Wolfenstein potentials for neutrinos induced by ultra-light mediators
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Springer
Received: October 8, 2019 Accepted: November 20, 2019 Published: December 5, 2019
Alexei Yu. Smirnova,b and Xun-Jie Xua a
Max-Planck-Institut f¨ ur Kernphysik, Postfach 103980, D-69029 Heidelberg, Germany b Abdus Salam International Centre for Theoretical Physics (ICTP), I-34100 Trieste, Italy
E-mail: [email protected], [email protected] Abstract: New physics can emerge at low energy scales, involving very light and very weakly interacting new particles. These particles can mediate interactions between neutrinos and usual matter and contribute to the Wolfenstein potential relevant for neutrino oscillations. We compute the Wolfenstein potential in the presence of ultra-light scalar and vector mediators and study the dependence of the potential on the mediator mass mA , taking the finite size of matter distribution (Earth, Sun, supernovae) into consideration. For ultra-light mediators with m−1 A comparable to the size of the medium (R), the usual −2 mA dependence of the potential is modified. In particular, when m−1 A R, the potential does not depend on mA . Taking into account existing bounds on light mediators, we find that for the scalar case significant effects on neutrino propagation are not possible, while for the vector case large matter effects are allowed for mA ∈ [2 × 10−17 , 4 × 10−14 ] eV and the gauge coupling g ∼ 10−25 . Keywords: Neutrino Physics, Solar and Atmospheric Neutrinos ArXiv ePrint: 1909.07505
c The Authors. Open Access, Article funded by SCOAP3 .
https://doi.org/10.1007/JHEP12(2019)046
JHEP12(2019)046
Wolfenstein potentials for neutrinos induced by ultra-light mediators
Contents 1
2 Effects of light mediators on neutrino propagation
2
3 Effective potentials for spherically symmetric density distributions
4
4 Phenomenology
8
5 Conclusion
1
11
Introduction
Coherent forward scattering of neutrinos on particles of medium ψ (ψ = e− , n, p) generates the Wolfenstein potential VW [1]. Being added to the neutrino evolution equation, VW can significantly affect neutrino oscillations, known as the Mikheyev-Smirnov-Wolfenstein (MSW) effect [1–3]. When neutrino-matter interactions are mediated by a heavy boson with the interaction radius m−1 A (where mA is the mediator mass) much smaller than the object in which neutrinos propagate (or the distance over which the density varies), the Wolfenstein potential equals gν gψ VW = nψ , (1.1) m2A where nψ is the number density of the ψ particles, gν and gψ are the couplings of mediator to ν and ψ respectively. The potential depends on the local number density nψ while the size and shape of the object are not relevant. The medium can be considered as infinite. In the standard model (SM), the mediators are the W and Z bosons, satisfying the condition for (1.1). New heavy particles beyond the SM can generate via non-standard interactions additional contributions to the Wolfenstein potential with the same form as (1.1). New neutrino interactions may be mediated by light particles as well, if the light mediators are very weakly c
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