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Chen, H.

Publications and source records attributed to Chen, H..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Study of η′ → π+π−l+l− decays at BESIII

Abstract With a sample of (10087±44)×10 6 J/ψevents accumulated with the BESIII detector, we analyze the decaysη′→ π + π − l + l − (l=e, μ) via the processJ/ψ → γη′. The branching fractions are measured to be$$ \mathcal{B} $$ B (η′→ π + π − e + e − ) = (2.45±0.02(stat.)±0.08(syst.))×10 −3 and$$ \mathcal{B} $$ B (η′→ π + π − μ + μ − ) = (2.16±0.12(stat.)±0.06(syst.))×10 −5 , and the ratio is$$ \frac{\mathcal{B}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{e}^{+}{e}^{-}\right)}{\mathcal{B}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{\mu}^{+}{\mu}^{-}\right)}=113.4\pm 0.9\left(\textrm{stat}.\right)\pm 3.7\left(\textrm{syst}.\right) $$ B η ′ → π + π − e + e − B η ′ → π + π − μ + μ − = 113.4 ± 0.9 stat . ± 3.7 syst . . In addition, by combining theη′ →π + π − e + e − andη′ →π + π − μ + μ − decays, the slope parameter of the electromagnetic transition form factor is measured to beb η′ = 1.30 ± 0.19 (GeV/c 2 ) −2 , which is consistent with previous measurements from BESIII and theoretical predictions from the VMD model. The asymmetry in the angle between theπ + π − andl + l − decay planes, which has the potential to reveal theCP-violation originating from an unconventional electric dipole transition, is also investigated. The asymmetry parameters are determined to be$$ {\mathcal{A}}_{CP}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{e}^{+}{e}^{-}\right)=\left(-0.21\pm 0.73\left(\textrm{stat}.\right)\pm 0.01\left(\textrm{syst}.\right)\right)\% $$ A CP η ′ → π + π − e + e − = − 0.21 ± 0.73 stat . ± 0.01 syst . % and$$ {\mathcal{A}}_{CP}\left({\eta}^{\prime}\to {\pi}^{+}{\pi}^{-}{\mu}^{+}{\mu}^{-}\right)=\left(0.62\pm 4.71\left(\textrm{stat}.\right)\pm 0.08\left(\textrm{syst}.\right)\right)\% $$ A CP η ′ → π + π − μ + μ − = 0.62 ± 4.71 stat . ± 0.08 syst . % , implying that no evidence ofCP-violation is observed at the present statistics. Finally, an axion-like particle is searched for via the decayη′ →π + π − a, a→e + e − , and upper limits of the branching fractions are presented for the mass assumptions of the axion-like particle in the range of 0−500 MeV/c 2 .

Physics↗
DOE OSTI2024

Measurement of the cross sections of $$ {e}^{+}{e}^{-}\to {K}^{-}{\overline{\Xi}}^{+}\Lambda /{\Sigma}^0 $$ at center-of-mass energies between 3.510 and 4.914 GeV

Abstract Usinge + e − collision data collected with the BESIII detector at the BEPCII collider at center-of-mass energies between 3.510 and 4.914 GeV, corresponding to an integrated luminosity of 25 fb −1 , we measure the Born cross sections for the process$$ {e}^{+}{e}^{-}\to {K}^{-}{\overline{\Xi}}^{+}\Lambda /{\Sigma}^0 $$ e + e − → K − Ξ ¯ + Λ / Σ 0 at thirty-five energy points with a partial-reconstruction strategy. By fitting the dressed cross sections of$$ {e}^{+}{e}^{-}\to {K}^{-}{\overline{\Xi}}^{+}\Lambda /{\Sigma}^0 $$ e + e − → K − Ξ ¯ + Λ / Σ 0 , evidence for$$ \psi (4160)\to {K}^{-}{\overline{\Xi}}^{+}\Lambda $$ ψ 4160 → K − Ξ ¯ + Λ is found for the first time with a significance of 4.4σ, including systematic uncertainties. No evidence for other possible resonances is found. In addition, the products of electronic partial width and branching fraction for all assumed resonances decaying into$$ {K}^{-}{\overline{\Xi}}^{+}\Lambda /{\Sigma}^0 $$ K − Ξ ¯ + Λ / Σ 0 are determined.

Physics↗
DOE OSTI2024

Properties of Cosmic Deuterons Measured by the Alpha Magnetic Spectrometer

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of the deuteron (𝐷) flux are presented. The measurements are based on 21 × 10 6 𝐷 nuclei in the rigidity range from 1.9 to 21 GV collected from May 2011 to April 2021. We observe that over the entire rigidity range the 𝐷 flux exhibits nearly identical time variations with the 𝑝, 3 He, and 4 He fluxes. Above 4.5 GV, the 𝐷/ 4 He flux ratio is time independent and its rigidity dependence is well described by a single power law ∝𝑅 Δ with Δ 𝐷/ 4 He = −0.108 ± 0.005. This is in contrast with the 3 He/ 4 He flux ratio for which we find Δ 3 He/ 4 He = −0.289 ± 0.003. Above ∼13 GV we find a nearly identical rigidity dependence of the 𝐷 and 𝑝 fluxes with a 𝐷/𝑝 flux ratio of 0.027 ± 0.001. These unexpected observations indicate that cosmic deuterons have a sizable primarylike component. With a method independent of cosmic ray propagation, we obtain the primary component of the 𝐷 flux equal to 9.4 ± 0.5% of the 4 He flux and the secondary component of the 𝐷 flux equal to 58 ± 5% of the 3 He flux.

cosmic ray acceleration↗
DOE OSTI2024

Laboratory realization of relativistic pair-plasma beams

Relativistic electron-positron plasmas are ubiquitous in extreme astrophysical environments such as black-hole and neutron-star magnetospheres, where accretion-powered jets and pulsar winds are expected to be enriched with electron-positron pairs. Their role in the dynamics of such environments is in many cases believed to be fundamental, but their behavior differs significantly from typical electron-ion plasmas due to the matter-antimatter symmetry of the charged components. So far, our experimental inability to produce large yields of positrons in quasi-neutral beams has restricted the understanding of electron-positron pair plasmas to simple numerical and analytical studies, which are rather limited. We present the first experimental results confirming the generation of high-density, quasi-neutral, relativistic electron-positron pair beams using the 440 GeV/c beam at CERN’s Super Proton Synchrotron (SPS) accelerator. Monte Carlo simulations agree well with the experimental data and show that the characteristic scales necessary for collective plasma behavior, such as the Debye length and the collisionless skin depth, are exceeded by the measured size of the produced pair beams. Our work opens up the possibility of directly probing the microphysics of pair plasmas beyond quasi-linear evolution into regimes that are challenging to simulate or measure via astronomical observations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

New constraints on ultraheavy dark matter from the LZ experiment

Searches for dark matter with liquid xenon time projection chamber experiments have traditionally focused on the region of the parameter space that is characteristic of weakly interacting massive particles, ranging from a few GeV / c 2 to a few TeV / c 2 . Models of dark matter with a mass much heavier than this are well motivated by early production mechanisms different from the standard thermal freeze-out, but they have generally been less explored experimentally. In this work, we present a reanalysis of the first science run of the LZ experiment, with an exposure of 0.9 tonne × yr , to search for ultraheavy particle dark matter. The signal topology consists of multiple energy deposits in the active region of the detector forming a straight line, from which the velocity of the incoming particle can be reconstructed on an event-by-event basis. Zero events with this topology were observed after applying the data selection calibrated on a simulated sample of signal-like events. New experimental constraints are derived, which rule out previously unexplored regions of the dark matter parameter space of spin-independent interactions beyond a mass of 10 17 GeV / c 2 . Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

The influence of laser focusing conditions on the direct laser acceleration of electrons

Direct laser acceleration of electrons during a high-energy, picosecond laser interaction with an underdense plasma has been demonstrated to be substantially enhanced by controlling the laser focusing geometry. Experiments using the OMEGA EP facility measured electrons accelerated to maximum energies exceeding 120 times the ponderomotive energy under certain laser focusing, pulse energy, and plasma density conditions. Two-dimensional particle-in-cell simulations show that the laser focusing conditions alter the laser field evolution, channel fields generation, and electron oscillation, all of which contribute to the final electron energies. The optimal laser focusing condition occurs when the transverse oscillation amplitude of the accelerated electron in the channel fields matches the laser beam width, resulting in efficient energy gain. Through this observation, a simple model was developed to calculate the optimal laser focal spot size in more general conditions and is validated by experimental data.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

First constraints on WIMP-nucleon effective field theory couplings in an extended energy region from LUX-ZEPLIN

Following the first science results of the LUX-ZEPLIN (LZ) experiment, a dual-phase xenon time projection chamber operating from the Sanford Underground Research Facility in Lead, South Dakota, USA, we report the initial limits on a model-independent nonrelativistic effective field theory describing the complete set of possible interactions of a weakly interacting massive particle (WIMP) with a nucleon. These results utilize the same 5.5 t fiducial mass and 60 live days of exposure collected for the LZ spin-independent and spin-dependent analyses while extending the upper limit of the energy region of interest by a factor of 7.5 to 270 keV. No significant excess in this high energy region is observed. Using a profile-likelihood ratio analysis, we report 90% confidence level exclusion limits on the coupling of each individual nonrelativistic WIMP-nucleon operator for both elastic and inelastic interactions in the isoscalar and isovector bases. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Measurement of Born cross section of $$ {e}^{+}{e}^{-}\to {\Sigma}^{+}{\overline{\Sigma}}^{-} $$ at center-of-mass energies between 3.510 and 4.951 GeV

Abstract Using 24.1 fb −1 ofe + e − collision data collected with the BESIII detector at the BEPCII collider, the Born cross sections and effective form factors of the$$ {e}^{+}{e}^{-}\to {\Sigma}^{+}{\overline{\Sigma}}^{-} $$ e + e − → Σ + Σ ¯ − reaction are measured. The measurements are performed at center-of-mass energies ranging from 3.510 to 4.951 GeV. No significant evidence for the decay of the charmonium(-like) states,ψ(3770),ψ(4040),ψ(4160),Y(4230),Y(4360),ψ(4415), andY(4660), into a$$ {\Sigma}^{+}{\overline{\Sigma}}^{-} $$ Σ + Σ ¯ − final state is observed. Consequently, upper limits for the products of the branching fractions and the electronic partial widths at the 90% confidence level are reported for these decays.

Physics↗
DOE OSTI2024

Search for ∆S = 2 nonleptonic hyperon decays Ω− → Σ0π− and Ω− → nK−

Abstract Using (27.12 ± 0.14) × 10 8 ψ(3686) events collected by the BESIII detector at the center-of-mass energy of$$ \sqrt{s} $$ s = 3.686 GeV, we search for the first time for two nonleptonic hyperon decays that change strangeness by two units, Ω − → Σ 0 π − and Ω − →nK − . No significant signal is observed. The upper limits on their decay branching fractions are determined to be$$ \mathcal{B} $$ B (Ω − → Σ 0 π − )<5.4 × 10 −4 and$$ \mathcal{B} $$ B (Ω − →nK − )<2.4 × 10 −4 at the 90% confidence level.

Physics↗
DOE OSTI2024

Measurement of absolute branching fractions of $$ {\textrm{D}}_{\textrm{s}}^{+} $$ hadronic decays

Abstract Usinge + e − collision data collected at the BESIII detector at center-of-mass energies between 4.128 and 4.226 GeV, corresponding to an integrated luminosity of 7.33 fb −1 , we determine the absolute branching fractions of fifteen hadronic$$ {D}_s^{+} $$ D s + decays with a double-tag technique. In particular, we make precise measurements of the branching fractions$$ \mathcal{B}\left({D}_s^{+}\to {K}^{+}{K}^{-}{\pi}^{+}\right)=\left(5.49\pm 0.04\pm 0.07\right)\% $$ B D s + → K + K − π + = 5.49 ± 0.04 ± 0.07 % ,$$ \mathcal{B}\left({D}_s^{+}\to {K}_S^0{K}^{+}\right)=\left(1.50\pm 0.01\pm 0.01\right)\% $$ B D s + → K S 0 K + = 1.50 ± 0.01 ± 0.01 % and$$ \mathcal{B}\left({D}_s^{+}\to {K}^{+}{K}^{-}{\pi}^{+}{\pi}^0\right)=\left(5.50\pm 0.05\pm 0.11\right)\% $$ B D s + → K + K − π + π 0 = 5.50 ± 0.05 ± 0.11 % , where the first uncertainties are statistical and the second ones are systematic. TheCPasymmetries in these decays are also measured and all are found to be compatible with zero.

Physics↗
DOE OSTI2024

Characterization of the ATLAS Liquid Argon Front-End ASIC ALFE2 for the HL-LHC upgrade

In this study, ALFE2 is an ATLAS Liquid Argon Calorimeter (LAr) Front-End ASIC designed for the HL-LHC upgrade. ALFE2 comprises four channels of pre-amplifiers and CR-(RC) 2 shapers with adjustable input impedance. ALFE2 features two separate gain outputs to provide 16-bit dynamic-range coverage and an optimum resolution. ALFE2 is characterized using a Front-End Test Board (FETB) based on a Zynq UltraScale+ MPSoC and two octal-channel 16-bit high-speed ADCs. The test results indicate that ALFE2 fulfills or greatly exceeds all specifications on gain, noise, linearity, uniformity, and radiation tolerance.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Observation of ψ(3686) → $$ {\varOmega}^{-}{K}^{+}{\overline{\Xi}}^0 $$ + c.c.

Abstract Using (27.12±0.14)×10 8 ψ(3686) events collected with the BESIII detector at BEPCII, the decay ofψ(3686)→$$ {\varOmega}^{-}{K}^{+}{\overline{\Xi}}^0 $$ Ω − K + Ξ ¯ 0 + c.c.is observed for the first time. The branching fraction of this decay is measured to be$$ {\mathcal{B}}_{\psi (3686)\to {\varOmega}^{-}{K}^{+}{\overline{\Xi}}^0+\textrm{c}.\textrm{c}.} $$ B ψ 3686 → Ω − K + Ξ ¯ 0 + c . c . = (2.78 ± 0.40 ± 0.18) × 10 −6 , where the first uncertainty is statistical and the second is systematic. Possible baryon excited states are searched for in this decay, but no evident intermediate state is observed with the current sample size.

Physics↗
DOE OSTI2024

First Measurement of Discrimination between Helium and Electron Recoils in Liquid Xenon for Low-Mass Dark Matter Searches

We report the first measurement of discrimination between low-energy helium recoils and electron recoils in liquid xenon. This result is relevant to proposed low-mass dark matter searches which seek to dissolve light target nuclei in the active volume of liquid-xenon time projection chambers. Low-energy helium recoils were produced by degrading α particles from Po 210 with a gold foil situated on the cathode of a liquid xenon time-projection chamber. The resulting population of helium recoil events is well separated from electron recoils and is also offset from the expected position of xenon nuclear recoil events. Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Why would you put a flashlight in a dark matter detector?

Silicon photomultipliers (SiPMs) are solid-state, single-photon sensitive, pixelated sensors whose usage for scintillation detection has rapidly increased over the past decade. It is known that the avalanche process within the device, which renders a single photon detectable, can also generate secondary photons which may be detected by a separate device. This effect, known as external crosstalk, could potentially degrade the science goals of future xenon dark matter experiments. In this article, we measure the effect of external crosstalk in a dual-phase, liquid xenon time projection chamber fully instrumented with SiPMs. We then consider the implications for a future xenon dark matter experiment utilizing SiPMs and discuss possible solutions.

47 OTHER INSTRUMENTATION↗
DOE OSTI2024

Search for the semi-muonic charmonium decay J/ψ → D−μ+νμ + c.c.

Abstract Using (10087 ± 44) × 10 6 J/ψevents collected with the BESIII detector at the BEPCIIe + e − storage ring at the center-of-mass energy of$$ \sqrt{s} $$ s = 3.097 GeV, we present a search for the rare semi-muonic charmonium decayJ/ψ→D − μ + ν μ + c.c.. Since no significant signal is observed, we set an upper limit of the branching fraction to be$$ \mathcal{B} $$ B (J/ψ→D − μ + ν μ + c.c.) < 5.6 × 10 −7 at 90% confidence level. This is the first search for the weak decay of charmonium with a muon in the final state.

Physics↗
DOE OSTI2024

Measurement of the e+e− → $$ {K}_S^0{K}_L^0 $$π0 cross sections from $$ \sqrt{s} $$ = 2.000 to 3.080 GeV

Abstract Based one + e − collision data collected at center-of-mass energies from 2.000 to 3.080 GeV by the BESIII detector at the BEPCII collider, a partial wave analysis is performed for the processe + e − →$$ {K}_S^0{K}_L^0 $$ K S 0 K L 0 π 0 . The results allow the Born cross sections of the processe + e − →$$ {K}_S^0{K}_L^0 $$ K S 0 K L 0 π 0 , as well as its subprocessese + e − →K ∗ (892) 0 $$ \overline{K} $$ K ¯ 0 and$$ {K}_2^{\ast } $$ K 2 ∗ (1430) 0 $$ \overline{K} $$ K ¯ 0 to be measured. The Born cross sections fore + e − →$$ {K}_S^0{K}_L^0 $$ K S 0 K L 0 π 0 are consistent with previous measurements by BaBar, but with substantially improved precision. The Born cross section lineshape of the processe + e − K ∗ (892) 0 $$ \overline{K} $$ K ¯ 0 is consistent with a vector meson state around 2.2 GeV with a significance of 3.2σ. A Breit-Wigner fit determines its mass asM Y = (2164.7±9.1±3.1) MeV/c 2 and its width as Γ Y = (32.4±21.0±1.8) MeV.

Physics↗