Speaker
Description
In this work, we introduce a novel technique for measuring the longitudinal and transverse polarization fractions of boosted hadronic $W$ boson decays. We propose a jet substructure observable, $p_{\theta}$, derived from subjet energies, serving as a proxy for the
$W$ boson's parton-level decay polar angle in its rest-frame. This observable is sensitive to $W$ boson polarization and offers lower reconstruction errors than existing proxies, especially for highly boosted $W$ bosons. Looking forward to an optimistic scenario with $10 \, \text{ab}^{-1}$ of data at the High Luminosity LHC, our technique could achieve a 20% error in measuring the transverse $W$ polarization fraction. Although detecting longitudinal polarization consistent with the Standard Model at the $2\sigma$ level may remain challenging, this method holds potential for identifying enhancements in Beyond Standard Model scenarios, thereby contributing to unitarity restoration studies.
| Field of contribution | Phenomenology |
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