John March-Russell

Abstract:

Maximally Natural Supersymmetry, an unusual weak-scale supersymmetric extension of the Standard Model based upon the inherently higher-dimensional mechanism of Scherk-Schwarz supersymmetry breaking (SSSB), possesses remarkably good fine tuning given present LHC limits. Here we construct a version with precision $SU(2)_{\rm L} \times U(1)_{\rm Y} $ unification: $\sin^2 \theta_W(M_Z) \simeq 0.231$ is predicted to $\pm 2\%$ by unifying $SU(2)_{\rm L} \times U(1)_{\rm Y} $ into a 5D $SU(3)_{\rm EW}$ theory at a Kaluza-Klein scale of $1/R_5 \sim 4.4\,{\rm TeV}$, where SSSB is simultaneously realised. Full unification with $SU(3)_{\rm C}$ is accommodated by extending the 5D theory to a $N=4$ supersymmetric $SU(6)$ gauge theory on a 6D rectangular orbifold at $1/R_6 \sim 40 \,{\rm TeV}$. TeV-scale states beyond the SM include exotic charged fermions implied by $SU(3)_{\rm EW}$ with masses lighter than $\sim 1.2\,{\rm TeV}$, and squarks in the mass range $1.4\,{\rm TeV} - 2.3\,{\rm TeV}$, providing distinct signatures and discovery opportunities for LHC run II.

Abstract:

CP violation, which is crucial for producing the baryon asymmetry of the Universe, is enhanced in particle-antiparticle oscillations. We study particle-antiparticle oscillations [of a particle with mass O(100 GeV)] with CP violation in the early Universe in the presence of interactions with O(ab-fb) cross sections. We show that if baryon-number-violating interactions exist, a baryon asymmetry can be produced via out-of-equilibrium decays of oscillating particles. As a concrete example we study a U(1)R-symmetric, R-parity-violating supersymmetry model with pseudo-Dirac gauginos, which undergo particle-antiparticle oscillations. Taking bino to be the lightest U(1)R-symmetric particle, and assuming it decays via baryon-number-violating interactions, we show that bino-antibino oscillations can produce the baryon asymmetry of the Universe.