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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
DOE OSTI2017

Light-front holographic distribution amplitudes of pseudoscalar mesons and their application to B -meson decays

In this article the dynamical spin effects of the light-front holographic wave functions for light pseudoscalar mesons are studied. These improved wave functions are then confronted with a number of hadronic observables: the decay constants of π and K mesons, their ξ -moments, the pion-to-photon transition form factor, and the pure annihilation $\bar{B}_s$ → π + π - and $\bar{B}_d$ → K + K - decays. Taking f π , fK , and their ratio fK / f π as constraints, we perform a χ 2 analysis for the holographic parameters, including the mass scale parameter $\sqrtλ$ and the effective quark masses, and find that the fitted results are quite consistent with the ones obtained from the light-quark hadronic Regge trajectories. In addition, we also show that the end point divergence appearing in the pure annihilation $\bar{B}_s$ → π + π - and $\bar{B}_d$ → K + K - decays can be controlled well by using these improved light-front holographic distribution amplitudes.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Photoproduction of the f 1 ( 1285 ) meson

The f 1 (1285) meson with mass 1281.0 ± 0.8 MeV/c 2 and width 18.4 ± 1.4 MeV (full width at half maximum) was measured for the first time in photoproduction from a proton target using CLAS at Jefferson Lab. Differential cross sections were obtained via the ηπ + π - , K + K 0 π - , and K - K 0 π + decay channels from threshold up to a center-of-mass energy of 2.8 GeV. The mass, width, and an amplitude analysis of the ηπ + π - final-state Dalitz distribution are consistent with the axial-vector J P = 1 + f 1 (1285) identity, rather than the pseudoscalar 0-η (1295). The production mechanism is more consistent with s -channel decay of a high-mass N * state and not with t -channel meson exchange. Decays to η π π go dominantly via the intermediate a$^±_0$ (980) π ∓ states, with the branching ratio Γ [a 0 π (no $\overline{K}K$) ] / Γ [ηππ (all) ] = 0.74 ± 0.09 . The branching ratios Γ ($\overline{K}K$ π )/ Γ (ηππ) = 0.216 ± 0.033 and Γ (γρ 0 ) / Γ (ηππ) = 0.047 ± 0.018 were also obtained. The first is in agreement with previous data for the f 1 (1285), while the latter is lower than the world average.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2026

Baryon-baryon, meson-meson, and meson-baryon interactions in nonrelativistic QCD

Van der Waals potentials describing interactions between color-singlet mesons and/or baryons vanish at leading order in potential nonrelativistic quantum chromodynamics (pNRQCD). This result and constraints from Gauss’s law are used to prove that weakly coupled pNRQCD van der Waals potentials in generic non-Abelian gauge theories with only heavy quarks are too weak to form bound states whose color state is a product of color singlets. Quantum Monte Carlo calculations of four, five, and six quarks with equal masses provide numerical evidence that exotic color configurations are higher energy than products of color-singlet hadrons, suggesting that equal-mass fully heavy tetraquark, pentaquark, and hexaquark bound states do not exist at next-to-leading order in pNRQCD and at all orders in QCD-like theories in which all quark masses are asymptotically large. Mechanisms for generating hadron-hadron bound states are identified, which necessarily involve large quark-mass hierarchies, relativistic effects arising from the presence of sufficiently light quarks, or nonperturbative effects outside the scope of weakly coupled pNRQCD.

Effective field theory↗
DOE OSTI2024

QED Meson Description of the Anomalous Particles at ∼17 and ∼38 MeV

The Schwinger confinement mechanism stipulates that a massless fermion and a massless antifermion are confined as a massive boson when they interact in the Abelian QED interaction in (1+1)D.If we approximate light quarks as massless and apply the Schwinger confinement mechanism to quarks, we can infer that a light quark and a light antiquark interacting in the Abelian QED interaction are confined as a QED meson in (1+1)D. Similarly, a light quark and a light antiquark interacting in the QCD interaction in the quasi-Abelian approximation will be confined as a QCD meson in (1+1)D. The QED and QCD mesons in (1+1)D can represent physical mesons in (3+1)D when the flux tube radius is properly taken into account. Such a theory leads to a reasonable description of the masses of π0,η, and η′, and its extrapolation to the unknown QED sector yields an isoscalar QED meson at about 17 MeV and an isovector QED meson at about 38 MeV. The observations of the anomalous soft photons, the hypothetical X17 particle, and the hypothetical E38 particle bear promising evidence for the possible existence of the QED mesons. Pending further confirmation, they hold important implications on the properties on the quarks and their interactions.

Wong, Cheuk-Yin (ORCID:0000000182230659)↗
DOE OSTI2023

Measurement of beauty-strange meson production in Pb–Pb collisions at s NN = 5.02 TeV via non-prompt D s + mesons

The production yields of non-prompt ${D}^{+}_{s}$ mesons, namely ${D}^{+}_{s}$ mesons from beauty-hadron decays, were measured for the first time as a function of the transverse momentum ($p_T$) at midrapidity (|$y$| < 0.5) in central and semi-central Pb–Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s{NN}}$ = 5.02 TeV with the ALICE experiment at the LHC. The ${D}^{+}_{s}$ mesons and their charge conjugates were reconstructed from the hadronic decay channel ${D}^{+}_{s}$ → $φπ^+$, with $φ$ → K - K + , in the 4 < $p_T$ < 36 GeV/c and 2 < $p_T$ < 24 GeV/ $c$ intervals for the 0–10% and 30–50% centrality classes, respectively. The measured yields of non-prompt ${D}^{+}_{s}$ mesons are compared to those of prompt ${D}^{+}_{s}$ and non-prompt $D^0$ mesons by calculating the ratios of the production yields in Pb–Pb collisions and the nuclear modification factor $R_{AA}$. The ratio between the $R_{AA}$ of non-prompt ${D}^{+}_{s}$ prompt ${D}^{+}_{s}$ mesons, and that between the $R_{AA}$ of non-prompt ${D}^{+}_{s}$ and non-prompt $D^0$ mesons in central Pb–Pb collisions are found to be on average higher than unity in the 4 < $p_T$ < 12 GeV/ $c$ interval with a statistical significance of about 1.6σ and 1.7σ, respectively. The measured $R_{AA}$ ratios are compared with the predictions of theoretical models of heavy-quark transport in a hydrodynamically expanding QGP that incorporate hadronisation via quark recombination.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2021

Revealing the structure of light pseudoscalar mesons at the electron–ion collider

The questions of how the bulk of the Universe's visible mass emerges and how it is manifest in the existence and properties of hadrons are profound, and probe the heart of strongly interacting matter. Paradoxically, the lightest pseudoscalar mesons appear to be key to a further understanding of the emergent mass and structure mechanisms. These mesons, namely, the pion and kaon, are the Nambu-Goldstone boson modes of quantum chromodynamics (QCD). Unravelling their partonic structure and the interplay between emergent and Higgs-boson mass mechanisms is a common goal of three interdependent approaches - continuum QCD phenomenology, lattice-regularised QCD, and the global analysis of parton distributions - linked to experimental measurements of hadron structure. Experimentally, the anticipated electron-ion collider will enable a revolution in our ability to study pion and kaon structures, accessed by scattering from the 'meson cloud' of the proton through the Sullivan process. With the goal of enabling a suite of measurements that can address these questions, we examine key reactions that identify the critical detector-system requirements needed to map tagged pion and kaon cross-sections over a wide range of kinematics. The excellent prospects for extracting pion structural, functional, and form-factor data are outlined, and similar prospects for kaon structures are discussed in the context of a worldwide programme. Finally, the successful completion of the programme outlined herein will deliver deep, far-reaching insights into the emergence of pions and kaons, their properties, and their role as QCD's Goldstone boson modes.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Photoproduction of ω mesons off nuclei and impact of polarization on the meson-nucleon interaction

We consider photoproduction of ω mesons off complex nuclei to study interactions of transversely and longitudinally polarized vector mesons with nucleons. Whereas the total cross section for interactions of the transversely polarized vector mesons with nucleons σ T = σ(V T N) can be obtained from coherent photoproduction, measurements of vector meson photoproduction in the incoherent region provide a unique opportunity to extract the not-yet-measured total cross section for longitudinally polarized mesons σ L = σ(V L N). The predictions for the latter strongly depend on the theoretical approaches. Furthermore, this work is stimulated by the construction of the new experiment GlueX at Jefferson Lab, designed to study the photoproduction of mesons in a large beam energy range up to 12 GeV.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2015

B -meson decay constants from 2 + 1 -flavor lattice QCD with domain-wall light quarks and relativistic heavy quarks

We calculate the B-meson decay constants f B , f B s , and their ratio in unquenched lattice QCD using domain-wall light quarks and relativistic b quarks. We use gauge-field ensembles generated by the RBC and UKQCD collaborations using the domain-wall fermion action and Iwasaki gauge action with three flavors of light dynamical quarks. We analyze data at two lattice spacings of a ≈ 0.11, 0.086 fm with unitary pion masses as light as M π ≈ 290 MeV; this enables us to control the extrapolation to the physical light-quark masses and continuum. For the b quarks we use the anisotropic clover action with the relativistic heavy-quark interpretation, such that discretization errors from the heavy-quark action are of the same size as from the light-quark sector. We renormalize the lattice heavy-light axial-vector current using a mostly nonperturbative method in which we compute the bulk of the matching factor nonperturbatively, with a small correction, that is close to unity, in lattice perturbation theory. We also improve the lattice heavy-light current through O(α s a). We extrapolate our results to the physical light-quark masses and continuum using SU(2) heavy-meson chiral perturbation theory, and provide a complete systematic error budget. We obtain f B 0 = 199.5(12.6) MeV, f B + =195.6(14.9) MeV, f B s =235.4(12.2) MeV, f B s /f B 0 =1.197(50), and f B s /f B + =1.223(71), where the errors are statistical and total systematic added in quadrature. Finally, these results are in good agreement with other published results and provide an important independent cross-check of other three-flavor determinations of B-meson decay constants using staggered light quarks.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Beam spin asymmetry in the electroproduction of a pseudoscalar meson or a scalar meson off the scalar target

In this paper, we discuss the electroproduction of a pseudoscalar (0⁻⁺) meson or a scalar (0⁺⁺) meson off the scalar target. The most general formulation of the differential cross section for the 0⁻⁺ or 0⁺⁺ meson process involves only one or two hadronic form factors, respectively, on a scalar target. The Rosenbluth-type separation of the differential cross section provides the explicit relation between the hadronic form factors and the different parts of the differential cross section in a completely model-independent manner. The absence of the beam spin asymmetry for the pseudoscalar meson production provides a benchmark for the experimental data analysis. The measurement of the beam spin asymmetry for the scalar meson production may also provide a unique opportunity not only to explore the imaginary part of the hadronic amplitude in the general formulation but also to examine the significance of the chiral-odd generalized parton distribution (GPD) contribution in the leading-twist GPD formulation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2026

Review of Particle Physics

The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 3,200 new measurements from 903 papers, we list, evaluate, and average measured properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Most of the 118 reviews are updated, including many that are heavily revised.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Transverse momentum dependence of D-meson production in Pb-Pb collisions at $ \sqrt{{\mathrm{s}}_{\mathrm{NN}}}=2.76 $ TeV

The production of prompt charmed mesons D 0 , D + and D* + , and their antiparticles, was measured with the ALICE detector in Pb-Pb collisions at the centre-of-mass energy per nucleon pair, √ s NN, of 2.76 TeV. The production yields for rapidity |y| < 0.5 are presented as a function of transverse momentum, p T , in the interval 1–36 GeV/c for the centrality class 0–10% and in the interval 1–16 GeV/c for the centrality class 30–50%. The nuclear modification factor R AA was computed using a proton-proton reference at √s = 2.76 TeV, based on measurements at √s = 7 TeV and on theoretical calculations. A maximum suppression by a factor of 5-6 with respect to binary-scaled pp yields is observed for the most central collisions at p T of about 10 GeV/c. A suppression by a factor of about 2-3 persists at the highest p T covered by the measurements. At low pT (1-3 GeV/c), the R AA has large uncertainties that span the range 0.35 (factor of about 3 suppression) to 1 (no suppression). In all p T intervals, the R AA is larger in the 30-50% centrality class compared to central collisions. Furthermore, the D-meson R AA is also compared with that of charged pions and, at large p T , charged hadrons, and with model calculations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2023

Pattern of global spin alignment of ϕ and K*0 mesons in heavy-ion collisions

The strong force, as one of the four fundamental forces at work in the universe, governs interactions of quarks and gluons, and binds together the atomic nucleus. Notwithstanding decades of progress since Yukawa first developed a description of the force between nucleons in terms of meson exchange 1 , a full understanding of the strong interaction remains a major challenge in modern science. One remaining difficulty arises from the non-perturbative nature of the strong force, which leads to the phenomenon of quark confinement at distance scales on the order of the size of the proton. Here we show that in relativistic heavy-ion collisions, where quarks and gluons are set free over an extended volume, two species of produced vector (spin-1) mesons, namely φ and K∗0 , emerge with a surprising pattern of global spin alignment. In particular, the global spin alignment for φ is unexpectedly large, while that for K∗0 is consistent with zero. The observed spin-alignment pattern and magnitude for the φ cannot be explained by conventional mechanisms, while a model with strong force fields2, 3 accommodates the current data. This is the first time that the strong force field is experimentally supported as a key mechanism that leads to global spin alignment. We extract a quantity proportional to the intensity of the field of the strong force. Within the framework of the Standard Model, where the strong force is typically described in the quark and gluon language of Quantum Chromodynamics, the field being considered here is an effective proxy description. This is a qualitatively new class of measurement, which opens a new avenue for studying the behaviour of strong force fields via their imprint on spin alignment.

Abdallah, M. S.↗
DOE OSTI2017

Measurement of the inclusive electron spectrum from B meson decays and determination of | V u b |

Based on the full BABAR data sample of 466.5 million $B\bar{B}$ pairs, we present measurements of the electron spectrum from semileptonic B meson decays. We fit the inclusive electron spectrum to distinguish Cabibbo-Kobayashi-Maskawa (CKM) suppressed B → X u eν decays from the CKM-favored B → X c eν decays, and from various other backgrounds, and determine the total semileptonic branching fraction B (B → Xeν) = ( 10.34 ± 0.04 stat ± 0.2 6 syst )%, averaged over B ± and B 0 mesons. We determine the spectrum and branching fraction for charmless B → X u eν decays and extract the CKM element | V ub | , by relying on four different QCD calculations based on the heavy quark expansion. While experimentally, the electron momentum region above 2.1 GeV / c is favored, because the background is relatively low, the uncertainties for the theoretical predictions are largest in the region near the kinematic endpoint. Detailed studies to assess the impact of these four predictions on the measurements of the electron spectrum, the branching fraction, and the extraction of the CKM matrix element |V ub | are presented, with the lower limit on the electron momentum varied from 0.8 GeV / c to the kinematic endpoint. We determine |V ub | using each of these different calculations and find, |V ub | = ( 3.794 ± 0.107 exp $+ 0.292\atop{ - 0.219 SF}$ $+ 0.078 \atop{- 0.068 theory}$ ) × 10 - 3 (De Fazio and Neubert), (4.563 ± 0.126 exp $+ 0.230\atop {- 0.208 SF}$ $+ 0.162\atop{- 0.163 theory}$ ) ×10 -3 (Bosch, Lange, Neubert, and Paz), (3.959 ± 0.104 exp $+ 0.164\atop{- 0.154 SF}$ $+ 0.042\atop{ - 0.079 theory}$ ) × 10 -3 (Gambino, Giordano, Ossola, and Uraltsev), (3.848 ± 0.108 exp $+ 0.084\atop{ - 0.070 theory}$) × 10 -3 (dressed gluon exponentiation), where the stated uncertainties refer to the experimental uncertainties of the partial branching fraction measurement, the shape function parameters, and the theoretical calculations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗