$B_s \to \phi l^+ l^-$ decays in the topcolor-assisted technicolor model

TL;DR

This paper investigates how the topcolor-assisted technicolor model affects rare B_s decays into phi mesons and leptons, revealing significant sensitivity to new particles and potential deviations from Standard Model predictions.

Contribution

It provides updated calculations of new physics effects on B_s decays using light-cone QCD sum rules, highlighting the impact of charged top-pions and Z' bosons in the TC2 model.

Findings

Branching ratios can increase by a factor of 2 to 4 due to TC2 effects.

Forward-backward asymmetry varies by -9% to 22% for muons and -10% to 0% for taus.

Longitudinal polarization asymmetry P_L increases by over 30% for muons.

Abstract

Using the updated form factors within the light-cone QCD sum rule approach, we calculate the new physics contributions to rare semileptonic $\bar{B}_s \to \phi\mu^+\mu^-, \phi \tau^+\tau^-$ decays from the new particles appearing in the topcolor-assisted technicolor (TC2) model. In our evaluations, we find that: (i) the branching ratio, normalized forward-backward asymmetry and lepton polarization show highly sensitivity to charged top-pions contributions and little sensitivity to $Z'$ contributions. The TC2 enhancements to the branching ratios of these decays can reach a factor of $2 \sim 4$; (ii) the NP enhancement to the forward-backward asymmetry of the decay $B_s\to \phi \mu^+\mu^-$ is in the range -9% to 22%, but -10% to 0% for decay $B_s\to \phi \tau^+\tau^-$ compared to the SM predictions; (iii) the TC2 model provide an enhancement of more than 30% to the longitudinal polarization asymmetry $P_L$ for decay $B_s\to \phi \mu^+\mu^-$, but a decrease of about 20% to the transverse polarization asymmetry $P_T$ for the decay $B_s\to \phi \tau^+\tau^-$.