Supersymmetry Breaking through Transparent Extra Dimensions

TL;DR

The paper introduces a brane-world mechanism for supersymmetry breaking in extra dimensions, where MSSM matter is confined to a brane and gauge fields live in the bulk. SUSY breaking on a distant source brane communicates predominantly to gauginos, while direct scalar masses are highly suppressed, so the MSSM at the compactification scale has nonzero gaugino masses with negligible scalar masses; these scalars are then generated radiatively through renormalization group running, yielding positive masses and addressing the flavor problem. A concrete gauge-mediation–like example shows gaugino masses $m_ extlambda$ arise with four-dimensional strength, while scalar masses are suppressed by $(M L)^2$ relative to usual gauge mediation, making the high-scale boundary condition nearly gaugino-dominated. Phenomenologically, the spectrum after RG running features a gravitino LSP with a stau NLSP in most cases, a spectrum that depends on the compactification scale $L^{-1}$, and distinctive collider signals; the approach remains compatible with gauge unification and offers a potential window into the size of the extra dimensions.

Abstract

We propose a new framework for mediating supersymmetry breaking through an extra dimension. It predicts positive scalar masses and solves the supersymmetric flavor problem. Supersymmetry breaks on a ``source'' brane that is spatially separated from a parallel brane on which the standard model matter fields and their superpartners live. The gauge and gaugino fields propagate in the bulk, the latter receiving a supersymmetry breaking mass from direct couplings to the source brane. Scalar masses are suppressed at the high scale but are generated via the renormalization group. We briefly discuss the spectrum and collider signals for a range of compactification scales.

Figures (4)

• Figure 1: Loop diagram through the bulk, illustrating how scalar masses are acquired (and suppressed).
• Figure 2: Evolution of several soft masses as a function of the renormalization scale with the input parameters $L^{-1} = 10^{16}$ GeV, $M_{1/2} = 350$ GeV, and $\tan\beta = 10$. The (top, middle, bottom) dashed lines correspond to ($M_3$, $M_2$, $M_1$), while the solid lines from top to bottom correspond to $m_{\tilde{Q}_1}$, $m_{H_d}$, $m_{\tilde{\tau}_1}$, ${\rm sign}(m_{H_u}^2) |m_{H_u}^2|^{1/2}$ respectively. (The kink in the up-type Higgs mass is due to taking the square-root.)
• Figure 3: The weak scale masses for several sparticles are shown as a function of the compactification scale $L^{-1}$ with $M_{1/2} = 500$ GeV and $\tan\beta = 3$. The top dotted line is $m_{\tilde{g}}$, the top and bottom solid lines are $m_{\tilde{u}_L}$ and $m_{\tilde{\tau}_1}$, and the top and bottom dashed lines are $m_{\tilde{N}_3}$ and $m_{\tilde{N_1}}$. We emphasize that $L^{-1}$ is parameter of our model not to be confused with the renormalization scale.
• Figure 4: The lower bound on $M_{1/2}$ as a function of the compactification scale obtained by requiring that all charged sparticles and the lightest Higgs are heavier than the current LEP limit (of about $90$ GeV). The contours correspond to the limits for particular values of $\tan\beta$.