arXiv subjects

Y. K. Heng

Publications and source records attributed to Y. K. Heng.

At least 19 recordsLinked to original sources

arXiv2025

Comprehensive Measurement of the Reactor Antineutrino Spectrum and Flux at Daya Bay

This Letter reports the precise measurement of reactor antineutrino spectrum and flux based on the full data set of 4.7 million inverse-beta-decay (IBD) candidates collected at Daya Bay near detectors. Expressed in terms of the IBD yield per fission, the antineutrino spectra from all reactor fissile isotopes and the specific $\mathrm{^{235}U}$ and $\mathrm{^{239}Pu}$ isotopes are measured with 1.3$\%$, 3$\%$ and 8$\%$ uncertainties respectively near the 3 MeV spectrum peak in reconstructed energy, reaching the best precision in the world. The total antineutrino flux and isotopic $\mathrm{^{235}U}$ and $\mathrm{^{239}Pu}$ fluxes are precisely measured to be $5.84\pm0.07$, $6.16\pm0.12$ and $4.16\pm0.21$ in units of $10^{-43} \mathrm{cm^2/fission}$. These measurements are compared with the Huber-Mueller (HM) model, the reevaluated conversion model based on the Kurchatov Institute (KI) measurement and the latest Summation Model (SM2023). The Daya Bay flux shows good consistency with KI and SM2023 models, but disagrees with HM model. The Daya Bay spectrum, however, disagrees with all model predictions.

nucl-ex↗

arXiv2024

Measurement of Electron Antineutrino Oscillation Amplitude and Frequency via Neutron Capture on Hydrogen at Daya Bay

This Letter reports the first measurement of the oscillation amplitude and frequency of reactor antineutrinos at Daya Bay via neutron capture on hydrogen using 1958 days of data. With over 3.6 million signal candidates, an optimized candidate selection, improved treatment of backgrounds and efficiencies, refined energy calibration, and an energy response model for the capture-on-hydrogen sensitive region, the relative $\overlineν_{e}$ rates and energy spectra variation among the near and far detectors gives $\mathrm{sin}^22θ_{13} = 0.0759_{-0.0049}^{+0.0050}$ and $Δm^2_{32} = (2.72^{+0.14}_{-0.15})\times10^{-3}$ eV$^2$ assuming the normal neutrino mass ordering, and $Δm^2_{32} = (-2.83^{+0.15}_{-0.14})\times10^{-3}$ eV$^2$ for the inverted neutrino mass ordering. This estimate of $\sin^2 2θ_{13}$ is consistent with and essentially independent from the one obtained using the capture-on-gadolinium sample at Daya Bay. The combination of these two results yields $\mathrm{sin}^22θ_{13}= 0.0833\pm0.0022$, which represents an 8% relative improvement in precision regarding the Daya Bay full 3158-day capture-on-gadolinium result.

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arXiv2024

Search for a sub-eV sterile neutrino using Daya Bay's full dataset

This Letter presents results of a search for the mixing of a sub-eV sterile neutrino with three active neutrinos based on the full data sample of the Daya Bay Reactor Neutrino Experiment, collected during 3158 days of detector operation, which contains $5.55 \times 10^{6}$ reactor \anue candidates identified as inverse beta-decay interactions followed by neutron-capture on gadolinium. The analysis benefits from a doubling of the statistics of our previous result and from improvements of several important systematic uncertainties. No significant oscillation due to mixing of a sub-eV sterile neutrino with active neutrinos was found. Exclusion limits are set by both Feldman-Cousins and CLs methods. Light sterile neutrino mixing with $\sin^2 2θ_{14} \gtrsim 0.01$ can be excluded at 95\% confidence level in the region of $0.01$ eV$^2 \lesssim |Δm^{2}_{41}| \lesssim 0.1 $ eV$^2$. This result represents the world-leading constraints in the region of $2 \times 10^{-4}$ eV$^2 \lesssim |Δm^{2}_{41}| \lesssim 0.2 $ eV$^2$.

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arXiv2024

Charged-current non-standard neutrino interactions at Daya Bay

The full data set of the Daya Bay reactor neutrino experiment is used to probe the effect of the charged current non-standard interactions (CC-NSI) on neutrino oscillation experiments. Two different approaches are applied and constraints on the corresponding CC-NSI parameters are obtained with the neutrino flux taken from the Huber-Mueller model with a $5\%$ uncertainty. For the quantum mechanics-based approach (QM-NSI), the constraints on the CC-NSI parameters $ε_{eα}$ and $ε_{eα}^{s}$ are extracted with and without the assumption that the effects of the new physics are the same in the production and detection processes, respectively. The approach based on the weak effective field theory (WEFT-NSI) deals with four types of CC-NSI represented by the parameters $[\varepsilon_{X}]_{eα}$. For both approaches, the results for the CC-NSI parameters are shown for cases with various fixed values of the CC-NSI and the Dirac CP-violating phases, and when they are allowed to vary freely. We find that constraints on the QM-NSI parameters $ε_{eα}$ and $ε_{eα}^{s}$ from the Daya Bay experiment alone can reach the order $\mathcal{O}(0.01)$ for the former and $\mathcal{O}(0.1)$ for the latter, while for WEFT-NSI parameters $[\varepsilon_{X}]_{eα}$, we obtain $\mathcal{O}(0.1)$ for both cases.

hep-ph↗

arXiv2024

First measurement of the yield of $^8$He isotopes produced in liquid scintillator by cosmic-ray muons at Daya Bay

Daya Bay presents the first measurement of cosmogenic $^8$He isotope production in liquid scintillator, using an innovative method for identifying cascade decays of $^8$He and its child isotope, $^8$Li. We also measure the production yield of $^9$Li isotopes using well-established methodology. The results, in units of 10$^{-8}μ^{-1}$g$^{-1}$cm$^{2}$, are 0.307$\pm$0.042, 0.341$\pm$0.040, and 0.546$\pm$0.076 for $^8$He, and 6.73$\pm$0.73, 6.75$\pm$0.70, and 13.74$\pm$0.82 for $^9$Li at average muon energies of 63.9~GeV, 64.7~GeV, and 143.0~GeV, respectively. The measured production rate of $^8$He isotopes is more than an order of magnitude lower than any other measurement of cosmogenic isotope production. It replaces the results of previous attempts to determine the ratio of $^8$He to $^9$Li production that yielded a wide range of limits from 0 to 30\%. The results provide future liquid-scintillator-based experiments with improved ability to predict cosmogenic backgrounds.

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arXiv2023

Search for $\barΛ$-$Λ$ oscillations in the decay $J/ψ\to p K^- \barΛ+c.c.$

We report the first search for $\barΛ$--$Λ$ oscillations in the decay $J/ψ\to p K^- \barΛ + c.c.$ by analyzing $1.31\times10^9$ $J/ψ$ events accumulated with the BESIII detector at the BEPCII collider. The $J/ψ$ events are produced using $e^+e^-$ collisions at a center of mass energy $\sqrt{s}= 3.097$~GeV. No evidence for hyperon oscillations is observed. The upper limit for the oscillation rate of $\barΛ$ to $Λ$ hyperons is determined to be $\mathcal{P}(Λ)=\frac{\mathcal{B}(J/ψ\to pK^-Λ+c.c.)}{\mathcal{B}(J/ψ\to pK^-\barΛ+c.c.)}<4.4\times10^{-6}$ corresponding to an oscillation parameter $δm_{Λ\barΛ}$ of less than $3.8\times10^{-18}$~GeV at the 90\% confidence level.

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arXiv2022

Precision measurement of reactor antineutrino oscillation at kilometer-scale baselines by Daya Bay

We present a new determination of the smallest neutrino mixing angle $θ_{13}$ and the mass-squared difference $Δ{\rm m}^{2}_{32}$ using a final sample of $5.55 \times 10^{6}$ inverse beta-decay (IBD) candidates with the final-state neutron captured on gadolinium. This sample was selected from the complete data set obtained by the Daya Bay reactor neutrino experiment in 3158 days of operation. Compared to the previous Daya Bay results, selection of IBD candidates has been optimized, energy calibration refined, and treatment of backgrounds further improved. The resulting oscillation parameters are ${\rm sin}^{2}2θ_{13} = 0.0851 \pm 0.0024$, $Δ{\rm m}^{2}_{32} = (2.466 \pm 0.060) \times 10^{-3}{\rm eV}^{2}$ for the normal mass ordering or $Δ{\rm m}^{2}_{32} = -(2.571 \pm 0.060) \times 10^{-3} {\rm eV}^{2}$ for the inverted mass ordering.

hep-ex↗

arXiv2022

First measurement of high-energy reactor antineutrinos at Daya Bay

This Letter reports the first measurement of high-energy reactor antineutrinos at Daya Bay, with nearly 9000 inverse beta decay candidates in the prompt energy region of 8-12~MeV observed over 1958 days of data collection. A multivariate analysis is used to separate 2500 signal events from background statistically. The hypothesis of no reactor antineutrinos with neutrino energy above 10~MeV is rejected with a significance of 6.2 standard deviations. A 29\% antineutrino flux deficit in the prompt energy region of 8-11~MeV is observed compared to a recent model prediction. We provide the unfolded antineutrino spectrum above 7 MeV as a data-based reference for other experiments. This result provides the first direct observation of the production of antineutrinos from several high-$Q_β$ isotopes in commercial reactors.

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arXiv2022

Joint Determination of Reactor Antineutrino Spectra from $^{235}$U and $^{239}$Pu Fission by Daya Bay and PROSPECT

A joint determination of the reactor antineutrino spectra resulting from the fission of $^{235}$U and $^{239}$Pu has been carried out by the Daya Bay and PROSPECT collaborations. This Letter reports the level of consistency of $^{235}$U spectrum measurements from the two experiments and presents new results from a joint analysis of both data sets. The measurements are found to be consistent. The combined analysis reduces the degeneracy between the dominant $^{235}$U and $^{239}$Pu isotopes and improves the uncertainty of the $^{235}$U spectral shape to about 3\%. The ${}^{235}$U and $^{239}$Pu antineutrino energy spectra are unfolded from the jointly deconvolved reactor spectra using the Wiener-SVD unfolding method, providing a data-based reference for other reactor antineutrino experiments and other applications. This is the first measurement of the $^{235}$U and $^{239}$Pu spectra based on the combination of experiments at low- and highly enriched uranium reactors.

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arXiv2021

Antineutrino Energy Spectrum Unfolding Based on the Daya Bay Measurement and Its Applications

The prediction of reactor antineutrino spectra will play a crucial role as reactor experiments enter the precision era. The positron energy spectrum of 3.5 million antineutrino inverse beta decay reactions observed by the Daya Bay experiment, in combination with the fission rates of fissile isotopes in the reactor, is used to extract the positron energy spectra resulting from the fission of specific isotopes. This information can be used to produce a precise, data-based prediction of the antineutrino energy spectrum in other reactor antineutrino experiments with different fission fractions than Daya Bay. The positron energy spectra are unfolded to obtain the antineutrino energy spectra by removing the contribution from detector response with the Wiener-SVD unfolding method. Consistent results are obtained with other unfolding methods. A technique to construct a data-based prediction of the reactor antineutrino energy spectrum is proposed and investigated. Given the reactor fission fractions, the technique can predict the energy spectrum to a 2% precision. In addition, we illustrate how to perform a rigorous comparison between the unfolded antineutrino spectrum and a theoretical model prediction that avoids the input model bias of the unfolding method.

hep-ex↗

arXiv2021

Gain and charge response of 20 inch MCP and dynode PMTs

JUNO is a 20-kton liquid scintillator detector aiming to determine the neutrino mass ordering, precisely measure the oscillation parameters, detect the astrophysical neutrinos and search for exotic physics. It is designed to reach an energy resolution of 3% at 1 MeV with the highest ever PMT coverage, using two types of 20 inch phototubes: MCP-PMT from NNVT and dynode-PMT from Hamamatsu. In this article, the gain and charge response of the MCP and dynode PMTs are investigated with the study of JUNO Central Detector prototype. The linearity of the MCP-PMT charge output is measured too to check the effect of a long tail on its charge spectrum.

physics.ins-det↗

arXiv2021

Evidence for $Z_{c}^{\pm}$ decays into the $ρ^{\pm} η_{c}$ final state

We study $e^{+}e^{-}$ collisions with a $π^{+}π^{-}π^{0}η_{c}$ final state using data samples collected with the BESIII detector at center-of-mass energies $\sqrt{s}=4.226$, $4.258$, $4.358$, $4.416$, and $4.600$ GeV. Evidence for the decay $\zcpm\to\rhopm\etac$ is reported with a statistical significance of $3.9σ$ with various systematic uncertainties taken into account at $\sqrt{s} = 4.226$ GeV, and the Born cross section times branching fraction $σ^{B}(\EE\to \pimp\zcpm)\times \BR(\zcpm\to\rhopm\etac)$ is measured to be $(48 \pm 11 \pm 11)\,\rm{pb}$. The $\zcpm\to \rhopm\etac$ signal is not significant at the other center-of-mass energies and the corresponding upper limits are determined. In addition, no significant signal is observed in a search for $\zcppm\to ρ^{\pm}\etac$ with the same data samples. The ratios $R_{\zc}=\BR(\zcpm\to ρ^{\pm} \etac)/\BR(\zcpm\to π^{\pm} \jpsi)$ and $R_{\zcp}=\BR(\zcppm\to ρ^{\pm} \etac)/\BR(\zcppm\to π^{\pm} \hc)$ are obtained and used to discriminate between different theoretical interpretations of the $\zcpm$ and $\zcppm$.

hep-ex↗

arXiv2021

Cross section measurement of $e^+e^- \to p\bar{p}η$ and $e^+e^- \to p\bar{p}ω$ at center-of-mass energies between 3.773 GeV and 4.6 GeV

Based on $14.7~\textrm{fb}^{-1}$ of $e^+e^-$ annihilation data collected with the BESIII detector at the BEPCII collider at 17 different center-of-mass energies between $3.7730~\textrm{GeV}$ and $4.5995~\textrm{GeV}$, Born cross sections of the two processes $e^+e^- \to p\bar{p}η$ and $e^+e^- \to p\bar{p}ω$ are measured for the first time. No indication of resonant production through a vector state $V$ is observed, and upper limits on the Born cross sections of $e^+e^- \to V \to p\bar{p}η$ and $e^+e^- \to V \to p\bar{p}ω$ at the $90\%$ confidence level are calculated for a large parameter space in resonance masses and widths. For the current world average parameters of the $ψ(4230)$ of $m=4.2187~\textrm{GeV}/c^{2}$ and $Γ=44~\textrm{MeV}$, we find upper limits on resonant production of the $p\bar{p}η$ and $p\bar{p}ω$ final states of $7.5~\textrm{pb}$ and $10.4~\textrm{pb}$ at the $90\%$ CL, respectively.

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arXiv2020

Search For Electron-Antineutrinos Associated With Gravitational-Wave Events GW150914, GW151012, GW151226, GW170104, GW170608, GW170814, and GW170817 at Daya Bay

Providing a possible connection between neutrino emission and gravitational-wave (GW) bursts is important to our understanding of the physical processes that occur when black holes or neutron stars merge. In the Daya Bay experiment, using data collected from December 2011 to August 2017, a search has been performed for electron-antineutrino signals coinciding with detected GW events, including GW150914, GW151012, GW151226, GW170104, GW170608, GW170814, and GW170817. We used three time windows of $\mathrm{\pm 10~s}$, $\mathrm{\pm 500~s}$, and $\mathrm{\pm 1000~s}$ relative to the occurrence of the GW events, and a neutrino energy range of 1.8 to 100 MeV to search for correlated neutrino candidates. The detected electron-antineutrino candidates are consistent with the expected background rates for all the three time windows. Assuming monochromatic spectra, we found upper limits (90% confidence level) on electron-antineutrino fluence of $(1.13~-~2.44) \times 10^{11}~\rm{cm^{-2}}$ at 5 MeV to $8.0 \times 10^{7}~\rm{cm^{-2}}$ at 100 MeV for the three time windows. Under the assumption of a Fermi-Dirac spectrum, the upper limits were found to be $(5.4~-~7.0)\times 10^{9}~\rm{cm^{-2}}$ for the three time windows.

astro-ph.HE↗

arXiv2020

Improved Constraints on Sterile Neutrino Mixing from Disappearance Searches in the MINOS, MINOS+, Daya Bay, and Bugey-3 Experiments

Searches for electron antineutrino, muon neutrino, and muon antineutrino disappearance driven by sterile neutrino mixing have been carried out by the Daya Bay and MINOS+ collaborations. This Letter presents the combined results of these searches, along with exclusion results from the Bugey-3 reactor experiment, framed in a minimally extended four-neutrino scenario. Significantly improved constraints on the $θ_{μe}$ mixing angle are derived that constitute the most stringent limits to date over five orders of magnitude in the sterile mass-squared splitting $Δm^2_{41}$, excluding the 90% C.L. sterile-neutrino parameter space allowed by the LSND and MiniBooNE observations at 90% CL$_s$ for $Δm^2_{41}<5\,$eV$^2$.Furthermore, the LSND and MiniBooNE 99% C.L. allowed regions are excluded at 99% CL$_s$ for $Δm^2_{41}$ $<$ 1.2 eV$^2$.

hep-ex↗

arXiv2020

Observation of a resonant structure in $e^{+}e^{-} \to K^{+}K^{-}π^{0}π^{0}$

Using $e^{+}e^{-}$ collision data samples with center-of-mass energies ranging from 2.000 to 2.644 GeV, collected by the BESIII detector at the BEPCII collider, and with a total integrated luminosity of 300 pb^{-1}, a partial-wave analysis is performed for the process $e^{+}e^{-} \to K^{+}K^{-}π^{0}π^{0}$. The total Born cross sections for the process $e^{+}e^{-} \to K^{+}K^{-}π^{0}π^{0}$, as well as the Born cross sections f or the subprocesses $e^{+}e^{-} \to ϕπ^{0}π^{0}$, $K^{+}(1460)K^{-}$, $K^{+}_{1}(1400)K^{-}$, $K^{+}_{1}(1270)K^{-}$ and $K^{*+}(892)K^{*-}(892)$, are measured versus the center-of-mass energy. The corresponding results for $e^{+}e^{-} \to K^{+}K^{-}π^{0}π^{0}$ and $ϕπ^{0}π^{0}$ are consistent with those of BaBar and have much improved precision.By analyzing the cross sections for the four subprocesses, $K^{+}(1460)K^{-}$, $K^{+}_{1}(1400)K^{-}$, $K^{+ }_{1}(1270)K^{-}$ and $K^{*+}K^{*-}$, a structure with mass $M$ = (2126.5 $\pm$ 16.8 $\pm$ 12.4)~MeV/c^{2} and width $Γ$ = (106.9 $\pm$ 32.1 $\pm$ 28.1)~MeV is observed with an overall statistical significance of 6.3 $σ$, although with very limited significance in the subprocesses $e^{+}e^{-} \to K^{+}_{1}(1270)K^{-}$ and $K^{*+}(892)K^{*-}(892)$. The resonant parameters of the observed structure suggest it can be identified with the $ϕ(2170)$, thus the results provide valuable input to the internal nature of the $ϕ(2170)$.

hep-ex↗

arXiv2019

Extraction of the $^{235}$U and $^{239}$Pu Antineutrino Spectra at Daya Bay

This Letter reports the first extraction of individual antineutrino spectra from $^{235}$U and $^{239}$Pu fission and an improved measurement of the prompt energy spectrum of reactor antineutrinos at Daya Bay. The analysis uses $3.5\times 10^6$ inverse beta-decay candidates in four near antineutrino detectors in 1958 days. The individual antineutrino spectra of the two dominant isotopes, $^{235}$U and $^{239}$Pu, are extracted using the evolution of the prompt spectrum as a function of the isotope fission fractions. In the energy window of 4--6~MeV, a 7\% (9\%) excess of events is observed for the $^{235}$U ($^{239}$Pu) spectrum compared with the normalized Huber-Mueller model prediction. The significance of discrepancy is $4.0σ$ for $^{235}$U spectral shape compared with the Huber-Mueller model prediction. The shape of the measured inverse beta-decay prompt energy spectrum disagrees with the prediction of the Huber-Mueller model at $5.3σ$. In the energy range of 4--6~MeV, a maximal local discrepancy of $6.3σ$ is observed.

hep-ex↗

arXiv2019

Comparison on PMT Waveform Reconstructions with JUNO Prototype

JUNO is proposed to determine the neutrino mass hierarchy and rich in many other neutrino topics. A prototype is designed and set up for better understanding sub-systems of future detector. The preliminary results show that its threshold reaches ~0.3MeV with trigger rate ~290 Hz on the ground with cosmic muon rate ~35 Hz. Aiming for a better detector understanding from PMT signal, three reconstruction algorithms are compared for PMT waveforms with different overshoot ratios, including charge integration, waveform fitting, and deconvolution. It is concluded that the three methods have similar performance on uncertainty and systematic bias while deconvolution algorithm is best to handle larger overshoot and the simplest charge integration could be considered with controlled overshoot for future fast preliminary reconstruction.

physics.ins-det↗