872 research outputs found
The Lamb shift contribution of very light millicharged particles
The leading order vacuum polarization contribution of very light millicharged
fermions and scalar (spin-0) particles with charge \epsilon e and mass \mu to
the Lamb shift of the hydrogen atom is shown to imply universal, i.e.
\mu-independent, upper bounds on \epsilon: \epsilon \lsim 10^{-4} for \mu \lsim
1 keV in the case of fermions, and for scalars this bound is increased by a
factor of 2. This is in contrast to expectations based on the commonly used
approximation to the Uehling potential relevant only for conventionally large
fermion (and scalar) masses.Comment: 10 pages including 3 figures, version to appear in Physical Review D
(Rapid Communications
Effect of Thermal Annealing on Boron Diffusion, Micro-structural, Electrical and Magnetic properties of Laser Ablated CoFeB Thin Films
We report on Boron diffusion and subsequent crystallization of
CoFeB (CoFeB) thin films on SiO/Si(001) substrate
using pulsed laser deposition. Secondary ion mass spectroscopy reveals Boron
diffusion at the interface in both amorphous and crystalline phase of CoFeB.
High-resolution transmission electron microscopy reveals a small fraction of
nano-crystallites embedded in the amorphous matrix of CoFeB. However, annealing
at 400C results in crystallization of CoFe with \textit{bcc} structure
along (110) orientation. As-deposited films are non-metallic in nature with the
coercivity (H) of 5Oe while the films annealed at 400C are metallic
with a H of 135Oe.Comment: 16 pages, 6 figure
On the transport equations of cosmic neutrinos passing through Earth and secondary nu_mu fluxes
The convergence of the iterative solutions of the transport equations of
cosmic muon and tau neutrinos propagating through Earth is studied and
analyzed. For achieving a fast convergence of the iterative solutions of the
coupled transport equations of nu_tau, nubar_tau and the associated tau^{\pm}
fluxes, a new semi-analytic input algorithm is presented where the peculiar
tau-decay contributions are implemented already in the initial zeroth order
input. Furthermore, the common single transport equation for muon neutrinos is
generalized by taking into account the contributions of secondary nu_mu and
nubar_mu fluxes due to the prompt tau-decay tau -> nu_mu initiated by the
associated tau flux. Differential and total nadir angle integrated upward-going
mu^- + mu^+ event rates are presented for underground neutrino telescopes and
compared with the muon rates initiated by the primary nu_mu, nu_tau and tau
fluxes.Comment: Version to appear in PR
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