Spin correlations and new physics in $\tau$-lepton decays at the LHC

Abstract

We use spin correlations to constrain anomalous $\tau$-lepton couplings at the LHC including its anomalous magnetic moment, electric dipole moment and weak dipole moments. Single spin correlations are ideal to probe interference terms between the SM and new dipole-type couplings as they are not suppressed by the $\tau$-lepton mass. Double spin asymmetries give rise to $T$-odd correlations useful to probe $CP$ violation purely within the new physics amplitudes, as their appearance from interference with the SM is suppressed by $m_{\tau }$. We compare our constraints to those obtained earlier on the basis of deviations from the Drell-Yan cross-section.

25 pages, 11 figures, 14 tables. v2: added two subsections and relevant discussions, corresponds to version to be published at JHEP

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• $H\to {\tau }^{+}{\tau }^{-}\gamma$ as a Probe of the $\tau$ Magnetic Dipole Moment
• T-odd correlations from top-quark CEDM in lepton plus jets top-pair events
• Michel parameters in radiative muon decay
• Constraints on $\tau$ electromagnetic moments via tau pair production at the Muon colliders
• Measuring $CP$ nature of $h\tau \bar{\tau }$ coupling at $e^{-}p$ collider