Limits on Neutrino Mixing with new Heavy Particles

D. Tommasini; E. Nardi; E. Roulet

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Limits on Neutrino Mixing with new Heavy Particles

E. Nardi, E. Roulet, D. Tommasini

High Energy Physics - Phenomenology · Submitted 3 Feb 1994

abstract compiled · 2026-09-23 · no language-model review

The authors' main claim If no assumption on the type of neutrinos involved in the mixing is made, we find $\snue^2<0.0071$, $\snumu^2<0.0014$ and $\snutau^2<0.033$.

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What the abstract itself states, as probabilities: claims first 0.03 · states limitation 0.39 · human participants 0.02 · controlled comparison 0.07 · randomized assignment 0.01 · states quantitative result 0.99 · compares with prior results 0.85 · mentions code or data availability 0.02.

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We study the effects induced by new neutral fermions below their mass threshold, due to their possible mixing with the standard neutrinos. We use as experimental constraints the recent results on lepton universality, together with the measurement of the $\mu$ decay rate and the updated LEP data. In particular, the inclusion in our data set of the most recent determinations of the $\tau$ branching fractions, mass and lifetime implies that a previous indication of a non-vanishing mixing for $\nu_\tau$ is no longer present. We obtain new stringent limits on the mixing parameters between $\nu_e$, $\nu_\mu$, $\nu_\tau$ and heavy neutral states of different weak isospin. If no assumption on the type of neutrinos involved in the mixing is made, we find $\snue^2<0.0071$, $\snumu^2<0.0014$ and $\snutau^2<0.033$.

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#	sentence	role	the authors' own work	states the main conclusion	strength
s0	We study the effects induced by new neutral fermions below their mass threshold, due to their possible mixing with the standard neutrinos.	contribution 0.99	0.81	0.04	asserted 0.47
s1	We use as experimental constraints the recent results on lepton universality, together with the measurement of the $\mu$ decay rate and the updated LEP data.	method 1.00	0.54	0.02	asserted 0.99
s2	In particular, the inclusion in our data set of the most recent determinations of the $\tau$ branching fractions, mass and lifetime implies that a previous indication of a non-vanishing mixing for $\nu_\tau$ is no longer present.	result 0.59	0.72	0.13	asserted 0.96
s3	We obtain new stringent limits on the mixing parameters between $\nu_e$, $\nu_\mu$, $\nu_\tau$ and heavy neutral states of different weak isospin.	result 0.82	0.95	0.58	asserted 1.00
s4	If no assumption on the type of neutrinos involved in the mixing is made, we find $\snue^2<0.0071$, $\snumu^2<0.0014$ and $\snutau^2<0.033$.	result 1.00	0.97	0.78	asserted 1.00

What kind of paper the classifier reports this is: theoretical result 0.90 · evidence from analysis of existing data 1.00.

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Original abstract

We study the effects induced by new neutral fermions below their mass threshold, due to their possible mixing with the standard neutrinos. We use as experimental constraints the recent results on lepton universality, together with the measurement of the $\mu$ decay rate and the updated LEP data. In particular, the inclusion in our data set of the most recent determinations of the $\tau$ branching fractions, mass and lifetime implies that a previous indication of a non-vanishing mixing for $\nu_\tau$ is no longer present. We obtain new stringent limits on the mixing parameters between $\nu_e$, $\nu_\mu$, $\nu_\tau$ and heavy neutral states of different weak isospin. If no assumption on the type of neutrinos involved in the mixing is made, we find $\snue^2<0.0071$, $\snumu^2<0.0014$ and $\snutau^2<0.033$.

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32 arXiv papers cite this in 41 sentences

Each citing sentence is taken from the citing paper's LaTeX source and typed by Pith's classifier. A label appears at probability 0.8 or more (0.95 for support), a contest at 0.7 or more; the quoted words are the citing authors'. How each label was checked · JSON

Papers citing it · 25 sentences without a confident label

Uses its data or values 4 papers

A combined analysis of an old set of unitarity bounds [ref] , which does not include the one from the CKM matrix determination, leads to the following limits at 90% C.L. $|V_e4|^2 < 0.012, |V_μ4|^2< 0.0096 |V_τ4|^2 <0.016.$ If the CKM matrix constraint is included and partial cancellations between the contributions of different flavors are taken into account, a previous combined study [ref] then gives the more robust limits at $90%$ C.L., $|V_e4|^2 < 0.0066, |V_μ4|^2< 0.0060$ and $|V_τ4|^2 <0.018$.

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If we parametrize the non-unitary leptonic mixing matrix $N$ as [ref] [equation] where $η$ is Hermitian and $U$ is unitary, then $η_αβ$ is related to the coefficient matrix $c_αβ^d=6$ by [equation] In [ref] , the following constraints on these parameters at the $90 %$ C.L. were derived: $η_ee<2.0 ·10^-3$, $η_e μ<5.9 ·10^-5$, $η_e τ<1.6 ·10^-3$, $η_μμ<8.2 ·10^-4$, $η_μτ<1.0 ·10^-3$ and $η_ττ<2.6 ·10^-3$.

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They are constrained by global fits to high precision electroweak data at the level of $δ_e ≲2×10^-3$, $δ_μ≲2×10^-4$ and $δ_τ≲5×10^-3$ [ref] .

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Compares with it 1 paper

In the cases that had been analyzed before [ref] , we find more stringent limits (at the few per cent level).

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Cites it as background 10 papers

Universality constraints derived from the CKM matrix elements [ref] as well as from pion decay [ref] has been extensevily analyzed and dedicated studies have been devoted to this subject [ref] .

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Commonly, the non-unitary effects are searched in the oscillation experiments, searching an anomaly in the number of neutrino species that are detected [ref] .

Non-unitary limits on different textures for low-scale seesaw models · Non-unitary effects · 0.93
The non-unitarity of the leptonic mixing matrix induced by the presence of heavy neutrinos has been studied in several works (see for instance [ref] ).

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