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Henry T. Wong

Publications and source records attributed to Henry T. Wong.

At least 19 recordsLinked to original sources
arXiv2026

Many-body atomic response functions of xenon and germanium for leading-order sub-GeV dark matter-electron interactions in effective field theory

Direct searches of dark matter candidates with mass energies less than 1 GeV is an active research field. The energy depositions are comparable to the scale of atomic, molecular, or condensed matter systems, therefore many-body physics plays an important role in understanding the detector's response in dark matter scattering. We present in this work a comprehensive data set of atomic response functions for xenon and germanium with 12.2 and 80 eV energy thresholds, respectively, using the (multiconfiguration) relativistic random phase approximation. This approach takes into account the relativistic, exchange, and correlation effects in one self-consistent framework, and is benchmarked successfully by photoabsorption data from thresholds to 30 keV with $\lesssim5\%$ errors. Comparisons with our previous and some other independent particle approaches in literature are made. It is also found that the spin-dependent (SD) response has significant difference from the spin-independent (SI) one such that the dark matter SD and SI interactions with electrons can be distinguished in unpolarized scattering, which is typical for direct search detectors. Finally, the exclusion limits set by current experiments are updated with our new results.

astro-ph.CO↗
arXiv2022

Spherically Symmetric Noncommutative Spacetime via Exotic Atomic Transitions

In discussing non-commutative spacetime, the generally studied $θ$-Poincare model is inconsistent with bound states. In this Letter, we develop the formalism and study the phenomenology of another model $\mathcal{B}_{χ\hat{n}}$ by the twisted permutation algebra and extend the Pauli Exclusion Principle(PEP) into non-commutative spacetime. The model also implies time quantization and can avoid UV/IR mixing. Applying it to atomic systems, we show that the model with newly induced phase factors can cause exotic transitions consisting of three electrons in the 1S orbit of atoms. The transition rate is derived, and the upper bound of non-commutative parameter $χ$ is thus set by utilizing data from the low-energy and low-background experiments, where strongest constraint $χ\leq4.05\times10^{-30}$ eV$^{-1}$ at 90\% C.L. is given by XENONnT, with the time quanta $Δt\sim 2.67\times 10^{-45} s$, equivalent to twenty times smaller than the Planck time.

hep-ph↗
arXiv2021

Constraints from a many-body method on spin-independent dark matter scattering off electrons using data from germanium and xenon detectors

Scattering of light dark matter (LDM) particles with atomic electrons is studied in the context of effective field theory. Contact and long-range interactions between dark matter and an electron are both considered. A state-of-the-art many-body method is used to evaluate the spin-independent atomic ionization cross sections of LDM-electron scattering, with an estimated error about 20%. New upper limits are derived on parameter space spanned by LDM mass and effective coupling strengths using data from the CDMSlite, XENON10, XENON100, and XENON1T experiments. Comparison with existing calculations shows the importance of atomic structure. Two aspects particularly important are relativistic effect for inner-shell ionization and final-state free electron wave function which sensitively depends on the underlying atomic approaches.

hep-ph↗
arXiv2021

Spin-dependent dark matter-electron interactions

Detectors with low thresholds for electron recoil open a new window to direct searches of sub-GeV dark matter (DM) candidates. In the past decade, many strong limits on DM-electron interactions have been set, but most on the one which is spin-independent (SI) of both dark matter and electron spins. In this work, we study DM-atom scattering through a spin-dependent (SD) interaction at leading order (LO), using well-benchmarked, state-of-the-art atomic many-body calculations. Exclusion limits on the SD DM-electron cross section are derived with data taken from experiments with xenon and germanium detectors at leading sensitivities. In the DM mass range of 0.1 - 10 GeV, the best limits set by the XENON1T experiment: $σ_e^{\textrm{(SD)}}<10^{-41}-10^{-40}\,\textrm{cm}^2$ are comparable to the ones drawn on DM-neutron and DM-proton at slightly bigger DM masses. The detector's responses to the LO SD and SI interactions are analyzed. In nonrelativistic limit, a constant ratio between them leads to an indistinguishability of the SD and SI recoil energy spectra. Relativistic calculations however show the scaling starts to break down at a few hundreds of eV, where spin-orbit effects become sizable. We discuss the prospects of disentangling the SI and SD components in DM-electron interactions via spectral shape measurements, as well as having spin-sensitive experimental signatures without SI background.

hep-ph↗
arXiv2019

Discovery potential of multi-ton xenon detectors in neutrino electromagnetic properties

Next-generation xenon detectors with multi-ton-year exposure are powerful direct probes of dark matter candidates, in particular the favorite weakly-interacting massive particles. Coupled with the features of low thresholds and backgrounds, they are also excellent telescopes of solar neutrinos. In this paper, we study the discovery potential of ton-scale xenon detectors in electromagnetic moments of solar neutrinos. Relevant neutrino-atom scattering processes are calculated by applying a state-of-the-arts atomic many-body method--relativistic random phase approximation (RRPA). Limits on these moments are derived from existing data and estimated with future experiment specifications. With one ton-year exposure, XENON-1T can improve the effective milli-charge constraint by a factor two. With LZ and DARWIN, the projected improvement on the solar neutrino effective milli-charge(magnetic moment) is around 7(2) times smaller than the current bound. If LZ can keep the same background level and push the electron recoil threshold to 0.5 keV, the projected improvement on milli-charge(magnetic moment) is about 10(3) times smaller than the current bound.

hep-ph↗
arXiv2018

Response of gadolinium doped liquid scintillator to charged particles: measurement based on intrinsic U/Th contamination

A measurement is reported for the response to charged particles of a liquid scintillator named EJ-335 doped with 0.5% gadolinium by weight. This liquid scintillator was used as the detection medium in a neutron detector. The measurement is based on the in-situ $α$-particles from the intrinsic Uranium and Thorium contamination in the scintillator. The $β$-$α$ and the $α$-$α$ cascade decays from the U/Th decay chains were used to select $α$-particles. The contamination levels of U/Th were consequently measured to be $(5.54\pm0.15)\times 10^{-11}$ g/g, $(1.45\pm0.01)\times 10^{-10}$ g/g and $(1.07\pm0.01)\times 10^{-11}$ g/g for $^{232}$Th, $^{238}$U and $^{235}$U, respectively, assuming secular equilibrium. The stopping power of $α$-particles in the liquid scintillator was simulated by the TRIM software. Then the Birks constant, $kB$, of the scintillator for $α$-particles was determined to be $(7.28\pm0.23)$ mg/(cm$^{2}\cdot$MeV) by Birks' formulation. The response for protons is also presented assuming the $kB$ constant is the same as for $α$-particles.

physics.ins-det↗
arXiv2018

The China Jinping Underground Laboratory and its Early Science

The China Jinping Underground Laboratory, inaugurated in 2010, is an underground research facility with the deepest rock overburden and largest space by volume in the world. The first-generation science programs include dark matter searches conducted by the CDEX and PandaX experiments. These activities are complemented by measurements of ambient radioactivity and installation of low-background counting systems. Phase II of the facility is being constructed, and its potential research projects are being formulated. In this review, we discuss the history, key features, results, and status of this facility and its experimental programs, as well as their future evolution and plans.

hep-ex↗
arXiv2017

Measurement of the fast neutron background at the China Jinping Underground Laboratory

We report on the measurements of the fluxes and spectra of the environmental fast neutron background at the China Jinping Underground Laboratory (CJPL) with a rock overburden of about 6700 meters water equivalent, using a liquid scintillator detector doped with 0.5% gadolinium. The signature of a prompt nuclear recoil followed by a delayed high energy $γ$-ray cascade is used to identify neutron events. The large energy deposition of the delayed $γ$-rays from the $(n, γ)$ reaction on gadolinium, together with the excellent n-$γ$ discrimination capability provides a powerful background suppression which allows the measurement of a low intensity neutron flux. The neutron flux of $(1.51\pm0.03(stat.)\pm0.10(syst.))\times10^{-7}$ cm$^{-2}$s$^{-1}$ in the energy range of 1 -- 10 MeV in the Hall A of CJPL was measured based on 356 days of data. In the same energy region, measurement with the same detector placed in a one meter thick polyethylene room gives a significantly lower flux of $(4.9\pm0.9(stat.)\pm0.5(syst.))\times10^{-9}$ cm$^{-2}$s$^{-1}$ with 174 days of data. This represents a measurement of the lowest environmental fast neutron background among the underground laboratories in the world, prior to additional experiment-specific attenuation. Additionally, the fast neutron spectra both in the Hall A and the polyethylene room were reconstructed with the help of GEANT4 simulation.

physics.ins-det↗
arXiv2016

The CDEX Dark Matter Program at the China Jinping Underground Laboratory

The China Jinping Underground Laboratory (CJPL) is a new facility for conducting low event-rate experiments. We present an overview of CJPL and the CDEX Dark Matter program based on germanium detectors with sub-keV sensitivities. The achieved results, status as well as the R&D and technology acquisition efforts towards a ton-scale experiment are reported.

physics.ins-det↗
arXiv2016

Atomic ionization by sterile-to-active neutrino conversion and constraints on dark matter sterile neutrinos with germanium detectors

The transition magnetic moment of a sterile-to-active neutrino conversion gives rise to not only radiative decay of a sterile neutrino, but also its non-standard interaction (NSI) with matter. For sterile neutrinos of keV-mass as dark matter candidates, their decay signals are actively searched for in cosmic X-ray spectra. In this work, we consider the NSI that leads to atomic ionization, which can be detected by direct dark matter experiments. It is found that this inelastic scattering process for a nonrelativistic sterile neutrino has a pronounced enhancement in the differential cross section at energy transfer about half of its mass, manifesting experimentally as peaks in the measurable energy spectra. The enhancement effects gradually smear out as the sterile neutrino becomes relativistic. Using data taken with germanium detectors that have fine energy resolution in keV and sub-keV regimes, constraints on sterile neutrino mass and its transition magnetic moment are derived and compared with those from astrophysical observations.

hep-ph↗
arXiv2014

Constraining neutrino electromagnetic properties by germanium detectors

The electromagnetic properties of neutrinos, which are either trivial or negligible in the context of the Standard Model, can probe new physics and have significant implications in astrophysics and cosmology. The current best direct limits on the neutrino millicharges and magnetic moments are both derived from data taken with germanium detectors with low thresholds at keV levels. In this paper, we discuss in detail a robust, ab initio method: the multiconfiguration relativistic random phase approximation, that enables us to reliably understand the germanium detector response at the sub-keV level, where atomic many-body physics matters. Using existing data with sub-keV thresholds, limits on reactor antineutrino's millicharge, magnetic moment, and charge radius squared are derived. The projected sensitivities for next generation experiments are also given and discussed.

hep-ph↗
arXiv2014

Constraints on millicharged neutrinos via analysis of data from atomic ionizations with germanium detectors at sub-keV sensitivities

With the advent of detectors with sub-keV sensitivities, atomic ionization has been identified as a promising avenue to probe possible neutrino electromagnetic properties. The interaction cross-sections induced by millicharged neutrinos are evaluated with the ab-initio multi-configuration relativistic random-phase approximation. There is significant enhancement at atomic binding energies compared to that when the electrons are taken as free particles. Positive signals would distinctly manifest as peaks at specific energies with known intensity ratios. Selected reactor neutrino data with germanium detectors at analysis threshold as low as 300 eV are studied. No such signatures are observed, and a combined limit on the neutrino charge fraction of | \numq | < 1.0 X 10^{-12} at 90% confidence level is derived.

hep-ph↗
arXiv2013

Atomic ionization of germanium due to neutrino magnetic moments

An ab initio calculation of atomic ionization of germanium (Ge) by neutrinos was carried out in the framework of multiconfiguration relativistic random phase approximation. The main goal is to provide a more accurate cross section formula than the conventional one, which is based on the free electron approximation, for searches of neutrino magnetic moments with Ge detectors whose threshold is reaching down to the sub-keV regime. Limits derived with both methods are compared, using reactor neutrino data taken with low threshold germanium detectors.

hep-ph↗
arXiv2012

Final results of nu-e-bar electron scattering cross-section measurements and constraints on new physics

The nu-e-bar electron elastic scattering cross-section was measured with a CsI(Tl) scintillating crystal detector array with a total mass of 187 kg at the Kuo-Sheng Nuclear Power Station. The detectors were exposed to a reactor nu-e-bar flux of 6.4 X 10^{12} cm^{-2}s^{-1} originated from a core with 2.9 GW thermal power. Using 29882/7369 kg-days of Reactor ON/OFF data, the Standard Model (SM) of electroweak interaction was probed at the 4-momentum transfer range of Q^2 ~ 3 X 10^{-6} GeV^2. A cross-section ratio of R_{expt} = [1.08 +- 0.21(stat) +- 0.16(sys)] X R_{SM} was measured. Constraints on the electroweak parameters (g_V,g_A) were placed, corresponding to a weak mixing angle measurement of $\s2tw$ = [0.251 +- 0.031(stat) +- 0.024(sys)]. Destructive interference in the SM nu-e-bar+e processes was verified. Bounds on neutrino anomalous electromagnetic properties (neutrino magnetic moment and neutrino charge radius), non-standard neutrino interactions, upparticle physics and non-commutative physics were placed. We summarize the experimental details and results, and discuss projected sensitivities with realistic and feasible hardware upgrades.

hep-ex↗
arXiv2010

Derivations of Atomic Ionization Effects Induced by Neutrino Magnetic Moments

A recent paper [M.B. Voloshin, Phys. Rev. Lett. 105, 201801 (2010)] pointed out that our earlier derivations of atomic ionization cross-section due to neutrino magnetic moments (arXiv:1001.2074v2) involved unjustified assumptions. We confirm and elaborate on this comment with these notes. We caution that the results of the sum-rule approach in this paper contradict the expected behaviour in atomic transitions.

hep-ph↗
arXiv2008

Ultra-Low-Energy Germanium Detector for Neutrino-Nucleus Coherent Scattering and Dark Matter Searches

The status and plans of a research program on the development of ultra-low-energy germanium detectors with sub-keV sensitivities are reported. We survey the scientific goals which include the observation of neutrino-nucleus coherent scattering, the studies of neutrino magnetic moments, as well as the searches of WIMP dark matter. In particular, a threshold of 100-200 eV and a sub-keV background comparable to underground experiments were achieved with prototype detectors. New limits were set for WIMPs with mass between 3-6 GeV. The prospects of the realization of full-scale experiments are discussed.

hep-ex↗
arXiv2006

Research Program towards Observation of Neutrino-Nucleus Coherent Scattering

The article describes the research program pursued by the TEXONO Collaboration towards an experiment to observe coherent scattering between neutrinos and the nucleus at the power reactor. The motivations of studying this process are surveyed. In particular, a threshold of 100-200 eV has been achieved with an ultra-low-energy germanium detector prototype. This detection capability at low energy can also be adapted to conduct searches of Cold Dark Matter in the low-mass region as well as to enhance the sensitivities in the study of neutrino magnetic moments.

hep-ex↗