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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Parameterized spectral distributions for meson production in proton-proton collisions

Accurate semiempirical parameterizations of the energy-differential cross sections for charged pion and kaon production from proton-proton collisions are presented at energies relevant to cosmic rays. The parameterizations, which depend on both the outgoing meson parallel momentum and the incident proton kinetic energy, are able to be reduced to very simple analytical formulas suitable for cosmic ray transport through spacecraft walls, interstellar space, the atmosphere, and meteorites.

Schneider, John P.↗
DOE OSTI2021

Partial Wave Analysis of Meson Resonances That Decay K*K¯ Using Data from the GlueX Experiment

The GlueX experiment housed in Hall D of the Thomas Jefferson National Laboratory was created to map the light meson spectrum in order to contribute to the Standard Model of particle physics by strengthening our understanding of the strong interaction. GlueX is a medium-energy photoproduction experiment that utilizes a linearly polarized photon beam to create hadronic forms of matter.

Cole, Sebastian↗
DOE OSTI2022

The Experimental Programs on Light Pseudoscalar Meson Decays

The decays of the low-lying pseudoscalar mesons (?0, ?, and ??) allow access to a plethora of physics probes, from measurements of fundamental properties of matter such as the up-down quark mass ratio, to studies of channels that access higher-order terms in Chiral Perturbation theory, to tests of fundamental symmetries and searches for signatures of physics beyond the Standard Model. Several experiments have studied pseudoscalar decays: these experiments include PrimEx in Hall B at Jefferson Lab, A2 at the MAMI electron accelerator facility, the KLOE-II experiment at the DA?NE ?-factory, WASA-at-COSY at the cooler synchrotron COSY storage ring, and BESIII at the Beijing charm factory. In Hall D at Jefferson Lab, PrimEx-eta uses the Primakoff process to measure the ? radiative width using the GlueX spectrometer. In the near future the Jefferson Lab Eta Factory (JEF) experiment will use the GlueX spectrometer with an upgraded forward calorimeter to study ?(?) decay channels with a focus on all-neutral final states. Finally, a proposal for a new experiment, ``Rare Eta Decays with a TPC for Optical Photons'' (REDTOP) utilizing a proton beam on fixed targets, is under development. Highlights from previous and ongoing experiments and plans for future experiments will be presented.

Taylor, Simon↗
DOE OSTI2024

Cross Section Measurement of Exclusive ¿-Meson Electroproduction off the Proton at CLAS12

This analysis studies the exclusive ¿ meson electroproduction process ep ¿ e 'p ' at CLAS12 in the kinematic region 0.39 = Q2 = 8.38 GeV2 , 1.97 = W = 4.03 GeV, and 0.17 = -t = 7.26 GeV2 . Cross section s(Q2 , W) and differential cross section ds dt (Q2 , W, t) measurements are reported. The scaling of the overall cross section was determined to be 1/Q6.47±0.97, which is consistent with the Generalized Parton Distribution (GPD) prediction of 1/Q6 . The ratios of the longitudinal and transverse cross sections, R = sL sT , are extracted from the angular decay distributions for four values of Q2 and are found to be consistent with the GPD scaling prediction. The mean-square gluonic radius of the proton ¿b 2 ¿g is extracted from the t-dependence of the differential cross sections ds dt in the kinematic region 0.12 = xB = 0.39, the first such measurement in the valence regime.

Moran, Patrick (ORCID:0000000273437292)↗
DOE OSTI2020

First measurement of direct photoproduction of the a 2 (1320) 0 meson on the proton

We present the first measurement of the reaction γ p → a 2 ( 1320 ) 0 p in the photon energy range 3.5– 5.5 Ge V and four-momentum transfer squared 0.2 < - t < 2.0 Ge V 2 . Data were collected with the CEBAF Large Acceptance Spectrometer detector at the Thomas Jefferson National Accelerator Facility. The a 2 resonance was detected by measuring the reaction γ p → π 0 η p and reconstructing the π 0 η invariant mass. The most prominent feature of the differential cross section is a dip at -t ≈ 0.55 Ge V 2 . This can be described in the framework of Regge phenomenology, where the exchange degeneracy hypothesis predicts a zero in the reaction amplitude for this value of the four-momentum transfer.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Lattice QCD calculation of 𝑥-dependent meson distribution amplitudes at physical pion mass with threshold logarithm resummation

We present a lattice quantum chromodynamics (QCD) calculation of the 𝑥-dependent pion and kaon distribution amplitudes (DA) in the framework of large momentum effective theory. This calculation is performed on a fine lattice of 𝑎 = 0.076 fm at physical pion mass, with the pion boosted to 1.8 GeV and kaon boosted to 2.3 GeV. We renormalize the matrix elements in the hybrid scheme and match to Math output error with a subtraction of the leading renormalon in the Wilson-line mass. The perturbative matching is improved by resumming the large logarithms related to the small quark and gluon momenta in the soft-gluon limit. After resummation, we demonstrate that we are able to calculate a range of 𝑥 ∈[𝑥 0 ,1 − 𝑥 0 ] with 𝑥 0 = 0.25 for pion and 𝑥 0 = 0.2 for kaon with theoretical systematic errors under control. The kaon DA is shown to be slighted skewed, and narrower than pion DA. Although the 𝑥-dependence cannot be direct calculated beyond these ranges, we estimate higher moments of the pion and kaon DAs by complementing our calculation with short-distance factorization.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2023

Observation of the Rare Decay of the 𝜂 Meson to Four Muons

A search for the rare η → μ + μ − μ + μ − double-Dalitz decay is performed using a sample of proton-proton collisions, collected by the CMS experiment at the CERN LHC with high-rate muon triggers in 2017-2018 and corresponding to an integrated luminosity of 101 fb −1 . A signal having a statistical significance well in excess of 5 standard deviations is observed. Using the η → μ + μ − decay as normalization, the branching fraction B(η → μ + μ − μ + μ − ) = [5.0 ± 0.8 (stat) ± 0.7 (syst) ± 0.7 (B 2μ )] × 10 −9 is measured, where the last term is the uncertainty in the normalization channel branching fraction. This work achieves an improved precision of over five orders of magnitude compared to previous results, leading to the first measurement of this branching fraction, which is found to agree with theoretical predictions.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗