arXiv subjects

Guey-Lin Lin

Publications and source records attributed to Guey-Lin Lin.

At least 37 records · Page 2Linked to original sources

arXiv2014

Probing Dark Matter Self-Interaction in the Sun with IceCube-PINGU

We study the capture, annihilation and evaporation of dark matter (DM) inside the Sun. It has been shown that the DM self-interaction can increase the DM number inside the Sun. We demonstrate that this enhancement becomes more significant in the regime of small DM mass, given a fixed DM self-interaction cross section. This leads to the enhancement of neutrino flux from DM annihilation. On the other hand, for DM mass as low as a few GeVs, not only the DM-nuclei scatterings can cause the DM evaporation, DM self-interaction also provides non-negligible contributions to this effect. Consequently, the critical mass for DM evaporation (typically 3 $\sim$ 4 GeV without the DM self-interaction) can be slightly increased. We discuss the prospect of detecting DM self-interaction in IceCube-PINGU using the annihilation channels $χχ\rightarrow τ^{+}τ^{-}, ν\barν$ as examples. The PINGU sensitivities to DM self-interaction cross section $σ_{χχ}$ are estimated for track and cascade events.

hep-ph↗

arXiv2014

Probing the coupling of heavy dark matter to nucleons by detecting neutrino signature from the Earth's core

We argue that the detection of neutrino signature from the Earth's core can effectively probe the coupling of heavy dark matter ($m_χ>10^{4}$ GeV) to nucleons. We first note that direct searches for dark matter (DM) in such a mass range provide much less stringent constraint than the constraint provided by such searches for $m_χ\sim 100$ GeV. Furthermore the energies of neutrinos arising from DM annihilation inside the Sun cannot exceed a few TeVs at the Sun surface due to the attenuation effect. Therefore the sensitivity to the heavy DM coupling is lost. Finally, the detection of neutrino signature from galactic halo can only probe DM annihilation cross sections. We present neutrino event rates in IceCube and KM3NeT arising from the neutrino flux produced by annihilation of Earth-captured DM heavier than $10^{4}$ GeV. The IceCube and KM3NeT sensitivities to spin independent DM-proton scattering cross section $σ_{χp}$ in this mass range are presented for both isospin symmetric and isospin violating cases.

hep-ph↗

arXiv2014

Probing the coupling of heavy dark matter to nucleons by detecting neutrino signature from the Earth core

We argue that the detection of neutrino signature from the Earth core is an ideal approach for probing the coupling of heavy dark matter ($m_χ>10^{4}$ GeV) to nucleons. We first note that direct searches for dark matter (DM) in such a mass range do not provide stringent constraints. Furthermore the energies of neutrinos arising from DM annihilations inside the Sun cannot exceed a few TeV at the Sun surface due to the attenuation effect. Therefore the sensitivity to the heavy DM coupling is lost. Finally, the detection of neutrino signature from galactic halo can only probe DM annihilation cross sections. After presenting the rationale of our studies, we discuss the event rates in IceCube and KM3NeT arising from the neutrino flux produced by annihilations of Earth-captured DM heavier than $10^{4}$ GeV. The IceCube and KM3NeT sensitivities to spin independent DM-proton scattering cross section $σ_{χp}$ and isospin violation effect in this mass range are presented. The implications of our results are also discussed.

hep-ph↗

arXiv2013

Probing Neutrino Flavor Transition Mechanism with Ultra High Energy Astrophysical Neutrinos

Observation of ultra-high energy astrophysical neutrinos and identification of their flavors have been proposed for future neutrino telescopes. The flavor ratio of astrophysical neutrinos observed on the Earth depends on both the initial flavor ratio at the source and flavor transitions taking place during propagations of these neutrinos. The flavor transition mechanisms are well-classified with our model-independent parametrization. We find a new parameter R=ϕ_e/(ϕ_μ + ϕ_τ) can probe directly the flavor transition in the framework of our model-independent parametrization, without the assumption of the ν_μ-ν_τ symmetry. A few flavor transition models are employed to test our parametrization with this new observable. The observational constraints on flavor transition mechanisms by the new observable is discussed through our model-independent parametrization.

hep-ph↗

arXiv2013

Constraining dark matter capture and annihilation cross sections by searching for neutrino signature from the Earth core

We study the sensitivity of IceCube/DeepCore detector to dark matter annihilations in the Earth core. We focus on annihilation modes $χχ\to ν\barν, \, τ^+ τ^-, \, b \bar{b}$, and $W^+W^-$. Both track and cascade events are considered in our analysis. By fixing the dark matter annihilation cross section $\langle σ\upsilon\rangle$ at some nominal values, we study the sensitivity of IceCube/DeepCore detector to dark matter spin-independent cross section $σ_p^{\rm SI}$ for $m_χ$ ranging from few tens of GeV to 10 TeV. This sensitivity is compared with the existing IceCube 79-string constraint on the same cross section, which was obtained by searching for dark matter annihilations in the Sun. We compare this sensitivity to dark matter direct detection results as well, in particular the XENON100 (2012) limit and the parameter regions preferred by DAMA and CRESST-II experiments. We also present IceCube/DeepCore sensitivity to $\langle σ\upsilon \rangle$ as a function of $m_χ$ by fixing $σ_p^{\rm SI}$ at XENON100 (2012) and XENON1T limits, respectively. This sensitivity is compared with the preferred dark matter parameter range derived from the combined fitting to PAMELA and AMS02 positron fraction data. We conclude that the search for dark matter annihilations in the Earth core provides competitive constraints on $σ_p^{\rm SI}$ and $\langle σ\upsilon \rangle$ in the case of low-mass dark matter. Particularly, the expected constraint on $\sigsip$ for 5 years of data taking in IceCube/DeepCore is more stringent than the current IceCube 79-string limit mentioned above.

hep-ph↗

arXiv2013

Sensitivities of IceCube DeepCore Detector to Signatures of Low-Mass Dark Matter in the Galactic Halo

We discuss the event rate in DeepCore array due to neutrino flux produced by annihilations and decays of galactic dark matter. This event rate is calculated with a 10 GeV threshold energy, which is smaller than the threshold energy taken in previous works. Taking into account the background event rate due to the atmospheric neutrino flux, we evaluate the sensitivity of DeepCore array for probing dark matter annihilation cross section and decay time. The sensitivity studies include the annihilation modes $χχ\to b\bar{b}, \ τ^+ τ^-$, \ $μ^+μ^-$, and $ν\barν$, and decay modes $χ\to b\bar{b}, \ τ^+ τ^-$, \ $μ^+μ^-$, and $ν\barν$. We compare our results with corresponding constraints derived from observations of WMAP, ACT and Fermi-LAT.

hep-ph↗

arXiv2012

Probing annihilations and decays of low-mass galactic dark matter in IceCube DeepCore array: Track events

The deployment of DeepCore array significantly lowers IceCube's energy threshold to about 10 GeV and enhances the sensitivity of detecting neutrinos from annihilations and decays of light dark matter. To match this experimental development, we calculate the track event rate in DeepCore array due to neutrino flux produced by annihilations and decays of galactic dark matter. We also calculate the background event rate due to atmospheric neutrino flux for evaluating the sensitivity of DeepCore array to galactic dark matter signatures. Unlike previous approaches, which set the energy threshold for track events at around 50 GeV (this choice avoids the necessity of including oscillation effect in the estimation of atmospheric background event rate), we have set the energy threshold at 10 GeV to take the full advantage of DeepCore array. We compare our calculated sensitivity with those obtained by setting the threshold energy at 50 GeV. We conclude that our proposed threshold energy significantly improves the sensitivity of DeepCore array to the dark matter signature for $m_χ< 100$ GeV in the annihilation scenario and $m_χ<300$ GeV in the decay scenario.

hep-ph↗

arXiv2011

Determination of the Source Flavor Ratio of Ultrahigh Energy Neutrinos

We discuss the reconstruction of neutrino flavor neutrino at a distant source in the very high en- ergy regime. This reconstruction procedure is relevant to the confirmation of detecting cosmogenic neutrinos, for example. To facilitate such a reconstruction, it is imperative to achieve effective flavor discriminations in terrestrial neutrino telescopes. We note that, for energies beyond few tens of PeV, a tau-lepton behaves like a track similar to a muon. Hence, while it is rather challenging to separate νμ from ντ in this case, one can expect to isolate νe from the rest by a distinctive shower signature. We present the result of flavor ratio reconstruction given the anticipated accuracies of flavor measurement in neutrino telescopes and current uncertainties of neutrino mixing parame- ters. It is shown that the further separation between νμ and ντ events does not improve the flavor reconstruction due to the approximate νμ - ντ symmetry.

hep-ph↗

arXiv2010

Flavor Transition Mechanisms of Propagating Astrophysical Neutrinos -A Model Independent Parametrization

One of the important goals for future neutrino telescopes is to identify the flavors of astrophysical neutrinos and therefore determine the flavor ratio. The flavor ratio of astrophysical neutrinos observed on the Earth depends on both the initial flavor ratio at the source and flavor transitions taking place during propagations of these neutrinos. We propose a model independent parametrization for describing the above flavor transitions. A few flavor transition models are employed to test our parametrization. The observational test for flavor transition mechanisms through our parametrization is discussed.

hep-ph↗

arXiv2010

Neutrino Flavor Ratio on Earth and at Astrophysical Sources

We present the reconstruction of neutrino flavor ratios at astrophysical sources. For distinguishing the pion source and the muon-damped source to the 3$σ$ level, the neutrino flux ratios, $R\equivϕ(ν_μ)/(ϕ(ν_e)+ϕ(ν_τ))$ and $S\equivϕ(ν_e)/ϕ(ν_τ)$, need to be measured in accuracies better than 10%.

hep-ph↗

arXiv2009

Determination of the Neutrino Flavor Ratio at the Astrophysical Source

We discuss the reconstruction of neutrino flavor ratios at astrophysical sources through the future neutrino-telescope measurements. Taking the ranges of neutrino mixing parameters $θ_{ij}$ as those given by the current global fit, we demonstrate by a statistical method that the accuracies in the measurements of energy-independent ratios $R\equivϕ(ν_μ)/(ϕ(ν_{e})+ϕ(ν_τ))$ and $S\equivϕ(ν_e)/ϕ(ν_τ)$ among integrated neutrino flux should both be better than 10% in order to distinguish between the pion source and the muon-damped source at the $3 σ$ level. The 10% accuracy needed for measuring $R$ and $S$ requires an improved understanding on the background atmospheric neutrino flux to a better than 10% level in the future. We discuss the applicability of our analysis to practical situations that the diffuse astrophysical neutrino flux arises from different types of sources and each point source has a neutrino flavor ratio varying with energies. We also discuss the effect of leptonic CP phase on the flavor-ratio reconstruction.

hep-ph↗

arXiv2009

GeoSynchrotron Radiation from Earth Skimming Tau Neutrino Shower

Cosmogenic neutrinos are expected from ultrahigh energy cosmic rays undergoing the GZK process and anticipated to be observed by detecting air showers from the decays of tau leptons. We use CORSIKA simulated shower structure to calculate the coherent geosynchrotron radio emissions of the tau decay showers above $10^{17}$eV. We present the pattern and spectrum of radio waves and discuss their detections by radio antennae.

astro-ph.HE↗

arXiv2008

A New Type of Plasma Wakefield Accelerator Driven by Magnetowaves

We present a new concept for a plasma wakefield accelerator driven by magnetowaves (MPWA). This concept was originally proposed as a viable mechanism for the "cosmic accelerator" that would accelerate cosmic particles to ultra high energies in the astrophysical setting. Unlike the more familiar Plasma Wakefield Accelerator (PWFA) and the Laser Wakefield Accelerator (LWFA) where the drivers, the charged-particle beam and the laser, are independently existing entities, MPWA invokes the high-frequency and high-speed whistler mode as the driver, which is a medium wave that cannot exist outside of the plasma. Aside from the difference in drivers, the underlying mechanism that excites the plasma wakefield via the ponderomotive potential is common. Our computer simulations show that under appropriate conditions, the plasma wakefield maintains very high coherence and can sustain high-gradient acceleration over many plasma wavelengths. We suggest that in addition to its celestial application, the MPWA concept can also be of terrestrial utility. A proof-of-principle experiment on MPWA would benefit both terrestrial and celestial accelerator concepts.

physics.acc-ph↗

arXiv2008

Ultra High Energy Cosmic Ray Puzzle and the Plasma Wakefield Acceleration

Magnetowave induced plasma wakefield acceleration (MPWA) in a relativistic astrophysical outflow has been proposed as a viable mechanism for the acceleration of cosmic particles to ultra high energies. Here we present simulation results that demonstrate the viability of this mechanism. We invoke the high frequency and high speed whistler mode for the driving pulse. The plasma wakefield so induced validates precisely the theoretical prediction. This mechanism is shown capable of accelerating charged particles to ZeV energies in Active Galactic Nuclei (AGN).

astro-ph↗

arXiv2008

GZK Horizons and the Anisotropy of Highest-energy Cosmic Ray Sources

Motivated by recent Pierre Auger result on the correlation of the highest-energy cosmic rays with the nearby active galactic nuclei, we explore possible ultrahigh energy cosmic ray (UHECR) source distributions and their effects on GZK horizons. Effects on GZK horizons by local over-density of UHECR sources are examined carefully with constraints on the degree of local over-density inferred from the measured UHECR spectrum. We include the energy calibration effect on the Pierre Auger data in our studies. We propose possible local over-densities of UHECR sources which are testable in the future cosmic ray astronomy.

astro-ph↗

arXiv2008

GZK Horizons and the Recent Pierre Auger Result on the Anisotropy of Highest-energy Cosmic Ray Sources

astro-ph↗

arXiv2007

Magnetowave Induced Plasma Wakefield Acceleration for Ultra High Energy Cosmic Rays

Magnetowave induced plasma wakefield acceleration (MPWA) in a relativistic astrophysical outflow has been proposed as a viable mechanism for the acceleration of cosmic particles to ultra high energies. Here we present simulation results that clearly demonstrate the viability of this mechanism for the first time. We invoke the high frequency and high speed whistler mode for the driving pulse. The plasma wakefield so induced validates precisely the theoretical prediction. We show that under appropriate conditions, the plasma wakefield maintains very high coherence and can sustain high-gradient acceleration over a macroscopic distance. Invoking gamma ray burst (GRB) as the source, we show that MPWA production of ultra high energy cosmic rays (UHECR) beyond ZeV 10^21 eV is possible.

astro-ph↗

arXiv2006

Probing the octant of $θ_{23}$ with very long baseline neutrino oscillation experiments: a global look

We investigate the baseline range in which the $θ_{23}$ degeneracy in neutrino oscillation probabilities is absent for fixed values of $θ_{13}$ and CP violation phase $δ_{\rm CP}$. We begin by studying sensitivities of neutrino oscillation probabilities to $θ_{13}$, $θ_{23}$ and $δ_{\rm CP}$ for very-long-baseline neutrino oscillations. We show contour graphs of the muon-neutrino survival probability $P(ν_μ\to ν_μ)$ and the appearance probability $P(ν_e\to ν_μ)$ on the $\cos 2θ_{23}-\sin 2θ_{13}$ plane for baseline lengths $L=1000, 5000, \ 10000$, and 12000 km. For each baseline length, it is found that $P(ν_μ\to ν_μ)$ is more sensitive to $\sin 2θ_{13}$ at energies around its local maximum while it is more sensitive to $\cos 2θ_{23}$ at energies around its local minimum. On the other hand, the appearance probability $P(ν_e\to ν_μ)$ is sensitive to $\sin2θ_{13}$ and $\cos2θ_{23}$ only near its local maximum. We observe that the $θ_{23}$ degeneracy in $P(ν_μ\to ν_μ)$ is absent at energies around the local maximum of this probability, provided $θ_{13}$ is sufficiently large. The $θ_{23}$ degeneracy is also absent in general near the local maximum of $P(ν_e\to ν_μ)$. Using analytic approximations for neutrino oscillation probabilities, we demonstrate that the above observations for $L=1000, 5000, 10000, {\rm and} 12000$ km are in fact valid for all distances. The implications of these results on probing the octant of $θ_{23}$ are discussed in details.

hep-ph↗