Cross-correlation Power Spectra and Cosmic Birefringence of the CMB via Photon-neutrino Interaction

TL;DR

This paper investigates how photon-neutrino interactions can generate observable TB and EB power spectra in the CMB, offering insights into the cosmic neutrino background and its properties through polarization measurements.

Contribution

It introduces a novel analysis of CMB polarization induced by photon-neutrino interactions, considering both Majorana and Dirac neutrinos, and constrains neutrino asymmetries using Planck data.

Findings

Photon-neutrino interactions generate non-zero TB and EB spectra.

Estimated cosmic birefringence angle for Majorana neutrinos is about 0.2 radians.

The predicted birefringence exceeds Planck's observed value by two orders.

Abstract

In the context of the standard model of particles, the weak interaction of cosmic microwave background (CMB) and cosmic neutrino background (C$\nu$B), can generate non-vanishing TB and EB power spectra in the order of one loop forward scattering, in the presence of scalar perturbation, which is in contrast with the standard scenario cosmology. Comparing our results with the current experimental data may provide, significant information about the nature of C$\nu$B, including CMB-C$\nu$B forward scattering for TB, TE, and EB power spectra. To this end, different cases were studied, including Majorana C$\nu$B and Dirac C$\nu$B. On the other hand, it was shown that the mean opacity due to cosmic neutrino background could behave as an anisotropic birefringent medium and change the linear polarization rotation angle. Considering the contributions from neutrino and anti-neutrino forward scattering with CMB photons (in the case of Dirac neutrino), we introduce relative neutrino and anti-neutrino density asymmetry ($\delta_\nu=\frac{\Delta n_\nu}{n_\nu}=\frac{n_\nu-n_{\bar{\nu}}}{n_\nu}$). Then, using the cosmic birefringence angle reported by the Planck data release $\beta=0.30^\circ\pm0.11^\circ$ ($68\%C.L.$), some constraints can be put on $\delta_\nu$. Also, the value of cosmic birefringence due to Majorana C$\nu$B medium is estimated at about $\beta|_\nu\simeq0.2$ rad. In this respect, since Majorana neutrino and anti-neutrino are exactly the same, both CB contributions will be added together. However, this value is at least two orders larger than the cosmic birefringence angle reported by the Planck data release, $\beta=0.30^\circ\pm0.11^\circ$ ($68\%C.L.$).