# Looking for $B\rightarrow X_s \ell^+\ell^-$ in non-minimal Universal Extra Dimensional model

## TL;DR

This paper investigates how non-minimal Universal Extra Dimensional models affect the decay process B→Xsℓ+ℓ−, calculating contributions from Kaluza-Klein states and deriving constraints on the size of extra dimensions based on experimental data.

## Contribution

It introduces the effects of boundary localized terms in UED models on B decay observables and provides new lower bounds on the compactification radius from experimental constraints.

## Key findings

- Lower limit on inverse radius R^{-1} ≥ 760 GeV from branching ratio data.
- Boundary localized terms significantly alter Kaluza-Klein contributions.
- Forward Backward asymmetry offers limited constraints in this model.

## Abstract

Non-vanishing boundary localised terms significantly modify the mass spectrum and various interactions among the Kaluza-Klein excited states of 5-Dimensional Universal Extra Dimensional scenario. In this scenario we compute the contributions of Kaluza-Klein excitations of gauge bosons and third generation quarks for the decay process $B\rightarrow X_s\ell^+\ell^-$ incorporating next-to-leading order QCD corrections. We estimate branching ratio as well as Forward Backward asymmetry associated with this decay process. Considering the constraints from some other $b \to s$ observables and electroweak precision data we show that significant amount of parameter space of this scenario has been able to explain the observed experimental data for this decay process. From our analysis we put lower limit on the size of the extra dimension by comparing our theoretical prediction for branching ratio with the corresponding experimental data. Depending on the values of free parameters of the present scenario, lower limit on the inverse of the radius of compactification ($R^{-1}$) can be as high as $\geq 760$ GeV. {Even this value could slightly be higher if we project the upcoming measurement by Belle II experiment.} Unfortunately, the Forward Backward asymmetry of this decay process would not provide any significant limit on $R^{-1}$ in the present model.