Spinning Pulsars Contain Quark Matter? appeared first on Universe Today.

Nuclear theorists at Brookhaven National Laboratory and Argonne National Laboratory have successfully employed a new theoretical approach to calculate the Collins-Soper kernel, a quantity that describes how the distribution of quarks' transverse momentum inside a proton changes with the collision energy.

The quarks that make up the nuclei of all atoms around us are known to "mix": the different types of quark occasionally change into one another. The amounts in which these processes happen are not very well known, though—and the theoretical values don't even add up to 100%. UvA-IoP physicist Jordy de Vries and colleagues from Los Alamos, Seattle, and Bern have now published work that takes a step towards solving these mysteries.

Author(s): Matthias Berwein, Nora Brambilla, Abhishek Mohapatra, and Antonio VairoThe authors develop an effective theory, based on the nonrelativistic Born-Oppenheimer approximation, to treat systems with two heavy quarks or a heavy quark-antiquark pair and light degrees of freedom. This allows for a unified treatment of quarkonia, doubly heavy baryons, and exotic states such as hybrids, tetraquarks, and pentaquarks. [Phys. Rev. D 110, 094040] Published Wed Nov 20, 2024

At a talk held at CERN this week, the ATLAS collaboration at the Large Hadron Collider (LHC) reported observing top quarks in collisions between lead ions, marking the first observation of this process in interactions between atomic nuclei.

Author(s): Nikhil KarthikA low-energy signature of physics beyond the standard model fails to appear in proton collisions at the Large Hadron Collider. [Physics 17, s137] Published Tue Nov 05, 2024

In collisions between protons at the Large Hadron Collider (LHC), pairs of top quarks—the heaviest known elementary particles—are frequently produced along with other heavy quarks, including bottom and charm quarks. These collision events can provide physicists with valuable insights into quantum chromodynamics (QCD), the theory that describes the strong force. Precisely determining the production rates (or "cross-sections") of these processes also enables researchers to more effectively distinguish them from rarer phenomena.

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.

In an article recently published in Physical Review X, the ALICE collaboration presented its studies of correlations in the kaon–deuteron and proton–deuteron systems, opening the door to precise studies of the forces in three-body nuclear systems.

Physicists report the first observations of quantum entanglement in quarks, the heaviest known fundamental particles, inside the Large Hadron Collider

Scientists are conducting experiments in search of evidence of a possible critical point in the Quantum Chromodynamics phase diagram. Quantum chromodynamics describes how the strong force binds quarks and antiquarks together to form protons, neutrons, and other particles known as hadrons.

The discovery of two entangled quarks at the large Hadron Collider is the highest-energy observation of entanglement ever made.

A central aim of the ATLAS Higgs physics program is to measure, with increasing precision, the strength of interactions of the Higgs boson with elementary fermions and bosons.

His research enabled the discovery that protons and neutrons are made of smaller particles, contributing to a fuller picture of the subatomic universe.

When neutron stars dance together, the grand smash finale they experience might create the densest known form of matter known in the Universe. It’s called “quark matter, ” a highly weird combo of liberated quarks and gluons. It’s unclear if the stuff existed in their cores before the end of their dance. However, in the … Continue reading "Neutron Star Mergers Could Be Producing Quark Matter" The post Neutron Star Mergers Could Be Producing Quark Matter appeared first on Universe Today.

Neutron stars are the remnants of old stars that have run out of nuclear fuel and undergone a supernova explosion and a subsequent gravitational collapse. Although their collisions—or binary mergers—are rare, when they do occur, these violent events can perturb spacetime itself, producing gravitational waves detectable on Earth from hundreds of millions of light years away.

Author(s): Volker Koch, Larry McLerran, Gerald A. Miller, and Volodymyr VovchenkoLattice QCD calculations at finite temperature and zero or small baryon chemical potential have shown that there is no phase transition separating quasi-free quarks and those confined in baryons. Quarkyonic matter is a hypothetical state where quarks and baryons can coexist in a single Fermi sphere; quarks occupy the low momenta levels, hadrons the high momenta ones. This paper puts forward the idea that normal nuclear matter may, in fact, be quarkyonic and that the existence of this exotic phase may already have been seen in current electron-nucleus scattering data. [Phys. Rev. C 110, 025201] Published Mon Aug 05, 2024

In high-energy physics, researchers have unveiled how high-energy partons lose energy in nucleus-nucleus collisions, an essential process in studying quark-gluon plasma (QGP). This finding could enhance our knowledge of the early universe moments after the Big Bang.

Researchers from the School of Physics & Astronomy have been involved in an important new measurement of the top quark made using data provided by the Large Hadron Collider (LHC).

Researchers from the HEFTY Topical Collaboration investigated the recombination of charm and bottom quarks into Bc mesons in the quark-gluon plasma (QGP). They have developed a transport model that simulates the kinetics of heavy-quark bound states through the expanding QGP fireball formed in high-energy heavy-ion collisions. Previous research has successfully used this model to describe the production of charm-anticharm and bottom-antibottom bound states, and thus can provide predictions for Bc particles (charm-antibottom bound states).

Author(s): Nikhil KarthikResearchers at CERN have significantly increased the precision of the measured value of the top-quark mass, a key input for making standard-model calculations. [Physics 17, s57] Published Thu Jun 27, 2024

Author(s): A. Hayrapetyan et al. (CMS Collaboration † ["id", "col1"], ATLAS Collaboration ‡ ["id", "col2"])Researchers at CERN have significantly increased the precision of the measured value of the top-quark mass, a key input for making standard-model calculations. [Phys. Rev. Lett. 132, 261902] Published Thu Jun 27, 2024

An experiment by a group of physicists led by University of Rochester physics professor Regina Demina has produced a significant result related to quantum entanglement—an effect that Albert Einstein called "spooky action at a distance."

Exploring the complex domain of subatomic particles, researchers at the The Institute of Mathematical Science (IMSc) and the Tata Institute of Fundamental Research (TIFR) have recently published a novel finding in the journal Physical Review Letters. Their study illuminates a new horizon within quantum chromodynamics (QCD), shedding light on exotic subatomic particles and pushing the boundaries of our understanding of the strong force.

Author(s): Giuseppe De Laurentis, Harald Ita, and Vasily SotnikovScattering processes that produce multiple jets in the final states are abundant at the Large Hadron Collider, which makes the computation of the corresponding theoretical high-precision predictions a crucial task to perform. By using different methods, two different collaborations computed the five-parton scattering amplitudes at two-loops in Quantum Chromodynamics (QCD) for any number of colors, that is including all non-planar Feynman diagrams. In DN13078 and DN13084, the authors employed analytic reconstruction methods for amplitude computations, which expose drastically simpler structures in two-loop helicity amplitudes. The authors of the other collaboration in LM18078D used tensor projection in the ’t Hooft-Veltman scheme and found analytic results for the scattering amplitudes

Author(s): Giuseppe De Laurentis, Harald Ita, Maximillian Klinkert, and Vasily SotnikovScattering processes that produce multiple jets in the final states are abundant at the Large Hadron Collider, which makes the computation of the corresponding theoretical high-precision predictions a crucial task to perform. By using different methods, two different collaborations computed the five-parton scattering amplitudes at two-loops in Quantum Chromodynamics (QCD) for any number of colors, that is including all non-planar Feynman diagrams. In DN13078 and DN13084, the authors employed analytic reconstruction methods for amplitude computations, which expose drastically simpler structures in two-loop helicity amplitudes. The authors of the other collaboration in LM18078D used tensor projection in the ’t Hooft-Veltman scheme and found analytic results for the

A large international team of physicists working on the BES III collaboration has announced possible physical evidence of glueballs. In their study, published in the journal Physical Review Letters, the group analyzed decaying particles in a particle collider and uncovered what they believe to be evidence of glueballs.

Author(s): Jinwei Chu and Savan KharelIn a series of two papers, the authors introduce a new method to compute the tree-level n -gluon scattering amplitudes in anti-de Sitter spacetime (AdS) space within the AdS/CFT duality. Working with Mellin amplitudes, the authors propose Feynman rules and show that they take a similar form as those in flat space. This intriguing similarity led the authors to propose a novel dictionary: comprehensive rules that bridge AdS Mellin amplitudes with flat-space gluon amplitudes. [Phys. Rev. D 109, 106003] Published Thu May 02, 2024

Author(s): Jinwei Chu and Savan KharelIn a series of two papers, the authors introduce a new method to compute the tree-level n -gluon scattering amplitudes in anti-de Sitter spacetime (AdS) space within the AdS/CFT duality. Working with Mellin amplitudes, the authors propose Feynman rules and show that they take a similar form as those in flat space. This intriguing similarity led the authors to propose a novel dictionary: comprehensive rules that bridge AdS Mellin amplitudes with flat-space gluon amplitudes. [Phys. Rev. D 109, L101901] Published Thu May 02, 2024

For over a decade, the CMS Collaboration, a large team of researchers based at different institutes worldwide, has been analyzing data collected at the Compact Muon Solenoid, a general-purpose particle detector at CERN's Large Hadron Collider (LHC). This large-scale international scientific collaboration has been trying to observe various elusive physical phenomena, including exotic particles and dark matter candidates.

The U.S. nuclear physics community is preparing to build the electron–ion collider (EIC), a flagship facility for probing the properties of matter and the strong nuclear force that holds matter together. The EIC will allow scientists to study how nucleons (protons and neutrons) arise from the complex interactions of quarks and gluons.

Author(s): Long-Bin Chen, Hai Tao Li, Zhao Li, Jian Wang, Yefan Wang, and Quan-feng WuThe authors compute the leading color contribution to the third-order QCD correction to the top quark decay width analytically. They additionally obtain the leading color third-order QCD correction to the inclusive semileptonic b → u decay. [Phys. Rev. D 109, L071503] Published Mon Apr 08, 2024

Author(s): Y. Aoki, B. Colquhoun, H. Fukaya, S. Hashimoto, T. Kaneko, R. Kellermann, J. Koponen, and E. Kou (JLQCD Collaboration)The authors compute the semileptonic form factors for B → D * decay in lattice QCD with a sophisticated chiral fermion formulation. They control all systematic errors. They use their result to obtain a standard model prediction for the decay ratio R ( D * ) that is consistent with previous lattice QCD results. [Phys. Rev. D 109, 074503] Published Thu

Today, the word "quantum" is everywhere—in company names, movie titles, even theaters. But at its core, the concept of a quantum—the tiniest, discrete amount of something—was first developed to explain the behavior of the smallest bits of matter and energy.

The team of physicists working on the LHCb Collaboration at CERN has found that bottom quarks are more likely to exist in baryons than mesons as the density of the environment in which they exist increases. In their paper published in Physical Review Letters, the group describes studying the production of b quarks in proton-to-proton collisions.

Author(s): Ryan WilkinsonBottom quarks are increasingly more likely to exist in three-quark states rather than two-quark ones as the density of their environment increases. [Physics 17, s20] Published Tue Feb 20, 2024

Neutron stars in the universe, ultracold atomic gases in the laboratory, and the quark–gluon plasma created in collisions of atomic nuclei at the Large Hadron Collider (LHC): they may seem totally unrelated but, surprisingly enough, they have something in common. They are all a fluid-like state of matter made up of strongly interacting particles. Insights into the properties and behavior of any of these almost-perfect liquids may be key to understanding nature across scales that are orders of magnitude apart.

Collisions of high energy particles produce "jets" of quarks, anti-quarks, or gluons. Due to the phenomenon called confinement, scientists cannot directly detect quarks. Instead, the quarks from these collisions fragment into many secondary particles that can be detected.

Author(s): Marco Cè, Tim Harris, Ardit Krasniqi, Harvey B. Meyer, and Csaba TörökOne of the most important applications of lattice gauge theory is the computation of transport coefficients at nonzero temperature. The authors compute moments of the photon emissivity with respect to the imaginary frequency, and find promising results. [Phys. Rev. D 109, 014507] Published Thu Jan 18, 2024

Atoms are made of three things: protons, neutrons, and electrons. Electrons are a type of fundamental particle, but protons and neutrons are composite particles made of up and down quarks. Protons have 2 ups and 1 down, while neutrons have 2 downs and 1 up. Because of the curious nature of the strong force, these quarks are always bound to each other, so they can never be truly free particles like electrons, at least in the vacuum of empty space. But a new study in Nature Communications finds that they can liberate themselves within the hearts of neutron stars.

When a star with several times the mass of the Sun dies in a supernova explosion, it ends up as a neutron star, compressing its protons and electrons into neutrons. But neutron stars have layers, and the most massive ones there might have a core made of an even denser material called "deconfined quark matter." A new supercomputer simulation predicts that the most massive neutron stars almost certainly have these quark-matter cores. The post The Most Massive Neutron Stars Probably Have Cores of Quark Matter appeared first on Universe Today.

New theoretical analysis places the likelihood of massive neutron stars hiding cores of deconfined quark matter between 80 and 90 percent. The result was reached through massive supercomputer runs utilizing Bayesian statistical inference.

Atomic nuclei are made of nucleons (like protons and neutrons), which themselves are made of quarks. When crushed at high densities, nuclei dissolve into a liquid of nucleons and, at even higher densities, the nucleons themselves dissolve into a quark liquid.

New theoretical analysis places the likelihood of massive neutron stars hiding cores of deconfined quark matter between 80 and 90 percent. The result was reached through massive supercomputer runs utilizing Bayesian statistical inference.

Neutron-star cores contain matter at the highest densities reached in our present-day universe, with as much as two solar masses of matter compressed inside a sphere of 25 km in diameter. These astrophysical objects can indeed be thought of as giant atomic nuclei, with gravity compressing their cores to densities exceeding those of individual protons and neutrons many-fold.

Quark gluon plasma (QGP) is an exciting state of matter that scientists create in a laboratory by colliding two heavy nuclei. These collisions produce a QGP fireball. The fireball expands and cools following the laws of hydrodynamics, which govern how fluids behave in various conditions. Eventually, subatomic particles (protons, pions, and other hadrons, or particles made up of two or more quarks) emerge and are observed and counted by detectors surrounding the collision.

When two lead ions collide at the Large Hadron Collider (LHC), they produce an extremely hot and dense state of matter in which quarks and gluons are not confined inside composite particles called hadrons. This fireball of particles—known as quark–gluon plasma and believed to have filled the universe in the first few millionths of a second after the Big Bang—expands and cools down rapidly. The quarks and gluons then transform back into hadrons, which fly out of the collision zone towards particle detectors.

Studying nuclear matter under extreme conditions allows scientists to better understand how the universe might have looked right after its creation. Scientists at the Large Hadron Collider achieve the conditions for recreating mini-Big Bangs in the lab by colliding nuclei at speeds close to that of light. These collisions create temperatures about one million times hotter than the sun's center.

Author(s): Luca Buonocore, Simone Devoto, Massimiliano Grazzini, Stefan Kallweit, Javier Mazzitelli, Luca Rottoli, and Chiara SavoiniSignificant reduction in the perturbative uncertainty due to the first second-order QCD calculation of the hadroproduction of a W boson in association with a top-antitop quark pair could lead to stringent tests of the standard model. [Phys. Rev. Lett. 131, 231901] Published Tue Dec 05, 2023

Experiments at CERN and the Accelerator Laboratory in Jyväskylä, Finland, have revealed that the radius of an exotic nucleus of aluminum, 26mAl, is much larger than previously thought. The result, described in a paper just published in Physical Review Letters, sheds light on the effects of the weak force on quarks—the elementary particles that make up protons, neutrons and other composite particles.

Physicists from the Eötvös Loránd University (ELTE) have been conducting research on the matter constituting the atomic nucleus utilizing the world's three most powerful particle accelerators. Their focus has been on mapping the "primordial soup" that filled the universe in the first millionth of a second following its inception.

Author(s): Thomas Elias CocoliosA measurement of the charge radius of an aluminum nucleus probes the assumption that there are only three families of quarks. [Physics 16, 199] Published Mon Nov 27, 2023

Author(s): P. Plattner et al.A measurement of the charge radius of an aluminum nucleus probes the assumption that there are only three families of quarks. [Phys. Rev. Lett. 131, 222502] Published Mon Nov 27, 2023

The idea that protons and neutrons were composed of even smaller particles, with non-integral electric charges, was proposed in 1963/64 by Andre Petermann, George Zweig and Murray Gell-Mann, who dubbed them "quarks." It was not until the mid-1970s, however, that the quark model became widely accepted.

Author(s): Ken MimasuThe Large Hadron Collider’s ATLAS Collaboration observes, for the first time, the coincident production of a photon and a top quark. [Physics 16, 187] Published Tue Oct 31, 2023

Author(s): G. Aad et al. (ATLAS Collaboration)The first observation of a rare process producing a single top quark and a photon at high statistical significance could result in a better understanding of the electroweak coupling of the top quark. [Phys. Rev. Lett. 131, 181901] Published Mon Oct 30, 2023

Author(s): Peter Arnold, Omar Elgedawy, and Shahin IqbalA theoretical study demonstrates that in-medium showers of high-energy gluons can be approximately treated as a sequence of individual splitting processes. [Phys. Rev. D 108, 074015] Published Thu Oct 19, 2023

Author(s): Peter Arnold, Omar Elgedawy, and Shahin IqbalA theoretical study demonstrates that in-medium showers of high-energy gluons can be approximately treated as a sequence of individual splitting processes. [Phys. Rev. Lett. 131, 162302] Published Thu Oct 19, 2023

Author(s): Yan Lyu, Sinya Aoki, Takumi Doi, Tetsuo Hatsuda, Yoichi Ikeda, and Jie MengA lattice QCD computation close to the physical point finds a near-threshold virtual state in the D D * scattering channel, that suggests the formation of a loosely bound state at the physical point consistent with the experimental observation of a doubly charmed tetraquark T c c + . [Phys. Rev. Lett. 131, 161901] Published Mon Oct 16, 2023

This week, researchers reported on two-dimensional gold sheets, a tidy little meson made of four quarks (and its buddy!) and a big and almost unimaginably dense exoplanet with an exciting backstory.

The observation of elusive, exotic particles is the key objective of countless studies, as it could open new avenues for research, while also improving present knowledge of the matter contained in the universe and its underlying physics. The quark model, a theoretical model introduced in 1964, predicted the existence of elementary subatomic particles known as quarks in their different configurations.

Scientists can use powerful colliders to smash atomic nuclei together to create a quark-gluon plasma (QGP). This "soup" of quarks and gluons, some of the fundamental building blocks of matter, filled the early universe. Tracking how high energy jets of quarks travel through the QGP can reveal information about the QGP's properties.

Author(s): A. Tumasyan et al. (CMS Collaboration)Decays of Z bosons to charm quark-antiquark pairs have been observed for the first time at a hadron collider, as part of a search for decays of Higgs bosons to charm quark-antiquark pairs, which are bounded at 14 times the standard model value. [Phys. Rev. Lett. 131, 061801] Published Mon Aug 07, 2023

A collaboration of nuclear theorists at the U.S. Department of Energy's (DOE) Brookhaven National Laboratory, Argonne National Laboratory, Temple University, Adam Mickiewicz University of Poland, and the University of Bonn, Germany, has used supercomputers to predict the spatial distributions of charges, momentum, and other properties of "up" and "down" quarks within protons. The results, just published in Physical Review D, revealed key differences in the characteristics of the up and down quarks.

Author(s): Marric StephensCERN’s Large Hadron Collider has detected the signals of two new four-quark states that are unusual because of their charges and their quark compositions. [Physics 16, s42] Published Thu Jul 27, 2023

Author(s): R. Aaij et al. (LHCb Collaboration)CERN’s Large Hadron Collider has detected the signals of two new four-quark states that are unusual because of their charges and their quark compositions. [Phys. Rev. Lett. 131, 041902] Published Thu Jul 27, 2023

Nature is the foremost international weekly scientific journal in the world and is the flagship journal for Nature Portfolio. It publishes the finest peer-reviewed research in all fields of science and technology on the basis of its originality, importance, interdisciplinary interest, timeliness, accessibility, elegance and surprising conclusions. Nature publishes landmark papers, award winning news, leading comment and expert opinion on important, topical scientific news and events that enable readers to share the latest discoveries in science and evolve the discussion amongst the global scientific community.

A new type of particle called the strange pentaquark has been found using the Large Hadron Collider. The particle could help researchers catalogue the states of exotic matter and figure out how fundamental particles stick together

Author(s): R. Aaij et al. (LHCb Collaboration)A pentaquark candidate that has strange quark content, seen as a resonant structure in B − → J ψ Λ p ¯ decay, is observed for the first time. [Phys. Rev. Lett. 131, 031901] Published Mon Jul 17, 2023

In the Large Hadron Collider (LHC), proton and lead beams travel close to the speed of light. They carry a strong electromagnetic field that acts like a flux of photons as the beam moves through the accelerator. When the two beams at the LHC pass by close to each other without colliding, one of the beams may emit a photon of very high energy that strikes the other beam. This can result in photon—nucleus, photon—proton, and even photon—photon collisions.

New measurements of how particles flow from collisions of different types of particles at the Relativistic Heavy Ion Collider (RHIC) have provided new insights into the origin of the shape of hot specks of matter generated in these collisions. The results may lead to a deeper understanding of the properties and dynamics of this form of matter, known as a quark-gluon plasma (QGP).

A new publication by the PHENIX Collaboration at the Relativistic Heavy Ion Collider (RHIC) provides definitive evidence that gluon "spins" are aligned in the same direction as the spin of the proton they're in. The result, just published in Physical Review Letters, provides theorists with new input for calculating how much gluons—the gluelike particles that hold quarks together within protons and neutrons—contribute to a proton's spin.

Author(s): R. J. Hudspith and D. MohlerThe authors use six splittings between bottomonium levels to nonperturbatively tune an NRQCD action on four gauge field ensembles. They then use the tuned action for the b antiquarks in their study of the binding energies of exotic tetraquark states with two b antiquarks, achieving a roughly 10% precision in the computed binding energies. [Phys. Rev. D 107, 114510] Published Fri Jun 16, 2023

Using some of the world's most powerful supercomputers, a group of theorists has produced a major advance in the field of nuclear physics—a calculation of the "heavy quark diffusion coefficient." This number describes how quickly a melted soup of quarks and gluons—the building blocks of protons and neutrons, which are set free in collisions of nuclei at powerful particle colliders—transfers its momentum to heavy quarks.