Browsing by Author "Liu, T. C."

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Classifying and probing flavor transition mechanisms of astrophysical high energy neutrinos
(2012-01-01)
Lai, Kwang-Chang
;
Lin, Guey-Lin
;
Liu, T. C.
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物理研究所
;
Institute of Physics
The future neutrino telescopes are expected to identify the flavors of astrophysical neutrinos and therefore determine the flavor ratio. The flavor ratio of astrophysical neutrinos observed at the Earth depends on both the initial flavor ratio at the source and flavor transitions taking place during the propagations of these neutrinos. We propose a model-independent way to parameterize the above flavor transitions, including standard oscillations and beyond. A systematical way is also described to probe those mechanisms taking advantage of R equivalent to phi(mu)/(phi(e) + phi(tau)) and S equivalent to phi(e)/phi(tau) the observables in neutrino telescope measurements.
Determination of the neutrino flavor ratio at the astrophysical source
(2009-11-01)
Lai, Kwang-Chang
;
Lin, Guey-Lin
;
Liu, T. C.
;
物理研究所
;
Institute of Physics
We discuss the reconstruction of neutrino flavor ratios at astrophysical sources through the future neutrino-telescope measurements. Taking the ranges of neutrino mixing parameters theta(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 equivalent to phi(nu(mu))/(phi(nu(e))+phi(nu(tau))) and S equivalent to phi(nu(e))/phi(nu(tau)) 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 sigma level. The 10% accuracy needed for measuring R and S requires an improved understanding of 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 the leptonic CP phase on the flavor-ratio reconstruction.
Determinations of flavor ratios and flavor transitions of astrophysical neutrinos
(2010)
Lin, Guey-Lin
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Liu, T. C.
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Lai, Kwang-Chang
;
Huang, M. A.
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物理研究所
We argue that an effective flavor discrimination in neutrino telescopes is the key to probe the flavor ratios of astrophysical neutrinos at the source and flavor transition mechanisms of these neutrinos during their propagations from the source to the Earth. We first discuss how well one can reconstruct the flavor ratios of astrophysical neutrinos at the source. We then discuss how to probe flavor transition mechanisms of propagating astrophysical neutrinos. In this regard, we propose a model independent parametrization for neutrino flavor transitions, with the neutrino oscillation as a special case.
FLASH-TW experiment status report
(2005)
Liu, T. C.
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Chang, F. Y.
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Chen, C. C.
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Chen, C. W.
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Huang, M. A.
FLASH-TW is an experiment to measure the shower lateral and longitudinal profiles. We perform the shower profile measurement by shooting the 1.5 GeV electron beams in NSRRC on targets made of 15 aluminum blocks, each with a thickness of 2.9 cm. A scintillator (Al2O3: Cr)) is placed behind the targets, converting the secondary shower particles into light. The light from the central region of the shower is recorded by a CCD camera while the light from the outer region is monitored by PMTs. The CCD system is successfully implemented in the run 2 and run 3 of experiment FLASH at SLAC. A test run of the current experiment has been conducted in NSRRC in the past June to study the scintillator spectrum. Two more runs are planned from now to the year 2006 to measure the shower lateral and longitudinal profiles.
Flavor transition mechanisms of propagating astrophysical neutrinos: A model independent parametrization
(2010-11-05)
Lai, Kwang-Chang
;
Lin, Guey-Lin
;
Liu, T. C.
;
物理研究所
;
Institute of Physics
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.
Lasing characteristics at different band edges in GaN photonic crystal surface emitting lasers
(2010-02-15)
Chen, S. W.
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Lu, T. C.
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Hou, Y. J.
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Liu, T. C.
;
Kuo, H. C.
We have investigated the lasing characteristics of GaN-based two-dimensional photonic crystal surface emitting lasers (PCSELs) with different PC lattice constants by using angled resolved spectroscopy. Due to the Bragg diffraction theory, normalized frequency of lasing wavelength of PCSELs can be exactly matched with three distinct band-edge frequencies (Gamma 1, K2, and M3) in the photonic band diagram. The three band-edge frequencies (Gamma 1, K2, and M3) have different emission angles corresponding to the normal direction of the sample (0 degrees, 29 degrees, and 59.5 degrees).
Neutrino flavor ratio on Earth and at astrophysical sources
(2010-04-01)
Lai, Kwang-Chang
;
Lin, Guey-Lin
;
Liu, T. C.
;
物理研究所
;
Institute of Physics
We present the reconstruction of neutrino flavor ratios at astrophysical sources. For distinguishing the pion source and the muon-damped source to the 3 a level, the neutrino flux ratios, R equivalent to phi(nu(mu))/(phi(nu(e)) + phi(nu(r))) and S equivalent to phi(nu(e))/(phi(nu(r))), need to be measured in accuracies better than 10%. (C) 2010 Elsevier B.V. All rights reserved.
NEUTRINO FLAVOR RATIOS ON EARTH UNDER DECAY AND OSCILLATION SCENARIOS
(2013)
Liu, T. C.
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Lai, Kwang-Chang
;
Lin, Guey-Lin
;
物理研究所
;
Institute of Physics
In the neutrino propagation mechanisms, both neutrino oscillation and decay mechanisms, the actual neutrinos flavor ratio at astrophysical sources can be quite different from observed ratios on Earth.(1) We introduce the recent global fitting result of the mixing angle values(2) into the analysis to point out the allowed neutrino flavor ratios on Earth for standard neutrino oscillation and general decay mechanisms. In this analysis, four types of the neutrino decay mechanisms can be separated from the oscillation case easily with arbitary initial neutrino flavor ratio and the other four types of neutrino decay mechanisms can be identified from the oscillation case with the specified source. The rest types of neutrino decays strongly overlape with the oscillation and cannot be identified.
NEUTRINO FLAVOR RATIOS ON THE EARTH FOR DECAY AND OSCILLATION SCENARIOS
(2013-01-20)
Liu, T. C.
;
Lai, Kwang-Chang
;
Lin, Guey-Lin
;
物理研究所
;
Institute of Physics
Due to flavor transition mechanisms in neutrino propagations, both neutrino oscillation and decay, neutrinos flavor ratio at astrophysical sources can quite different from observed ratios on the Earth.(1) We use the recent global fitting result of the mixing angle values(2) to determine the allowed neutrino flavor ratios on the Earth for standard neutrino oscillation and general decay mechanisms. In this analysis, four types of the neutrino decay mechanisms can be distinguished from the oscillation case easily with arbitrary initial neutrino flavor ratio and the other four types of neutrino decay mechanisms can be distinguished from the oscillation case with the specified source. The rest types of neutrino decays strongly overlap with the oscillation and cannot be identified.
Simulation of the cosmic ray tau neutrino telescope (CRTNT) experiment
(2009-07-01)
Liu, J. L.
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Zhang, S. S.
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Cao, Z.
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He, H. H.
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Huang, M. A.
A tau lepton can be produced in a charged current interaction by a cosmic ray tau neutrino with material inside a mountain. If it escapes from the mountain, it will decay and initiate a shower in the air, which can be detected by an air shower fluorescence/Cherenkov light detector. Designed according to such a principle, the cosmic ray tau neutrino telescope (CRTNT) experiment, located at the foothill of Mt Balikun in Xinjiang, China, will search for very high-energy cosmic tau neutrinos from energetic astrophysical sources by detecting those showers. This paper describes a Monte Carlo simulation for a detection of t events by the CRTNT experiment. Ultra-high-energy cosmic ray events are also simulated to estimate the potential contamination. With the CRTNT experiment composed of four detector stations, each covering 64 degrees x 14 degrees field of view, the expected event rates are 28.6, 21.9 and 4.7 per year assuming an AGN neutrino flux according to Semikoz and Sigl (2004 J. Cosmol. Astropart. Phys. JCAP 04(2004)003), Mannheim-Protheroe-Rachen (MPR) active galactic nucleus (AGN) jet model and Stecker-Done-Salamon-Sommers (SDSS) AGN core model, respectively. Null detection of such a tau event by the CRTNT experiment in 1 year could set a 90% C. L. upper limit on 19.9 (eV cm(-2) s(-1) sr(-1)) for an E(-2) neutrino spectrum.