Write compensation using the thermal transfer function in an optical disk.
The theoretical basis for a write-compensation scheme is developed with a simplified thermal transfer function in an optical disk. The thermal transfer function is analytically approximated to a first-order exponential filter similar to that of an integrating circuit. A write-compensation method is then given directly by the inverse function of the filter. A simplified form of the compensation is also derived, and this is verified by experiments. This method eliminates the thermal interference and shows how to form mark edges uniformly for an arbitrary optical disk.
Simplified analysis of the readout waveform for an elliptical mark
A new, simplified readout waveform equation for an elliptical mark is analytically derived and confirmed. This approach easily treats an elliptical mark by using an equivalent rectangular mark having (delta) function width and equivalent readout beam spot. The equation is verified by comparison with precise numerical calculations. Good agreement is obtained for practical dimensions of optical recording. The equation gives the characteristics of the readout waveform directly from the elliptical mark.
Monte carlo simulation of events with Drell-Yan lepton pairs from antiproton-proton collisions
The complete knowledge of the nucleon spin structure at leading twist requires also addressing the transverse spin distribution of quarks, or transversity, which is yet unexplored because of its chiral-odd nature. Transversity can be best extracted from single-spin asymmetries in fully polarized Drell-Yan processes with antiprotons, where valence contributions are involved anyway. Alternatively, in single-polarized Drell-Yan the transversity happens convoluted with another chiral-odd function, which is likely to be responsible for the well known (and yet unexplained) violation of the Lam-Tung sum rule in the corresponding unpolarized cross section. We present Monte Carlo simulations for the unpolarized and single-polarized Drell-Yan pp{sup ({up_arrow}}{sup )}{yields}{mu}{sup +}{mu}{sup -}X at different center-of-mass energies in both configurations where the antiproton beam hits a fixed proton target or it collides on another proton beam. The goal is to estimate the minimum number of events needed to extract the above chiral-odd distributions from future measurements at the high energy storage ring (HESR) at GSI. It is important to study the feasibility of such experiments at HESR in order to demonstrate that interesting spin physics can be explored already using unpolarized antiprotons.