Abstract
We study the potential observation at the LHC of CP-violating effects in stop production and subsequent cascade decays, $gg\to \tilde{t}_{i}\tilde{t}_{i}$ , $\tilde{t}_{i}\to t\tilde{\chi}^{0}_{j}$ , $\tilde{\chi}^{0}_{j}\to \tilde{\chi}^{0}_{1}\ell^{+}\ell^{-}$ , within the Minimal Supersymmetric Standard Model. We study T-odd asymmetries based on triple products between the different decay products. There may be a large CP asymmetry at the parton level, but there is a significant dilution at the hadronic level after integrating over the parton distribution functions. Consequently, even for scenarios where large CP intrinsic asymmetries are expected, the measurable asymmetry is rather small. High luminosity and precise measurements of masses, branching ratios and CP asymmetries may enable measurements of the CP-violating parameters in cascade decays at the LHC.
Highlights
We study the potential observation at the Large Hadron Collider (LHC) of CP-violating effects in stop production and subsequent cascade decays, gg → ti ti, ti → tχj0, χj0 → χ10 + −, within the Minimal Supersymmetric Standard Model
The Minimal Supersymmetric Standard Model (MSSM) is a compelling extension of the Standard Model that may soon be explored at the Large Hadron Collider (LHC)
If the MSSM is realised in Nature, the supersymmetry scale should be within reach of the LHC design centre-of-mass energy of 14 TeV [1, 2]
Summary
The Minimal Supersymmetric Standard Model (MSSM) is a compelling extension of the Standard Model that may soon be explored at the Large Hadron Collider (LHC). We consider the situation where the χ20 decay is a three-body decay; this leads to CP violation as there is a non-negligible contribution from interference diagrams This process involves the three phases φM1 , φμ and φAt ; we discuss below the combinations to which this process is sensitive. In [21], further CP sensitive asymmetries formed from the momentum of the b quark in the top decay were studied under the assumption of 2-body neutralino decays into on-shell sleptons, namely Tb = pb · (p + × p − ) and Ttb = pb · (pt × p ± ) These variables are sensitive to φM1 and φAt , but they have different dependences on the CP-violating phases as described in Sect. The appendices contain details of the Lagrangian, the expression for the squared amplitude including full spin correlations, and the kinematics of the phase space in the laboratory system
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