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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Multi-wavelength modeling of globular clusters–the millisecond pulsar scenario

The potentially large number of millisecond pulsars (MSPs) in globular cluster (GC) cores makes these parent objects ideal laboratories for studying the collective properties of an ensemble of MSPs. Such a population is expected to radiate several spectral components in the radio through γ-ray waveband. First, pulsed emission is expected via curvature and synchrotron radiation (CR and SR) and possibly even via inverse Compton (IC) scattering inside the pulsar magnetospheres. Second, unpulsed emission should transpire through the continuous injection of relativistic leptons by the MSPs into the ambient region, which in turn produce SR and IC emission when they encounter the cluster magnetic field, as well as several background photon components. In this paper we continue to develop the MSP scenario for explaining the multi-wavelength properties of GCs by considering the entire modeling chain, including the full transport equation, refined emissivities of stellar and Galactic background photons, integration of the flux along the line of sight, and comparison with observations. As an illustration, we apply the model to Terzan 5, where we can reasonably fit both the (line-of-sight-integrated) X-ray surface flux and spectral energy density data, using the first to constrain the leptonic diffusion coefficient within the GC. We lastly discuss possible future extensions to and applications of this maturing model.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Future high energy colliders and options for the U.S.

The United States has a rich history in high energy particle accelerators and colliders — both lepton and hadron machines, which have enabled several major discoveries in elementary particle physics. To ensure continued progress in the field, U.S. leadership as a key partner in building next generation collider facilities abroad is essential; also critically important is to prepare to host an energy frontier collider in the U.S. once the construction of the LBNF/DUNE project is completed. In this paper, we briefly discuss the ongoing and potential U.S. engagement in proposed collider projects abroad and present a number of future collider options we have studied for hosting an energy frontier collider in the U.S. Further, we also call for initiating an integrated national R&D program in the U.S. now, focused on future colliders.

43 PARTICLE ACCELERATORS↗
NASA NTRS1982

Particle physics meets cosmology - The search for decaying neutrinos

The fundamental physical implications of the possible detection of massive neutrinos are discussed, with an emphasis on the Grand Unified Theories (GUTs) of matter. The Newtonian and general-relativistic pictures of the fundamental forces are compared, and the reduction of electromagnetic and weak forces to one force in the GUTs is explained. The cosmological consequences of the curved-spacetime gravitation concept are considered. Quarks, leptons, and neutrinos are characterized in a general treatment of elementary quantum mechanics. The universe is described in terms of quantized fields, the noninteractive 'particle' fields and the force fields, and cosmology becomes the study of the interaction of gravitation with the other fields, of the 'freezing out' of successive fields with the expansion and cooling of the universe. While the visible universe is the result of the clustering of the quark and electron fields, the distribution of the large number of quanta in neutrino field, like the mass of the neutrino, are unknown. Cosmological models which attribute anomalies in the observed motions of galaxies and stars to clusters or shells of massive neutrinos are shown to be consistent with a small but nonzero neutrino mass and a universe near the open/closed transition point, but direct detection of the presence of massive neutrinos by the UV emission of their decay is required to verify these hypotheses.

Henry, R. C.↗
DOE OSTI2020

Search for new non-resonant phenomena in high-mass dilepton final states with the ATLAS detector

A search for new physics with non-resonant signals in dielectron and dimuon final states in the mass range above 2 TeV is presented. This is the first search for non-resonant signals in dilepton final states at the LHC to use a background estimate from the data. The data, corresponding to an integrated luminosity of 139 fb –1 , were recorded by the ATLAS experiment in proton-proton collisions at a center-of-mass energy of √s = 13 TeV during Run 2 of the Large Hadron Collider. The benchmark signal signature is a two-quark and two-lepton contact interaction, which would enhance the dilepton event rate at the TeV mass scale. To model the contribution from background processes a functional form is fit to the dilepton invariant-mass spectra in data in a mass region below the region of interest. It is then extrapolated to a high-mass signal region to obtain the expected background there. No significant deviation from the expected background is observed in the data. Upper limits at 95% CL on the number of events and the visible cross-section times branching fraction for processes involving new physics are provided. Observed (expected) 95% CL lower limits on the contact interaction energy scale reach 35.8 (37.6) TeV.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Search for Heavy Neutral Leptons in the MicroBooNE LArTPC

aHeavy Neutral Leptons (HNLs) offer a possible extension of the Standard Model via mixing with the three active neutrino flavours. HNLs with masses between 1 and 493 MeV can be produced from kaon and pion decays in the high-intensity Booster Neutrino Beam. These particles would then travel to the MicroBooNE detector where some fraction would decay in-flight to detectable Standard Model particles. This poster presents work to perform the first search for these particles in a liquid argon TPC. A number of methods are used to distinguish the HNL decays from the neutrino and cosmic ray background including utilising the time of flight of the massive HNL with respect to the active neutrinos. As the first search of its kind in a LArTPC this work pioneers techniques applicable for future large scale searches in the both the full Short Baseline Neutrino program and DUNE.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Inclusive and differential cross-section measurements of $ t\overline{t}Z$ production in pp collisions at $\sqrt{s}$ = 13 TeV with the ATLAS detector, including EFT and spin-correlation interpretations

Measurements of both the inclusive and differential production cross sections of a top-quark-top-antiquark pair in association with a Z boson ($t\overline{t}Z$) are presented. Final states with two, three or four isolated leptons (electrons or muons) are targeted. The measurements use the data recorded by the ATLAS detector in pp collisions at $\sqrt{s}$ = 13 TeV at the Large Hadron Collider during the years 2015–2018, corresponding to an integrated luminosity of 140 fb -1 . The inclusive cross section is measured to be ${\sigma}_{t\overline{t}Z}$ = 0.86 ± 0.04 (stat.) ± 0.04 (syst.) pb and found to be in agreement with the most advanced Standard Model predictions. The differential measurements are presented as a function of a number of observables that probe the kinematics of the $t\overline{t}Z$ system. Both the absolute and normalised differential cross-section measurements are performed at particle level and parton level for specific fiducial volumes, and are compared with NLO+NNLL theoretical predictions. The results are interpreted in the framework of Standard Model effective field theory and used to set limits on a large number of dimension-6 operators involving the top quark. The first measurement of spin correlations in $t\overline{t}Z$ events is presented: the results are in agreement with the Standard Model expectations, and the null hypothesis of no spin correlations is disfavoured with a significance of 1.8 standard deviations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Search for $\mathrm{t\overline{t}}$H production in the H $\rightarrow$ $\mathrm{b\overline{b}}$ decay channel with leptonic $\mathrm{t\overline{t}}$ decays in proton-proton collisions at $\sqrt{s} =$ 13 TeV

A search is presented for the associated production of a standard model Higgs boson with a top quark-antiquark pair ($\mathrm{t\overline{t}}$H), in which the Higgs boson decays into a b quark-antiquark pair, in proton-proton collisions at a centre-of-mass energy $\sqrt{s} =$ 13 TeV. The data correspond to an integrated luminosity of 35.9 fb$^{-1}$ recorded with the CMS detector at the CERN LHC. Candidate $\mathrm{t\overline{t}}$H events are selected that contain either one or two electrons or muons from the $\mathrm{t\overline{t}}$ decays and are categorised according to the number of jets. Multivariate techniques are employed to further classify the events and eventually discriminate between signal and background. The results are characterised by an observed $\mathrm{t\overline{t}}$H signal strength relative to the standard model cross section, $\mu = \sigma$ / $\sigma_{\mathrm{SM}}$, under the assumption of a Higgs boson mass of 125 GeV. A combined fit of multivariate discriminant distributions in all categories results in an observed (expected) upper limit on $\mu$ of 1.5 (0.9) at 95% confidence level, and a best fit value of 0.72 $\pm$ 0.24 (stat) $\pm$ 0.38 (syst), corresponding to an observed (expected) signal significance of 1.6 (2.2) standard deviations above the background-only hypothesis.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Measurement of the inclusive $\textrm{t}\overline{\textrm{t}}$ cross section in final states with at least one lepton and additional jets with 302 pb −1 of pp collisions at $\sqrt{\textrm{s}}$ = 5.02 TeV

A measurement of the top quark pair ($ \textrm{t}\overline{\textrm{t}} $) production cross section in proton-proton collisions at a centre-of-mass energy of 5.02 TeV is presented. The data were collected at the LHC in autumn 2017, in dedicated runs with low-energy and low-intensity conditions with respect to the default configuration, and correspond to an integrated luminosity of 302 pb$^{−1}$. The measurement is performed using events with one electron or muon, and multiple jets, at least one of them being identified as originating from a b quark (b tagged). Events are classified based on the number of all reconstructed jets and of b-tagged jets. Multivariate analysis techniques are used to enhance the separation between the signal and backgrounds. The measured cross section is $ 62.5\pm 1.6{\left(\textrm{stat}\right)}_{-2.5}^{+2.6}\left(\textrm{syst}\right)\pm 1.2\left(\textrm{lumi}\right) $ pb. A combination with the result in the dilepton channel based on the same data set yields a value of 62.3 ± 1.5 (stat) ± 2.4 (syst) ± 1.2 (lumi) pb, to be compared with the standard model prediction of $ {69.5}_{-3.7}^{+3.5} $ pb at next-to-next-to-leading order in perturbative quantum chromodynamics.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Spectroscopy and decay properties of the D{sub s} meson

Using hydrogenic and Gaussian wave functions, mass spectra and decay properties of the D{sub s}(cs) meson are investigated in the framework of phenomenological quark-antiquark potential (Coulomb plus power) model consisting of a relativistic kinetic energy term. The spin-hyperfine, spin-orbit, and tensor interactions are employed to obtain the pseudoscalar and vector meson masses incorporating the effect of mixing. The decay constants (f{sub P/V}) are computed with QCD correction using the wave function at the origin. The leptonic branching fractions and electromagnetic transition rates are also calculated in this scheme. Our predictions at potential index {nu}=1 are in good agreement with experimental results as well as other theoretical models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Anomalously interacting new extra vector bosons and their first LHC constraints

In this review phenomenological consequences of the Standard Model extension by means of new spin-1 chiral fields with the internal quantum numbers of the electroweak Higgs doublets are summarized. The prospects for resonance production and detection of the chiral vector Z* and W*{sup ±} bosons at the LHC energies are considered on the basis of quantitative simulations within the CompHEP/CalcHEP package. The Z* boson can be observed as a Breit-Wigner resonance peak in the invariant dilepton mass distributions in the same way as the well-known extra gauge Z′ bosons. However, the Z* bosons have unique signatures in transverse momentum, angular and pseudorapidity distributions of the final leptons, which allow one to distinguish them from other heavy neutral resonances. In 2010, with 40 pb{sup −1} of the LHC proton-proton data at the energy 7 TeV, the ATLAS detector was used to search for narrow resonances in the invariant mass spectrum of e{sup +} e{sup −} and μ{sup +}μ{sup −} final states and high-mass charged states decaying to a charged lepton and a neutrino. No statistically significant excess above the Standard Model expectation was observed. The exclusion mass limits of 1.15 and 1.35 TeV/c{sup 2} were obtained for the chiral neutral Z* and charged W* bosons, respectively. These are the first direct limits on the W* and Z* boson production. Based on the above, a novel strategy for the chiral boson search in the LHC dijet data is discussed. For almost all currently considered exotic models the relevant signal is expected in the central dijet rapidity region y{sub 1,2} ≃ 0 and |y{sub 1} − y{sub 2}| ≃ 0. On the contrary, the chiral bosons do not contribute to this region but produce an excess of dijet events far away from it. In particular, for these bosons the appropriate kinematical restrictions lead to a dip in the centrality ratio distribution over the dijet invariant mass instead of a bump expected in the most exotic models.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2012

Search for $ZW/ZZ \to \ell^+ \ell^-$ + Jets Production in $p\bar{p}$ Collisions at CDF

The Standard Model of particle physics describes weak interactions mediated by massive gauge bosons that interact with each other in well-defined ways. Observations of the production and decay of WW, WZ, and ZZ boson pairs are an opportunity to check that these self-interactions agree with the Standard Model predictions. Furthermore, final states that include quarks are very similar to the most prominent final state of Higgs bosons produced in association with a W or Z boson. Diboson production where WW is a significant component has been observed at the Tevatron collider in semi-hadronic decay modes. We present a search for ZW and ZZ production in a final state containing two charged leptons and two jets using 8.9 fb -1 of data recorded with the CDF detector at the Tevatron. We select events by identifying those that contain two charged leptons, two hadronic jets, and low transverse missing energy (E T ). We increase our acceptance by using a wide suite of high-p T lepton triggers and by relaxing many lepton identification requirements. We develop a new method for calculating corrections to jet energies based on whether the originating parton was a quark or gluon to improve the agreement between data and the Monte Carlo simulations used to model our diboson signal and dominant backgrounds. We also make use of neural-network-based discriminants that are trained to pick out jets originating from b quarks and light-flavor quarks, thereby increasing our sensitivity to Z → b$\bar{b}$ and W=Z → q$\bar{p'}$0 decays, respectively. The number of signal events is extracted through a simultaneous fit to the dijet mass spectrum in three channels: a heavy-flavor tagged channel, a light-flavor tagged channel, and an untagged channel. We measure σ ZW/ZZ = 2.5 +2.0 -1.0 pb, which is consistent with the SM cross section of 5.1 pb. We establish an upper limit on the cross section of σ ZW/ZZ < 6.1 pb at 95% CL.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2025

Puzzling Variation of Gamma Rays from the Sun over the Solar Cycle Revealed with Fermi-LAT

The steady-state gamma-ray emission from the Sun is thought to consist of two emission components due to interactions with Galactic cosmic rays: (1) a hadronic disk component, and (2) a leptonic extended component peaking at the solar edge and extending into the heliosphere. The flux of these components is expected to vary with the 11 yr solar cycle, being highest during solar minimum and lowest during solar maximum, as it varies with the cosmic-ray flux. No study has yet analyzed the flux variation of each component over solar cycles. In this work, we measure the temporal variations of the flux of each component over 15 yr of Fermi Large Area Telescope observations and compare them with the sunspot number and Galactic cosmic-ray flux from AMS-02 near Earth. We find that the flux variation of the disk anticorrelates with the sunspot number and correlates with cosmic-ray protons, as expected, confirming its emission mechanism. In contrast, the extended component exhibits a more complex variation: despite an initial anticorrelation with the sunspot number, we find neither anticorrelation with the sunspot number nor correlation with cosmic-ray electrons over the full 15 yr period. This most likely suggests that cosmic-ray transport and modulation in the inner heliosphere are unexpectedly complex and may differ for electrons and protons or, alternatively, that there is an additional, unknown component of gamma rays or cosmic rays. These findings impact space weather research and emphasize the need for close monitoring of Cycle 25 and the ongoing polarity reversal.

Acharyya, A. [Univ. of Southern Denmark, Odense (D↗
DOE OSTI2011

Transition nucleon resonance electrocouplings from CLAS data on {pi}{sup +}{pi}{sup -}p electroproduction off protons

Electrocouplings of excited proton states with masses less than 1.8 GeV were determined for the first time from the CLAS data on {pi}{sup +}{pi}{sup -}p electroproduction at photon virtualities Q{sup 2}<1.5 GeV{sup 2}. Electrocouplings were obtained from a combined fit of all available observables within the framework of a phenomenological reaction model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2014

Impulsive and long duration high-energy gamma-ray emission from the very bright 2012 March 7 solar flares

The Fermi Large Area Telescope (LAT) detected gamma-rays up to 4 GeV from two bright X-class solar flares on 2012 March 7, showing both an impulsive and temporally extended emission phases. The gamma-rays appear to originate from the same active region as the X-rays associated with these flares. The >100 MeV gamma-ray flux decreases monotonically during the first hour (impulsive phase) followed by a slower decrease for the next 20 hr. A power law with a high-energy exponential cutoff can adequately describe the photon spectrum. Assuming that the gamma rays result from the decay of pions produced by accelerated protons and ions with a power-law spectrum, we find that the index of that spectrum is ∼3, with minor variations during the impulsive phase. During the extended phase the photon spectrum softens monotonically, requiring the proton index varying from ∼4 to >5. The >30 MeV proton flux observed by the GOES satellites also shows a flux decrease and spectral softening, but with a harder spectrum (index ∼2-3). Based on these observations, we explore the relative merits of prompt or continuous acceleration scenarios, hadronic or leptonic emission processes, and acceleration at the solar corona or by the fast coronal mass ejections. We conclude that the most likely scenario is continuous acceleration of protons in the solar corona that penetrate the lower solar atmosphere and produce pions that decay into gamma rays. However, acceleration in the downstream of the shock cannot be definitely ruled out.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Development of online pulse-finding algorithms for the Mu2e Stopping Target Monitor and an evaluation of the signal to background ratio for the Mu2e stopped-muon rate determination

This thesis presents a determination of the acceptance of the Mu2e Stopping Target Monitor (STM) detector for both signal and background events. The rate of X-rays of a specific energy in the STM is used to determine the rate of stopped muons in the aluminium stopping target, which is used as the normalisation for all Mu2e measurements, particularly the branching ratio for a charged lepton flavour violating (cLFV) process. The acceptance for the 347\,keV $2p-1s$ aluminium signal X-ray is determined to be $(8.03 \pm 0.05) \times 10^{-10}$\,cm$^{-2}$ and the acceptance for the background photons (at 347\,keV) to be $(3.19 \pm 0.21) \times 10^{-8}$\,cm$^{-2}$. This results in a signal-to-background ratio of approximately two which is significantly higher than had previously been estimated. These signal-to-background rates are used to determine the time required to achieve a statistical uncertainty of 10\% on the number of 347\,keV X-rays as a function of the detector resolution and back ground rate. For a resolution of 2\,keV, and the background rate determined in this thesis, approximately one minute of data is required. The three corrections needed to be applied to the measured 347\,keV rate to determine the rate of stopped muons are also determined and potential sources of bias arising from the background shape, background fit range and energy calibration are investigated and found to be insignificant. The raw energy of the particles in the STM detector comes from a 16-bit ADC digitising at $\sim 300$\,MHz. It is not possible to store all the raw digitisations and online algorithms have been developed to rapidly select pulses in the detector and reconstruct their energy. The performance of these algorithms has been characterised with simulated data as a function of detector rate and resolution and optimum operating points for the algorithms have been defined. The integrity of the algorithms has also been demonstrated and characterised on test-beam data at high r ates and with radioactive sources at low rates.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2011

Spectral probes of the holographic Fermi ground state: Dialing between the electron star and AdS Dirac hair

We argue that the electron star and the anti-de Sitter (AdS) Dirac hair solution are two limits of the free charged Fermi gas in AdS. Spectral functions of holographic duals to probe fermions in the background of electron stars have a free parameter that quantifies the number of constituent fermions that make up the charge and energy density characterizing the electron star solution. The strict electron star limit takes this number to be infinite. The Dirac hair solution is the limit where this number is unity. This is evident in the behavior of the distribution of holographically dual Fermi surfaces. As we decrease the number of constituents in a fixed electron star background the number of Fermi surfaces also decreases. An improved holographic Fermi ground state should be a configuration that shares the qualitative properties of both limits.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1981

Particle physics in the very early universe

Events in the very early big bang universe in which elementary particle physics effects may have been dominant are discussed, with attention to the generation of a net baryon number by way of grand unification theory, and emphasis on the possible role of massive neutrinos in increasing current understanding of various cosmological properties and of the constraints placed on neutrino properties by cosmology. It is noted that when grand unification theories are used to describe very early universe interactions, an initially baryon-symmetrical universe can evolve a net baryon excess of 10 to the -9th to 10 to the -11th per photon, given reasonable parameters. If neutrinos have mass, the bulk of the mass of the universe may be in the form of leptons, implying that the form of matter most familiar to physical science may not be the dominant form of matter in the universe.

Schramm, D. N.↗
DOE OSTI2017

The Deep Underground Neutrino Experiment: The precision era of neutrino physics

The last decade was remarkable for neutrino physics. In particular, the phenomenon of neutrino flavor oscillations has been firmly established by a series of independent measurements. All parameters of the neutrino mixing are now known, and we have the elements to plan a judicious exploration of new scenarios that are opened by these recent advances. With precise measurements, we can test the three-neutrino paradigm, neutrino mass hierarchy, and charge conjugation parity (CP) asymmetry in the lepton sector. The future long-baseline experiments are considered to be a fundamental tool to deepen our knowledge of electroweak interactions. The Deep Underground Neutrino Experiment (DUNE) will detect a broadband neutrino beam from Fermilab in an underground massive liquid argon time-projection chamber at an L/E of about 103 km GeV-1 to reach good sensitivity for CP-phase measurements and the determination of the mass hierarchy. The dimensions and the depth of the far detector also create an excellent opportunity to look for rare signals like proton decay to study violation of the baryonic number, as well as supernova neutrino bursts, broadening the scope of the experiment to astrophysics and associated impacts in cosmology. In this paper, we discuss the physics motivations and the main experimental features of the DUNE project required to reach its scientific goals.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗