Abstract
Based on the standard model (SM) of particle physics, we study the decays $\Lambda_b \to \Lambda \ell^+ \ell^-$ in light of the available inputs from lattice and the data from LHCb. We fit the form-factors of this decay mode using the available theory and experimental inputs after defining different fit scenarios and checking their consistencies. The theory inputs include the relations between the form-factors in heavy quark effective theory (HQET) and soft collinear effective theory (SCET) at the endpoints of di-lepton invariant mass squared $q^2$. Utilizing the fit results, we have predicted a few observables related to this mode. We have also predicted the observable $R_{\Lambda} = Br(\Lambda_b \to \Lambda \ell_i^+\ell_i^- )/Br(\Lambda_b \to \Lambda \ell_j^+\ell_j^-)$ where $\ell_{i}$ and $\ell_j$ are charged leptons of different generations ($i \ne j$). At the moment, we do not observe noticeable differences in the extracted values of the observables in fully data-driven and SM like fit scenarios.
Highlights
The flavor-changing neutral current (FCNC) b → s transitions play an important role in indirect searches for new physics (NP)
The theory inputs include the relations between the form factors in heavy quark effective theory and soft collinear effective theory at the end points of the dilepton invariant mass squared q2
We present a couple of fits after incorporating the available inputs on the form factors at max recoil from QCD light-cone sum rules (LCSR) at nextto-leading logarithmic accuracy [16]
Summary
The flavor-changing neutral current (FCNC) b → s transitions play an important role in indirect searches for new physics (NP). In addition to the uncertainty in the form factors, some angular observables of Λb decays are plagued by the dependence of the detection efficiencies on the production polarization (PΛb). Our main objective in this analysis is to test whether or not all of the available inputs (for example, experimental data, lattice data, and other theory inputs from the QCD modeling of the form factors) for the form factors in Λb → Λlþl− decays are consistent with each other. There exists a number of relations between the form factors of the above-mentioned decay modes in the heavy quark effective theory (HQET). On the other hand, using these HQET and SCET relations as inputs while extracting the q2 distributions of the form factors may help to reduce the uncertainties of the extracted values of the Λb → Λlþl− observables. RlΛi=lj 1⁄4 ðBrðΛb → Λlþi l−i ÞÞ=ðBrðΛb → Λlþj l−j ÞÞ, where li and lj are charged leptons of different generations (i ≠ j), and give predictions for these observables using our fit results
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