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Guo, Y.

Publications and source records attributed to Guo, Y..

At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Sub-kiloparsec ALMA imaging of compact star-forming galaxies at z ∼ 2.5: revealing the formation of dense galactic cores in the progenitors of compact quiescent galaxies

We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) 870 μm dust continuum maps of six massive, compact, dusty star-forming galaxies at z ∼ 2.5. These galaxies are selected for their small rest-frame optical sizes (r{sub e,F160W}∼1.6 kpc) and high stellar mass densities that suggest that they are direct progenitors of compact quiescent galaxies at z ∼ 2. The deep observations yield high far-infrared (FIR) luminosities of L{sub IR}=10{sup 12.3−12.8} L{sub ⊙} and star formation rates (SFRs) of SFR = 200–700 M {sub ⊙} yr{sup −1}, consistent with those of typical star-forming “main sequence” galaxies. The high spatial resolution (FWHM ∼ 0.″12–0.″18) ALMA and Hubble Space Telescope photometry are combined to construct deconvolved, mean radial profiles of their stellar mass and (UV+IR) SFR. We find that the dusty, nuclear IR–SFR overwhelmingly dominates the bolometric SFR up to r ∼ 5 kpc, by a factor of over 100× from the unobscured UV–SFR. Furthermore, the effective radius of the mean SFR profile (r{sub e,SFR}∼1 kpc) is ∼30% smaller than that of the stellar mass profile. The implied structural evolution, if such nuclear starburst last for the estimated gas depletion time of Δt = ±100 Myr, is a 4× increase of the stellar mass density within the central 1 kpc and a 1.6× decrease of the half-mass–radius. This structural evolution fully supports dissipation-driven, formation scenarios in which strong nuclear starbursts transform larger, star-forming progenitors into compact quiescent galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

Beam-energy dependence of charge balance functions from Au + Au collisions at energies available at the BNL Relativistic Heavy Ion Collider

Balance functions have been measured in terms of relative pseudorapidity ( Δη ) for charged particle pairs at the BNL Relativistic Heavy Ion Collider (RHIC) from Au + Au collisions at $\sqrt{s}$$_{NN}$ = 7.7 GeV to 200 GeV using the STAR detector. These results are compared with balance functions measured at the CERN Large Hadron Collider from Pb + Pb collisions at $\sqrt{s}$$_{NN}$ = 2.76 TeV by the ALICE Collaboration. The width of the balance function decreases as the collisions become more central and as the beam energy is increased. In contrast, the widths of the balance functions calculated using shuffled events show little dependence on centrality or beam energy and are larger than the observed widths. Balance function widths calculated using events generated by UrQMD are wider than the measured widths in central collisions and show little centrality dependence. The measured widths of the balance functions in central collisions are consistent with the delayed hadronization of a deconfined quark gluon plasma (QGP). Finally, the narrowing of the balance function in central collisions at $\sqrt{s}$$_{NN}$ = 7.7 GeV implies that a QGP is still being created at this relatively low energy.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Near-side azimuthal and pseudorapidity correlations using neutral strange baryons and mesons in d + Au , Cu + Cu, and Au + Au collisions at s N N = 200 GeV

Here we present measurements of the near side of triggered di-hadron correlations using neutral strange baryons ( $Λ,\overline{Λ}$) and mesons (K$0\atop{S}$ ) at intermediate transverse momentum (3 < pT< 6 GeV/c) to look for possible flavor and baryon-meson dependence. This study is performed in d+Au, Cu+Cu, and Au+Au collisions at $\sqrt{s}$$_{NN}$ = 200 GeV measured by the STAR experiment at RHIC. The near-side di-hadron correlation contains two structures, a peak which is narrow in azimuth and pseudorapidity consistent with correlations from jet fragmentation, and a correlation in azimuth which is broad in pseudorapidity. The particle composition of the jet-like correlation is determined using identified associated particles. The dependence of the conditional yield of the jet-like correlation on the trigger particle momentum, associated particle momentum, and centrality for correlations with unidentified trigger particles are presented. The neutral strange particle composition in jet-like correlations with unidentified charged particle triggers is not well described by PYTHIA. However, the yield of unidentified particles in jet-like correlations with neutral strange particle triggers is described reasonably well by the same model.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Tutorial: Crystal orientations and EBSD — Or which way is up?

Electron backscatter diffraction (EBSD) is an automated technique that can measure the orientation of crystals in a sample very rapidly. There are many sophisticated software packages that present measured data. Unfortunately, due to crystal symmetry and differences in the set-up of microscope and EBSD software, there may be accuracy issues when linking the crystal orientation to a particular microstructural feature. In this paper we outline a series of conventions used to describe crystal orientations and coordinate systems. These conventions have been used to successfully demonstrate that a consistent frame of reference is used in the sample, unit cell, pole figure and diffraction pattern frames of reference. We establish a coordinate system rooted in measurement of the diffraction pattern and subsequently link this to all other coordinate systems. A fundamental outcome of this analysis is to note that the beamshift coordinate system needs to be precisely defined for consistent 3D microstructure analysis. This is supported through a series of case studies examining particular features of the microscope settings and/or unambiguous crystallographic features. These case studies can be generated easily in most laboratories and represent an opportunity to demonstrate confidence in use of recorded orientation data. Finally, we include a simple software tool, written in both MATLAB® and Python, which the reader can use to compare consistency with their own microscope set-up and which may act as a springboard for further offline analysis. - Highlights: • Presentation of conventions used to describe crystal orientations • Three case studies that outline how conventions are consistent • Demonstrates a pathway for calibration and validation of EBSD based orientation measurements • EBSD computer code supplied for validation by the reader.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Improved measurement of the absolute branching fraction of $D^{+}\rightarrow \bar{K}^0 \mu ^{+}\nu _{\mu }$

Here, by analyzing 2.93 fb -1 of data collected at √s = 3.773 GeV with the BESIII detector, we measure the absolute branching fraction B(D + → K¯ 0 μ + ν μ ) = (8.72 ± 0.07 stat. ± 0.18 sys. )%, which is consistent with previous measurements within uncertainties but with significantly improved precision. Combining the Particle Data Group values of B(D 0 → K - μ + ν μ ), B(D + → K¯ 0 e + ν e ), and the lifetimes of the D 0 and D + mesons with the value of B(D + → K¯ 0 μ + ν μ ) measured in this work, we determine the following ratios of partial widths: Γ(D 0 → K - μ + ν μ )/Γ(D + → K¯ 0 μ + ν μ ) = 0.963 ± 0.044 and Γ(D + → K¯ 0 μ + ν μ )/Γ(D + → K¯ 0 e + ν e ) = 0.988 ± 0.033.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Measurements of the center-of-mass energies at BESIII via the di-muon process

From 2011 to 2014, the BESIII experiment collected about 5 fb -1 data at center-of-mass energies around 4 GeV for the studies of the charmonium-like and higher excited charmonium states. By analyzing the di-muon process e + e - → γ ISR/FSR μ + μ - , the center-of-mass energies of the data samples are measured with a precision of 0.8 MeV. The center-of-mass energy is found to be stable for most of the time during data taking.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

AlN and Al oxy-nitride gate dielectrics for reliable gate stacks on Ge and InGaAs channels

AlN and Al oxy-nitride dielectric layers are proposed instead of Al{sub 2}O{sub 3} as a component of the gate dielectric stacks on higher mobility channels in metal oxide field effect transistors to improve their positive bias stress instability reliability. It is calculated that the gap states of nitrogen vacancies in AlN lie further away in energy from the semiconductor band gap than those of oxygen vacancies in Al{sub 2}O{sub 3}, and thus AlN might be less susceptible to charge trapping and have a better reliability performance. The unfavourable defect energy level distribution in amorphous Al{sub 2}O{sub 3} is attributed to its larger coordination disorder compared to the more symmetrically bonded AlN. Al oxy-nitride is also predicted to have less tendency for charge trapping.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

Measurement of the Transverse Single-Spin Asymmetry in p ↑ + p → W ± / Z 0 at RHIC

In this paper, we present the measurement of the transverse single-spin asymmetry of weak boson production in transversely polarized proton-proton collisions at $\sqrt{s}$ = 500 GeV by the STAR experiment at RHIC. The measured observable is sensitive to the Sivers function, one of the transverse-momentum-dependent parton distribution functions, which is predicted to have the opposite sign in proton-proton collisions from that observed in deep inelastic lepton-proton scattering. In conclusion, these data provide the first experimental investigation of the nonuniversality of the Sivers function, fundamental to our understanding of QCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Beam Energy Dependence of the Third Harmonic of Azimuthal Correlations in Au+Au Collisions at RHIC

In this paper, we present results from a harmonic decomposition of two-particle azimuthal correlations measured with the STAR detector in Au + Au collisions for energies ranging from √sNN = 7.7 to 200 GeV. The third harmonic v$2\atop{3}${ 2 } = , where Φ1 - Φ2 is the angular difference in azimuth, is studied as a function of the pseudorapidity difference between particle pairs Δη = η1-η2 . Nonzero v$2\atop{3}${ 2 } is directly related to the previously observed large- Δη narrow- ΔΦ ridge correlations and has been shown in models to be sensitive to the existence of a low viscosity quark gluon plasma phase. For sufficiently central collisions, v$2\atop{3}${ 2 } persist down to an energy of 7.7 GeV, suggesting that quark gluon plasma may be created even in these low energy collisions. In peripheral collisions at these low energies, however, v$2\atop{3}${ 2 } is consistent with zero. Finally, when scaled by the pseudorapidity density of charged-particle multiplicity per participating nucleon pair, v$2\atop{3}${ 2 } for central collisions shows a minimum near √sNN = 20 GeV .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2016

Modeling of advanced divertor configuration on experimental advanced superconducting tokamak by SOLPS5.0/B2.5-Eirene

Heat exhaust is one of the most challenging issues to be addressed for tokamak magnetic confinement fusion research. Detailed modeling with SOLPS5.0/B2.5-Eirene code package is carried out to examine an alternative advanced divertor configuration, i.e., quasi snowflake (QSF), for long pulse operation in EAST. Comparison is also made with the lower single null (LSN) divertor configuration. SOLPS predicts that the quasi snowflake configuration significantly reduces the peak heat flux at the lower divertor outer target, by a factor of 2–3, owing to the magnetic flux expansion. Furthermore, the density threshold for detachment is much lower for QSF, compared to LSN under the same upstream conditions. This indicates that QSF provides a promising tool for controlling heat flux at divertor target while maintaining a lower separatrix density, which is highly desirable for current drive, thus greatly facilitating long-pulse operation in EAST.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗