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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Calibrations for charged particle tracking and measurements of w photoproduction with the GlueX detector

The GlueX experiment is a new experimental facility at Jefferson Lab in Newport News, VA. The experiment aims to map out the spectrum of hybrid mesons in the light quark sector. Measurements of the spin-density matrix elements in omega photoproduction are performed with a linear polarized photon beam on an unpolarized proton target, and presented in bins of Mandelstam t for beam energies of 8.4-9.0 GeV. The spin-density matrix elements are exclusively measured through two decays of the omega meson: omega -> pi^+ pi^- pi^0 and omega ->pi^0 gamma. A description of the experimental apparatus is presented. Several methods used in the calibration of the charged particle tracking system are described. These measurements greatly improve the world statistics in this energy range. These are the first results measured through the omega ->pi^0 gamma decay at this energy. Results are generally consistent with a theoretical model based on diffractive production with Pomeron and pseudoscalar exchange in the t-channel.

Staib, Michael↗
DOE OSTI2015

Measurement of the E Polarization Observable for yd --> pi^-p(p_s), yd-->K^0Lambda(p_s), and yd-->pi^+pi^-d(0) using CLAS g14 data at Jefferson Lab

Photoproduction of mesons from the nucleon has a long and ongoing tradition for exploring nucleon excitations and the baryon-baryon interaction. Polarization observables which play a role in the photoproduction mechanism are, therefore, essential in addition to the differential cross section. The CLAS collaboration at Jefferson Lab, has been active in measuring these observables, but until now only on a proton targets. However, a comprehensive picture of the pseudoscalar meson photoproduction requires neutron data as well. That is, paired measurements of observables in p and n reactions are necessary to disentangle the photoproduction mechanism on the basis of isospin I = 0, and I = 1 photo-coupling transition amplitudes. The g14 experiment with 'HDIce,' a longitudinally polarized solid target of molecular hydrogen-deuteride with low background contamination from other nuclear species, provided an unique opportunity to measure several polarization observables|for the first time|on the neutron for different channels. In particular, we present our measurements of the E beam-target polarization observable, which requires circularly polarized beam and a longitudinally polarized target, for p pi^-, K^0Lambda, and K^0Sigma^0 channels in the energy range of 1.5 lte W lte 2.3 GeV. In addition, we also utilized the g14 dataset to investigate the intrinsic spin of a possible dibaryonic ND bound state by measuring the E (beam-target) observable on the d-pi^+/-d channel of the reaction yd --> pi^+pi^-d(0). Finally, this thesis also discusses a highly efficient multivariate analysis method called Boosted Decision Trees, which we employed extensively for this work and which has not been used before in CLAS data analysis.

Ho, Dao↗
DOE OSTI2018

Hadronic Decays of the D s Meson

The $D^+ _s$ (formerly F + ) is the lowest-lying pseudoscalar meson containing charm and anti-strange quarks. Evidence for this state was first reported in 1977, although more recent observations disagree with some of the early results. Since 1983 the weakly decaying $D^+ _s$ has been observed in many experiments.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Transverse Momentum at Work in High-Energy Scattering Experiments

I will review some aspects of the definition and the phenomenology of Transverse-Momentum-Dependent distributions (TMDs) which are potentially interesting for the physics program at several current and future experimental facilities. First of all, I will review the definition of quark, gluon and Wilson loop TMDs based on gauge invariant hadronic matrix elements. Looking at the phenomenology of quarks, I will address the flavor dependence of the intrinsic transverse momentum in unpolarized TMDs, focusing on its extraction from Semi-Inclusive Deep-Inelastic Scattering. I will also present an estimate of its impact on the transverse momentum spectrum of W and Z bosons produced in unpolarized hadronic collisions and on the determination of the W boson mass. Moreover, the combined effect of the flavor dependence and the evolution of TMDs with the energy scale will be discussed for electron-positron annihilation. Concerning gluons, I will present from an effective theory point of view the TMD factorization theorem for the transverse momentum spectrum of pseudoscalar quarkonium produced in hadronic collisions. Relying on this, I will discuss the possibility of extracting precise information on (un)polarized gluon TMDs at a future Fixed Target Experiment at the LHC (AFTER@LHC).

Signori, Andrea↗
DOE OSTI2023

New limits on WR from meson decays

In this work we show that pseudoscalar meson leptonic data can be used to set stringetn limits on the mass of a right handed gauge boson, such as the one that appears in left-right symmetric models. We have shown that for a heavy neutrino with mass in the range 50 to 1900 MeV one can constrain the right hand gauge boson mass to be bigger than 4-19 TeV at 90% confidence level depending on the heavy neutrino mass.

Alves, Gustavo↗
DOE OSTI2023

Light long-lived particles at colliders

Searches for long-lived particles (LLPs) are a rapidly expanding frontier at the LHC and other collider experiments. Still, many gaps remain in the current search program, in particular for LLPs with masses at the GeV or sub-GeV scale and with very large decay lengths. In this talk, I will illustrate two different approaches to filling this gap by discussing two models of light LLPs and their associated collider signals. First, I will show that the dominant decay mode of vectorlike leptons can be a very long-lived pseudoscalar and a tau lepton and argue that the muon chambers of CMS or ATLAS are ideal places to search for this final state. Second, I will illustrate the excellent sensitivity of Belle II to light LLPs with meter-scale decay lengths using the example of displaced vertex signals from strongly interacting dark sectors.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Nucleon Isovector Axial Form Factors

We present results for the isovector axial vector form factors obtained using thirteen 2 + 1 + 1-flavor highly improved staggered quark (HISQ) ensembles generated by the MILC collaboration. The calculation of nucleon two- and three-point correlation functions has been done using Wilson-clover fermions. In the analysis of these data, we quantify the sensitivity of the results to strategies used for removing excited state contamination and invoke the partially conserved axial current relation between the form factors to choose between them. Our data driven analysis includes removing contributions from multihadron $Nπ$ states that make significant contributions. Our final results are $g_A$ = 1.292(53) stat (24) sys for the axial charge; $g_S$ = 1.085(50) stat (103) sys and $g_T$ = 0.991(21) stat (10) sys for the scalar and tensor charges; $\langle{r^2_A}\rangle$ = 0.439(56) sta t(34) sys fm 2 for the mean squared axial charge radius, $g^*_P$ = 9.03(47) stat (42) sys for the induced pseudoscalar charge; and $g_{πNN}$ = 14.14(81) stat (85) sys for the pion-nucleon coupling. We also provide a parametrization of the axial form factor $G_A(Q^2)$ over the range 0 ≤ $Q^2$ ≤ 1 GeV 2 for use in phenomenology and a comparison with other lattice determinations. We find that the various lattice data agree within 10% but are significantly different from the extraction of $G_A(Q^2)$ from the $ν$-deuterium scattering data.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2025

Amplitude Analysis of ωπ0 Photoproduction at GlueX

spectrum of light mesons produced from a linearly polarized photon beam. The production and decays of a light meson resonance X such as γp → Xp′ →ωπ0p′ can be modeled with polarized vector-pseudoscalar ampli- tudes, which can describe the contribution of individual amplitudes to the total measured intensity. The status of mass-independent fits to the ωπ0 mass spectrum over a wide range of mass and momentum transfer−twill be presented, with an emphasis on interactions with the b1(1235) meson. We will also present in parallel an analysis of moments of the angular dis- tributions for the same process, as a means of verifying the stability of the amplitude-based results. These results will help to improve the broader knowledge of light meson states and how they are produced.

Scheuer, Kevin [College of William and Mary, Willi↗
DOE OSTI2017

Operators for scattering of particles with spin

Operators for simulating the scattering of two particles with spin are constructed. Three methods are shown to give the consistent lattice operators for PN, PV, VN and NN scattering, where P, V and N denote pseudoscalar meson, vector meson and nucleon. The projection method leads to one or several operators OG;r;n that transform according to a given irreducible representation G and row r. However, it gives little guidance on which continuum quantum numbers of total J, spin S, orbital momentum L or single-particle helicities l1;2 will be related with a given operator. This is remedied with the helicity and partial-wave methods. There first the operators with good continuum quantum numbers (J;P;l1;2) or (J;L;S) are constructed and then subduced to the irreps G of the discrete lattice group. The results indicate which linear combinations OG;r;n of various n have to be employed in the simulations in order to enhance couplings to the states with desired continuum quantum numbers. The total momentum of two hadrons is restricted to zero since parity P is a good quantum number in this case.

Prelovsek, Sasa↗
DOE OSTI2025

Status of the PrimEx $\eta$ experiment at Jefferson Lab

The GlueX detector in the experimental Hall D at Jefferson Lab offers a unique opportunity to perform a measurement of the decay width of eta mesons through the Primakoff effect. The experiment complements the physics program at Jefferson Lab on measuring the decay width of light pseudoscalar mesons via the Primakoff process. The goal of the experiment is to measure differential cross sections of eta mesons at forward angles using a beam of tagged photons incident on a liquid 4He target, which will be used for the extraction of the decay width. This measurement is vital for understanding fundamental properties like the ratios of the light quark masses and the eta - eta' mixing angle, and will provide an important test of chiral symmetry breaking in QCD. Our experimental results will help reduce uncertainties on partial widths of all other eta decays. The experiment collected data during three physics runs between 2019 and 2022. We will give an overview of the PrimEx eta experiment and the current status of our data analyses. We will also discuss the feasibility of conducting future Primakoff measurements in light of the recent upgrade of the GlueX forward calorimeter and the potential accelerator energy upgrade to 22 GeV.

Somov, Alexander↗
DOE OSTI2024

Search for Neutral Heavy Scalars in ttZ Events Using 13 TeV pp Collisions at CMS

This thesis presents a search for a heavy pseudoscalar particle, A, which decays into a lighterscalar, H, and a Z boson within the Two-Higgs-Doublet Model (2HDM). We focus on Zboson decays to leptons, with H decays into a t t ̄ pair. The search uses the Asimov dataset–a theoretical dataset generated to predict the expected results for discovery and exclusion based on conditions from proton-proton collisions at the LHC, atintegrated luminosity of 138f b−1, as recorded by the CMS detector. The analysis focuses on events with three charged leptons, two of which come from the Z boson decay and one from a top quark decay. The expected results suggest the search has high sensitivity, showing discovery potential across much of the 2HDM Type-II parameter space, with possible deviations from the Standard Model background exceeding 5σ significance. The search sets upper limits on the cross-section times branching ratio, assuming narrow particle widths, for A masses up to 2100 GeV and H masses up to 1900 GeV. The results are interpreted in the 2HDM Type-II framework to exclude certain regions of parameter space at the 95% confidence level as a function of particle masses and variables such as tanβ and cos(β−α). The findings highlight the potential reach implications of future search in this parameter region.

Rudrabhatla, Sahithi [Illinois U., Chicago]↗
DOE OSTI2024

Isovector Axial Charge and Form Factors of Nucleons from Lattice QCD

A survey of the calculations of the isovector axial vector form factor of the nucleon using lattice QCD is presented. Attention is paid to statistical and systematic uncertainties, in particular those due to excited state contributions. Based on a comparison of results from various collaborations, a case is made that lattice results are consistent within 10%. A similar level of uncertainty is in the axial charge gAu−d, the mean squared axial charge radius ⟨rA2⟩, the induced pseudoscalar charge gP∗, and the pion–nucleon coupling gπNN. Even with the current methodology, a significant reduction in errors is expected over the next few years with higher statistics data on more ensembles closer to the physical point. Lattice QCD results for the form factor GA(Q2) are compatible with those obtained from the recent MINERνA experiment but lie 2–3σ higher than the phenomenological extraction from the old ν–deuterium bubble chamber scattering data for Q2>0.3 GeV2. Current data show that the dipole ansatz does not have enough parameters to fit the form factor over the range 0≤Q2≤1 GeV2, whereas even a z2 truncation of the z expansion or a low order Padé are sufficient. Looking ahead, lattice QCD calculations will provide increasingly precise results over the range 0≤Q2≤1 GeV2, and MINERνA-like experiments will extend the range to Q2∼2 GeV2 or higher. Nevertheless, improvements in lattice methods to (i) further control excited state contributions and (ii) extend the range of Q2 are needed.

Astronomy & Astrophysics↗
DOE OSTI2025

Gluonic Structure from Instantons

The instanton vacuum provides an effective description of chiral symmetry breaking by local topological fluctuations of the gauge fields, as observed in lattice QCD simulations. The resulting effective dynamics at momenta below 1/$\bar{ρ}$ ≈ 0.6 GeV explains the basic features of light-quark correlation functions and is used extensively in studies of hadron structure. The instanton fields also make definite contributions to the gluonic structure of light hadrons, as expressed in the matrix elements of composite quark– gluon or gluon operators. The article reviews the gluonic structure of light hadrons (nucleon, pion) induced by instantons. This includes: (i) twist-2 parton distributions and momentum sum rule; (ii) twist-3 angular momentum and spin-orbit interactions; (iii) twist-3 and twist-4 quark–gluon correlations and power corrections; (iv) trace anomaly and hadron mass decomposition; (v) scalar gluon form factors and mechanical properties; (vi) axial anomaly and pseudoscalar gluon form factors. It also discusses possible further applications of the methods and recent developments including gauge field configurations beyond instantons.

Weiss, C. [Thomas Jefferson National Accelerator F↗
NASA NTRS1980

Effects of field interactions upon particle creation in Robertson-Walker universes

Particle creation due to field interactions in an expanding Robertson-Walker universe is investigated. A model in which pseudoscalar mesons and photons are created as a result of their mutual interaction is considered, and the energy density of created particles is calculated in model universes which undergo a bounce at some maximum curvature. The free-field creation of non-conformally coupled scalar particles and of gravitons is calculated in the same space-times. It is found that if the bounce occurs at a sufficiently early time the interacting particle creation will dominate. This result may be traced to the fact that the model interaction chosen introduces a length scale which is much larger than the Planck length.

Birrell, N. D.↗
NASA NTRS1986

Laser-induced axion photoproduction

Axion photoproduction is suggested as a systematic technique for investigating the coupling of new elementary pseudoscalar or scalar particles in the megaelectronvolt mass range to leptons, photons, and hadronic matter. The experiments involve a configuration where a low-energy photon collides with a relativistic electron beam. Threshold production energies of 300 GeV can be accomplished with an optical laser, and those of 14.5-50 GeV can be achieved with wigglers directed onto an electron beam. With this scheme, at least 10 to the -7th of the electrons can be converted to axions, providing a 1-100 thousand/s relativistic beam of axions.

Brodsky, S. J.↗
NASA NTRS1988

New theoretical results for the Lehmann effect in cholesteric liquid crystals

The Lehmann effect arising in a cholesteric liquid crystal drop when a temperature gradient is applied parallel to its helical axis is investigated theoretically using a local approach. A pseudoscalar quantity is introduced to allow for cross couplings which are absent in nematic liquid crystals, and the statics and dissipative dynamics are analyzed in detail. It is shown that the Lehmann effect is purely dynamic for the case of an external electric field and purely static for an external density gradient, but includes both dynamic and static coupling contributions for the cases of external temperature or concentration gradients.

Brand, Helmut R.↗