Phenomenological consequences of supersymmetry with anomaly-induced masses

TL;DR

AMSB proposes that soft SUSY-breaking terms arise from the super-Weyl conformal anomaly, yielding gaugino masses tied to beta-functions via $M_\lambda = (\beta_g/g) m_{3/2}$ and a spectrum dominated by anomaly-induced contributions. The authors define a minimal model with four inputs ($m_{3/2}$, $m_0$, $\tan\beta$, sign$(\mu)$), demonstrate viable electroweak symmetry breaking, and highlight distinctive phenomenology: a nearly degenerate Wino LSP, nearly degenerate sleptons, and unique collider signatures including dileptons with displaced vertices. They also analyze gravitino cosmology, showing that a heavy gravitino alleviates Big Bang nucleosynthesis constraints and can yield a non-thermal Wino relic density compatible with dark matter. Collectively, AMSB provides a tightly constrained, testable framework that yields clear experimental and cosmological signatures differentiating it from more conventional SUSY-breaking mechanisms.

Abstract

In the supersymmetric standard model there exist pure gravity contributions to the soft mass parameters which arise via the superconformal anomaly. We consider the low-energy phenomenology with a mass spectrum dominated by the anomaly-induced contributions. In a well-defined minimal model we calculate electroweak symmetry breaking parameters, scalar masses, and the full one-loop splitting of the degenerate Wino states. The most distinctive features are gaugino masses proportional to the corresponding gauge coupling beta-functions, the possibility of a Wino as the lightest supersymmetric particle, mass degeneracy of sleptons, and a very massive gravitino. Unique signatures at high-energy colliders include dilepton and single lepton final states, accompanied by missing energy and displaced vertices. We also point out that this scenario has the cosmological advantage of ameliorating the gravitino problem. Finally, the primordial gravitino decay can produce a relic density of Wino particles close to the critical value.

Figures (7)

• Figure 1: Masses of several states in the supersymmetric spectrum as a function of $m_0$ with $m_{3/2} =36\hbox{\rm,TeV}$, $\tan\beta =5$, and $\mu < 0$. The gaugino masses for this choice are $M_1=333\hbox{\rm,GeV}$, $M_2=119\hbox{\rm,GeV}$, and $M_3 =850\hbox{\rm,GeV}$.
• Figure 2: The mass splitting as a function of $M_2$ for $\tan\beta =2$. The solid curves, from top to bottom, represent $\mu=2M_2$, $\mu=3M_2$, $\mu=5M_2$, and $\mu=\infty$. The dashed curves are the same except for the opposite sign of $\mu$. The dot-dashed curve is the charged pion mass $m_{\pi^\pm}$.
• Figure 3: The mass splitting as a function of $M_2$ for $\tan\beta =10$. The solid curves, from top to bottom, represent $\mu=2M_2$, $\mu=3M_2$, $\mu=5M_2$, and $\mu=\infty$. The dashed curves are the same except for the opposite sign of $\mu$. The dot-dashed curve is the charged pion mass $m_{\pi^\pm}$.
• Figure 4: Dilepton signal from left-handed smuon and sneutrino production at the Fermilab Tevatron with $2\hbox{\rm,TeV}$ center of mass energy and $M_2=90\hbox{\rm,GeV}$. Acceptance cuts of the leptons are described in the text. The different curves are for $\tan\beta =1$, which makes $m_{\tilde{\mu}_L}=m_{\tilde{\nu}_L}$, and for $\tan\beta = \infty$ which maximizes the hypercharge $D$-term splitting such that $m_{\tilde{\mu}_L}^2=m_{\tilde{\nu}_L}^2+m_W^2$. With $30\hbox{\rm, fb}^{-1}$ the Tevatron will record more than 10 such events for each lepton flavor if $m_{\tilde{\nu}_L}<200\hbox{\rm,GeV}$.
• Figure 5: Contours of $100\% \times (m_{\tilde{e}_L}-m_{\tilde{e}_R})/m_{\tilde{e}_R}$ in the $M_2$-$m_{\tilde{e}_R}$ mass plane with large $\tan\beta$, which maximizes the mass splitting.