Hadrons have finite interaction size with dense material, a basic feature common to known forms of hadronic calorimeters (HCAL). We argue that substructure variables cannot use HCAL information to access the microscopic nature of jets much narrower t
han the hadronic shower size, which we call superboosted massive jets. It implies that roughly 15% of their transverse energy profile remains inaccessible due to the presence of long-lived neutral hadrons. This part of the jet substructure is also subject to order-one fluctuations. We demonstrate that the effects of the fluctuations are not reduced when a global correction to jet variables is applied. The above leads to fundamental limitations in the ability to extract intrinsic information from jets in the superboosted regime. The neutral fraction of a jet is correlated with its flavor. This leads to an interesting and possibly useful difference between superboosted W/Z/h/t jets and their corresponding backgrounds. The QCD jets that form the background to the signal superboosted jets might also be qualitatively different in their substructure as their mass might lie at or below the Sudakov mass peak. Finally, we introduce a set of zero-cone longitudinal jet substructure variables and show that while they carry information that might be useful in certain situations, they are not in general sensitive to the jet substructure.
Polarization of strange quarks is preserved to a high degree when they hadronize into Lambda baryons, as observed in Z decays at LEP. This opens up the possibility for ATLAS and CMS to use strange-quark polarization measurements as a characterization
tool for new physics scenarios that produce such quarks. Measurements in ttbar samples would be useful for obtaining additional information about the polarization transfer from the strange quark to the Lambda baryon. Already with 100/fb in Run 2, ttbar samples in ATLAS and CMS become competitive in sensitivity with the Z samples of the LEP experiments. Moreover, while the LEP measurements were done inclusively over all quark flavors, which makes their interpretation dependent on various modeling assumptions, ttbar events at the LHC offer multiple handles for disentangling the different contributions experimentally. We also discuss the possibility of measuring polarizations of up and down quarks.
