Polarized $\Lambda_b$ baryon decay to $p\pi$ and a dilepton pair

TL;DR

This paper provides a comprehensive angular analysis of polarized $ ext{Lambda}_b$ decay to $ ext{p} ext{π}$ and dileptons, aiming to identify potential signals of New Physics beyond the Standard Model through detailed observable tests.

Contribution

It introduces a full angular distribution analysis including lepton mass effects, considering extended operators beyond the Standard Model, and proposes tests to discriminate New Physics.

Findings

Derives simplified angular observables at low recoil using Heavy Quark Effective Theory.

Constructs null tests of the Standard Model and chirality-flipped operators.

Provides a framework for experimental tests to detect New Physics signals.

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.