Academia Sinica

About: Academia Sinica is a facility organization based out in Taipei, Taiwan. It is known for research contribution in the topics: Population & Galaxy. The organization has 52086 authors who have published 65998 publications receiving 1728114 citations. The organization is also known as: Central Research Academy.

Planck 2013 results. XVII. Gravitational lensing by large-scale structure

Abstract: On the arcminute angular scales probed by Planck, the cosmic microwave background (CMB) anisotropies are gently perturbed by gravitational lensing. Here we present a detailed study of this e_ect, detecting lensing independently in the 100, 143, and 217 GHz frequency bands with an overall significance of greater than 25_.We use the temperature-gradient correlations induced by lensing to reconstruct a (noisy) map of the CMB lensing potential, which provides an integrated measure of the mass distribution back to the CMB last-scattering surface. Our lensing potential map is significantly correlated with other tracers of mass, a fact which we demonstrate using several representative tracers of large-scale structure. We estimate the power spectrum of the lensing potential, finding generally good agreement with expectations from the best-fitting _CDM model for the Planck temperature power spectrum, showing that this measurement at z = 1100 correctly predicts the properties of the lower-redshift, latertime structures which source the lensing potential. When combined with the temperature power spectrum, our measurement provides degeneracy breaking power for parameter constraints; it improves CMB-alone constraints on curvature by a factor of two and also partly breaks the degeneracy between the amplitude of the primordial perturbation power spectrum and the optical depth to reionization, allowing a measurement of the optical depth to reionization which is independent of large-scale polarization data. Discarding scale information, our measurement corresponds to a 4% constraint on the amplitude of the lensing potential power spectrum, or a 2% constraint on the root-mean-squared amplitude of matter fluctuations at z _ 2.

Measurement of the J/ψ meson and b-hadron production cross sections in pp̄ collisions at √s = 1960 GeV

Abstract: The authors present a new measurement of the inclusive and differential production cross sections of J/{psi} mesons and b-hadrons in proton-antiproton collisions at {radical}s = 1960 GeV The data correspond to an integrated luminosity of 397 pb{sup -1} collected by the CDF Run II detector They find the integrated cross section for inclusive J/{psi} production for all transverse momenta from 0 to 20 GeV/c in the rapidity range |y| 125 GeV/c They find the total cross section for b-hadrons, including both hadrons and anti-hadrons, decaying to J/{psi} with transverse momenta greater than 125 GeV/c in the rapidity range |y(J/{psi})| < 06, is 0330 {+-} 0005(stat){sub -0033}{sup +0036}(syst) {mu}b Using a Monte Carlo simulation of the decay kinematics of b-hadrons to all final states containing a J/{psi}, they extract the first measurement of the total single b-hadron cross section down to zero transverse momentum at {radical}s = 1960 GeV They find the total single b-hadron cross section integrated over all transverse momenta for b-hadrons in themore » rapidity range |y| < 06 to be 176 {+-} 04(stat){sub -23}{sup +25}(syst) {mu}b« less

Temperature-Dependent Fluorescence in Carbon Dots

Abstract: Carbon dots are cost-effective, environmental friendly, and biocompatible nanoparticles with many potential applications in optoelectronics and biophotonics. Their dual fluorescence bands were observed and could be attributed to core and surface state emission. We also conduct temperature-dependent fluorescence measurements from cryogenic to room temperatures. The dual emission bands exhibit similar temperature dependence. The strong electron–electron interactions and weak electron–phonon interactions could account for the very broad photoluminescence (PL) band even at 77 K. Our experimental results also suggest that carbon dots exhibit similar temperature behavior as metallic quantum dots (nanoclusters) but are different from inorganic semiconductor quantum dots. Here, for the first time, we present the temperature-dependent spectroscopic results to shed some light on the presently unclear fluorescence mechanism.