Abstract
We present a simple extension of the Standard Model that leads to renormalizable long-range vector-mediated neutrino self-interactions. This model can resolve the Hubble tension by delaying the onset of neutrino free-streaming during recombination, without conflicting with other measurements. The extended gauge, scalar and neutrino sectors lead to observable signatures, including invisible Higgs and $Z$ decays, thereby relating the Hubble tension to precision measurements at the LHC and future colliders. The model has a new neutrinophilic gauge boson with $m_{Z'}\sim\mathcal{O}(10~\mathrm{eV})$ and charged Higgses at a few $100~\mathrm{GeV}$. It requires hidden neutrinos with active-hidden mixing angles larger than $5\times10^{-4}$ and masses in the range $1\div300\mathrm{eV}$, which could also play a role for short baseline neutrino oscillation anomalies.
Highlights
There is convincing evidence that neutrinos played a substantial role during the epoque of big bang nucleosynthesis (BBN) at T ∼ MeV, closely monitored by early element abundances
The lowest temperature scale indirectly probed for neutrinos is T ∼ eV, where observations of the cosmic microwave background (CMB) fit well to a history of our universe that does comply with the cosmological standard model (ΛCDM), and with the expectation of the Standard Model of particle physics (SM), including exactly three generations of neutrinos
We have presented a consistent model that leads to vectormediated neutrino self-interactions
Summary
There is convincing evidence that neutrinos played a substantial role during the epoque of big bang nucleosynthesis (BBN) at T ∼ MeV, closely monitored by early element abundances. Evidence is accumulating for a discrepancy between local measurements of today’s Hubble rate H0 [1,2,3,4,5] and therelike global determinations based on ΛCDM together with CMB [6], baryonic acoustic oscillations (BAO) and large scale structure (LSS) datasets [7,8,9,10,11,12,13,14,15,16], and for an increasing tension in other parameters [17,18] Resolving these discrepancies might require a modification of ΛCDM, preferentially, perhaps, shortly before the era of recombination [19,20]. Scale, say after a phase transition, and subsequently integrate it out to obtain a decoupling behavior of neutrinos during CMB resembling (1) In this way, neutrinos recouple by the new interactions only after BBN, and fall out of equilibrium during recombination, see Fig. 1.
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