arXiv subjects

Hsiu-Hsien Lin

Publications and source records attributed to Hsiu-Hsien Lin.

26 records · Page 2Linked to original sources

arXiv2017

Improved Pulsar Timing via Principle Component Mode Tracking

We present a principal component analysis method which tracks and compensates for short-timescale variability in pulsar profiles, with a goal of improving pulsar timing precision. We couple this with a fast likelihood technique for determining pulse time of arrival, marginalizing over the principal component amplitudes. This allows accurate estimation of timing errors in the presence of pulsar variability. We apply the algorithm to the slow pulsar PSR J2139+0040 using an archived set of untargeted raster-scan observations at arbitrary epochs across four years, obtaining an improved timing solution. The method permits accurate pulsar timing in data sets with short contiguous on-source observations, opening opportunities for commensality between pulsar timing and mapping surveys.

astro-ph.IM↗

arXiv2016

Constraints on the FRB rate at 700-900 MHz

Estimating the all-sky rate of fast radio bursts (FRBs) has been difficult due to small-number statistics and the fact that they are seen by disparate surveys in different regions of the sky. In this paper we provide limits for the FRB rate at 800 MHz based on the only burst detected at frequencies below 1.4 GHz, FRB 110523. We discuss the difficulties in rate estimation, particularly in providing an all-sky rate above a single fluence threshold. We find an implied rate between 700-900 MHz that is consistent with the rate at 1.4 GHz, scaling to $6.4^{+29.5}_{-5.0} \times 10^3$\,sky$^{-1}$\,day$^{-1}$ for an HTRU-like survey. This is promising for upcoming experiments below a GHz like CHIME and UTMOST, for which we forecast detection rates. Given 110523's discovery at 32$σ$ with nothing weaker detected, down to the threshold of 8$σ$, we find consistency with a Euclidean flux distribution but disfavour steep distributions, ruling out $γ> 2.2$.

astro-ph.HE↗

arXiv2015

Dense magnetized plasma associated with a fast radio burst

Fast Radio Bursts are bright, unresolved, non-repeating, broadband, millisecond flashes, found primarily at high Galactic latitudes, with dispersion measures much larger than expected for a Galactic source. The inferred all-sky burst rate is comparable to the core-collapse supernova rate out to redshift 0.5. If the observed dispersion measures are assumed to be dominated by the intergalactic medium, the sources are at cosmological distances with redshifts of 0.2 to 1. These parameters are consistent with a wide range of source models. One fast radio burst showed circular polarization [21(7)%] of the radio emission, but no linear polarization was detected, and hence no Faraday rotation measure could be determined. Here we report the examination of archival data revealing Faraday rotation in a newly detected burst - FRB 110523. It has radio flux at least 0.6 Jy and dispersion measure 623.30(5) pc cm$^{-3}$. Using Galactic contribution 45 pc cm$^{-3}$ and a model of intergalactic electron density, we place the source at a maximum redshift of 0.5. The burst has rotation measure -186.1(1.4) rad m$^{-2}$, much higher than expected for this line of sight through the Milky Way and the intergalactic medium, indicating magnetization in the vicinity of the source itself or within a host galaxy. The pulse was scattered by two distinct plasma screens during propagation, which requires either a dense nebula associated with the source or a location within the central region of its host galaxy. Keeping in mind that there may be more than one type of fast radio burst source, the detection in this instance of source-local magnetization and scattering favours models involving young stellar populations such as magnetars over models involving the mergers of older neutron stars, which are more likely to be located in low density regions of the host galaxy.

astro-ph.HE↗

arXiv2013

CP Violation in $B^0_s \to K^-π^+$, $B^0 \to K^+π^-$ Decays and Tests for SU(3) Flavor Symmetry Predictions

The LHCb collaboration has recently measured the first direct CP violation in $B^0_s$ decays with a rate asymmetry $A_{CP}(B^0_s\to K^- π^+)$ given by $0.27 \pm 0.04(stat)\pm 0.01(syst)$. At the same time they also made the most precise measurement for $A_{CP}(B^0 \to K^+ π^-) = -0.080\pm 0.007(stat)\pm 0.003(syst)$. These data confirm the predicted relation, $A_{CP}(B^0 \to K^+ π^-)/A_{CP}(B^0_s \to K^- π^+) = - Br(B^0_s\to K^- π^+)τ_{B^0}/Br(B^0 \to K^+ π^-)τ_{B^0_s}$, in the standard model with SU(3) flavor symmetry. We discuss possible modifications due to SU(3) breaking effects to this relation. There are several other similar relations in B decays. Using current available data we study whether relevant relations hold in $B^0$ and $B^0_s$ to $PP$ and $PV$ decays. Here $P$ and $V$ indicate pesudoscalar and vector mesons in the flavor octet representations.

hep-ph↗

arXiv2013

Further Studies of Higgs Properties at An ILC $γγ$ Collider

Recently the ATLAS and CMS experiments at the LHC have found a Higgs like boson $h$ with a mass around 125 GeV from several decay modes. The decay mode $h \to γγ$ is one of the most important modes in studying whether $h$ is actually the standard model (SM) Higgs boson. Current data indicate that $h\to γγ$ has a branching ratio larger than the SM prediction for $h$ being identified as the SM Higgs boson. To decide whether the $h$ discovered at the LHC is the SM Higgs boson, more data are needed. We study how $γγ$ collider can help to provide some of the most important information about the Higgs boson properties. We show that a $γγ$ collider can easily verify whether the enhanced $h \to γγ$ observed at the LHC hold. Different models can be tested by studying Higgs boson decay to $γZ$. Studying angular distribution of the $γγ$ through on-shell production of $h$ and its subsequent decays into a $γγ$ pair can decide whether the Higgs like boson $h$ at the LHC is a spin-0 or a spin-2 boson.

hep-ph↗

arXiv2013

The $β$ angle as the CP violating phase in the CKM matrix

The CKM matrix describing quark mixing with three generations can be parameterized by three Euler mixing angles and one CP violating phase. In most of the parameterizations, the CP violating phase chosen is not a directly measurable quantity and is parametrization dependent. In this work, we propose to use the most accurately measured CP violating angle $β$ in the unitarity triangleas the phase in the CKM matrix, and construct an explicit $β$ parameterization. We also derive an approximate Wolfenstein-like expression for this parameterization.

hep-ph↗

arXiv2012

The $α$, $β$ and $γ$ parameterizations of CP violating CKM phase

The CKM matrix describing quark mixing with three generations can be parameterized by three mixing angles and one CP violating phase. In most of the parameterizations, the CP violating phase chosen is not a directly measurable quantity and is parametrization dependent. In this work, we propose to use experimentally measurable CP violating quantities, $α$, $β$ or $γ$ in the unitarity triangle as the phase in the CKM matrix, and construct explicit $α$, $β$ and $γ$ parameterizations. Approximate Wolfenstein-like expressions are also suggested.

hep-ph↗

arXiv2012

Comment on Reparametrization Invariance of Quark-Lepton Complementarity

We study the complementarity between quark and lepton mixing angles (QLC), the sum of an angle in quark mixing and the corresponding angle in lepton mixing is $π/4$. Experimentally in the standard PDG parametrization, two such relations exist approximately. These QLC relations are accidental which only manifest themselves in the PDG parametrization. We propose reparametrization invariant expressions for the complementarity relations in terms of the magnitude of the elements in the quark and lepton mixing matrices. In the exact QLC limit, it is found that $|V_{us}/V_{ud}| + |V_{e2}/V_{e1}| + |V_{us}/V_{ud}| |V_{e2}/V_{e1}| =1$ and $|V_{cb}/V_{tb}| + |V_{μ3}/V_{τ3}| +|V_{cb}/V_{tb}|| {V_{μ3}}/V_{τ3}| =1$. Expressions with deviations from exact complementarity are obtained. Implications of these relations are also discussed.

hep-ph↗