Engineering topics

Chen, C. H.

Publications and source records attributed to Chen, C. H..

At least 55 records · Page 3

DOE OSTI2024

Search for e + e − → η ′ ψ ( 2 S ) at center-of-mass energies from 4.66 to 4.95 GeV

Using data samples with an integrated luminosity of 4.67 fb − 1 collected by the BESIII detector operating at the BEPCII Collider, we search for the process e + e − → η ′ ψ ( 2 S ) at center-of-mass energies from 4.66 to 4.95 GeV. No significant signal is observed, and upper limits for the Born cross sections σ B ( e + e − → η ′ ψ ( 2 S ) ) at the 90% confidence level are determined. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Measurement of the e + e − → p p ¯ π 0 cross section at s = 2.1000 − 3.0800 GeV

The process e + e − → p p ¯ π 0 is studied at 20 center-of-mass energies ranging from 2.1000 to 3.0800 GeV using 636.8 pb − 1 of data collected with the BESIII detector operating at the BEPCII collider. The Born cross sections for e + e − → p p ¯ π 0 are measured with high precision. Since the lowest center-of-mass energy, 2.1000 GeV, is less than 90 MeV above the p p ¯ π 0 energy threshold, we can probe the threshold behavior for this reaction. However, no anomalous threshold enhancement is found in the cross sections for e + e − → p p ¯ π 0 . Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Search for X ( 1870 ) via the decay J / ψ → ω K + K − η

Using a sample of ( 10087 ± 44 ) × 10 6 J / ψ events collected by the BESIII detector at the BEPCII collider, we search for the decay X ( 1870 ) → K + K − η via the J / ψ → ω K + K − η process for the first time. No significant X ( 1870 ) signal is observed. The upper limit on the branching fraction of the decay J / ψ → ω X ( 1870 ) → ω K + K − η is determined to be 9.55 × 10 − 7 at the 90% confidence level. In addition, the branching faction B ( J / ψ → ω K + K − η ) is measured to be ( 3.33 ± 0.02 ( stat ) ± 0.12 ( syst ) ) × 10 − 4 . Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Search for Rare Decays of D s + to Final States π + e + e − , ρ + e + e − , π + π 0 e + e − , K + π 0 e + e − , and K S 0 π + e + e −

Using 7.33 fb − 1 of e + e − collision data collected by the BESIII detector at center-of-mass energies in the range of s = 4.128 – 4.226 GeV , we search for the rare decays D s + → h + ( h 0 ) e + e − , where h represents a kaon or pion. By requiring the e + e − invariant mass to be consistent with a ϕ ( 1020 ) , 0.98 < M ( e + e − ) < 1.04 GeV / c 2 , the decay D s + → π + ϕ , ϕ → e + e − is observed with a statistical significance of 7.8 σ , and evidence for the decay D s + → ρ + ϕ , ϕ → e + e − is found for the first time with a statistical significance of 4.4 σ . The decay branching fractions are measured to be B ( D s + → π + ϕ , ϕ → e + e − ) = ( 1.1 7 − 0.21 + 0.23 ± 0.03 ) × 10 − 5 , and B ( D s + → ρ + ϕ , ϕ → e + e − ) = ( 2.4 4 − 0.62 + 0.67 ± 0.16 ) × 10 − 5 , where the first uncertainties are statistical and the second systematic. No significant signals for the three four-body decays of D s + → π + π 0 e + e − , D s + → K + π 0 e + e − , and D s + → K S 0 π + e + e − are observed. For D s + → π + π 0 e + e − , the ϕ mass region is vetoed to minimize the long-distance effects. The 90% confidence level upper limits set on the branching fractions of these decays are in the range of ( 7.0 – 8.1 ) × 10 − 5 . Published by the American Physical Society 2024

Physics↗

DOE OSTI2024

Measurement of the branching fraction of D s + → ℓ + ν ℓ via e + e − → D s * + D s * −

Based on 10.64 fb − 1 of e + e − collision data taken at center-of-mass energies between 4.237 and 4.699 GeV with the BESIII detector, we study the leptonic D s + decays using the e + e − → D s * + D s * − process. The branching fractions of D s + → ℓ + ν ℓ ( ℓ = μ , τ ) are measured to be B D s + → μ + ν μ = ( 0.547 ± 0.02 6 stat ± 0.01 6 syst ) % and B D s + → τ + ν τ = ( 5.60 ± 0.1 6 stat ± 0.2 0 syst ) % , respectively. The product of the decay constant and Cabibbo-Kobayashi-Maskawa matrix element | V c s | is determined to be f D s + | V c s | = ( 246.5 ± 5.9 stat ± 3.6 syst ± 0.5 input ) μ ν and f D s + | V c s | = ( 252.7 ± 3.6 stat ± 4.5 syst ± 0.6 input ) τ ν MeV , respectively. Taking the value of | V c s | from a global fit in the Standard Model, we obtain f D s + = ( 253.2 ± 6.0 stat ± 3.7 syst ± 0.6 input ) μ ν and f D s + = ( 259.6 ± 3.7 stat ± 4.6 syst ± 0.6 input ) τ ν MeV , respectively. Conversely, taking the value for f D s + from the latest lattice quantum chromodynamics calculation, we obtain | V c s | = ( 0.986 ± 0.02 3 stat ± 0.01 4 syst ± 0.00 3 input ) μ ν and | V c s | = ( 1.011 ± 0.01 4 stat ± 0.01 8 syst ± 0.00 3 input ) τ ν , respectively. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Strong and Weak C P Tests in Sequential Decays of Polarized Σ 0 Hyperons

The J / ψ , ψ ( 3686 ) → Σ 0 Σ ¯ 0 processes and subsequent decays are studied using the world’s largest J / ψ and ψ ( 3686 ) data samples collected with the BESIII detector. The parity-violating decay parameters of the decays Σ 0 → Λ γ and Σ ¯ 0 → Λ ¯ γ , α Σ 0 = − 0.0017 ± 0.0021 ± 0.0018 and α ¯ Σ 0 = 0.0021 ± 0.0020 ± 0.0022 , are measured for the first time. The strong C P symmetry is tested in the decays of the Σ 0 hyperons for the first time by measuring the asymmetry A C P Σ = α Σ 0 + α ¯ Σ 0 = ( 0.4 ± 2.9 ± 1.3 ) × 10 − 3 . The weak C P test is performed in the subsequent decays of their daughter particles Λ and Λ ¯ . Also for the first time, the transverse polarizations of the Σ 0 hyperons in J / ψ and ψ ( 3686 ) decays are observed with opposite directions, and the ratios between the S -wave and D -wave contributions of the J / ψ , ψ ( 3686 ) → Σ 0 Σ ¯ 0 decays are obtained. These results are crucial to understand the decay dynamics of the charmonium states and the production mechanism of the Σ 0 − Σ ¯ 0 pairs. Published by the American Physical Society 2024

Physics↗

DOE OSTI2024

Measurements of the branching fractions of the P -wave charmonium spin-singlet state h c ( P 1 1 ) → h + h − π 0 / η

Based on ( 2712.4 ± 14.3 ) × 10 6 ψ ( 3686 ) events, we investigate four hadronic decay modes of the P -wave charmonium spin-singlet state h c ( 1 P 1 ) → h + h − π 0 / η ( h = π or K ) via the process ψ ( 3686 ) → π 0 h c at BESIII. The h c → π + π − π 0 decay is observed with a significance of 9.6 σ after taking into account systematic uncertainties. Evidences for h c → K + K − π 0 and h c → K + K − η are found with significances of 3.5 σ and 3.3 σ , respectively, after considering the systematic uncertainties. The branching fractions of these decays are measured to be B ( h c → π + π − π 0 ) = ( 1.36 ± 0.16 ± 0.14 ) × 10 − 3 , B ( h c → K + K − π 0 ) = ( 3.26 ± 0.84 ± 0.36 ) × 10 − 4 , and B ( h c → K + K − η ) = ( 3.13 ± 1.08 ± 0.38 ) × 10 − 4 , where the first uncertainties are statistical and the second are systematic. No significant signal of h c → π + π − η is found, and the upper limit of its decay branching fraction is determined to be B ( h c → π + π − η ) < 4.0 × 10 − 4 at the 90% confidence level. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Study of the decays χ c J → Λ Λ ¯ ω

Using ( 27.12 ± 0.14 ) × 10 8 ψ ( 3686 ) events collected with the BESIII detector, we present the first observation of the decays χ c J → Λ Λ ¯ ω , where J = 0 , 1, 2, with statistical significances of 11.7 σ , 11.2 σ , and 11.8 σ . The branching fractions of these decays are determined to be B ( χ c 0 → Λ Λ ¯ ω ) = ( 2.37 ± 0.22 ± 0.25 ) × 10 − 4 , B ( χ c 1 → Λ Λ ¯ ω ) = ( 1.01 ± 0.10 ± 0.11 ) × 10 − 4 , and B ( χ c 2 → Λ Λ ¯ ω ) = ( 1.40 ± 0.13 ± 0.17 ) × 10 − 4 , where the first uncertainties are statistical and the second are systematic. We observe no clear intermediate structures. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Search for C -even states decaying to D s ± D s * ∓ with masses between 4.08 and 4.32 GeV / c 2

Six C -even states, denoted as X , with quantum numbers J P C = 0 − + , 1 ± + , or 2 ± + , are searched for via the e + e − → γ D s ± D s * ∓ process using ( 1667.39 ± 8.84 ) pb − 1 of e + e − collision data collected with the BESIII detector operating at the BEPCII storage ring at center-of-mass energy of s = ( 4681.92 ± 0.30 ) MeV . No statistically significant signal is observed in the mass range from 4.08 GeV / c 2 to 4.32 GeV / c 2 . The upper limits of σ [ e + e − → γ X ] · B [ X → D s ± D s * ∓ ] at a 90% confidence level are determined. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Study of the decays χ c J → Λ Λ ¯ ϕ

Based on ( 2712.4 ± 14.3 ) × 10 6 e + e − → ψ ( 3686 ) events collected with the BESIII detector operating at the BEPCII Collider, we report the first evidence of χ c 0 → Λ Λ ¯ ϕ decays and the first observation of χ c 1 , 2 → Λ Λ ¯ ϕ decays, with significances of 4.1 σ , 11.3 σ and 13.0 σ , respectively. The decay branching fractions of χ c 0 , 1 , 2 → Λ Λ ¯ ϕ are measured to be ( 2.99 ± 1.24 ± 0.19 ) × 10 − 5 , ( 6.01 ± 0.90 ± 0.40 ) × 10 − 5 , and ( 7.13 ± 0.81 ± 0.36 ) × 10 − 5 , where the first uncertainties are statistical and the second systematic. No obvious enhancement near the Λ Λ ¯ production threshold or excited Λ state is found in the Λ ϕ (or Λ ¯ ϕ ) system. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

DOE OSTI2024

Search for the e + e − → ϕ χ c 1 ( 3872 ) process at BESIII

Based on 368.5 p b − 1 of e + e − collision data collected at center-of-mass energies 4.914 and 4.946 GeV by the BESIII detector, the e + e − → ϕ χ c 1 ( 3872 ) process is searched for the first time. No significant signal is observed and the upper limits at the 90% confidence level on the product of the Born cross section σ ( e + e − → ϕ χ c 1 ( 3872 ) ) and the branching fraction B [ χ c 1 ( 3872 ) → π + π − J / ψ ] at 4.914 and 4.946 GeV are set to be 0.85 and 0.96 pb, respectively. These measurements provide useful information for the production of the χ c 1 ( 3872 ) at e + e − colliders and deepen our understanding about the nature of this particle. Published by the American Physical Society 2024

Astronomy & Astrophysics↗

NASA NTRS2019

A Long-Term Vision for Space-Based Interferometry

The processes leading to the formation of planets; the extreme physics occurring near the event horizon of black holes; detailed studies of exoplanets through spectral-spatial mapping: new and unique insights into the physical processes involved across nearly the whole gamut of astrophysics await discovery at small angular scales. The fine spatial resolution needed to explore these processes, however, lies beyond the capabilities of current astronomical facilities and nearly all proposed future facilities. Interferometers can crack this angular resolution problem, and space-based interferometry missions promise to explore entirely new regions of scientific phase space, providing unique new insights into the physical processes lurking at small angular scales.

Rinehart, S. A.↗

NASA NTRS2011

Spitzer Evidence for a Late Heavy Bombardment and the Formation of Urelites in {eta}Corvi at Approximately 1 Gyr

We have analyzed Spitzer and NASA/IRTF 2 - 35 micrometer spectra of the warm, ~350 K circumstellar dust around the nearby MS star eta Corvi (F2V, 1.4 plus or minus 0.3 Gyr). The spectra show clear evidence for warm, water- and carbon-rich dust at ~3 AU from the central star, in the system's Terrestrial Habitability Zone. Spectral features due to ultra-primitive cometary material were found, in addition to features due to impact produced silica and high temperature carbonaceous phases. At least 9 x 10(exp 18) kg of 0.1 - 100 micrometer warm dust is present in a collisional equilibrium distribution with dn/da ~ a(exp -3.5), the equivalent of a 130 km radius KBO of 1.0 grams per cubic centimeter density and similar to recent estimates of the mass delivered to the Earth at 0.6 - 0.8 Gyr during the Late Heavy Bombardment. We conclude that the parent body was a Kuiper-Belt body or bodies which captured a large amount of early primitive material in the first Myrs of the system's lifetime and preserved it in deep freeze at approximately 150 AU. At approximately 1.4 Gyr they were prompted by dynamical stirring of their parent Kuiper Belt into spiraling into the inner system, eventually colliding at 5-10 kilometers per second with a rocky planetary body of mass less than or equal to M(sub Earth at approximately 3 AU, delivering large amounts of water (greater than 0.1 % of M(sub Earth's Oceans)) and carbon-rich material. The Spitzer spectrum also closely matches spectra reported for the Ureilite meteorites of the Sudan Almahata Sitta fall in 2008, suggesting that one of the Ureilite parent bodies was a KBO.

Lisse, C. M.↗

NASA NTRS2005

The Accretion Disk of the Lithium-Depleted Young Binary St 34

We presented the infrared spectrum of the young binary system St 34 obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope. The IRS spectrum clearly shows excess dust emission, consistent with the suggestion of White & Hillenbrand that St 34 is accreting from a circumbinary disk. The disk emission of St 34 is low in comparison with the levels observed in typical T Tauri stars; silicate features at 10 and 20 microns are much weaker than typically seen in T Tauri stars; and excess emission is nearly absent at the shortest wavelengths observed. These features of the infrared spectrum suggest substantial grain growth (to eliminate silicate features) and possible settling of dust to the disk midplane (to reduce the continuum excess emission levels), along with a relatively evacuated inner disk, as expected due to gravitational perturbations by the binary system. Although the position of St 34 in the H-R diagram suggests an age of 8f Myr, assuming that it lies at the distance of the Taurus-Auriga molecular clouds, White & Hillenbrand could not detect any Li I absorption, which would indicate a Li depletion age of roughly 25 Myr or more. We suggest that St 34 is closer than the Taurus clouds by about 30-40 pc and has an age roughly consistent with Li depletion models. Such an advanced age would make St 34 the oldest known low-mass pre-main-sequence object with a dusty accretion disk. The persistence of optically thick dust emission well outside the binary orbit may indicate a failure to make giant planets that could effectively remove dust particles.

Hartmann, Lee↗

NASA NTRS2004

Are gaint planets forming around HR 4796A?

We have obtained Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope STIS spectra of HR 4796A, a nearby 8 Myr old main-sequence star that possesses a dusty circumstellar disk whose inclination has been constrained from high-resolution near-infrared observations to be 17 degrees from edge-on.

circumstellar matter planetary systems stars↗

NASA NTRS2003

The Mid-Infrared Emitting Dust Around AB Aurigae

Using the Keck I telescope, we have obtained 11.7 and 18.7 microns images of the circumstellar dust emission from AB Aur, a Herbig Ae star. We find that AB Aur is probably resolved at 18.7 microns with an angular diameter of 1.2 in. at a surface brightness of 3.5 Jy arc/sq sec. Most of the dust mass detected at millimeter wavelengths does not contribute to the 18.7 microns emission, which is plausibly explained if the system possesses a relatively cold massive disk. We find that models with an optically thick, geometrically thin disk surrounded by an optically thin spherical envelope fit the data somewhat better than flared disk models.

Chen, C. H.↗

NASA NTRS1991

High resolution ultrasonic spectroscopy system for nondestructive evaluation

With increased demand for high resolution ultrasonic evaluation, computer based systems or work stations become essential. The ultrasonic spectroscopy method of nondestructive evaluation (NDE) was used to develop a high resolution ultrasonic inspection system supported by modern signal processing, pattern recognition, and neural network technologies. The basic system which was completed consists of a 386/20 MHz PC (IBM AT compatible), a pulser/receiver, a digital oscilloscope with serial and parallel communications to the computer, an immersion tank with motor control of X-Y axis movement, and the supporting software package, IUNDE, for interactive ultrasonic evaluation. Although the hardware components are commercially available, the software development is entirely original. By integrating signal processing, pattern recognition, maximum entropy spectral analysis, and artificial neural network functions into the system, many NDE tasks can be performed. The high resolution graphics capability provides visualization of complex NDE problems. The phase 3 efforts involve intensive marketing of the software package and collaborative work with industrial sectors.

Chen, C. H.↗

NASA NTRS1991

Laser surface interaction of high-Tc superconductors

During the past two years, one of the most exciting research fields in science has been the study of the newly discovered high-T(sub c) metal oxide superconductors. Although many theoretical models were proposed, there is no general agreement on any theory to explain these materials. One of the peculiar features of these high-T(sub c) materials is the noninteger number of oxygen atoms. The oxygen content is extremely critical to the superconductive properties. Take YBa2Cu3O(7-x) as an example. Its superconductive properties disappear whenever x is larger than 0.5. The existence of Cu(+ 3) was considered to account for x less than 0.5. However, results from mass spectroscopy of laser desorbed species indicate that significant quantities of oxygen molecules are trapped in the bulk of these high-T(sub c) superconductors. It appears that these trapped oxygen molecules may play key roles in superconductive properties. Preparation of superconductive thin films are considered very important for the applications of these new superconductors for the electronics industry. Fluorescence spectra and ion spectra following laser ablation of high-temperature superconductors were obtained. A real time monitor for preparation of superconductive thin films can possibly be developed.

Chen, C. H.↗