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Register a new userNucleon Decay and $n$-$bar n$ Oscillations in a Left-Right Symmetric Model with Large Extra Dimensions
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We study baryon-number-violating processes, including proton and bound neutron decays and $n-bar n$ oscillations, in a left-right-symmetric (LRS) model in which quarks and leptons have localized wavefunctions in extra dimensions. In this model we show that, while one can easily suppress baryon-number-violating nucleon decays well below experimental bounds, this does not suppress $n-bar n$ transitions, which may occur at levels comparable to current limits. This is qualitatively similar to what was found in an extra-dimensional model with a Standard-Model low-energy effective field theory (SMEFT). We show that experimental data imply a lower limit on the mass scale $M_{n bar n}$ characterizing the physics responsible for $n-bar n$ oscillations in the LRS model that is significantly higher than in the extra-dimensional model using a SMEFT and explain the reason for this. Our results provide further motivation for new experiments to search for $n - bar n$ oscillations.
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We consider baryon-number-violating nucleon and dinucleon decays to leptonic final states in the context of a left-right symmetric (LRS) model with large extra dimensions. Specifically, we study (a) nucleon to trilepton decays with $Delta B=-1$ and $Delta L=-3$, and (b) dinucleon to dilepton decays with $Delta B=-2$ and $Delta L=-2$. In the LRS model, $B-L$ is gauged and is spontaneously broken by a Higgs vacuum expectation value $v_R$, which characterizes the scale at which processes violating $B-L$ occur. We show that together with the lower bound on $v_R$ from experimental limits on $n$-$bar n$ oscillations, constraints from searches for other nucleon decay modes imply sufficient suppression of these nucleon to trilepton and dinucleon to dilepton decay modes in this model to agree with experimental bounds.
We consider a model where right-handed neutrinos propagate in a large compactified extra dimension, engendering Kaluza-Klein (KK) modes, while the standard model particles are restricted to the usual 4-dimensional brane. A mass term mixes the KK modes with the standard left-handed neutrinos, opening the possibility of change the 3 generation mixing pattern. We derive bounds on the maximum size of the extra dimension from neutrino oscillation experiments. We show that this model provides a possible explanation for the deficit of nu_e in Ga solar neutrino calibration experiments and of the anti-nu_e in short baseline reactor experiments.
It is known that limits on baryon-violating nucleon decays do not, in general, imply corresponding suppression of $n - bar n$ transitions. In the context of a model with fermions propagating in higher dimensions, we investigate a related question, namely the implications of limits on $Delta L=-1$ proton and bound neutron decays mediated by four-fermion operators for rates of nucleon decays mediated by $k$-fermion operators with $k =6$ and $k=8$. These include a variety of nucleon and dinucleon decays to dilepton and trilepton final states with $Delta L=-3, -2, 1$, and $2$. We carry out a low-energy effective field theory analysis of relevant operators for these decays and show that, in this extra-dimensional model, the rates for these decays are strongly suppressed and hence are in accord with experimental limits.
Neutron-antineutron oscillations are considered in the light of recently proposed particle models, which claim to resolve the neutron lifetime anomaly, indicating the existence of baryon violating $Delta B=1$ interactions. Possible constraints are derived coming from the non-observation of neutron-antineutron oscillations, which can take place if the dark matter particle produced in neutron decay happens to be a Majorana fermion. It is shown that this can be realised in a simple MSSM extention where only the baryon number violating term $u^cd^cd^c$ is included whilst all other R-parity violating terms are prevented to avoid rapid proton decay. It is demostrated how this scenario can be implemented in a string motivated GUT broken to MSSM by fluxes.
We present a minimal left-right symmetric flavor model and analyze the predictions for the neutrino sector. In this scenario, the Yukawa sector is shaped by the dihedral $D_4$ symmetry which leads to correlations for the neutrino mixing parameters. We end up with four possible solutions within this model. We further analyzed the impact of the upcoming long-baseline neutrino oscillation experiment DUNE. Due to its high sensitivity, DUNE will be able to rule out two of the solutions. Finally, the prediction for the neutrinoless double beta decay for the model has also been examined.
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