arXiv subjects

K. Ding

Publications and source records attributed to K. Ding.

At least 19 recordsLinked to original sources

arXiv2024

Evidence of Coherent Elastic Neutrino-Nucleus Scattering with COHERENT's Germanium Array

We report the first detection of coherent elastic neutrino-nucleus scattering (CEvNS) on natural germanium, measured at the Spallation Neutron Source at Oak Ridge National Laboratory. The Ge-Mini detector of the COHERENT collaboration employs large-mass, low-noise, high-purity germanium spectrometers, enabling excellent energy resolution, and an analysis threshold of 1.5 keV electron-equivalent ionization energy. We observe a on-beam excess of 20.6 +7.1 -6.3 counts with a total exposure of 10.22 GWhkg and we reject the no-CEvNS hypothesis with 3.9 sigma significance. The result agrees with the predicted standard model of particle physics signal rate within 2 sigma.

hep-ex↗

arXiv2023

Accessing new physics with an undoped, cryogenic CsI CEvNS detector for COHERENT at the SNS

We consider the potential for a 10-kg undoped cryogenic CsI detector operating at the Spallation Neutron Source to measure coherent elastic neutrino-nucleus scattering and its sensitivity to discover new physics beyond the standard model. Through a combination of increased event rate, lower threshold, and good timing resolution, such a detector would significantly improve on past measurements. We considered tests of several beyond-the-standard-model scenarios such as neutrino non-standard interactions and accelerator-produced dark matter. This detector's performance was also studied for relevant questions in nuclear physics and neutrino astronomy, namely the weak charge distribution of CsI nuclei and detection of neutrinos from a core-collapse supernova.

hep-ex↗

arXiv2023

COHERENT Collaboration data release from the measurements of CsI[Na] response to nuclear recoils

Description of the data release 10.13139/OLCF/1969085 (https://doi.ccs.ornl.gov/ui/doi/426) from the measurements of the CsI[Na] response to low energy nuclear recoils by the COHERENT collaboration. The release corresponds to the results published in "D. Akimov et al 2022 JINST 17 P10034". We share the data in the form of raw ADC waveforms, provide benchmark values, and share plots to enhance the transparency and reproducibility of our results. This document describes the contents of the data release as well as guidance on the use of the data.

physics.ins-det↗

arXiv2023

Measurement of the Electron-Neutrino Charged-Current Cross Sections on ${}^{127}$I with the COHERENT NaI$\nu$E detector

Using an 185-kg NaI[Tl] array, COHERENT has measured the inclusive electron-neutrino charged-current cross section on ${}^{127}$I with pion decay-at-rest neutrinos produced by the Spallation Neutron Source at Oak Ridge National Laboratory. Iodine is one the heaviest targets for which low-energy ($\leq$ 50 MeV) inelastic neutrino-nucleus processes have been measured, and this is the first measurement of its inclusive cross section. After a five-year detector exposure, COHERENT reports a flux-averaged cross section for electron neutrinos of $9.2^{+2.1}_{-1.8} \times 10^{-40}$ cm$^2$. This corresponds to a value that is $\sim$41% lower than predicted using the MARLEY event generator with a measured Gamow-Teller strength distribution. In addition, the observed visible spectrum from charged-current scattering on $^{127}$I has been measured between 10 and 55 MeV, and the exclusive zero-neutron and one-or-more-neutron emission cross sections are measured to be $5.2^{+3.4}_{-3.1} \times 10^{-40}$ and $2.2^{+3.5}_{-2.2} \times 10^{-40}$ cm$^2$, respectively.

nucl-ex↗

arXiv2023

Performance of a liquid nitrogen cryostat setup for the study of nuclear recoils in undoped CsI crystals

There is a global trend to increase the light yield of CsI scintillators used in neutrino and dark matter detection by operating undoped crystals at cryogenic temperatures. However, high light yield alone is not sufficient to guarantee a low-energy threshold. The response of undoped crystals to nuclear recoils at cryogenic temperatures is equally important. A liquid nitrogen-based cryostat was developed to measure the nuclear quenching factor of a small undoped CsI crystal using monoenergetic neutron beams at the Triangle Universities Nuclear Laboratory (TUNL). To avoid neutron scattering in high-$Z$ materials, these materials were intentionally reduced around the crystal. The structure and performance of the cryostat are described in detail. Using this cryostat, a light yield of $33.4 \pm 1.7$ photoelectrons per keV electron-equivalent (PE/keV$_\text{ee}$) was observed at 5.9 keV$_\text{ee}$, enabling the measurement of nuclear quenching factors at very low energies. The results of the quenching factor measurement will be reported in a subsequent paper. Non-negligible negative overshoot was observed in the tails of the observed light pulses. The origin of this issue and the correction procedure are described in detail. This information may be useful for others who encounter similar technical challenges.

physics.ins-det↗

arXiv2022

Measurement of ${}^{nat}$Pb($\nu_e$,X$n$) production with a stopped-pion neutrino source

Using neutrinos produced at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL), the COHERENT collaboration has studied the Pb($\nu_e$,X$n$) process with a lead neutrino-induced-neutron (NIN) detector. Data from this detector are fit jointly with previously collected COHERENT data on this process. A combined analysis of the two datasets yields a cross section that is $0.29^{+0.17}_{-0.16}$ times that predicted by the MARLEY event generator using experimentally-measured Gamow-Teller strength distributions, consistent with no NIN events at 1.8$\sigma$. This is the first inelastic neutrino-nucleus process COHERENT has studied, among several planned exploiting the high flux of low-energy neutrinos produced at the SNS.

hep-ex↗

arXiv2022

A COHERENT constraint on leptophobic dark matter using CsI data

We use data from the COHERENT CsI[Na] scintillation detector to constrain sub-GeV leptophobic dark matter models. This detector was built to observe low-energy nuclear recoils from coherent elastic neutrino-nucleus scattering. These capabilities enable searches for dark matter particles produced at the Spallation Neutron Source mediated by a vector portal particle with masses between 2 and 400 MeV/c$^2$. No evidence for dark matter is observed and a limit on the mediator coupling to quarks is placed. This constraint improves upon previous results by two orders of magnitude. This newly explored parameter space probes the region where the dark matter relic abundance is explained by leptophobic dark matter when the mediator mass is roughly twice the dark matter mass. COHERENT sets the best constraint on leptophobic dark matter at these masses.

hep-ex↗

arXiv2022

The COHERENT Experimental Program

The COHERENT experiment located in Neutrino Alley at the Spallation Neutron Source (SNS), Oak Ridge National Laboratory (ORNL), has made the world's first two measurements of coherent elastic neutrino-nucleus scattering (CEvNS), on CsI and argon, using neutrinos produced at the SNS. The COHERENT collaboration continues to pursue CEvNS measurements on various targets as well as additional studies of inelastic neutrino-nucleus interactions, searches for accelerator-produced dark matter (DM) and physics beyond the Standard Model, using the uniquely high-quality and high-intensity neutrino source available at the SNS. This white paper describes primarily COHERENT's ongoing and near-future program at the SNS First Target Station (FTS). Opportunities enabled by the SNS Second Target Station (STS) for the study of neutrino physics and development of novel detector technologies are elaborated in a separate white paper.

hep-ex↗

arXiv2021

Monitoring the SNS basement neutron background with the MARS detector

We present the analysis and results of the first dataset collected with the MARS neutron detector deployed at the Oak Ridge National Laboratory Spallation Neutron Source (SNS) for the purpose of monitoring and characterizing the beam-related neutron (BRN) background for the COHERENT collaboration. MARS was positioned next to the COH-CsI coherent elastic neutrino-nucleus scattering detector in the SNS basement corridor. This is the basement location of closest proximity to the SNS target and thus, of highest neutrino flux, but it is also well shielded from the BRN flux by infill concrete and gravel. These data show the detector registered roughly one BRN per day. Using MARS' measured detection efficiency, the incoming BRN flux is estimated to be $1.20~\pm~0.56~\text{neutrons}/\text{m}^2/\text{MWh}$ for neutron energies above $\sim3.5$ MeV and up to a few tens of MeV. We compare our results with previous BRN measurements in the SNS basement corridor reported by other neutron detectors.

physics.ins-det↗

arXiv2021

Measurement of scintillation response of CsI[Na] to low-energy nuclear recoils by COHERENT

We present results of several measurements of CsI[Na] scintillation response to 3-60 keV energy nuclear recoils performed by the COHERENT collaboration using tagged neutron elastic scattering experiments and an endpoint technique. Earlier results, used to estimate the coherent elastic neutrino-nucleus scattering (CEvNS) event rate for the first observation of this process achieved by COHERENT at the Spallation Neutron Source (SNS), have been reassessed. We discuss corrections for the identified systematic effects and update the respective uncertainty values. The impact of updated results on future precision tests of CEvNS is estimated. We scrutinize potential systematic effects that could affect each measurement. In particular we confirm the response of the H11934-200 Hamamatsu photomultiplier tube (PMT) used for the measurements presented in this study to be linear in the relevant signal scale region.

physics.ins-det↗

arXiv2021

First Probe of Sub-GeV Dark Matter Beyond the Cosmological Expectation with the COHERENT CsI Detector at the SNS

The COHERENT collaboration searched for scalar dark matter particles produced at the Spallation Neutron Source with masses between 1 and 220~MeV/c$^2$ using a CsI[Na] scintillation detector sensitive to nuclear recoils above 9~keV$_\text{nr}$. No evidence for dark matter is found and we thus place limits on allowed parameter space. With this low-threshold detector, we are sensitive to coherent elastic scattering between dark matter and nuclei. The cross section for this process is orders of magnitude higher than for other processes historically used for accelerator-based direct-detection searches so that our small, 14.6~kg detector significantly improves on past constraints. At peak sensitivity, we reject the flux consistent with the cosmologically observed dark-matter concentration for all coupling constants $\alpha_D<0.64$, assuming a scalar dark-matter particle. We also calculate the sensitivity of future COHERENT detectors to dark-matter signals which will ambitiously test multiple dark-matter spin scenarios.

hep-ex↗

arXiv2021

Measurement of the Coherent Elastic Neutrino-Nucleus Scattering Cross Section on CsI by COHERENT

We measured the cross section of coherent elastic neutrino-nucleus scattering (\cevns{}) using a CsI[Na] scintillating crystal in a high flux of neutrinos produced at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory. New data collected before detector decommissioning has more than doubled the dataset since the first observation of \cevns{}, achieved with this detector. Systematic uncertainties have also been reduced with an updated quenching model, allowing for improved precision. With these analysis improvements, the COHERENT collaboration determined the cross section to be $(165^{+30}_{-25})\times10^{-40}$~cm$^2$, consistent with the standard model, giving the most precise measurement of \cevns{} yet. The timing structure of the neutrino beam has been exploited to compare the \cevns{} cross section from scattering of different neutrino flavors. This result places leading constraints on neutrino non-standard interactions while testing lepton flavor universality and measures the weak mixing angle as $\sin^2\theta_{W}=0.220^{+0.028}_{-0.026}$ at $Q^2\approx(50\text{ MeV})^2$

hep-ex↗

arXiv2021

Simulating the neutrino flux from the Spallation Neutron Source for the COHERENT experiment

The Spallation Neutron Source (SNS) at Oak Ridge National Laboratory is a pulsed source of neutrons and, as a byproduct of this operation, an intense source of pulsed neutrinos via stopped-pion decay. The COHERENT collaboration uses this source to investigate coherent elastic neutrino-nucleus scattering and other physics with a suite of detectors. This work includes a description of our Geant4 simulation of neutrino production at the SNS and the flux calculation which informs the COHERENT studies. We estimate the uncertainty of this calculation at about 10% based on validation against available low-energy pion production data.

hep-ex↗

arXiv2021

A D$_{2}$O detector for flux normalization of a pion decay-at-rest neutrino source

We report on the technical design and expected performance of a 592 kg heavy-water-Cherenkov detector to measure the absolute neutrino flux from the pion-decay-at-rest neutrino source at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory (ORNL). The detector will be located roughly 20 m from the SNS target and will measure the neutrino flux with better than 5% statistical uncertainty in 2 years. This heavy-water detector will serve as the first module of a two-module detector system to ultimately measure the neutrino flux to 2-3% at both the First Target Station and the planned Second Target Station of the SNS. This detector will significantly reduce a dominant systematic uncertainty for neutrino cross-section measurements at the SNS, increasing the sensitivity of searches for new physics.

physics.ins-det↗

arXiv2019

Particle dynamics in deposition of porous films with a pulsed radio-frequency atmospheric pressure glow discharge

Nanoparticles grown in a plasma are used to visualize the process of film deposition in a pulsed radio-frequency (rf) atmospheric pressure glow discharge. Modulating the plasma makes it possible to successfully prepare porous TiO2 films. We study the trapping of the particles in the sheath during the plasma-on phase and compare it with numerical simulations. During the plasma-off phase, the particles are driven to the substrate by the electric field generated by residual ions, leading to the formation of porous TiO2 film. Using video microscopy, the collective dynamics of particles in the whole process is revealed at the most fundamental "kinetic" level.

physics.plasm-ph↗

arXiv2017

Polarization conversion of non-specular diffraction orders from metallic nanohole arrays studied by Fourier space polarimetry

We use Fourier space polarimetry to study the incident angle- and polarization-dependent rotation angle and ellipticity of different diffraction orders emerging from a two-dimensional periodic Au array. The array has square lattice and circular nanoholes and thus is achiral. We find no polarization conversion occurs if the diffraction orders lie in the incident plane. However, for the orders that are diffracted away from the incident plane, their rotation angle and ellipticity vary considerably with incident angle and polarization. In particular, dramatic changes in rotation angle and ellipticity are observed when Bloch-like surface plasmon polaritons (SPPs) are excited. The experimental results are consistent with the finite-difference time-domain simulations. The transverse spin carried by the SPPs and a discrete dipole model are used complementarily to elucidate such angular and polarization dependences.

physics.optics↗

arXiv2015

Second-order correlation function from asymmetric to symmetric transitions due to spectrally indistinguishable biexciton cascade emission

We report the observed photon bunching statistics of biexciton cascade emission at zero time delay in single quantum dots by second-order correlation function measurements under continuous wave excitation. It is found that the bunching phenomenon is independent of the biexciton binding energy when it varies from 0.59 meV to nearly zero. The photon bunching takes place when the exciton photon is not spectrally distinguishable from biexciton photon, and either of them can trigger the start in a Hanbury-Brown and Twiss setup. However, if the exciton energy is spectrally distinguishable from the biexciton the photon statistics becomes asymmetric and a cross-bunching lineshape is obtained. The theoretical calculations based on a model of three-level rate-equation analysis are consistent with the result of second-order correlation function measurements.

cond-mat.mes-hall↗

arXiv2012

Record Performance of Electrical Injection Sub-wavelength Metallic-Cavity Semiconductor Lasers at Room Temperature

Metallic-Cavity lasers or plasmonic nanolasers of sub-wavelength sizes have attracted great attentions in recent years, with the ultimate goal of achieving continuous wave (CW), room temperature (RT) operation under electrical injection. Despite great efforts, a conclusive and convincing demonstration of this goal has proven challenging. By overcoming several fabrication challenges imposed by the stringent requirement of such small scale devices, we were finally able to achieve this ultimate goal. Our metallic nanolaser with a cavity volume of 0.67{\lambda}3 ({\lambda}=1591 nm) shows a linewidth of 0.5 nm at RT, which corresponds to a Q-value of 3182 compared to 235 of the cavity Q, the highest Q under lasing condition for RT CW operation of any sub-wavelength laser. Such record performance provides convincing evidences of the feasibility of RT CW metallic nanolasers, thus opening a wide range of practical possibilities of novel nanophotonic devices based on metal-semiconductor structures.

physics.optics↗