U(1)_A symmetry in two-doublet models, U bosons or light scalars, and psi and Upsilon decays

TL;DR

This paper investigates how decays of psi and Upsilon mesons can be used to detect light bosons from an extra U(1) symmetry, constraining their couplings and implications for supersymmetric models.

Contribution

It provides new bounds on the couplings of light U(1)-associated bosons to quarks and leptons based on recent decay data, informing models with light scalars or vectors.

Findings

Constraints on axial, pseudoscalar, and scalar couplings to b quarks.

Limits on couplings to electrons from decay data.

Implications for the composition and decay rates of light bosons.

Abstract

psi and Upsilon decays may be used to search for light neutral spin-1 or spin-0 bosons associated with a broken extra-U(1) symmetry, local or global, acting axially on quarks and leptons, as may be present in supersymmetric theories with a lambda H_1 H_2 S superpotential term. Recent data on Upsilon --> gamma + invisible neutral constrain an axial, pseudoscalar or scalar coupling to b to f_bA < 4 10^-7 m_U(MeV)/ sqrt B_inv, f_bP < 4 10^-3/ sqrt B_inv or f_bS < 6 10^-3/ sqrt B_inv, respectively. This also constrains, from universality properties, couplings to electrons to f_eA < 4 10^-7 m_U(MeV)/ sqrt B_inv, f_eP < 4 10^-7/ sqrt B_inv or f_eS < 6 10^-7/ sqrt B_inv. The pseudoscalar a (possibly traded for a light gauge boson, or scalar particle) should then be, for invisible decays of the new boson, for > 96 % singlet and < 4 % doublet, for tan beta > 1. Or, more generally, < 4 % /(tan^2 beta B_inv) doublet, which implies a very small rate for the corresponding psi decay, B (psi --> gamma + neutral) B_inv <~ 10^-6/ tan^4 beta. Similar results are obtained for new spin-1 or spin-0 neutral bosons decaying into mu+ mu-.