Browsing by Author "Tseng, JJ"

Now showing 1 - 9 of 9

A new look at the pair-production width in a strong magnetic field
(2000-12-07)
Kao, WF
;
Lin, GL
;
Tseng, JJ
;
物理研究所
;
Institute of Physics
We reexamine the process gamma --> e(+) + e(-) in a background magnetic field comparable to B-c equivalent to m(e)(2)/e male. This process is known to be non-perturbative in the magnetic-field strength. However, it can be shown that the moments of the above pair production width are proportional to the derivatives of photon polarization function at the zero energy, which is perturbative in B. Hence, the pair-production width can be easily obtained from the latter by the inverse Mellin transform. The implications of our approach are discussed. (C) 2000 Published by Elsevier Science B.V.
Comparison of high-energy galactic and atmospheric tau neutrino flux
(2003-01-01)
Athar, H
;
Cheung, KM
;
Lin, GL
;
Tseng, JJ
;
物理研究所
We compare the tau neutrino flux arising from the galaxy and the earth atmosphere for 10(3) <= E/GeV <= 10(11). The intrinsic and oscillated tau neutrino fluxes from both sources are calculated. The intrinsic galactic v(tau) flux (E >= 10(3) GeV) is calculated by considering the interactions of high-energy cosmic-rays with the matter present in our galaxy, whereas the oscillated galactic v, flux is coming from the oscillation of the galactic v(mu), flux. For the intrinsic atmospheric v, flux, we extend the validity of a previous calculation from E <= 10(6) GeV up to E <= 10(11) GeV. The oscillated atmospheric v, flux is, on the other hand, rather suppressed. We find that, for 10(3) <= E/GeV <= 5.10(7), the oscillated v(tau) flux along the galactic plane dominates over the maximal intrinsic atmospheric v(tau) flux, i.e., the flux along the horizontal direction.
Comparison of high-energy galactic and atmospheric tau neutrino flux
(2003-03-01)
Athar, H
;
Cheung, K
;
Lin, GL
;
Tseng, JJ
;
物理研究所
We compare the tau neutrino flux arising from the galaxy and the earth atmosphere for 10(3) less than or equal to E/GeV less than or equal to 10(11). The intrinsic and oscillated tau neutrino fluxes from both sources are calculated. The intrinsic galactic nu(tau) flux (E greater than or equal to 10(3) GeV) is calculated by considering the interactions of high-energy cosmic-rays with the matter present in our galaxy, whereas the oscillated galactic nu(tau) flux is coming from the oscillation of the galactic nu(mu) flux. For the intrinsic atmospheric nu(tau) flux, we extend the validity of a previous calculation from E less than or equal to 10(6) GeV up to E less than or equal to 10(11) GeV. The oscillated atmospheric nu(tau) flux is, on the other hand, rather suppressed. We find that, for 10(3) less than or equal to E/GeV less than or equal to 5 x 10(7), the oscillated nu(tau) flux along the galactic plane dominates over the maximal intrinsic atmospheric nu(tau) flux, i.e., the flux along the horizontal direction. We also briefly mention the presently envisaged prospects for observing these high-energy tau neutrinos. (C) 2002 Elsevier Science B.V. All rights reserved.
Energy spectrum of tau leptons induced by the high energy Earth-skimming neutrinos
(2003-09-15)
Tseng, JJ
;
Yeh, TW
;
Athar, H
;
Huang, MA
;
Lee, FF
We present a semianalytic calculation of the tau-lepton flux emerging from the Earth induced by incident high energy neutrinos interacting inside the Earth for 10(5)less than or equal toE(nu)/GeVless than or equal to10(10). We obtain results for the energy dependence of the tau-lepton flux coming from the Earth-skimming neutrinos, because of the neutrino-nucleon charged-current scattering as well as the resonant (nu) over bar (e)e(-) scattering. We illustrate our results for several anticipated high energy astrophysical neutrino sources such as the active galactic nuclei, the gamma-ray bursts, and the Greisen-Zatsepin-Kuzmin neutrino fluxes. The tau-lepton fluxes resulting from rock-skimming and ocean-skimming neutrinos are compared. Such comparisons can render useful information about the spectral indices of incident neutrino fluxes.
Neutrino-photon scattering and its crossed processes in a background magnetic field
(1999-11-04)
Chyi, TK
;
Hwang, CW
;
Kao, WF
;
Lin, GL
;
Ng, KW
We study the neutrino-photon processes such as gamma gamma --> , v gamma --> v gamma, and --> gamma gamma in a background magnetic field smaller than the critical magnetic field Bc + m(e)(2)/e. Using Schwinger's formalism, we extract leading magnetic-field contributions to the above processes. Our result is valid throughout the kinematic regime where both neutrino and photon energies are significantly smaller than m(w). We briefly discuss the astrophysical implications of our result. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
On analytic properties of the photon polarization function in a background magnetic field
(2001-12-13)
Kao, WF
;
Lin, GL
;
Tseng, JJ
;
物理研究所
;
Institute of Physics
We examine the analytic properties of the photon polarization function in a background magnetic field, using the technique of inverse Mellin transform. The photon polarization function is first expressed as a power series of the photon energy omega with omega < 2m(e). Based upon this energy expansion and the branch cut of the photon polarization function in the complex omega plane. we compute the absorptive part of the polarization function with the inverse Mellin transform. Our results are valid for arbitrary photon energies and magnetic-fieid strengths. The applications of our approach are briefly discussed. (C) 2001 Published by Elsevier Science B.V.
Pev cosmic neutrinos from the mountains
(2004-05-30)
Yeh, P
;
Athar, H
;
La Barbera, N
;
Bouaissi, S
;
Catalano, O
The NuTel collaboration is building a wide field-of-view Cerenkov telescope to be installed on a mountain site for observing near horizontal air showers emerging from another mountain. Cosmic tau neutrinos is the primary source of such showers. This technique will be realized for the first time in the v, energy range of 2 PeV to 1000 PeV. The telescope has enough sensitivity to observe cosmic neutrinos from sources like Active Galactic Nuclei and Galactic Center assuming fluxes from current theoretical models.
Phenomenology of Higgs bosons in the Zee model
(2001-09-01)
Kanemura, S
;
Kasai, T
;
Lin, GL
;
Okada, Y
;
Tseng, JJ
To generate small neutrino masses radiatively, the Zee model introduces two Higgs doublets and one weak-singlet charged Higgs boson to its Higgs sector. From analyzing the renormalization group equations, we determine the possible range of the lightest CP-even Higgs boson (h) mass and the Higgs boson self-couplings as a function of the cutoff scale beyond which either some of the coupling constants are strong enough to invalidate the perturbative analysis or the stability of the electroweak vacuum is no longer guaranteed. Using the results obtained from the above analysis, we find that the singlet charged Higgs boson can significantly modify the partial decay width of h --> gamma gamma via radiative corrections, and its collider phenomenology can also be drastically different from that of the charged Higgs bosons in the usual two-Higgs-doublet models.
Weak-field expansion for processes in a homogeneous background magnetic field
(2000-11-15)
Chyi, TK
;
Hwang, CW
;
Kao, WF
;
Lin, GL
;
Ng, KW
The weak-field expansion of the charged fermion propagator under a uniform magnetic field is studied. Starting from Schwinger's proper-time representation, we express the charged fermion propagator as an infinite series corresponding to different Landau levels. This infinite series is then reorganized according to the powers of the external field strength B. For illustration, we apply this expansion to gamma --> nu<()over bar> and nu --> nu gamma decays, which involve charged fermions in the internal loop. The leading and subleading magnetic-field effects to the above processes are computed.