One-loop SQCD corrections to the decay of top squarks to charm and neutralino in the generic MSSM

Abstract

In this article we calculate the one-loop supersymmetric QCD (SQCD) corrections to the decay iq -► cx°{ in the minimal supersymmetric standard model with generic flavor structure. This decay mode is phenomenologically important if the mass difference between the lightest squark tq (which is assumed to be mainly stoplike) and the neutralino lightest supersymmetric particle/j is smaller than the top mass. In such a scenario fq -*• tx°{ is kinematically not allowed and searches for iq -> W bx\ and ii] -> cx® are performed. A large decay rate for iq -* c can weaken the LHC bounds from iq -► Wbx® which are usually obtained under the assumption Br[iq -» Wb/®} = 100%. We find the SQCD corrections enhance F[iq -> cx?] by approximately 10% if the flavor violation originates from bilinear terms. If flavor violation originates from trilinear terms, the effect can be ±50% or more, depending on the sign of A'. We note that connecting a theory of supersymmetry breaking to LHC observables, the shift from the DR to the on-shell mass is numerically very important for light stop decays.

The MSSM without gluinos; an effective field theory for the stop sector

“…The three-body decayt 1 → W bχ 0 1 was analyzed theoretically in [26] and experimentally in [27]. Finally the decayt 1 → cχ 0 1 and the less important four-body decayt 1 →χ 0 1 d i ff are treated in [28][29][30] and constraints were derived by the ATLAS collaboration from the monojet analysis in [31]. Some bounds can be avoided in kinematic boundary regions or once non-minimal flavour violation is included.…”

Improving the sensitivity of stop searches with on-shell constrained invariant mass variables

“…Stop production has long been recognized as a viable SUSY discovery channel [12][13][14][15][16][17][18][19][20] and has been looked for at LEP [21][22][23][24][25] and the Tevatron [26][27][28], as well as at the LHC [7,9,[29][30][31][32][33][34][35][36][37][38][39][40][41][42]. Searches for the stop are especially well-motivated theoretically because in many models, the stop is expected to be the lightest squark for three principal reasons:…”

“…[14,15,19,20]. Finally, there can also be loop-induced two-body decays, e.g.t → cχ 0 i [14][15][16]. In this paper we shall focus on the most challenging scenario, in which the stop produces 2 the same visible particles as a top quark decaying leptonically.…”

Resonant Higgs pair production as a probe of stop at the LHC

“…For instance, when mt 1 > m t + mχ0 1 andt 1 mainly decays to tχ 0 1 , the top quark from stop decay can be quite energetic and a stop mass up to 940 GeV for a massless lightest neutralino has been excluded by the very recent LHC run-2 data [17]. When the flavor-conserving two body decays channels liket 1 → tχ 0 1 andt 1 → bχ + 1 are kinematically forbidden, the primary decay channels of the light stop would be the three-body decayt 1 → W + bχ 0 1 , the two-body flavor-changing decayt 1 → cχ 0 1 or the four-body decayt 1 → bf fχ 0 1 [18][19][20][21][22][23][24][25]. The current null results of LHC searches for these decay channels have correspondingly excluded the stop mass up to ∼ 500 GeV, 310 GeV and 370 GeV for certain mass splitting between the stop and the LSP [17].…”