Xiaochuan Lu: Constraining BSM custodial violations beyond the oblique framework
BSM custodial violations are believed to be strongly constrained by electroweak precision measurements. In particular, they result in a nonzero Peskin-Takeuchi T parameter, which is experimentally bounded at the per-mille level. However, the T parameter constraint only applies to oblique BSM physics. When the BSM effects are not oblique, T parameter is no longer an observable, and it fails to serve as an indicator of BSM custodial violations. We take a first step at addressing this problem by working with SMEFT at the dim-6 and tree level. We identify new observables that can serve as unambiguous indicators of BSM custodial violations. March 15, 2021
BSM custodial violations are believed to be strongly constrained by electroweak precision measurements. In particular, they result in a nonzero Peskin-Takeuchi T parameter, which is experimentally bounded at the per-mille level. However, the T parameter constraint only applies to oblique BSM physics. When the BSM effects are not oblique, T parameter is no longer an observable, and it fails to serve as an indicator of BSM custodial violations. We take a first step at addressing this problem by working with SMEFT at the dim-6 and tree level. We identify new observables that can serve as unambiguous indicators of BSM custodial violations. March 15, 2021