Abstract
Interest has been directed recently towards low energy implications of a non-trivial conformal sector of an effective field theory with an IR fixed point (ΛU), manifest in terms of “unparticles” with bizarre properties. We re-examine the implications of the limits on decay lifetimes of solar neutrinos for unparticle interactions. We study in detail the fundamental parameter space (ΛU,M) and derive bounds on the energy scale M characterizing the new physics. We work strictly within the framework where conformal invariance holds down to low energies. We first assume that couplings of the unparticle sector to the Higgs field are suppressed and derive bounds with ΛU in the TeV region from neutrino decay into scalar unparticles. These bounds are significant for values of the anomalous dimension of the unparticle operator 1.0<d≲1.2. For a region of the parameter space, we show that the bounds are comparable to those arising from production rates at high energy colliders. We then relax our assumption, by considering a more natural framework which does not require a priori restrictions on couplings of Higgs-unparticle operators, and derive bounds with ΛU in meV region from neutrino decay into vector unparticles. Such low scales for the IR fixed point are relevant in gauge theories with many flavors.
Highlights
A conformal hidden sector, which couples to the various gauge and matter fields of the Standard Model (SM), has been advocated by Georgi [1]
The phenomenology of the unparticle has been explored by many groups [2] and lower bounds on ΛU have already been derived by considering production rates at high energy colliders [3, 4] and unparticle emission from the core of SN1987 A [5]
The striking agreement between solar and KamLAND data determines a unique solution in the mass-mixing parameter space, dubbed the Mikheyev-Smirnov-Wolfenstein Large Mixing Angle (LMA) solution [12]
Summary
A conformal hidden sector, which couples to the various gauge and matter fields of the Standard Model (SM), has been advocated by Georgi [1]. As shown in [7], one of the bizarre implications of the conformal hidden sector is that neutrinos would become unstable: a neutrino mass eigenstate νj can decay into a another eigenstate νi via νj → νi U, where U is the invisible unparticle. In this Letter we re-examine the impact of solar and KamLAND neutrino data on the effective couplings between neutrinos and unparticle operators.
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