Precision gaugino mass measurements as a probe of large trilinear soft terms at the ILC

In supersymmetric models with radiatively driven naturalness, Higgsino-like electroweak-inos are expected to lie in a mass range 100–300 GeV, the lighter the more natural. Such states can be pair produced at high rates at the International Linear $e^{+}{e}^{-}$ Collider where their masses are nearly equal to the value of the superpotential $\mu$ parameter while their mass splittings depend on the gaugino masses $M_1$ and $M_2$. The gaugino masses in turn depend on trilinear soft terms—the $A$ parameters, which are expected to lie in the multi-TeV range owing to the 125 GeV Higgs mass—via two-loop contributions to renormalization group running. We examine the extent to which the International Linear $e^{+}{e}^{-}$ Collider is sensitive to large $A$ terms via precision electroweak-ino mass measurement. Extraction of gaugino masses at the percent level or below should allow for interesting probes of large trilinear soft supersymmetry breaking terms under the assumption of unified gaugino masses.

Figure 1

The $A_0$ vs $m_0$ parameter plane for $\mu =150\mathrm{GeV}$, $m_{1/2}=1\mathrm{TeV}$, $\tan \beta =10$, and $m_A=2\mathrm{TeV}$. We show contours of $m_h=123$, 125, and 127 GeV (red, green, and blue). We also show contours of ${\mathrm{\Delta }}_{\mathrm{EW}}=30$, 100, and 400. The intersection of $m_h\simeq 125\mathrm{GeV}$ and low ${\mathrm{\Delta }}_{\mathrm{EW}}$ occurs along the edges of the allowed region at very large values of $A_0$.

Figure 2

Evolution of gaugino masses in radiatively driven natural SUSY for large positive and negative and small trilinear soft SUSY breaking terms.

Figure 3

Ratios of weak-scale gaugino masses vs $m_0$ for $A_0=\pm 1.6m_0$, $\pm 1.8m_0$, and $\pm 2m_0$ for $m_{1/2}=1\mathrm{TeV}$, $\tan \beta =10$, $\mu =150\mathrm{GeV}$, and $m_A=2\mathrm{TeV}$. Frame (a) shows gaugino mass ratio $M_2/M_1$, (b) shows $M_3/M_1$ and (c) shows $M_3/M_2$.

Figure 4

Ratios of weak-scale gaugino masses vs $A_0$ for $m_{1/2}=1\mathrm{TeV}$, $\tan \beta =10$, $\mu =150\mathrm{GeV}$, and $m_A=2\mathrm{TeV}$ but with $m_0$ scanned over the range 0–15 TeV and $-20\mathrm{TeV}<A_0<+20\mathrm{TeV}$. Frame (a) shows gaugino mass ratio $M_2/M_1$, (b) shows $M_3/M_1$ and (c) shows $M_3/M_2$.

Figure 5

In (a), we show the running of the gauge couplings, and in (b), we show the running of the gaugino masses in the G2 MSSM model of Ref. [56] with $m_0=24.2\mathrm{TeV}$; $A_0=25.2\mathrm{TeV}$ (or $m_{3/2}=35\mathrm{TeV}$, $C=0.52$); $\tan \beta =8$; $\mu =1.4\mathrm{TeV}$; and $M_1(m_{\mathrm{GUT}})=1.02\mathrm{TeV}$, $M_2(m_{\mathrm{GUT}})=0.73\mathrm{TeV}$, and $M_3(m_{\mathrm{GUT}})=0.59\mathrm{TeV}$.

Figure 6

Locus of benchmark point (black) and scan points (purple) which are consistent with the suite of ILC precision EW-ino and Higgs measurements as stated in text. Frame (a) shows gaugino mass ratio $M_2/M_1$, (b) shows $M_3/M_1$ and (c) shows $M_3/M_2$.

Figure 7

Locus of benchmark point (black) and scan points (red for $A_0>0$ and blue for $A_0<0$) which are consistent with the suite of ILC precision EW-ino and Higgs measurements as stated in text.