We point out that if neutron--antineutron oscillation is observed in a free neutron oscillation experiment, it will put an upper limit on the strengths of Lorentz invariance violating (LIV) mass operators for neutrons at the level of $10^{-23}$ GeV o
r so, which would be the most stringent LIV limit for neutrons. We also study constraints on $Delta B=2$ LIV operators and find that for one particular operator degaussing is not necessary to obtain a visible signal. We also note that observation of $n-bar{n}$ oscillation signal in the nucleon decay search experiment involving nuclei does not lead to any limit on LIV operators since the nuclear potential difference between neutron and antineutrons will mask any Lorentz violating effect.
This article provides a brief overview of some of the theoretical aspects of R-parity violation (RPV) in the minimal supersymmetric standard model (MSSM) and its extensions. Both spontaneous and explicit RPV models are discussed and some consequences
are outlined. In particular, it is emphasized that the simplest supersymmetric theories based on local B-L predict that R-parity must be a broken symmetry, a fact which makes a compelling case for taking R-parity breaking seriously in discussions of supersymmetry phenomenology.
The Baryon-Lepton difference ($B-L$) is increasingly emerging as a possible new symmetry of the weak interactions of quarks and leptons as a way to understand the small neutrino masses. There is the possibility that current and future searches at col
liders and in low energy rare processes may provide evidence for this symmetry. This paper provides a brief overview of the early developments that led to B-L as a possible symmetry beyond the standard model, and also discusses some recent developments.
We present a simple model for a 7 keV scalar dark matter particle which also explains the recently reported anomalous peak in the galactic X-ray spectrum at 3.55 keV in terms of its two photon decay. The model is arguably the simplest extension of th
e Standard Model, with the addition of a real scalar gauge singlet field subject to a reflection symmetry. This symmetry breaks spontaneously at an energy scale of a few MeV which triggers the decay of the dark matter particle into two photons. In this framework, the Higgs boson of the Standard Model is also the source of dark matter in the Universe. The model fits the relic dark matter abundance and the partial lifetime for two photon decay, while being consistent with constraints from domain wall formation and dark matter self-interactions. We show that all these features of the model are preserved in its natural embedding into a simple dark $U(1)$ gauge theory with a Higgs mechanism. The properties of the dark photon get determined in such a scenario. High precision cosmological measurements can potentially test these models, as there are residual effects from domain wall formation and non-negligible self-interactions of dark matter.
