Exploring observable effects of scalar operators beyond SMEFT in the angular distribution of $B\to K^{*0} \tau^+ \tau^- $

TL;DR

This paper investigates how deviations from SMEFT relations among scalar operators can be detected through angular distributions in B meson decays, revealing potential signs of new physics beyond the Standard Model.

Contribution

It identifies specific angular observables in B→K*τ+τ− decays that can signal physics beyond SMEFT even when branching ratios show no deviations.

Findings

Angular observables S6c and A7 are sensitive to beyond SMEFT physics.

Deviations from SMEFT relations can be detected via angular distributions.

Certain new physics scenarios remain undetectable in branching ratios but are observable in angular analysis.

Abstract

The $SU(2)_L\times U(1)_Y$ invariance of the Standard Model Effective Field Theory (SMEFT) imposes relations among different low-energy effective field theory Wilson coefficients (WCs), any deviations from which would signal the presence of physics beyond SMEFT. In this work, we investigate two such relations ($C_S = -C_P$, $C_S^\prime = C_P^\prime$) among the scalar and the pseudoscalar new-physics WCs that can contribute to $b\to s \,\tau \tau $ processes. We show that, even when new physics violating these relations would not be measurable in the branching ratios of $B_s \to \tau^+ \tau^-$ and $B\to K^{(*)}\,\tau^+ \tau^-$ at HL-LHC and FCC-ee, it can still manifest itself in the angular distribution of $B\to K^{*0}\,\tau^+ \tau^-$. We identify the combinations of angular observables in this decay channel that are sensitive to scenarios beyond SMEFT. We find that the two observables $S_6^c$ and $A_7$, and their combination, have the potential to identify physics beyond SMEFT.