Collisional production of sterile neutrinos via secret interactions and cosmological implications

Alessandro Mirizzi, Gianpiero Mangano, Ofelia Pisanti, and Ninetta Saviano
Phys. Rev. D 91, 025019 – Published 22 January 2015

Abstract

Secret interactions among sterile neutrinos have been recently proposed as an escape route to reconcile eV sterile neutrino hints from short-baseline anomalies with cosmological observations. In particular models with coupling gX102 and gauge boson mediators X with MX10MeV lead to large matter potential suppressing the sterile neutrino production before the neutrino decoupling. With this choice of parameter ranges, big-bang nucleosynthesis is left unchanged and gives no bound on the model. However, we show that at lower temperatures when active-sterile oscillations are no longer matter suppressed, sterile neutrinos are still in a collisional regime, due to their secret self-interactions. The interplay between vacuum oscillations and collisions leads to a scattering-induced decoherent production of sterile neutrinos with a fast rate. This process is responsible for a flavor equilibration among the different neutrino species. We explore the effect of this large sterile neutrino population on cosmological observables. We find that a signature of strong secret interactions would be a reduction of the effective number of neutrinos Neff at matter radiation equality down to 2.7. Moreover, for MXgXMeV sterile neutrinos would be free-streaming before becoming nonrelativistic and they would affect the large-scale structure power spectrum. As a consequence, for this range of parameters we find a tension of an eV mass sterile state with cosmological neutrino mass bounds.

  • Figure
  • Received 14 October 2014

DOI:https://doi.org/10.1103/PhysRevD.91.025019

© 2015 American Physical Society

Authors & Affiliations

Alessandro Mirizzi1, Gianpiero Mangano2, Ofelia Pisanti2,3, and Ninetta Saviano4

  • 1II Institut für Theoretische Physik, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
  • 2Istituto Nazionale di Fisica Nucleare - Sezione di Napoli, Complesso Universitario di Monte Sant’Angelo, I-80126 Napoli, Italy
  • 3Dipartimento di Fisica, Università di Napoli Federico II, Complesso Universitario di Monte Sant’Angelo, I-80126 Napoli, Italy
  • 4Department of Physics, Institute for Particle Physics Phenomenology, Durham University, Durham DH1 3LE, United Kingdom

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Issue

Vol. 91, Iss. 2 — 15 January 2015

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