The light stop window

Abstract

We show that a right-handed stop in the 200–400 GeV mass range, together with a nearly degenerate neutralino and, possibly, a gluino below 1.5 TeV, follows from reasonable assumptions, is consistent with present data, and offers interesting discovery prospects at the LHC. Triggering on an extra jet produced in association with stops allows the experimental search for stops even when their mass difference with neutralinos is very small and the decay products are too soft for direct observation. Using a razor analysis, we are able to set stop bounds that are stronger than those published by ATLAS and CMS.

Appendix

In this appendix we derive the four-body stop decay width given in (24). In the limit of small mass difference (ΔM≪M _W ,m _t ), the amplitude for pure right-handed stop decay $\tilde{t}_{R} \to N b e^{+}\nu$ is

(A.1)

where P _i are the quadri-momenta of the particles involved. The decay width is given by

(A.2)

The 4-body phase space integral dϕ ⁽⁴⁾ can be analytically performed at leading order in $\Delta M =m_{\tilde{t}}- M_{\mathrm{DM}}$. Indeed, by writing the decay as $\tilde{t}\to XY\to(Ne)(b\nu)$, the amplitude for each sub-decay is separately Lorentz invariant. Thus, using

(A.3)

(A.4)

we get

(A.5)

(A.6)

where we have kept only the leading order in ΔM. From these expressions we obtain (24).