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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
NASA NTRS1993

Mass spectra of the particle-antiparticle system with a Dirac oscillator interaction

The present view about the structure of mesons is that they are a quark-antiquark system. The mass spectrum corresponding to this system should, in principle, be given by chromodynamics, but this turns out to be a complex affair. Thus it is of some interest to consider relativistic systems of particle-antiparticle, with a simple type of interaction, which could give some insight on the spectra we can expect for mesons. This analysis is carried out when the interaction is of the Dirac oscillator type. It is shown that the Dirac equation of the antiparticle can be obtained from that of the particle by just changing the frequency omega into -omega. Following a procedure suggested by Barut, the equation for the particle-antiparticle system is derived and it is solved by a perturbation procedure. Thus, explicit expressions for the square of the mass spectra are obtained and its implications in the meson case is discussed.

Moshinsky, M.↗
NASA NTRS2001

Virtual Antiparticle Pairs, the Unit of Charge Epsilon and the QCD Coupling Alpha(sub s)

New semi-classical models of virtual antiparticle pairs are used to compute the pair lifetimes, and good agreement with the Heisenberg lifetimes from quantum field theory (QFT) is found. When the results of the new models and QFT are combined, formulae for e and alpha(sub s)(q) are derived in terms of only h and c. The modeling method applies to both the electromagnetic and color forces. Evaluation of the action integral of potential field fluctuation for each interaction potential yields approx. = h/2 for both electromagnetic and color fluctuations, in agreement with QFT. Thus each model is a quantized semiclassical representation for such virtual antiparticle pairs, to good approximation. This work reduces the number of arbitrary parameters of the Standard Model by two from 18 to 16. These are remarkable, unexpected results from a basically classical method.

Batchelor, David↗
NASA NTRS2001

Semi-Classical Models for Virtual Antiparticle Pairs

Virtual particle-antiparticle pairs of massive elementary particle& are predicted in Quantum Field Theory (QFT) to appear from the vacuum and annihilate each other again within their Heisenberg lifetimes h/4mc(exp 2). In this work, semiclassical models of this process - for the cases of massive leptons, quarks, and the massive weak bosons W and Z - are constructed. It is shown that the dynamical lifetime of the particle- antiparticle system in each case equals the Heisenberg lifetime to good approximation, and obeys appropriate quantization conditions on the field fluctuation action. In other words, the dynamical lifetime of the semiclassical model agrees with QED and QCD to good approximation. But the formula for the dynamical lifetime in each model includes the force strength coupling constant (e in the lepton case, alpha(sup s) (q(exp 2)) in the quark cases), while the Heisenberg lifetime formula does not. Observing the agreement of the Heisenberg and dynamical lifetimes, we may derive the QED and QCD coupling constants in terms of h, c, and numerical factors only.

Batchelor, David↗
NASA NTRS2001

Semiclassical Models for Virtual Antiparticle Pairs, the Unit of Charge e, and the QCD Coupling alpha(sub s)

New semiclassical models of virtual antiparticle pairs are used to compute the pair lifetimes, and good agreement with the Heisenberg lifetimes from quantum field theory (QFT) is found. The modeling method applies to both the electromagnetic and color forces. Evaluation of the action integral of potential field fluctuation for each interaction potential yields approximately Planck's constant/2 for both electromagnetic and color fluctuations, in agreement with QFT. Thus each model is a quantized semiclassical representation for such virtual antiparticle pairs, to good approximation. When the results of the new models and QFT are combined, formulae for e and alpha(sub s)(q) are derived in terms of only Planck's constant and c.

Batchelor, David↗
NASA NTRS1984

The case for antiparticles in the extragalactic cosmic radiation

The presence of an excess of low-energy antiprotons in the primary cosmic radiation has given rise to several possible explanations, some of which involve exotic processes such as mini-black holes and extragalactic antiparticles. The latter possibility is considered, and it is shown that there are interesting implications for the cosmic radiation at higher energies. Indeed, it may be possible to account for a previously puzzling feature of the cosmic ray spectrum (a 'bump' in the range between 10 to the 14th and 10 to the 15th eV) by hypothesizing a primary extragalactic origin for the bulk of the observed cosmic ray antiprotons, although such an explanation is not unique. In this model, most of the cosmic rays above 10 to the 15th eV are extragalactic. A method of testing this hypothesis experimentally is described.

Stecker, F. W.↗
DOE OSTI2026

The General Antiparticle Spectrometer (GAPS) Antarctic Balloon Payload

The General Antiparticle Spectrometer (GAPS) is an Antarctic stratospheric balloon mission designed to provide unmatched sensitivity to low-energy (<0.25 GeV/n) cosmic-ray antiprotons, antideuterons, and antihelium nuclei as signatures of dark matter. The distinctive GAPS particle identification technique relies on measuring the energy loss along the track of an incoming antinucleus as it slows down and is captured into an exotic atom, and then detecting the de-excitation X-rays and the nuclear annihilation products. This measurement is realized using a Tracker composed of more than 1000 custom silicon strip detectors and a plastic scintillator time-of-flight (TOF) system instrumenting more than 40m$^2$. Together, these subsystems provide the velocity and energy resolution, stopping power, particle tracking, and X-ray identification necessary to distinguish rare antinucleus signals from the abundant positive-nucleus backgrounds, all within the constraints of a high-altitude mission. A multi-loop capillary heat pipe system has been developed to maintain the tracker operating temperature with significant mass and power savings over a conventional pump-based system. The first GAPS science payload flew for 25 days during the 2025/26 NASA Antarctic balloon campaign. We detail the design, integration, and commissioning of the payload prior to flight.

Aoyama, Kazutaka [JAXA, Sagamihara]↗
NASA NTRS1984

The case for antiparticles in the extragalactic cosmic radiation

The presence of an excess of low energy antiprotons in the primary cosmic radiation has given rise to a number of possible explanations. The possibility that these are extragalactic in origin is considered and it is shown that there are interesting implications for the bulk of the cosmic radiation at higher energies. In particular, it may be possible to account for a previously puzzling feature, a bump in the cosmic ray energy spectrum in the energy range 10(14) to 10(15) eV, with this primary extragalactic origin hypothesis. A method for testing this hypothesis experimentally is also described.

Stecker, F. W.↗
NASA NTRS1985

Antiparticles in the extragalactic cosmic radiation

It may be possible to account for a previously puzzling feature - a bump in the energy range 10 to the 14th power eV to 10 to the 15th power - of the cosmic ray spectrum by hypothesizing a primary extragalactic origin for the bulk of the observed cosmic ray antiprotons, although such an explanation is not unique. In this model, most of the cosmic rays above 10 to the 15th power eV are extragalactic. A method is described of testing this hypothesis experimentally.

Stecker, F. W.↗
DOE OSTI2020

Plasma and trap-based techniques for science with antimatter

Positrons (i.e., antielectrons) find use in a wide variety of applications, and antiprotons are required for the formation and study of antihydrogen. Available sources of these antiparticles are relatively weak. To optimize their use, most applications require that the antiparticles be accumulated into carefully prepared plasmas. We present an overview of the techniques that have been developed to efficiently accumulate low energy antiparticles and create, in particular, tailored antiparticle plasmas. Techniques are also described to create tailored antiparticle beams. Many of these techniques are based on methods first developed by the nonneutral plasma community using electron plasmas for increased data rate. They have enabled the creation and trapping of antihydrogen, have been critical to studies of positron and positronium interactions with matter, including advanced techniques to characterize materials and material surfaces, and have led to the creation and study of the positronium molecule. Rather than attempting to be comprehensive, we focus on techniques that have proven most useful, applications where there has been significant, recent progress, and areas that hold promise for future advances. Examples of the latter include the ever more precise comparisons of the properties of antihydrogen and hydrogen, tests of gravity using antihydrogen and positronium atoms, and efforts to create and study phases of the many-electron, many-positron system.

36 MATERIALS SCIENCE↗
NASA NTRS2001

Antimatter Production at a Potential Boundary

Current antiproton production techniques rely on high-energy collisions between beam particles and target nuclei to produce particle and antiparticle pairs, but inherently low production and capture efficiencies render these techniques impractical for the cost-effective production of antimatter for space propulsion and other commercial applications. Based on Dirac's theory of the vacuum field, a new antimatter production concept is proposed in which particle-antiparticle pairs are created at the boundary of a steep potential step formed by the suppression of the local vacuum fields. Current antimatter production techniques are reviewed, followed by a description of Dirac's relativistic quantum theory of the vacuum state and corresponding solutions for particle tunneling and reflection from a potential barrier. The use of the Casimir effect to suppress local vacuum fields is presented as a possible technique for generating the sharp potential gradients required for particle-antiparticle pair creation.

LaPointe, Michael R.↗
DOE OSTI2021

Cosmic antihelium-3 nuclei sensitivity of the GAPS experiment

The General Antiparticle Spectrometer (GAPS) is an Antarctic balloon experiment designed for low-energy (0.1-0.3 GeV/n) cosmic antinuclei as signatures of dark matter annihilation or decay. GAPS is optimized to detect low-energy antideuterons, as well as to provide unprecedented sensitivity to low-energy antiprotons and antihelium nuclei. The novel GAPS antiparticle detection technique, based on the formation, decay, and annihilation of exotic atoms, provides greater identification power for these low-energy antinuclei than previous magnetic spectrometer experiments. This work reports the sensitivity of GAPS to detect antihelium-3 nuclei, based on full instrument simulation, event reconstruction, and realistic atmospheric influence simulations. The report of antihelium nuclei candidate events by AMS-02 has generated considerable interest in antihelium nuclei as probes of dark matter and other beyond the Standard Model theories. GAPS is in a unique position to detect or set upper limits on the cosmic antihelium nuclei flux in an energy range that is essentially free of astrophysical background. In three 35-day long-duration balloon flights, GAPS will be sensitive to an antihelium flux on the level of $1.3^{+4.5}_{-1.2} $ ∙ 10 -6 m -2 sr -1 s -1 (GeV/n) -1 (95% confidence level) in the energy range of 0.11-0.3 GeV/n, opening a new window on rare cosmic physics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

First Measurement of 𝐴 = 4 Hypernuclei and Antihypernuclei at the LHC

In this Letter, the first evidence of the $^4_{\bar{Λ}}$$\overline{He}$ antihypernucleus is presented, along with the first measurement at the LHC of the production of (anti)hypernuclei with mass number 𝐴 = 4, specifically (anti)⁢$^4_Λ$H and (anti)⁢$^4_Λ$He. In addition, the antiparticle-to-particle ratios for both hypernuclei ($^4_{\bar{Λ}}$$\bar{H}$⁡/$^4_Λ$H and $^4_{\bar{Λ}}$$\overline{He}$/$^4_Λ$He) are shown, which are sensitive to the baryochemical potential of the strongly interacting matter created in heavy-ion collisions. The results are obtained from a data sample of central Pb-Pb collisions, collected during the 2018 LHC data taking at a center-of-mass energy per nucleon pair of $\sqrt{𝑠_{NN}}$ = 5.02 TeV. The yields measured for the average of the charge-conjugated states are found to be [0.78 ± 0.19⁢(stat) ± 0.17⁢(syst)] × 10 −6 for the (anti)⁢$^4_Λ$H and [1.08 ± 0.34⁢(stat)± 0.20⁢(syst)] × 10 −6 for the (anti)⁢$^4_Λ$He, and the measured antiparticle-to-particle ratios are in agreement with unity. The presence of (anti)⁢$^4_Λ$H and (anti)⁢$^4_Λ$He excited states is expected to strongly enhance the production yield of these hypernuclei. The yield values exhibit a combined deviation of 3.3⁢𝜎 from the theoretical ground-state-only expectation, while the inclusion of the excited states in the calculations leads to an agreement within 0.6⁢𝜎 with the present measurements. Additionally, the measured (anti)$^4_Λ$H and (anti)⁢$^4_Λ$He masses are compatible with the world-average values within the uncertainties.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2023

Experimental results from the characterization of a 32-channels mixed-signal processor for the GAPS experiment

This work describes the experimental results obtained from the characterization of a 32-channels readout ASIC that is the core of a module composed by 4 Lithium-drifted Silicon, Si(Li), detectors. The module is the building block of a tracker in an upcoming balloon experiment. The activity is carried out within the General AntiParticle Spectrometer (GAPS) international collaboration, whose objective is the indirect detection of dark matter through the detection of antiparticles present in cosmic rays at low energies. The balloon flight is foreseen in 2024 from the McMurdo station in Antarctica. The ASIC is designed in a 180 nm CMOS technology and has 32 low-noise analog readout channels featuring a dynamic compression of the signal, an 11-bit SAR ADC, and a digital back-end section responsible for channel setting and for sending digital information to the data acquisition system of the tracker. This work has a twofold goal: it intends on the one hand to verify the performance of the circuit, on the other to select at least 300 good samples to be used for the assembly of the GAPS Si(Li) tracker.

Riceputi, Elisa↗
NASA NTRS1985

Search for heavy antinuclei in the cosmic radiation

The existence of significant amounts of antimatter in the Universe is demonstrated through cosmic radiation. The data from the Danish-French Cosmic Ray Spectrometer on the HEAO-3 satellite offers an opportunity to search for heavy antinuclei, since all the relevant parameters (charge, velocity, arrival direction, and satellite position at the time of arrival) are measured for each recorded nucleus. Using the 22676 positive only events in the data seletion corresponding to L 1.5 as a measure of our exposure factor to heavy antinuclei and noting that no corresponding antinuclei were found, an upper limit (95% confidence) is given to the ratio of antinuclei to nuclei as 1.4 x .0001 for particles with Z 9. The upper limit resulting from this work is compared with previous results of searches for heavy antimatter in the cosmic radiation. It is seen that, if one regards only antiparticles heavier than fluorine, then the present result represents a reduced upper limit over previous data. When taken together, all the available experiment data now push the upper limit for the ratio of antiparticles to particles well below .0001.

Lund, N.↗
DOE OSTI2021

Late-time dark matter oscillations and the core-cusp problem

The core-cusp problem persists as an unresolved tension between the pre- dictions of ΛCDM cosmology and observations of dark matter (DM) profiles in dwarf spheroidal and other galaxies. We present a novel scenario for converting cusps into cores through reactivation of DM annihilation in galaxies at late times. This can happen in asymmetric DM models when there is a very small DM-number violating mass term that causes oscillations between DM and its antiparticle. Using analytic methods as well as gravitational N-body simulations, we show that this mechanism can robustly eliminate cusps from galactic DM profiles for light fermionic DM of mass $m_χ$ ~ (0.1 – 1) GeV and a lighter mediator into which the DM can annihilate. We identify regions of parameter space where annihilation of DM particles is more efficient than elastic scattering at reducing the inner density of the DM profile. Dark matter annihilation is therefore a qualitatively distinct alternative to the mechanism of elastic self-interacting dark matter for addressing the cusp-core problem.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Observation of a $ {\varLambda}_b^0 $ - $ {\overline{\varLambda}}_b^0 $ production asymmetry in proton-proton collisions at $ \sqrt{s} $ = 7 and 8 TeV

This article presents differential measurements of the asymmetry between $ {\varLambda}_b^0 $ - $ {\overline{\varLambda}}_b^0 $ baryon production rates in proton-proton collisions at centre-of-mass energies of $\sqrt{s}$ = 7 and 8 TeV collected with the LHCb experiment, corresponding to an integrated luminosity of 3 fb -1 . The ${\varLambda}_b^0 $ baryons are reconstructed through the inclusive semileptonic decay ${\varLambda}_b^0 $ → Λ+c μ - $\overline{ν}$ μX. The production asymmetry is measured both in intervals of rapidity in the range 2.15 < y < 4.10 and transverse momentum in 2 < p T < 27 GeV/c. The results are found to be incompatible with symmetric production with a significance of 5.8 standard deviations for both $\sqrt{s}$ = 7 and 8 TeV data, assuming no CP violation in the decay. There is evidence for a trend as a function of rapidity with a significance of 4 standard deviations. Comparisons to predictions from hadronisation models in PYTHIA and heavy-quark recombination are provided. This result constitutes the first observation of a particle-antiparticle asymmetry in b-hadron production at LHC energies.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Transient phenomena in the axion assisted Schwinger effect

Particle production induced by a time-dependent background is well understood as the projection of the time-evolved initial state onto a set of final states. While the asymptotic initial and final states are well defined in the usual way, the definition of particles and antiparticles at intermediate times in the presence of external fields is ambiguous. These external fields moreover induce divergences which require regularization. In this paper we clarify some subtleties in the computation of transient effects in physical quantities for fermions in a homogeneous axion background, including Schwinger production in background electromagnetic fields. The presence of the axion requires particular care as well as knowledge of the UV theory when regulating the theory and computing the vacuum contribution to the fermion energy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗