Split extended supersymmetry from intersecting branes

TL;DR

The paper shows how split extended supersymmetry can arise from intersecting D-brane constructions in string theory by turning on small angle deformations $ε$, which generate tree-level scalar masses $m_0^2\sim ε M_s^2$ while permitting loop-induced Dirac gaugino masses $m_{1/2}^D \sim m_0^2/M_s$ and a Higgsino mass $μ \sim m_0^4/M_s^3$ in extended SUSY gauge sectors. The key theoretical tool is a one-loop annulus amplitude with appropriate vertex operators, whose bosonic and fermionic correlators reveal the dominant contributions from $N=2$ sectors; in the SUSY limit, oscillators cancel and the result depends on the momentum lattice and brane separation. A detailed calculation shows how Dirac gaugino and Higgsino masses arise, with $ ilde{D}$-term breaking and messenger sectors mediating SUSY breaking to the visible sector. The authors also present a concrete string model with the Standard Model gauge group, three generations, and gauge coupling unification, and discuss an alternative suppression mechanism via large extra dimensions. Overall, the work provides a explicit, calculable mechanism for realizing TeV-scale fermionic superpartners alongside heavy scalars in a string-theoretic framework, with clear predictions for the mass hierarchy and potential phenomenological implications.

Abstract

We study string realizations of split extended supersymmetry, recently proposed in hep-ph/0507192. Supersymmetry is broken by small ($ε$) deformations of intersection angles of $D$-branes giving tree-level masses of order $m_0^2\sim εM_s^2$, where $M_s$ is the string scale, to localized scalars. We show through an explicit one-loop string amplitude computation that gauginos acquire hierarchically smaller Dirac masses $m_{1/2}^D \sim m_0^2/M_s$. We also evaluate the one-loop Higgsino mass, $μ$, and show that, in the absence of tree-level contributions, it behaves as $μ\sim m_0^4/M_s^3$. Finally we discuss an alternative suppression of scales using large extra dimensions. The latter is illustrated, for the case where the gauge bosons appear in N=4 representations, by an explicit string model with Standard Model gauge group, three generations of quarks and leptons and gauge coupling unification.

Figures (3)

• Figure 1: Rectangular (left panel) and tilted (right panel) tori.
• Figure 2: Non-supersymmetric states stretching between the two-branes induce at one-loop masses for the gauginos on each brane.
• Figure 3: Higgsinos are localized at the intersection of branes $a$ and $c$. Non-supersymmetric states stretching between the branes $(a,b)$ and $(c,b)$ induce at one-loop masses for the Higgsinos.