Engineering topics

Zhao, Y. X.

Publications and source records attributed to Zhao, Y. X..

6 records

DOE OSTI2022

Proton spin structure and generalized polarizabilities in the strong quantum chromodynamics regime

The strong interaction is not well understood at low energies or for interactions with low momentum transfer. Chiral perturbation theory gives testable predictions for the nucleonic generalized polarizabilities, which are fundamental quantities describing the nucleon’s response to an external field. We report a measurement of the proton’s generalized spin polarizabilities extracted with a polarized electron beam and a polarized solid ammonia target in the region where chiral perturbation theory is expected to be valid. The investigated structure function g2 characterizes the internal spin structure of the proton. From its moments, we extract the longitudinal–transverse spin polarizability δLT and twist-3 matrix element and polarizability d2¯. Our results provide discriminating power between existing chiral perturbation theory calculations and will help provide a better understanding of this strong quantum chromodynamics regime.

Ruth, D↗

DOE OSTI2018

Study of light backgrounds from relativistic electrons in air light-guides

The MOLLER experiment proposed at the Thomas Jefferson National Accelerator Facility plans a precision low energy determination of the weak mixing angle via the measurement of the parity-violating asymmetry in the scattering of high energy longitudinally polarized electrons from electrons bound in a liquid hydrogen target (Moller scattering). A relative measure of the scattering rate is planned to be obtained by intercepting the Moller scattered electrons with a circular array of thin fused silica tiles attached to air light guides, which facilitate the transport of Cherenkov photons generated within the tiles to photomultiplier tubes (PMTs). The scattered flux will also pass through the light guides of downstream tiles, generating additional Cherenkov as well as scintillation light and is a potential background. In order to estimate the rate of these backgrounds, a gas-filled tube detector was designed and deployed in an electron beam at the MAMI facility at Johannes Gutenberg University, Mainz, Germany. Described in this paper is the design of a detector to measure separately the scintillation and Cherenkov responses of gas mixtures from relativistic electrons, the results of studies of several gas mixtures with comparisons to simulations, and conclusions about the implications for the design of the MOLLER detector apparatus.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2017

Neutral-current weak interactions at an EIC

Here, a simulation study of measurements of neutral current structure functions of the nucleon at the future high-energy and high-luminosity polarized electron-ion collider (EIC) is presented. A new series of γ-Z interference structure functions, F γZ 1 , F γZ 3 , g γZ 1 , g γZ 5 become accessible via parity-violating asymmetries in polarized electron-nucleon deep inelastic scattering (DIS). Within the context of the quark-parton model, they provide a unique and, in some cases, yet-unmeasured combination of unpolarized and polarized parton distribution functions. The uncertainty projections for these structure functions using electron-proton collisions are considered for various EIC beam energy configurations. Also presented are uncertainty projections for measurements of the weak mixing angle sin 2 θ W using electron-deuteron collisions which cover a much higher Q 2 than that accessible in fixed target measurements. QED and QCD radiative corrections and effects of detector smearing are included with the calculations.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2014

Single spin asymmetries in charged kaon production from semi-inclusive deep inelastic scattering on a transversely polarized He 3 target

We report the first measurement of target single spin asymmetries of charged kaons produced in semi-inclusive deep inelastic scattering of electrons off a transversely polarized 3He target. Both the Collins and Sivers moments, which are related to the nucleon transversity and Sivers distributions, respectively, are extracted over the kinematic range of 0.1 < x bj <0.4 for K + and K – production. While the Collins and Sivers moments for K + are consistent with zero within the experimental uncertainties, both moments for K – favor negative values. The Sivers moments are compared to the theoretical prediction from a phenomenological fit to the world data. While the K + Sivers moments are consistent with the prediction, the K – results differ from the prediction at the 2-sigma level.

43 PARTICLE ACCELERATORS↗

DOE OSTI2014

Measurement of the Target-Normal Single-Spin Asymmetry in Deep-Inelastic Scattering from the Reaction He 3 ↑ ( e , e ' ) X

We report here the first measurement of the target-normal single-spin asymmetry in deep-inelastic scattering from the inclusive reaction He 3 ↑ ( e , e ' ) X on a polarized He 3 gas target. Assuming time-reversal invariance, this asymmetry is strictly zero in the Born approximation but can be nonzero if two-photon-exchange contributions are included. The experiment, conducted at Jefferson Lab using a 5.89 GeV electron beam, covers a range of 1.7 < W < 2.9 GeV , 1.0 < Q 2 < 4.0 GeV 2 and 0.16 < x < 0.65 . Neutron asymmetries were extracted using the effective nucleon polarization and measured proton-to- He 3 cross-section ratios. The measured neutron asymmetries shown are negative with an average value of ( - 1.09 ± 0.38 ) × 1 0 - 2 for invariant mass W > 2 GeV , which is nonzero at the 2.89 σ level. Our measured asymmetry agrees both in sign and magnitude with a two-photon-exchange model prediction that uses input from the Sivers transverse momentum distribution obtained from semi-inclusive deep-inelastic scattering.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2014

Single spin asymmetries of inclusive hadrons produced in electron scattering from a transversely polarized 3 He target

We report the first measurement of target single-spin asymmetries (A N ) in the inclusive hadron production reaction, e + 3 He↑→h+X, using a transversely polarized 3 He target. This experiment was conducted at Jefferson Lab in Hall A using a 5.9-GeV electron beam. Three types of hadrons (π ± , K ± and proton) were detected in the transverse hadron momentum range 0.54 < p T < 0.74 GeV/c. The range of x F for pions was -0.29 < x F < -0.23 and for kaons -0.25 < x F <-0.18. The observed asymmetry strongly depends on the type of hadron. A positive asymmetry is observed for π + and K + . A negative asymmetry is observed for π–. The magnitudes of the asymmetries follow |A π – |<|A π + |<|A K + |. The K – and proton asymmetries are consistent with zero within the experimental uncertainties. The π + and π – asymmetries measured for the 3 He target and extracted for neutrons are opposite in sign with a small increase observed as a function of p T .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗