arXiv subjects

J. Y. Xu

Publications and source records attributed to J. Y. Xu.

12 recordsLinked to original sources

arXiv2025

Role of nuclear and electromagnetic fragmentation in the charge-changing reactions of 18O on carbon and lead targets at around 370 MeV/nucleon

Charge-changing cross sections (CCCSs) of 18O on carbon (C) and lead (Pb) targets have been measured with an uncertainty of less than 4% at around 370MeV/nucleon. We evaluate the contributions of nucleon-nucleon (NN) and electromagnetic (EM) interactions to CCCSs by considering the direct proton removal process, the charged particle evaporation (CPE) after neutron removal, and the EM excitation. We conclude that the CPE accounts for 12.3% and 5% of CCCSs on C and Pb, respectively. Only less than 1% of CCCSs of 18O is attributed to the EM excitation. Further investigation of projectiles from 18O to 197Au on C, silver (Ag) and Pb targets at 300 and 900MeV/nucleon show that the contribution of EM to CCCSs on Ag and Pb increases with projectile mass numbers and incident energies, and can reach 10% for 197Au on Pb at 900MeV/nucleon. In contrast, the EM contribution to CCCS is negligible for all projectiles on C at both energies.

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arXiv2024

Charge radii of $^{11-16}$C, $^{13-17}$N and $^{15-18}$O determined from their charge-changing cross-sections and the mirror-difference charge radii

Charge-changing cross-sections of $^{11-16}$C, $^{13-17}$N and $^{15-18}$O on a carbon target have been determined at energies around 300 MeV/nucleon. A nucleon separation energy-dependent correction factor has been introduced to the Glauber model calculation for extracting the nuclear charge radii from the experimental CCCSs. The charge radii of $^{11}$C, $^{13,16}$N and $^{15}$O thus were determined for the first time. With the new radii, we studied the experimental mirror-difference charge radii ($ΔR_{\text {ch}}^{\text {mirror}}$) of $^{11}$B-$^{11}$C, $^{13}$C-$^{13}$N, $^{15}$N-$^{15}$O, $^{17}$N-$^{17}$Ne pairs for the first time. We find that the $ΔR_{\text {ch}}^{\text {mirror}}$ values of $^{13}$C-$^{13}$N and $^{15}$N-$^{15}$O pairs follow well the empirical relation to the isospin asymmetry predicted by the $ab$ $initio$ calculations, while $ΔR_{\text {ch}}^{\text {mirror}}$ of $^{11}$B-$^{11}$C and $^{17}$N-$^{17}$Ne pairs deviate from such relation by more than two standard deviations.

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arXiv2024

Burn-in Test and Thermal Performance Evaluation of Silicon Photomultipliers for the JUNO-TAO Experiment

This study evaluates more than 4,000 tiles made of Hamamatsu visual-sensitive silicon photomultipier (SiPM), each with dimensions of 5 $\times$ 5 cm$^2$, intended for the central detector of the Taishan Anti-neutrino Observatory (TAO), a satellite experiment of the Jiangmen Underground Neutrino Observatory (JUNO) aimed at measuring the reactor anti-neutrino energy spectrum with unprecedented energy resolution. All SiPM tiles underwent a room temperature burn-in test in the dark for two weeks, while cryogenic testing analyzed the thermal dependence of parameters for some sampled SiPMs. Results from these comprehensive tests provide crucial insights into the long-term performance and stability of the 10 square meters of SiPMs operating at -50°C to detect scintillation photons in the TAO detector. Despite some anomalies awaiting further inspection, all SiPMs successfully passed the burn-in test over two weeks at room temperature, which is equivalent to 6.7 years at -50°C. Results are also used to guide optimal SiPM selection, configuration, and operation, ensuring reliability and sustainability in reactor neutrino measurements. This work also provides insights for a rapid and robust quality assessment in future experiments that employ large-scale SiPMs as detection systems.

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arXiv2023

Isospin-dependence of the charge-changing cross-section shaped by the charged-particle evaporation process

We present the charge-changing cross sections (CCCS) of $^{11-15}$C, $^{13-17}$N, and $^{15,17-18}$O at around 300 MeV/nucleon on a carbon target, which extends to $p$-shell isotopes with $N < Z$ for the first time. The Glauber model, which considers only the proton distribution of projectile nuclei, underestimates the cross sections by more than 10\%. We show that this discrepancy can be resolved by considering the contribution from the charged-particle evaporation process (CPEP) following projectile neutron removal. Using nucleon densities from the deformed relativistic Hartree-Bogoliubov theory in continuum, we investigate the isospin-dependent CPEP contribution to the CCCS for a wide range of neutron-to-proton separation energy asymmetry. Our calculations, which include the CPEP contribution, agree well with existing systematic data and reveal an ``evaporation peak" at the isospin symmetric region where the neutron-to-proton separation energy is close to zero. These results suggest that analysis beyond the Glauber model is crucial for accurately determining nuclear charge radii from CCCSs.

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arXiv2022

Observation of the $π^2σ^2$-bond linear-chain molecular structure in $^{16}$C

Measurements of the $^2$H($^{16}$C,$^{16}$C$^{*}$$\rightarrow^4$He+$^{12}$Be or $^6$He+$^{10}$Be)$^2$H inelastic excitation and cluster-decay reactions have been carried out at a beam energy of about 23.5 MeV/u. A specially designed detection system, including one multi-layer silicon-strip telescope at around zero degrees, has allowed the high-efficiency three-fold coincident detection and therefore the event-by-event determination of the energy of the unstable nucleus beam. The decay paths from the $^{16}$C resonances to various states of the final $^{10}$Be or $^{12}$Be nucleus are recognized thanks to the well-resolved $Q$-value spectra. The reconstructed resonances at 16.5(1), 17.3(2), 19.4(1) and 21.6(2) MeV are assigned as the $0^+$, $2^+$, $4^+$ and $6^+$ members, respectively, of the positive-parity $(3/2_π^-)^2(1/2_σ^-)^2$-bond linear-chain molecular band in $^{16}$C, based on the angular correlation analysis for the 16.5 MeV state and the excellent agreement of decay patterns between the measurements and theoretical predictions. Moreover, another intriguing high-lying state was observed at 27.2(1) MeV which decays almost exclusively to the $\sim$6 MeV states of $^{10}$Be, in line with the newly predicted pure $σ$-bond linear-chain configuration.

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arXiv2021

Property investigation for different wedge-shaped CsI(Tl)s

Two types of wedge-shaped CsI(Tl)s were designed to be placed behind the annular double-sided silicon detectors (ADSSDs) to identify the light charged particles with the $ΔE-E$ method. The properties of CsI(Tl)s with different shapes and sizes, such as energy resolution, light output non-uniformity and particle identification capability, were compared by using a $α$-source and a radioactive beam of $^{15}$C. The big-size CsI(Tl) was finally adopted to form the $ΔE-E$ telescope due to better properties. The property differences of these two types of CsI(Tl)s can be interpreted based on the Geant4 simulation results.

physics.ins-det↗

arXiv2021

Study of $s$- and $d$-wave intruder strengths in $^{13}{\rm B}_{\rm g.s.}$ via a $p(^{13}{\rm B},d)^{12}{\rm B}$ reaction

Experimental results of the $p(^{13}{\rm B},d)^{12}{\rm B}$ transfer reaction to the low-lying states in $^{12}$B are reported. The optical potential parameters for the entrance channel are extracted from the elastic scattering $p$($^{13}{\rm B}$, $p$) measured in the same experiment, while those for the exit channel are global ones. Spectroscopic factors associated with the $p$-, $s$-, and $d$-wave neutron transfer to the known $^{12}$B states, are extracted by comparing the deuteron angular distributions with the calculation results. The separated $s$- and $d$-wave intruder strengths in $^{13}{\rm B}_{\rm g.s.}$ were determined to be $10(2)\%$ and $6(1)\%$, respectively, which follow roughly the systematics for the $N$ = 8 neutron-rich isotones. The measured total intruder strength is in good agreement with the shell model calculation, while the individual ones evolve quite differently. Particularly, the sudden change of the $d$-wave intensity between $^{13}$B and $^{12}$Be needs further theoretical interpretation.

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arXiv2020

Predictions of $α$ decay half-lives for even-even superheavy nuclei with $104 \leqslant Z \leqslant 128$ based on two-potential approach within cluster-formation model

In present work, we systematically study the $α$ decay half-lives of 170 even-even nuclei with $60 \leqslant Z \leqslant 118$ within the two-potential approach while the $α$ decay preformation factor $P_α$ is obtained by the cluster-formation model. The calculated results can well reproduce the experimental data. In addition, we extend this model to predict the $α$ decay half-lives of 64 even-even nuclei with $104 \leqslant Z \leqslant 128$ whose $α$ decay is energetically allowed or observed but not yet quantified. For comparing, the two famous models i.e. SemFIS proposed by D. Poenaru ${et\ al.}$ [\href {https://doi.org/10.1209/0295-5075/77/62001}{Europhys. Lett. \textbf{77} (2007) 62001}] and UDL proposed by C. Qi ${et\ al.}$ [\href {https://doi.org/10.1103/PhysRevLett.103.072501}{Phys. Rev. Lett. \textbf{103} (2009) 072501}] are used. The predicted results of these models are basically consistent. At the same time, through analyzing the changing trend of $α$ decay energy $Q_α$ of \emph{Z} = 118, 120, 122, 124, 126 and 128 isotopes nuclei with the increasing of neutron number \emph{N} and that of $α$ decay preformation factor $P_α$ of those isotopes even-even nuclei with the increasing of neutron number \emph{N}, \emph{N} = 178 may be a new neutron magic number.

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arXiv2020

Positive-parity linear-chain molecular band in $^{16}$C

An inelastic excitation and cluster-decay experiment $\rm {^2H}(^{16}C,~{^{4}He}+{^{12}Be}~or~{^{6}He}+{^{10}Be}){^2H}$ was carried out to investigate the linear-chain clustering structure in neutron-rich $\rm {^{16}C}$. For the first time, decay-paths from the $\rm {^{16}C}$ resonances to various states of the final nuclei were determined, thanks to the well-resolved $Q$-value spectra obtained from the three-fold coincident measurement. The close-threshold resonance at 16.5 MeV is assigned as the ${J^π}={0^+}$ band head of the predicted positive-parity linear-chain molecular band with ${(3/2_π^-)^2}{(1/2_σ^-)^2}$ configuration, according to the associated angular correlation and decay analysis. Other members of this band were found at 17.3, 19.4, and 21.6 MeV based on their selective decay properties, being consistent with the theoretical predictions. Another intriguing high-lying state was observed at 27.2 MeV which decays almost exclusively to $\rm {^{6}He}+{^{10}Be{(\sim6~ MeV)}}$ final channel, corresponding well to another predicted linear-chain structure with the pure $σ$-bond configuration.

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arXiv2018

Investigation of antineutrino spectral anomaly with reactor simulation uncertainty

Recently, three successful antineutrino experiments (Daya Bay, Double Chooz, and RENO) measured the neutrino mixing angle theta_{13}; however, significant discrepancies were found, both in the absolute flux and spectral shape. Much effort has been expended investigating the possible reasons for the discrepancies. In this study, Monte Carlo-based sampling was used to evaluate the fission fraction uncertainties. We found that fission cross-section uncertainties are an important source of uncertainty for $^{235}$U, $^{239}$Pu, and $^{241}$Pu, but for $^{238}$U, elastic and inelastic cross-sections are more important. Among uncertainty related to manufacturing parameters, fuel density is the main uncertainty; however, the total manufacturing uncertainty was very small. The uncertainties induced by burnup were evaluated through the atomic density uncertainty of the four isotopes. The total fission fraction uncertainties from reactor simulation were 0.83%, 2.24%, 1.79%, and 2.59% for235U, 238U, 239Pu, and 241Pu, respectively, at the middle of the fuel cycle. The total fission fraction uncertainty was smaller than the previously derived value of 5\%. These results are helpful for studying the reactor antineutrino anomaly and precisely measuring the antineutrino spectrum in the Daya Bay antineutrino experiment.

physics.ins-det↗

arXiv2003

Mode Repulsion and Mode Coupling in Random Lasers

We studied experimentally and theoretically the interaction of lasing modes in random media. In a homogeneously broadened gain medium, cross gain saturation leads to spatial repulsion of lasing modes. In an inhomogeneously broadened gain medium, mode repulsion occurs in the spectral domain. Some lasing modes are coupled through photon hopping or electron absorption and reemission. Under pulsed pumping, weak coupling of two modes leads to synchronization of their lasing action. Strong coupling of two lasing modes results in anti-phased oscillations of their intensities.

cond-mat.dis-nn↗

arXiv2003

Dynamic Nonlinear Effect on Lasing in a Random Medium

We have studied the dynamic effect of nonlinearity on lasing in disordered medium. The third-order nonlinearity not only changes the frequency and size of lasing modes, but also modifies the laser emission intensity and laser pulse width. When the nonlinear response time is comparable to or longer than the lifetime of the lasing mode, the nonlinearity changes the laser output through modifying the size of the lasing mode. When the nonlinear response is much faster than the buildup of the lasing mode, positive nonlinearity always extracts more laser emission from the random medium due to the enhancement of single particle scattering.

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