Signs of Gluon Saturation Emerge from Particle Collisions

By colliding protons with heavier ions and tracking particles from these collisions, scientists can study the quarks and gluons that make up protons and neutrons. Recent results revealed a suppression of certain back-to-back pairs of particles that emerge from interactions of single quarks from the proton with single gluons in the heavier ion. The results suggest that gluons in heavy nuclei recombine, a step toward proving that gluons reach a postulated steady state called saturation, where gluon splitting and recombination balance.

New Type of Entanglement Lets Scientists ‘See’ Inside Nuclei

Nuclear physicists have found a new way to see inside nuclei by tracking interactions between particles of light and gluons. The method relies on harnessing a new type of quantum interference between two dissimilar particles. Tracking how these entangled particles emerge from the interactions lets scientists map out the arrangement of gluons. This approach is unusual for making use of entanglement between dissimilar particles—something rare in quantum studies.

Imaging the Proton with Neutrinos

The interactions of the quarks and gluons that make up protons and neutrons are so strong that the structure of protons and neutrons is difficult to calculate from theory and must be instead measured experimentally. Neutrino experiments use targets that are nuclei made of many protons and neutrons bound together. This complicates interpreting those measurements to infer proton structure. By scattering neutrinos from the protons that are the nuclei of hydrogen atoms in the MINERvA detector, scientists have provided the first measurements of this structure with neutrinos using unbound protons.

Hitting Nuclei with Light May Create Fluid Primordial Matter

A new analysis supports the idea that photons colliding with heavy ions create a fluid of “strongly interacting” particles. The results indicate that photon-heavy ion collisions can create a strongly interacting fluid that responds to the initial collision geometry and that these collisions can form a quark-gluon plasma. These findings will help guide future experiments at the planned Electron-Ion Collider.

Laser shots at National Ignition Facility could spark additional discoveries in astrophysics

Using the Argonne Tandem Linac Accelerator System (ATLAS), a team of scientists is studying the environment created during laser shots at the National Ignition Facility to better understand its potential as a testbed for nuclear astrophysics research.

Clear Sign that QGP Production ‘Turns Off’ at Low Energy

Physicists report new evidence that production of an exotic state of matter in collisions of gold nuclei at the Relativistic Heavy Ion Collider (RHIC) can be ‘turned off’ by lowering the collision energy. The findings will help physicists map out the conditions of temperature and density under which the exotic matter, known as a quark-gluon plasma (QGP), can exist and identify key features of the phases of nuclear matter.

Shape-Shifting Experiment Challenges Interpretation of How Cadmium Nuclei Move

Atomic nuclei take a range of shapes, from spherical to football-like deformed. Spherical nuclei are often described by the motion of a small fraction of the protons and neutrons, while deformed nuclei tend to rotate as a collective whole. A third kind of motion, nuclear vibration, has been proposed since the 1950s. However, a new investigation of cadmium-106 nuclei found that these nuclei rotate, not vibrate, counter to scientists’ expectations.

U.S. Department of Energy Announces $68 Million For Small Businesses Developing Technologies to Cut Emissions and Study Climate

The U.S. Department of Energy (DOE) today announced awards totaling more than $68 million that will go to 53 small businesses that are solving scientific problems. Projects include developing tools for climate research and advanced materials and technologies for clean energy conversion. Understanding the climate and the ability to convert and store energy are instrumental to meeting President Biden’s goal of a completely clean electrical grid by 2035 and net-zero greenhouse-gas emissions by 2050.

A Plutonium Needle in a Haystack

Characterizing plutonium is important to environmental studies, nuclear plant and materials safety, and studies of nucleosynthesis and neutron star mergers. Scientists therefore need ways to detect ultra-trace amounts of plutonium. Researchers have now used special lasers to study the fingerprints of plutonium’s photoionization. The technique allowed researchers to identify ultra-trace amounts of plutonium atoms at record levels of efficiency.

Particles Pick Pair Partners Differently in Small Nuclei

The protons and neutrons that build the nucleus of the atom frequently pair up in fleeting partnerships called short-range correlations. These can form between a proton and a neutron, between two protons, or between two neutrons. Scientists recently discovered that in helium-3 and tritium, which have small, light nuclei, some types of correlations are less common than they are in larger, heavier nuclei.

PREX, CREX, and Nuclear Models: The Plot Thickens

Recent experiments involving a tiny left-right asymmetry in electron scattering off lead-208 and calcium-48 indicate a disagreement between the experiments’ results and the predictions of global nuclear models. This result indicates a need to investigate limitations of current nuclear models or other sources of uncertainty. This has repercussions for scientists studying topics from neutron skins to nuclear symmetry energy to neutron star physics.

Time Projection Chamber Installed at sPHENIX

Experts assembling sPHENIX, a state-of-the-art particle detector at the U.S. Department of Energy’s Brookhaven National Laboratory, successfully installed a major tracking component on Jan. 19. The Time Projection Chamber, or TPC, is one of the final pieces to move into place before sPHENIX begins tracking particle smash-ups at the Relativistic Heavy Ion Collider (RHIC) this spring.

Department of Energy Announces $9.1 Million for Research on Quantum Information Science and Nuclear Physics

Today, the U.S. Department of Energy (DOE) announced $9.1 million in funding for 13 projects in Quantum Information Science (QIS) with relevance to nuclear physics. Nuclear physics research seeks to discover, explore, and understand all forms of nuclear matter that can exist in the universe – from the subatomic structure of nucleons, to exploding stars, to the emergence of the quark-gluon plasma seconds after the Big Bang.

Argonne announces 2022 Postdoctoral Performance Awards

Nine postdoctoral appointees were recognized with Postdoctoral Performance Awards.

Data Reveal a Surprising Preference in Particle Spin Alignment

Given the choice of three different “spin” orientations, certain particles emerging from collisions at the Relativistic Heavy Ion Collider (RHIC), an atom smasher at Brookhaven National Laboratory, appear to have a preference. Recent results reveal a preference in global spin alignment of particles called phi mesons.

New Type of Entanglement Lets Scientists ‘See’ Inside Nuclei

Nuclear physicists have found a new way to use the Relativistic Heavy Ion Collider (RHIC)—a particle collider at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory—to see the shape and details inside atomic nuclei. The method relies on particles of light that surround gold ions as they speed around the collider and a new type of quantum entanglement that’s never been seen before.

Building Bridges and Ladders in Astrophysics: Theory and Experiment Inform the Equation of State

Researchers are combining experimental, theoretical, and observational data on neutron stars to constrain the equation of state (EOS) and to glean the composition of their interiors. Different techniques probe the EOS at different densities, thereby creating a “density ladder” that aims to connect the various rungs. The findings indicate a possible phase transition in the interior of neutron stars.

Decoding the Proton’s Response to an External Electromagnetic Field

The proton is the only composite building block of matter that is stable in nature, making its properties key to understanding the formation of matter. A team of physicists measured the proton’s electric polarizability, which characterizes the proton’s susceptibility to deformation, or its “stretchability,” in the presence of a photon’s electromagnetic field. The results reveal a puzzling new structure – a bump in the polarizability that nuclear theory cannot explain.

Deblurring Can Reveal 3D Features of Heavy-Ion Collisions

When the nuclei of atoms are about to collide in an experiment, their centers never perfectly align along the direction of relative motion, leading to complex collisions. A deblurring algorithm from optics can help nuclear physicists examine the pattern of emissions from these collisions as if the initial nuclear centers were under tight control.

Particles of Light May Create Fluid Flow, Data-Theory Comparison Suggests

A new computational analysis by theorists at Brookhaven National Laboratory and Wayne State University supports the idea that photons (a.k.a. particles of light) colliding with heavy ions can create a fluid of “strongly interacting” particles. In a new paper they show that calculations describing such a system match up with data collected by the ATLAS detector at Europe’s Large Hadron Collider (LHC).

Department of Energy Announces $11.24 Million for Research on Nuclear Theory Topical Collaborations

Today, the U.S. Department of Energy (DOE) announced $11.24 million for five topical theory collaborations in nuclear physics (NP). These projects bring together leading nuclear theorists to collaboratively focus on solving challenging problems central to advancing knowledge in nuclear physics.

Nuclear Physics Gets a Boost for High-Performance Computing

Efforts to harness the power of supercomputers to better understand the hidden worlds inside the nucleus of the atom recently received a big boost. A project led by the U.S. Department of Energy’s (DOE’s) Thomas Jefferson National Accelerator Facility is one of three to split $35 million in grants from the DOE via a partnership program of DOE’s Scientific Discovery through Advanced Computing (SciDAC). The $13 million project includes key scientists based at six DOE national labs and two universities, including Jefferson Lab, Argonne National Lab, Brookhaven National Lab, Oak Ridge National Lab, Lawrence Berkeley National Lab, Los Alamos National Lab, Massachusetts Institute of Technology and William & Mary.

Scientists Measure Calcium Nuclei’s Thin Skin

Scientists measuring the nucleus of calcium-48 to determine how its 20 protons and 28 neutrons are distributed inside its nucleus found that the protons and neutrons aren’t simply sprinkled throughout the nucleus. Instead, they form a neutron-rich “thin skin” around a core of evenly distributed protons and neutrons. This skin is thinner than many theoretical models predicted and not consistent with expectations based on recent observations of lead’s thick skin.

Chicago Pile 1: A bold nuclear physics experiment with enduring impact

Enrico Fermi’s Chicago Pile 1 experiment in 1942 launched an atomic age, an unrivaled national laboratory system, fleets of submarines, cancer treatments and the unending promise of clean nuclear energy. Argonne National Laboratory builds on its legacy.

Machine Learning Takes Hold in Nuclear Physics

Scientists have begun turning to new tools offered by machine learning to help save time and money. In the past several years, nuclear physics has seen a flurry of machine learning projects come online, with many papers published on the subject. Now, 18 authors from 11 institutions summarize this explosion of artificial intelligence-aided work in “Machine Learning in Nuclear Physics,” a paper recently published in Reviews of Modern Physics.

Unveiling the Existence of the Elusive Tetraneutron

Nuclear physicists have experimentally confirmed the existence of the tetraneutron, a meta-stable nuclear system that can decay into four free neutrons. Researchers have predicted the tetraneutron’s existence since 2016. The new results, which agree with predictions from supercomputer simulations, will help scientists understand atomic nuclei, neutron stars, and other neutron-rich systems.

Tracking Jets in Hot Quark Soup Reveals a Mechanism of ‘Quenching’

Colliding atomic nuclei at very high energies “melts” the boundaries of individual protons and neutrons, setting quarks and gluons to form a quark-gluon plasma (QGP). Quarks or gluons in the colliding ions sometimes scatter off one another and then split, forming parallel sprays of particles called jets. Tracking how jets lose energy, called “quenching,” allows scientists to learn about the QGP and the nuclear strong force. New results find that some quarks lose energy even before they split to form a jet.

Simons Foundation Announces New Collaboration on Confinement and QCD Strings

The Simons Foundation has announced a new research collaboration to explore the “glue” that holds the visible matter of the universe together. This team will delve into the details of quantum chromodynamics (QCD) — the theory that describes the interactions among the most fundamental building blocks of visible matter.

Department of Energy Announces $3.6 Million for Research Traineeships to Broaden and Diversify Nuclear Physics

Today, the U.S. Department of Energy (DOE) awarded more than $3.6 million with a focus on broadening and diversifying the nuclear and particle physics research communities through research traineeships for undergraduates from Historically Black Colleges and Universities (HBCUs) and other Minority Serving Institutions (MSIs). The goal of this program is to increase the recruitment and retention of students from groups under-represented in nuclear physics and to create new partnerships with HBCUs and MSIs. Only by accessing the broadest possible pool of potential physicists can the community produce the best possible science.

‘Shining’ Light on the Inner Details and Breakup of Deuterons

Scientists have found a way to “see” inside deuterons, the simplest atomic nuclei, to better understand how particles called gluons are arranged within the deuteron. These collisions can also break the deuteron apart, giving insights into what holds the proton and neutron together. The research helps scientists understand how nuclei emerge from quarks and gluons, and how the masses of nuclei are dynamically generated by gluons.

RHIC/AGS Users’ Meeting Emphasizes Diverse Workforce Opportunities

Many of the nuclear physicists tuning in to the 2022 Relativistic Heavy Ion Collider (RHIC) & AGS (Alternating Gradient Synchrotron) Users’ Meeting participated in a half-day workshop on June 8 dedicated to diversity, equity, and inclusion (DEI) and workforce development in the nuclear physics community.

Physicists confront the neutron lifetime puzzle

To solve a long-standing puzzle about how long a neutron can “live” outside an atomic nucleus, physicists entertained a wild but testable theory positing the existence of a right-handed version of our left-handed universe.

Theoretical calculations predicted now-confirmed tetraneutron, an exotic state of matter

Iowa State University’s James Vary and an international team of nuclear physicists used supercomputers to theorize and predict that a four-neutron structure, a tetraneutron, could form for just billions of billionths of a second. Experiments in Japan have now confirmed the reality of a tetraneutron.

Energy Secretary Granholm Announces 2021 Ernest Orlando Lawrence Award Winners

Today, U.S. Secretary of Energy Jennifer Granholm announced ten U.S. scientists and engineers as recipients of the prestigious Ernest Orlando Lawrence Award for their exceptional contributions in research and development supporting the Energy Department’s missions in science, energy, and national security. Established in 1959, the Lawrence Award recognizes mid-career U.S. scientists and engineers who have advanced new research and scientific discovery in nine categories representing the broad science and engineering missions of DOE and its programs. The awards are among the longest running and most prestigious science and technology awards bestowed by the U.S. Government.

Direct Neutrino-Mass Measurement Achieves New, Sub-Electronvolt Sensitivity

The international KArlsruhe TRItium Neutrino (KATRIN) experiment in Germany recently reported a new upper limit on the mass of the neutrino. This limit—0.8 electronvolts (eV)—is the lowerst scientists have achieved. As the results are confirmed and refined, they will help scientists better understand the neutrino and its role in the evolution of the universe.

Study Reveals How Some High-Energy Particle ‘Jets’ Lose Energy

Scientists studying particle collisions at the Relativistic Heavy Ion Collider (RHIC) have revealed how certain particle-jets lose energy as they traverse the unique form of nuclear matter created in these collisions. The results should help them learn about key transport properties of this hot particle soup, known as a quark-gluon plasma (QGP).

ORNL, partners launch first experiments using new facility to make cosmic isotopes on Earth

A new flagship facility for nuclear physics has opened, and scientists from Oak Ridge National Laboratory have a hand in 10 of its first 34 experiments.