Microwave polarization in the direction of galaxy clusters induced by the CMB quadrupole anisotropy

Electron scattering induces a polarization in the cosmic microwave background (CMB) signal measured in the direction of a galaxy cluster due to the presence of a quadrupole component in the CMB temperature distribution. Measuring the polarization towards distant clusters provides the unique opportunity to observe the evolution of the CMB quadrupole at moderate redshifts, z~0.5-3. We demonstrate that for the local cluster population the polarization degree will depend on the cluster celestial position. There are two extended regions in the sky, which are opposite to each other, where the polarization is maximal, 0.1(tau/0.02) microK in the Rayleigh-Jeans part of the CMB spectrum (tau being the Thomson optical depth across the cluster) exceeding the contribution from the cluster transverse peculiar motion if v_t<1300 km/s. One can hope to detect this small signal by measuring a large number of clusters, thereby effectively removing the systematic contribution from other polarization components produced in clusters. These polarization effects, which are of the order of (v_t/c)^2 tau, (v_t/c) tau^2 and (kT_e/m_ec^2) tau^2, as well as the polarization due to the CMB quadrupole, were previously calculated by Sunyaev and Zel'dovich for the Rayleigh-Jeans region. We fully confirm their earlier results and present exact frequency dependencies for all these effects. The polarization is considerably higher in the Wien region of the CMB spectrum.Comment: 8 pages, 5 figures, submitted to MNRA

Neutral-to-charged current events ratio in atmospheric neutrinos and neutrino oscillations

The atmospheric neutrinos produce isolated neutral pions ($\pi^0$-events) mainly in the neutral current interactions. We propose to study the ratios involving $\pi^0$-events and the events induced mainly by the charged currents. This minimizes uncertainties related to the original neutrino fluxes, and in certain cases, also to the cross-sections. Experimental study of these ratios will allow one to check the oscillation solution of the atmospheric neutrino problem and to identify the channel of oscillations. Illustrative analysis of existing data is presented.Comment: LaTeX, 17 pages, 1 figure. Major changes, illustrative analysis of the Super-Kamiokande results is presente