arXiv subjects

R. Han

Publications and source records attributed to R. Han.

At least 19 recordsLinked to original sources

arXiv2025

Pixel column issue in the ATLAS Inner Tracker modules

Pixel modules are currently being built for the ATLAS ITk Pixel detector upgrade. During the preproduction phase, recurring chip malfunctioning was observed during electrical testing. It was possible to bypass this issue by disabling some pixel core columns in the ITkPix readout chip. Therefore the issue is called "core column issue" which is a direct disqualifier for a pixel module. A concerning number of cases has been observed in pixel modules with ITkPix v1.1 as well as v2 chips which significantly impacts the module yield. However, the behaviour is erratic and there is not any evidence hinting at the origin of this issue. These proceedings outline the investigations of the issue, highlighting the electrical behaviour during testing, present findings from the data collected via our production database and through visual inspection, and point towards possible causes of the issue.

physics.ins-det↗

arXiv2023

Semi-relativistic antisymmetrized molecular dynamics for energetic neutron production in intermediate energy heavy-ion reactions

Relativistic corrections have been made in the non-relativistic antisymmetrized molecular dynamics (AMD) simulations to apply to the high energy neutron production in the $^{12}$C+$^{12}$C and $^{16}$O+$^{12}$C collisions at incident energies of 290 and 400 MeV/nucleon. The corrections are made in kinematics alone and no nucleon-nucleon inelastic scatterings nor meson productions are taken into account, and AMD with the relativistic corrections is called semi-relativistic AMD. The three-nucleon collision (3NC) and Fermi boost in the collision processes are taken into account in the non-relativistic AMD. Since the relativistic corrections tend to compensate in each other, the difference between the semi-relativistic and non-relativistic results become small. High energy tails of the available experimental neutron double differential cross sections, especially at larger angles, are well reproduced by AMD with the 3NC term both with non-relativistic and semi-relativistic simulations. These results indicate that the high energy neutrons are dominantly produced by the 3NC process in this incident energy range.

nucl-th↗

arXiv2021

Determining impact parameters of heavy-ion collisions at low-intermediate incident energies using deep learning with convolutional neural network

A deep learning based method with the convolutional neural network (CNN) algorithm for determining the impact parameters is developed using the constrained molecular dynamics model simulations, focusing on the heavy-ion collisions at the low-intermediate incident energies from several ten to one hundred MeV/nucleon in which the emissions of heavy fragments with the charge numbers larger than 3 become crucial. To make the CNN applicable in the task of the impact parameter determination at the present energy range, specific improvements are made in the input selection, the CNN construction and the CNN training. It is demonstrated from the comparisons of the deep CNN method and the conventional methods with the impact parameter-sensitive observables, that the deep CNN method shows better performance for determining the impact parameters, especially leading to the capability of providing better recognition of the central collision events. With a proper consideration of the experimental filter effect in both training and testing processes to keep consistency with the actual experiments, the good performance of the deep CNN method holds, and shows significantly better in terms of predicting the impact parameters and recognizing the central collision events, compared to that of the conventional methods, demonstrating the superiority of the present deep CNN method. The deep CNN method with the consideration of the filter effect is applied in the deduction of nuclear stopping power. Higher accuracy for the stopping power deduction is achieved benefitting from the better impact parameter determination using the deep CNN method, compared to using the the conventional methods. This result reveals the importance to select a reliable impact parameter determination method in the experimental deduction of the nuclear stopping power as well as other observables.

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arXiv2021

Scission configuration in the self-consistent calculations with neck constraint

The calculations of the potential energy surface are essential in the theoretical description of the fission process. In the constrained self-consistent approach, the smooth evolution of nuclear shape is described from the ground state until a very elongated one with a narrow neck. In all microscopic calculations, the rupture of the neck at scission is associated with a substantial change of nuclear matter density distribution and rapid energy decrease. In this paper, we show that there is no discontinuity of the potential energy surface at scission when multi-constrained calculations are applied with the neck constraint. An early rupture of the neck at lower quadrupole and octupole moments is discussed as competitive with the conventional fission path. We discuss the neck properties in the scission configuration. We find that the neck radius in the asymmetric fission mode cannot decrease below 2 fm, and the nuclear matter density cannot decrease below the saturation density. In the compact fission mode, nuclear density may go down to half of the saturation density before the rupture of the neck.

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arXiv2020

Effects of cluster correlations on fragment emission in 12C + 12C at 50 MeV/nucleon

The effects of cluster correlations have been studied in the $^{12}$C + $^{12}$C reaction at 50 MeV/nucleon, using three AMD models, the AMD (AMD/D) without any additional cluster correlations, AMD/D-COALS with nucleon correlations based on a coalescence prescription for light cluster formations with $A\leq4$ and AMD-Cluster with an extended cluster correlation in two-nucleon collision processes and a special treatment for intermediate fragment formation with A $\le 9$. The angular distributions and energy spectra of fragments have been simulated and compared with the available experimental data. It is found that the cluster correlations take a crucial role to describe the productions of light charged particles (LCPs) and intermediate mass fragments (IMFs), and the AMD-cluster studied here provides a consistent overall reproduction of the experimental data. It is also shown that the significant effects of the secondary decay processes are involved for the fragment production besides the dynamical productions in the AMD stage. Detailed LCP and IMF production mechanisms involved in the intermediate energy heavy ion collisions are discussed.

nucl-th↗

arXiv2020

Experimental density radiography of Wudalianchi volcano with cosmic ray muons

Muon radiography is a promising technique to image the internal density structures upto a few hundred meters scale, such as tunnels, pyramids and volcanos, by measuring the flux attenuation of cosmic ray muons after trvaling through these targets. In this study, we conducted an experimantal cosmic ray muon radiography of the Wudalianchi volcano in northeast China for imaging its internal density structures. The muon detector used in this study is made of plastic scintillator and silicon photomultiplier. After about one and a half month observation for the Laoheishan volcano cone in the Wudalianchi volcano, from September 23rd to November 10th, 2019, more than 3 million muon tracks passing the data selection criteria are obtained. Based on the muon observations and the high-resoluiton topography from aerial photogrammetry by unmanned aerial vehicle, the relative density image of the Laoheishan volcano cone is obtained. The experiment in this study is the first muon radiography of volcano performed in China, and the results suggest the feasibility of radiography technique based on plastic scintillator muon detector. As a new passive geophysical imaging method, cosmic ray muon radiography could become a promising method to obtain the high-resoution 2-D and 3-D density structures for shallow geological targets.

physics.ins-det↗

arXiv2019

Proceedings of The Magnificent CE$\nu$NS Workshop 2018

The Magnificent CE$\nu$NS Workshop (2018) was held November 2 & 3 of 2018 on the University of Chicago campus and brought together theorists, phenomenologists, and experimentalists working in numerous areas but sharing a common interest in the process of coherent elastic neutrino-nucleus scattering (CE$\nu$NS). This is a collection of abstract-like summaries of the talks given at the meeting, including links to the slides presented. This document and the slides from the meeting provide an overview of the field and a snapshot of the robust CE$\nu$NS-related efforts both planned and underway.

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arXiv2016

Solar, supernova, atmospheric and geo neutrino studies using JUNO detector

Aside from its primary purpose of shedding light on the mass hierarchy (MH) using reactor anti-neutrinos, the JUNO experiment in Jiangmen (China) will also contribute to study neutrinos from non-reactor sources. In this poster we review JUNO's goals in the realms of supernova, atmospheric, solar and geo-neutrinos; present the related experimental issues and provide the current estimates of its potential. For a typical galactic SN at a distance of 10 kpc, JUNO will record about 5000 events from inverse beta decay, 2000 events from elastic neutrino-proton scattering, 300 events from neutrino-electron scattering, and the charged current and neutral current interactions on the ${^{12}}{\rm C}$ nuclei. For atmospheric neutrinos, JUNO should be able to detect $\nu_e$ and $\nu_\mu$ charged current events. Optimistically, a determination of the MH could be achieved at the 1.8$\sigma$ (2.6$\sigma$) level after 10 (20) years of data taking. JUNO will also study solar neutrinos from ${^{7}}{\rm Be}$ and ${^{8}}{\rm B}$, at low ($\approx$1 MeV) and higher energies respectively, to improve our understanding of the matter effects on the oscillation mechanism and of the solar metallicity. Challenges come primarily from the radioactive and cosmogenic backgrounds: the expected performance for two benchmark scintillator radio-purities, are shown. The flux of geo-neutrinos gives us an insight on the Earth composition and formation. We will show how the increased sample size given by JUNO's large sensitive mass of 20 KTon liquid scintillator will provide data to answer to several geological questions among which the U/Th ratio and mantle measurements.

hep-ex↗

arXiv2016

Measurement of electron antineutrino oscillation based on 1230 days of operation of the Daya Bay experiment

A measurement of electron antineutrino oscillation by the Daya Bay Reactor Neutrino Experiment is described in detail. Six 2.9-GW$_{\rm th}$ nuclear power reactors of the Daya Bay and Ling Ao nuclear power facilities served as intense sources of $\overline{\nu}_{e}$'s. Comparison of the $\overline{\nu}_{e}$ rate and energy spectrum measured by antineutrino detectors far from the nuclear reactors ($\sim$1500-1950 m) relative to detectors near the reactors ($\sim$350-600 m) allowed a precise measurement of $\overline{\nu}_{e}$ disappearance. More than 2.5 million $\overline{\nu}_{e}$ inverse beta decay interactions were observed, based on the combination of 217 days of operation of six antineutrino detectors (Dec. 2011--Jul. 2012) with a subsequent 1013 days using the complete configuration of eight detectors (Oct. 2012--Jul. 2015). The $\overline{\nu}_{e}$ rate observed at the far detectors relative to the near detectors showed a significant deficit, $R=0.949 \pm 0.002(\mathrm{stat.}) \pm 0.002(\mathrm{syst.})$. The energy dependence of $\overline{\nu}_{e}$ disappearance showed the distinct variation predicted by neutrino oscillation. Analysis using an approximation for the three-flavor oscillation probability yielded the flavor-mixing angle $\sin^22\theta_{13}=0.0841 \pm 0.0027(\mathrm{stat.}) \pm 0.0019(\mathrm{syst.})$ and the effective neutrino mass-squared difference of $\left|{\Delta}m^2_{\mathrm{ee}}\right|=(2.50 \pm 0.06(\mathrm{stat.}) \pm 0.06(\mathrm{syst.})) \times 10^{-3}\ {\rm eV}^2$. Analysis using the exact three-flavor probability found ${\Delta}m^2_{32}=(2.45 \pm 0.06(\mathrm{stat.}) \pm 0.06(\mathrm{syst.})) \times 10^{-3}\ {\rm eV}^2$ assuming the normal neutrino mass hierarchy and ${\Delta}m^2_{32}=(-2.56 \pm 0.06(\mathrm{stat.}) \pm 0.06(\mathrm{syst.})) \times 10^{-3}\ {\rm eV}^2$ for the inverted hierarchy.

hep-ex↗

arXiv2016

Study of the wave packet treatment of neutrino oscillation at Daya Bay

The disappearance of reactor $\bar{\nu}_e$ observed by the Daya Bay experiment is examined in the framework of a model in which the neutrino is described by a wave packet with a relative intrinsic momentum dispersion $\sigma_\text{rel}$. Three pairs of nuclear reactors and eight antineutrino detectors, each with good energy resolution, distributed among three experimental halls, supply a high-statistics sample of $\bar{\nu}_e$ acquired at nine different baselines. This provides a unique platform to test the effects which arise from the wave packet treatment of neutrino oscillation. The modified survival probability formula was used to fit Daya Bay data, providing the first experimental limits: $2.38 \cdot 10^{-17} < \sigma_{\rm rel} < 0.23$. Treating the dimensions of the reactor cores and detectors as constraints, the limits are improved: $10^{-14} \lesssim \sigma_{\rm rel} < 0.23$, and an upper limit of $\sigma_{\rm rel} <0.20$ is obtained. All limits correspond to a 95\% C.L. Furthermore, the effect due to the wave packet nature of neutrino oscillation is found to be insignificant for reactor antineutrinos detected by the Daya Bay experiment thus ensuring an unbiased measurement of the oscillation parameters $\sin^22\theta_{13}$ and $\Delta m^2_{32}$ within the plane wave model.

hep-ex↗

arXiv2016

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

A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9~GW$_{\mathrm{th}}$ nuclear reactors and detected by eight antineutrino detectors deployed in two near (560~m and 600~m flux-weighted baselines) and one far (1640~m flux-weighted baseline) underground experimental halls. With 621 days of data, more than 1.2 million inverse beta decay (IBD) candidates were detected. The IBD yield in the eight detectors was measured, and the ratio of measured to predicted flux was found to be $0.946\pm0.020$ ($0.992\pm0.021$) for the Huber+Mueller (ILL+Vogel) model. A 2.9~$\sigma$ deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4-6~MeV was found in the measured spectrum, with a local significance of 4.4~$\sigma$. A reactor antineutrino spectrum weighted by the IBD cross section is extracted for model-independent predictions.

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arXiv2016

Limits on Active to Sterile Neutrino Oscillations from Disappearance Searches in the MINOS, Daya Bay, and Bugey-3 Experiments

Searches for a light sterile neutrino have been performed independently by the MINOS and the Daya Bay experiments using the muon (anti)neutrino and electron antineutrino disappearance channels, respectively. In this Letter, results from both experiments are combined with those from the Bugey-3 reactor neutrino experiment to constrain oscillations into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the LSND and MiniBooNE experiments in a minimally extended four-neutrino flavor framework. Stringent limits on $\sin^2 2\theta_{\mu e}$ are set over 6 orders of magnitude in the sterile mass-squared splitting $\Delta m^2_{41}$. The sterile-neutrino mixing phase space allowed by the LSND and MiniBooNE experiments is excluded for $\Delta m^2_{41} < 0.8$ eV$^2$ at 95% CL$_s$.

hep-ex↗

arXiv2016

Improved Search for a Light Sterile Neutrino with the Full Configuration of the Daya Bay Experiment

This Letter reports an improved search for light sterile neutrino mixing in the electron antineutrino disappearance channel with the full configuration of the Daya Bay Reactor Neutrino Experiment. With an additional 404 days of data collected in eight antineutrino detectors, this search benefits from 3.6 times the statistics available to the previous publication, as well as from improvements in energy calibration and background reduction. A relative comparison of the rate and energy spectrum of reactor antineutrinos in the three experimental halls yields no evidence of sterile neutrino mixing in the $2\times10^{-4} \lesssim |\Delta m^{2}_{41}| \lesssim 0.3$ eV$^{2}$ mass range. The resulting limits on $\sin^{2}2\theta_{14}$ are improved by approximately a factor of 2 over previous results and constitute the most stringent constraints to date in the $|\Delta m^{2}_{41}| \lesssim 0.2$ eV$^{2}$ region.

hep-ex↗

arXiv2016

Resistive Plate Chamber Digitization in a Hadronic Shower Environment

The CALICE Semi-Digital Hadron Calorimeter (SDHCAL) technological prototype is a sampling calorimeter using Glass Resistive Plate Chamber detectors with a three-threshold readout as the active medium. This technology is one of the two options proposed for the hadron calorimeter of the International Large Detector for the International Linear Collider. The prototype was exposed to beams of muons, electrons and pions of different energies at the CERN Super Proton Synchrotron. To be able to study the performance of such a calorimeter in future experiments it is important to ensure reliable simulation of its response. In this paper we present our prototype simulation performed with GEANT4 and the digitization procedure achieved with an algorithm called SimDigital. A detailed description of this algorithm is given and the methods to determinate its parameters using muon tracks and electromagnetic showers are explained. The comparison with hadronic shower data shows a good agreement up to 50 GeV. Discrepancies are observed at higher energies. The reasons for these differences are investigated.

physics.ins-det↗

arXiv2016

New measurement of $\theta_{13}$ via neutron capture on hydrogen at Daya Bay

This article reports an improved independent measurement of neutrino mixing angle $\theta_{13}$ at the Daya Bay Reactor Neutrino Experiment. Electron antineutrinos were identified by inverse $\beta$-decays with the emitted neutron captured by hydrogen, yielding a data-set with principally distinct uncertainties from that with neutrons captured by gadolinium. With the final two of eight antineutrino detectors installed, this study used 621 days of data including the previously reported 217-day data set with six detectors. The dominant statistical uncertainty was reduced by 49%. Intensive studies of the cosmogenic muon-induced $^9$Li and fast neutron backgrounds and the neutron-capture energy selection efficiency, resulted in a reduction of the systematic uncertainty by 26%. The deficit in the detected number of antineutrinos at the far detectors relative to the expected number based on the near detectors yielded $\sin^22\theta_{13} = 0.071 \pm 0.011$ in the three-neutrino-oscillation framework. The combination of this result with the gadolinium-capture result is also reported.

hep-ex↗

arXiv2016

Hadron shower decomposition in the highly granular CALICE analogue hadron calorimeter

The spatial development of hadronic showers in the CALICE scintillator-steel analogue hadron calorimeter is studied using test beam data collected at CERN and FNAL for single positive pions and protons with initial momenta in the range from 10 to 80 GeV/c. Both longitudinal and radial development of hadron showers are parametrised with two-component functions. The parametrisation is fit to test beam data and simulations using the QGSP_BERT and FTFP_BERT physics lists from Geant4 version 9.6. The parameters extracted from data and simulated samples are compared for the two types of hadrons. The response to pions and the ratio of the non-electromagnetic to the electromagnetic calorimeter response, h/e, are estimated using the extrapolation and decomposition of the longitudinal profiles.

physics.ins-det↗

arXiv2016

First results of the CALICE SDHCAL technological prototype

The CALICE Semi-Digital Hadronic Calorimeter (SDHCAL) prototype, built in 2011, was exposed to beams of hadrons, electrons and muons in two short periods in 2012 on two different beam lines of the CERN SPS. The prototype with its 48 active layers, made of Glass Resistive Plate Chambers and their embedded readout electronics, was run in triggerless and power-pulsing mode. The performance of the SDHCAL during the test beam was found to be very satisfactory with an efficiency exceeding 90% for almost all of the 48 active layers. A linear response (within 5%) and a good energy resolution are obtained for a large range of hadronic energies (5-80GeV) by applying appropriate calibration coefficients to the collected data for both the Digital (Binary) and the Semi-Digital (Multi-threshold) modes of the SDHCAL prototype. The Semi-Digital mode shows better performance at energies exceeding 30GeV

physics.ins-det↗

arXiv2015

JUNO Conceptual Design Report

The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine the neutrino mass hierarchy using an underground liquid scintillator detector. It is located 53 km away from both Yangjiang and Taishan Nuclear Power Plants in Guangdong, China. The experimental hall, spanning more than 50 meters, is under a granite mountain of over 700 m overburden. Within six years of running, the detection of reactor antineutrinos can resolve the neutrino mass hierarchy at a confidence level of 3-4$\sigma$, and determine neutrino oscillation parameters $\sin^2\theta_{12}$, $\Delta m^2_{21}$, and $|\Delta m^2_{ee}|$ to an accuracy of better than 1%. The JUNO detector can be also used to study terrestrial and extra-terrestrial neutrinos and new physics beyond the Standard Model. The central detector contains 20,000 tons liquid scintillator with an acrylic sphere of 35 m in diameter. $\sim$17,000 508-mm diameter PMTs with high quantum efficiency provide $\sim$75% optical coverage. The current choice of the liquid scintillator is: linear alkyl benzene (LAB) as the solvent, plus PPO as the scintillation fluor and a wavelength-shifter (Bis-MSB). The number of detected photoelectrons per MeV is larger than 1,100 and the energy resolution is expected to be 3% at 1 MeV. The calibration system is designed to deploy multiple sources to cover the entire energy range of reactor antineutrinos, and to achieve a full-volume position coverage inside the detector. The veto system is used for muon detection, muon induced background study and reduction. It consists of a Water Cherenkov detector and a Top Tracker system. The readout system, the detector control system and the offline system insure efficient and stable data acquisition and processing.

physics.ins-det↗