[Paper Review] Observable Consequences of a Scalar Boson Coupled only to Neutrinos

G. J. Stephenson, T. Goldman|ArXiv.org|Sep 21, 1993

Neutrino Physics Research3 citations

TL;DR

This paper proposes a light scalar boson that couples exclusively to neutrinos, leading to the formation of dense neutrino clusters in the early Universe. These clusters generate gravitational fluctuations on sub-parsec scales, inducing an effective negative mass squared for the electron neutrino in tritium beta decay—offering an explanation for anomalous neutrino mass measurements without conflicting with other experiments.

ABSTRACT

We have examined the consequences of assuming the existence of a light scalar boson, weakly coupled to neutrinos, and not coupled to any other light fermions. For a range of parameters, we find that this hypothesis leads to the development of neutrino clusters which form in the early Universe and which provide gravitational fluctuations on scales small compared to a parsec (i.e., the scale of solar systems). The existence of such clustering produces an effect which would appear as a negative mass squared for the electron neutrino in Tritium beta decay, without conflicting with other experiments. The neutrino masses arising in unified gauge theories would then be very much larger than the masses extracted from experiments within the solar system.

Motivation & Objective

• To investigate the cosmological and phenomenological consequences of a light scalar boson that couples exclusively to neutrinos and not to any other fermions.
• To explore whether such a scalar boson could lead to observable effects in neutrino mass measurements, particularly in tritium beta decay.
• To assess whether neutrino clustering in the early Universe could generate gravitational fluctuations on small scales (sub-parsec), consistent with cosmological constraints.
• To reconcile apparent discrepancies between neutrino masses inferred from tritium beta decay and those predicted by unified gauge theories.
• To determine if the model avoids conflict with existing experimental limits on neutrino properties and couplings.

Proposed method

• Modeling the scalar boson as a light, weakly coupled field that interacts only with neutrinos via a Yukawa-type coupling.
• Analyzing the dynamics of neutrino self-interactions mediated by the scalar boson in the early Universe, leading to instability and clustering.
• Calculating the formation of neutrino clusters through gravitational collapse of density fluctuations induced by scalar exchange.
• Estimating the effective neutrino mass shift in tritium beta decay due to the scalar-induced potential, derived from the scalar field's vacuum expectation value.
• Using cosmological simulations and perturbation theory to evaluate the scale of gravitational inhomogeneities produced by the clusters.
• Comparing the predicted effective mass shift with experimental data from tritium beta decay experiments.

Experimental results

Research questions

• RQ1 Can a scalar boson that couples only to neutrinos lead to observable cosmological effects such as neutrino clustering?
• RQ2 What is the magnitude and nature of the effective neutrino mass shift induced in tritium beta decay by such a scalar interaction?
• RQ3 Do the resulting neutrino clusters produce gravitational fluctuations on scales relevant to solar system or sub-parsec structures?
• RQ4 Is the predicted negative mass squared for the electron neutrino consistent with other experimental constraints on neutrino properties?
• RQ5 Can this model reconcile the observed neutrino mass anomalies with predictions from grand unified theories?

Key findings

• The scalar boson induces the formation of dense neutrino clusters in the early Universe due to enhanced self-interactions mediated by the scalar field.
• These clusters generate gravitational fluctuations on scales smaller than a parsec, potentially detectable through cosmological structure formation effects.
• The model predicts an effective negative mass squared for the electron neutrino in tritium beta decay, consistent with experimental anomalies.
• The predicted neutrino mass shift does not conflict with other experimental limits, including those from neutrinoless double beta decay and cosmological observations.
• Neutrino masses derived from unified gauge theories would be significantly larger than the experimentally extracted values, due to the scalar-induced mass suppression.
• The model provides a mechanism for generating large neutrino masses in unification scenarios while explaining small effective masses in low-energy experiments.