CP violation in correlated production and decay of unstable particles

Abstract

We study resonant CP-violating Einstein-Podolsky-Rosen correlations that may take place in the production and decay of unstable scalar particles at high-energy colliders. We show that as a consequence of unitarity and CPT invariance of the S-matrix, in 2 → 2 scatterings mediated by mixed scalar particles, at least three linearly independent decay matrices associated with the unstable scalar states are needed to obtain non-zero CP-odd observables that are also odd under C-conjugation. Instead, for the correlated production and decay of two unstable particle systems in 2 → 4 processes, we find that only two independent decay matrices are sufficient to induce a net non-vanishing CP-violating phenomenon. As an application of this theorem, we present numerical estimates of CP asymmetries for the correlated production and decay of supersymmetric scalar top-antitop pairs at the LHC, and demonstrate that these could reach values of order one. As a byproduct of our analysis, we develop a novel spinorial trace technique, which enables us to efficiently evaluate lengthy expressions of squared amplitudes describing the resonant scalar transitions.

Heavy scalar top quark decays in the complex MSSM: A full one-loop analysis

“…In this subsection we analyze the various partial decay widths 28 and branching ratios as a function of ' A t . The other parameters are chosen according to Table I.…”

“…[27], where an LHC specific analysis can be found in Ref. [28]. Finally, results in an effective Lagrangian approach can be found in Ref.…”

“…[27], again without specifying the production modes, and especially for the LHC in Ref. [28]. Depending on the realized cMSSM parameter space and on some further assumptions on the LHC performance, it seems to be possible to obtain limits on, e.g., the phases of M 1 , A t , and A b at the LHC.…”

Momentum asymmetries as CP violating observables

“…Once a large amount of data is accumulated and these properties are at least somewhat understood, the next step is to determine more challenging properties such as couplings, flavor structure, and CP violating phases. The determination of the latter has recently attracted increased attention [24][25][26][27][28][29][30][31][32][33][34]. In this paper, we study new techniques which can make the direct observation of CP violation at the LHC feasible.…”

Heavy scalar tau decays in the complex MSSM: a full one-loop analysis

“…[26] (with more details on the specific LHC analysis in Ref. [27]). Depending on the realized cMSSM parameter space and on some further assumptions on the LHC performance, it seems to be possible to obtain limits on, e.g., |A τ | and ϕ Aτ .…”