arXiv subjects

Yu-Heng Lin

Publications and source records attributed to Yu-Heng Lin.

23 records · Page 2Linked to original sources

arXiv2022

Towards a non-Gaussian Generative Model of large-scale Reionization Maps

High-dimensional data sets are expected from the next generation of large-scale surveys. These data sets will carry a wealth of information about the early stages of galaxy formation and cosmic reionization. Extracting the maximum amount of information from the these data sets remains a key challenge. Current simulations of cosmic reionization are computationally too expensive to provide enough realizations to enable testing different statistical methods, such as parameter inference. We present a non-Gaussian generative model of reionization maps that is based solely on their summary statistics. We reconstruct large-scale ionization fields (bubble spatial distributions) directly from their power spectra (PS) and Wavelet Phase Harmonics (WPH) coefficients. Using WPH, we show that our model is efficient in generating diverse new examples of large-scale ionization maps from a single realization of a summary statistic. We compare our model with the target ionization maps using the bubble size statistics, and largely find a good agreement. As compared to PS, our results show that WPH provide optimal summary statistics that capture most of information out of a highly non-linear ionization fields.

astro-ph.CO↗

arXiv2021

A Peculiar Type~II QSO Identified via Broad-band Detection of Extreme Nebular Line Emission

We present S82-20, an unusual redshift $\approx$3 object identified in SDSS-Stripe 82 broad-band images. The rest-frame ultraviolet spectrum of S82-20 shows emission lines from highly ionized species, including HeII $λ$1640, and the CIV $λλ$1548, 1550 and OVI $λλ$1032, 1038 doublets. The high Ly$α$ luminosity ($3.5\times 10^{44}$ erg s$^{-1}$), the high emission line equivalent widths ($>200$Å for Ly$α$), the FWHM of the emission lines ($<800$km s$^{-1}$), and the high ionization OVI line strongly support the interpretation that S82-20 is a Type~II QSO. However, photoionization models using Type~II QSO do not fully explain the measured CIV/HeII line ratio, which requires either some contribution from star-formation or high velocity shocks. Additionally, S82-20 is not detected at wavelengths longer than 2$μ$m, in tension with the expectation of isotropically IR emission of a luminous QSO. We consider the possibility that S82-20 is a rare example of a changing-look QSO, observed in a temporarily low state, where the broad line region has faded, while the narrow line region still emits emission line. Otherwise, it may be a rare case of the short phase of the life of a massive galaxy, in which active star formation and accretion onto a supermassive black hole coexist.

astro-ph.GA↗

arXiv2017

Non-leptonic two-body weak decays of $Λ_c(2286)$

We study the non-leptonic two-body weak decays of $Λ_c^+(2286)\to {\bf B}_n M$ with ${\bf B}_n$ ($M$) representing as the baryon (meson) states. Based on the $SU(3)$ flavor symmetry, we can describe most of the data reexamined by the BESIII Collaboration with higher precisions. However, our result of ${\cal B}(Λ_c^+ \to pπ^0)=(5.6\pm 1.5)\times 10^{-4}$ is larger than the current experimental limit of $3\times10^{-4}$ (90\% C.L.) by BESIII. In addition, we find that ${\cal B}(Λ_c^+ \to Σ^+ K^0)=(8.0\pm 1.6)\times 10^{-4}$, ${\cal B}(Λ_c^+ \to Σ^+ η^\prime)=(1.0^{+1.6}_{-0.8})\times 10^{-2}$, and ${\cal B}(Λ_c^+ \to p η^\prime)=(12.2^{+14.3}_{-\,\,\,8.7})\times 10^{-4}$, which are accessible to the BESIII experiments.

hep-ph↗

arXiv2016

Study of $Λ_b\to Λ(ϕ,η^{(\prime)})$ and $Λ_b\to ΛK^+K^-$ decays

We study the charmless two-body $Λ_b\to Λ(ϕ,η^{(\prime)})$ and three-body $Λ_b\to ΛK^+K^- $ decays. We obtain ${\cal B}(Λ_b\to Λϕ)=(3.53\pm 0.24)\times 10^{-6}$ to agree with the recent LHCb measurement. However, we find that ${\cal B}(Λ_b\to Λ(ϕ\to)K^+ K^-)=(1.71\pm 0.12)\times 10^{-6}$ is unable to explain the LHCb observation of ${\cal B}(Λ_b\toΛK^+ K^-)=(15.9\pm 1.2\pm 1.2\pm 2.0)\times 10^{-6}$, which implies the possibility for other contributions, such as that from the resonant $Λ_b\to K^- N^*,\,N^*\toΛK^+$ decay with $N^*$ as a higher-wave baryon state. For $Λ_b\to Λη^{(\prime)}$, we show that ${\cal B}(Λ_b\to Λη,\,Λη^\prime)= (1.47\pm 0.35,1.83\pm 0.58)\times 10^{-6}$, which are consistent with the current data of $(9.3^{+7.3}_{-5.3},<3.1)\times 10^{-6}$, respectively. Our results also support the relation of ${\cal B}(Λ_b\to Λη) \simeq {\cal B}(Λ_b\toΛη^\prime)$, given by the previous study.

hep-ph↗

arXiv2016

Roles of scalar mesons in charmless $Λ_b$ decays

We first study the charmless two-body $Λ_b$ decays with the scalar mesons as the final states and predict that ${\cal B}(Λ_b\to Λf_0(980,1500))=(2.9\pm 0.7,12.4\pm 3.8)\times 10^{-6}$ and ${\cal B}(Λ_b\to p K^{*-}_0(800,1430))=(1.9\pm 0.5,14.1\pm 4.5)\times 10^{-6}$. With the resonant $f_0(980,1500)\to (π^+π^-,K^+K^-)$ and $K^{*-}_0\to \bar K^0 π^-$ decays, we then obtain ${\cal B}(Λ_b\to Λ(π^+π^-,K^+K^-))=(4.2\pm 1.0,3.5\pm0.7)\times 10^{-6}$ and ${\cal B}(Λ_b\to p\bar K^0 π^-)=(10.4\pm2.9)\times 10^{-6}$, in comparison with the data of $(4.6\pm 1.9,15.9\pm2.6)\times 10^{-6}$ and $(12.6\pm 4.0)\times 10^{-6}$ from LHCb, respectively. Our results for $Λ_b\to Λπ^+π^-$ and $Λ_b\to p\bar K^0 π^-$ would be regarded as the first evidences of the scalar meson productions in the anti-triplet $b$-baryon decays. The smaller predicted value of ${\cal B}(Λ_b\to ΛK^+K^-)$ indicates the existences of other resonant contributions to the decay, such as $Λ_b\to K^-(N^{*+}\to)ΛK^+$.

hep-ph↗