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Results for “Subatomic and elementary particles”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Testing strong-field QED with the avalanche precursor

A two-beam high-power laser facility is essential for the study of one of the most captivating phenomena predicted by strong-field quantum electrodynamics (QED) and yet unobserved experimentally: the avalanche-type cascade. In such a cascade, the energy of intense laser light can be efficiently transformed into high-energy radiation and electron–positron pairs. The future 50-petawatt-scale laser facility NSF OPAL will provide unique opportunities for studying such strong-field QED effects, as it is designed to deliver two ultra-intense, tightly focused laser pulses onto the interaction point. In this work, we investigate the potential of such a facility for studying elementary particle and plasma dynamics deeply in the quantum radiation-dominated (RD) regime, and the generation of QED avalanches. With three-dimensional particle-in-cell simulations, we demonstrate that QED avalanche precursors can be reliably triggered under realistic laser parameters and layout (namely, focusing f/2, tilted optical axes, and non-ideal co-pointing) with the anticipated capabilities of NSF OPAL. We demonstrate that seed electrons can be efficiently injected into the laser focus by using targets of three types: a gas of heavy atoms, an overcritical plasma, and a thin foil. A strong positron and high-energy photon signal is generated in all cases. The cascade properties can be identified from the final particle distributions, which have a clear directional pattern. At increasing laser field intensity, such distributions provide signatures of the transition, first, to the RD interaction regime, and then to a QED avalanche. Our findings can also be used for designing related future experiments.

Lasers↗
DOE OSTI2023

Instabilities of heavy magnons in an anisotropic magnet

Abstract The search for new elementary particles is one of the most basic pursuits in physics, spanning from subatomic physics to quantum materials. Magnons are the ubiquitous elementary quasiparticle to describe the excitations of fully-ordered magnetic systems. But other possibilities exist, including fractional and multipolar excitations. Here, we demonstrate that strong quantum interactions exist between three flavors of elementary quasiparticles in the uniaxial spin-one magnet FeI 2 . Using neutron scattering in an applied magnetic field, we observe spontaneous decay between conventional and heavy magnons and the recombination of these quasiparticles into a super-heavy bound-state. Akin to other contemporary problems in quantum materials, the microscopic origin for unusual physics in FeI 2 is the quasi-flat nature of excitation bands and the presence of Kitaev anisotropic magnetic exchange interactions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Rosen Scholar

Dr. Tim Chupp is a professor of physics, applied physics, and biomedical engineering from the University of Michigan. As Rosen Scholar he will work with the Subatomic Physics group’s Neutron Team to develop the LANL RoomTemperature Neutron Electric Dipole Moment (nEDM) experiment that will used at LANSCE's world-leading Ultracold Neutron Facility. The electric dipole moment is the electrical stretching of neutrons or atoms along their spin axis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Is Physics in Crisis? The Mystery of the W Boson

The standard model of particle physics is the most successful theory describing the behavior of matter and energy in the subatomic realm. However, success doesn’t mean it is perfect, and a recent measurement of the mass of a particle called the W boson is puzzling, as it disagrees with theoretical predictions and earlier precise measurements. If this measurement and prediction are both correct, the standard model will have to be modified or replaced, potentially overturning half a century of accepted physics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurement of the effective leptonic weak mixing angle

Using pp collision data at $\sqrt{s}$ = 13 TeV, recorded by the LHCb experiment between 2016 and 2018 and corresponding to an integrated luminosity of 5.4 fb −1 , the forward-backward asymmetry in the pp → Z/γ* → μ + μ − process is measured. The measurement is carried out in ten intervals of the difference between the muon pseudorapidities, within a fiducial region covering dimuon masses between 66 and 116 GeV, muon pseudorapidities between 2.0 and 4.5 and muon transverse momenta above 20 GeV. These forward-backward asymmetries are compared with predictions, at next-to-leading order in the strong and electroweak couplings. The measured effective leptonic weak mixing angle is ${\sin}^2{\theta}_{\textrm{eff}}^{\ell }=0.23147\pm 0.00044\pm 0.00005\pm 0.00023,$ where the first uncertainty is statistical, the second arises from systematic uncertainties associated with the asymmetry measurement, and the third arises from uncertainties in the fit model used to extract ${\sin}^2{\theta}_{\textrm{eff}}^{\ell }$ from the asymmetry measurement. This result is based on an arithmetic average of results using the CT18, MSHT20, and NNPDF31 parameterisations of the proton internal structure, and is consistent with previous measurements and with predictions from the global electroweak fit.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

A Centennial of Protons

In the modern and exciting world of particle physics, in which scientists talk of Higgs bosons and supersymmetry, it would be natural for someone to dismiss the common proton as a particle too pedestrian to be interesting. Yet in the centennial year of the announcement of its discovery, studies of the humble nucleus of the hydrogen atom continue to teach us fascinating lessons about the subatomic world. As recently as 2018, scientists found themselves unable to definitively determine as simple a parameter as the radius of the proton. And uncertainties in the detailed internal structure of the proton continue to be the dominant limitation of precision measurements conducted at such particle accelerators as the Large Hadron Collider. Indeed, the final story of the proton has yet to be told.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

AC-LGADs Fermilab front-end electronics characterization

Here, we characterized the front-end electronics used to process high-frequency signals from low-gain avalanche diodes (LGADs) at the Fermilab Test Beam Facility. LGADs are silicon detectors employed for charged particle tracking, offering exceptional spatial and temporal resolution. The purpose of this characterization was to understand how the time resolution is influenced by the front-end electronics. To achieve this, we developed a setup capable of generating input signals with varying amplitudes. The output results demonstrated that signal processing by the front-end electronics plays a crucial role in enhancing time resolution. We showed that the time resolution achieved by the FEE board is better than 2 p s at the 1 σ level.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2025

Precision measurement of the $Ξ^0_b$ baryon lifetime

A sample of 𝑝⁢𝑝 collision data, corresponding to an integrated luminosity of 5.4 fb −1 and collected by the LHCb experiment during LHC Run 2, is used to measure the ratio of the lifetime of the $Ξ^0_b$ baryon to that of the $Λ^0_b$ baryon, 𝑟 𝜏 $≡$ $𝜏_{Ξ^0_b}$$/𝜏_{Λ^0_b}$. The value 𝑟$^{\textrm{Run 2}}_𝜏$ =1.004 ± 0.009 ± 0.006 is obtained, where the first uncertainty is statistical and the second systematic. This value is averaged with the corresponding value from Run 1 to obtain 𝑟 𝜏 =1.004 ± 0.008 ± 0.005. Multiplying by the known value of the $Λ^0_b$ lifetime yields $𝜏_{Ξ^0_b}$ = 1.475 ± 0.012 ± 0.008 ± 0.009 ps, where the last uncertainty is due to the limited knowledge of the $Λ^0_b$ lifetime. This measurement improves the precision of the current world average of the $Ξ^0_b$ lifetime by about a factor of two, and is in good agreement with the most recent theoretical predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Nature's Strongest Force

The strongest force in the universe is called, aptly, the strong force. We never get to witness its fearsome power because it works only across subatomic distances, where it binds quarks together inside protons and neutrons and joins those nucleons into atomic nuclei. Of the four basic forces of nature, the strong force is by far the most potent—it’s 100 trillion trillion trillion times stronger than the force of gravity. Additionally, it’s also the most mysterious.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

SNOLAB Deep Underground Scientific Research Operations

Investigations at the frontiers of particle physics are driving key experiments deep underground to escape cosmic-rays and other backgrounds that overwhelm sensitive searches for dark matter, exotic particles, and neutrino properties. The international neutrino physics community has come together to develop the Deep Underground Neutrino Experiment (DUNE), a leading-edge experiment for neutrino science and proton decay studies. This experiment, together with the facility that will support it, the Long Baseline Neutrino Facility (LBNF), will be an internationally designed, coordinated and funded program, hosted at Fermilab in Batavia, Illinois. The DUNE experimental facility will be sited deep underground (1.5km) at Sanford Underground Research Facility (SURF) in Lead, SD, and will become the deepest experimental facility operated by Fermilab. SNOLAB is a unique world-class international facility for deep underground scientific research. Located 2 km underground near Sudbury, Ontario, SNOLAB hosts a suite of surface facilities and laboratories. The science program at SNOLAB is primarily focused on subatomic and astroparticle physics, specifically the search for dark matter and neutrino studies. As the second-deepest underground lab facility, SNOLAB has gained considerable experience in deep underground scientific research operations. The purpose of this agreement is to leverage the unique capabilities of both Fermilab and SNOLAB to accomplish the following: Provide Fermilab with additional, direct experience in deep underground scientific research operations at SNOLAB to help improve the operational support for SURF. Provide SNOLAB with an experienced leader to serve as Interim Associate Director for Program Integration & Operations, while SNOLAB conducts its search for a permanent hire.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Sterile Neutrinos: Are They Real?

Neutrinos are perhaps the least understood of the known denizens of the subatomic world. They have nearly no mass, interact only via the weak nuclear force and gravity, and, perhaps most surprising, the three known species of neutrinos can transform from one variant into another. This transformation, called neutrino oscillation, has been demonstrated only relatively recently and has led to speculation that there might be another, even more mysterious, neutrino variant, called the sterile neutrino. While the sterile neutrino remains a hypothetical particle, it is an interesting one and searches for it are a key research focus of the world’s neutrino scientist community.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Observation of Exotic 𝐽/𝜓⁢𝜙 Resonant Structure in Diffractive Processes in Proton-Proton Collisions

The first study of 𝐽/𝜓⁢𝜙 production in diffractive processes in proton-proton collisions is presented. The study is based on an LHCb dataset recorded at center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 5 fb −1 . The data disfavor a nonresonant 𝐽/𝜓⁢𝜙 production but are consistent with a resonant model including several resonant states observed previously only in 𝐵 + →𝐽/𝜓⁢𝜙⁢𝐾 + decays. The 𝜒 𝑐⁢0⁡ (4500) state is observed with a significance over 6⁢𝜎 and the 𝜒 𝑐⁢1 ⁡(4274) is confirmed with a significance of more than 4⁢𝜎.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Context-Enriched Identification of Particles with a Convolutional Network for Neutrino Events

Particle detectors record the interactions of subatomic particles and their passage through matter. The identification of these particles is necessary for in-depth physics analysis. While particles can be identified by their individual behavior as they travel through matter, the full context of the interaction in which they are produced can aid the classification task substantially. We have developed the first convolutional neural network for particle identification which uses context information. This is also the first implementation of a four-tower siamese-type architecture both for separation of independent inputs and inclusion of context information. The network classifies clusters of energy deposits from the NOvA neutrino detectors as electrons, muons, photons, pions, and protons with an overall efficiency and purity of 83.3% and 83.5%, respectively. We show that providing the network with context information improves performance by comparing our results with a network trained without context information.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2019

Predicting the Flux: Models and Simulation for NOvA

The study of neutrinos provides a novel yet challenging way to probe the subatomic world and the fundamental laws of the universe. One experiment currently committed to such a study is the NuMI Off-axis 𝝂_𝒆 Appearance experiment, or NOvA. NOvA is composed of two detectors located about 810 kilometers apart. Both detectors receive neutrinos created by Fermilab's NuMI (Neutrinos at the Main Injector) beam. These neutrinos are produced in the decay of short-lived particles that are created when protons interact with a graphite target. Key to NOvA, and other neutrino experiments like the upcoming DUNE, is calculating the neutrino flux expected at the detectors. The main challenge is the uncertainties associated with the hadronic interactions. Hadronic cross sections used by the model must be extracted and corrected to data. This correction is sensitive to both the hadronic model and the software versions being used. The focus for this project is to satisfy the nee d for an automated update process and in turn produce better flux predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Nuclear cold QCD: Review and future strategy

This review examines data from hadron-nucleus collisions, primarily focusing on hard processes like Drell-Yan, heavy flavor, and quarkonium production. It highlights observed modifications of particle yields as functions of momentum and rapidity, aiming to clarify the underlying QCD effects on cold nuclear matter. It outlines strategies for future experiments, including the Electron-Ion Collider, to distinguish between these effects. Key questions address the universality of suppression mechanisms and the role of nonperturbative physics, providing a road map for upcoming measurements of hadrons on nuclei.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

High Energy Neutrino Physics

Of the twelve subatomic particles that are the building blocks of all the known matter in the universe, three are neutrinos, small neutral particles that interact through the weak interaction with other particles in the Universe. These three neutrinos, paired with the three charged leptons, the familiar electron, the heavier muon, and the still heavier tau, are some of the least well understood particles of these building blocks. Experiments using accelerator beams, like those that are the subject of this grant, can address some of the key questions scientists are posing with respect to the neutrino. Specifically, are there differences between neutrinos and their anti-particles, anti-neutrinos, that could give us some clue to the matter dominated universe, do we understand the spectrum of masses of the three neutrinos, and are there other kinds of neutirnos than the three neutrinos? Coupled with advances in precision neutrino detection, the US is addressing these questions from small scale experiments to the massive DUNE experiment. PI Fleming and her team play critical roles in accelerator based neutrino physics at short and long baseline with participation on MicroBooNE, SBND, and with the group's participation in DUNE. These experiments are at the heart of the US-based high energy physics program.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Results for pixel and strip centimeter-scale AC-LGAD sensors with a 120 GeV proton beam

Here, we present the results of an extensive evaluation of strip and pixel AC-LGAD sensors tested with a 120 GeV proton beam, focusing on the influence of design parameters on the sensor temporal and spatial resolutions. Results show that reducing the thickness of pixel sensors significantly enhances their time resolution, with 20-μm-thick sensors achieving around 20 ps. Uniform performance is attainable with optimized n + sheet resistance, making these sensors ideal for future timing detectors. Conversely, 20-μm-thick strip sensors exhibit higher jitter than similar pixel sensors, negatively impacting time resolution, despite reduced Landau fluctuations with respect to the 50-μm-thick versions. Additionally, it is observed that a low resistivity in strip sensors limits signal size and time resolution, whereas higher resistivity improves performance. This study highlights the importance of tuning the n+ sheet resistance and suggests that further improvements should target specific applications like the Electron–Ion Collider or other future collider experiments. In addition, the detailed performance of four AC-LGADs sensor designs is reported as examples of possible candidates for specific detector applications. These advancements position AC-LGADs as promising candidates for future 4D tracking systems, pending the development of specialized readout electronics.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2023

Rare K 40 Decay with Implications for Fundamental Physics and Geochronology

Potassium-40 is a widespread, naturally occurring isotope whose radioactivity impacts subatomic rare-event searches, nuclear structure theory, and estimated geological ages. A predicted electron-capture decay directly to the ground state of argon-40 has never been observed. Here, the KDK (potassium decay) collaboration reports strong evidence of this rare decay mode. A blinded analysis reveals a nonzero ratio of intensities of ground-state electron-captures (I EC 0 ) over excited-state ones (I EC $\star$ ) of I EC 0 /I EC $\star$ = 0.0095 $^{stat}_{±}$ 0.0022 $^{sys}_{±}$ 0.0010 (68% C.L.), with the null hypothesis rejected at 4σ. In terms of branching ratio, this signal yields I EC 0 = 0.098 % $^{stat}_{±}$ 0.023 % $^{sys}_{±}$ 0.010 % , roughly half of the commonly used prediction, with consequences for various fields [L. Hariasz et al., companion paper, Phys. Rev. C 108, 014327 (2023)].

39 ≤ A ≤ 58↗