Goran Senjanovi{ć} | Searcharxiv

arXiv1995

Stringy Unification Helps See-Saw Mechanism

In this paper we explore the possibility of intermediate scale physics in the context of superstring models with {\it higher Kac-Moody levels}, by focusing on left-right and Pati-Salam symmetries. We find that the left-right scale may lie in the range $10^{10} - 10^{12}$ GeV which is favored by neutrino physics, while the Pati-Salam scale is at most two or three orders of magnitude below the unification scale $M_X$. We also show that the scale of $B-L$ breaking can be as low as 1 TeV or so, providing protection against too rapid proton decay in supersymmetry. Our results allow a natural value for the scale $M_X \sim 10^{18}$ GeV and the agreement with the experiment requires the value of $\sin^2 {θ_w}$ at $M_X$ to be in general very different from the usually assumed $3/8$.

hep-ph↗

arXiv1994

Topologically Stable Z - Strings in the Supersymmetric Standard Model

We show that the minimal supergravity extension of the standard model automatically contains topologically stable electroweak strings if the hidden sector is invariant under the exact R-symmetry. These defects appear in the form of the semiglobal R-strings, which necessarily carry $Z$-flux inside their core. This result is independent from the particular structure of the hidden sector. Discussed strings differ fundamentally from the embedded $Z$-strings. If R-symmetry is explicitly broken (e.g. due to an anomaly), the decay of the semiglobal strings may have important implications for the baryogenesis.

hep-ph↗