Abstract
The recent anomalies in $b\to s\ell^+\ell^-$ transitions could originate from some New Physics beyond the Standard Model. Either to confirm or to rule out this assumption, more tests of $b\to s\ell^+\ell^-$ transition are needed. Polarized $\Lambda_b$ decay to a $\Lambda$ and a dilepton pair offers a plethora of observables that are suitable to discriminate New Physics from the Standard Model. In this paper, we present a full angular analysis of a polarized $\Lambda_b$ decay to a $\Lambda(\to p\pi)\ell^+\ell^-$ final state. The study is performed in a set of the operator where the Standard Model operator basis is supplemented with its chirality flipped counterparts, and new scalar and pseudo-scalar operators. The full angular distribution is calculated by retaining the mass of the final state leptons. At the low hadronic recoil, we use the Heavy Quark Effective Theory framework to relate the hadronic form factors which lead to simplified expression of the angular observables where short- and long-distance physics factorize. Using the factorized expressions of the observables, we construct a number of tests of short- and long-distance physics including null tests of the Standard Model and its chirality flipped counterparts that can be carried out using experimental data.
Highlights
Several experimental results in the rare b → slþl− processes have shown deviations from the Standard Model (SM) predictions
Polarized Λb decay to a Λ and a dilepton pair offers a plethora of observables that are suitable to discriminate new physics from the Standard Model
Using the factorized expressions of the observables, we construct a number of test of short- and long-distance physics including null tests of the Standard Model and its chirality flipped counterparts that can be carried out using experimental data
Summary
Several experimental results in the rare b → slþl− processes have shown deviations from the Standard Model (SM) predictions. In this paper we revisit the polarized Λb → Λð→ pπÞlþl− decay and extend the previous SM angular distribution by supplementing the SM operator basis by its chirality-flipped counterparts ( SM0), and new scalar and pseudoscalar operators ( SP operators). All the 36 angular observables depend on ten form factors that have been calculated at large recoil in the framework of light cone sum-rules [18,19,28]. Large dilepton invariant mass squared q2, the decay can be described by a heavy quark effective theory (HQET) framework [29,30,31], which ensures relations between the form factors known as Isgur-Wise relations [32,33,34]. We give several appendixes where details of the derivations can be found
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