Method to measure quarkonium wave function using $B_c$ decay

TL;DR

This paper introduces a novel experimental method to directly measure the quarkonium wave function via the three-body decay of the $B_c$ meson, linking decay product distributions to the wave function in pNRQCD.

Contribution

It presents a new approach to experimentally access the quarkonium wave function through $B_c$ decay, which was previously not possible.

Findings

Momentum distribution of the spectator c-quark is proportional to the wave function's square.

Method provides the first direct experimental probe of the quarkonium wave function.

Potential to improve understanding of quarkonium structure in QCD.

Abstract

We propose a method that enables a direct experimental probe of the quarkonium wave function defined in potential nonrelativistic QCD (pNRQCD) using the three-body decay of the $B_c$ meson. We show that the momentum distribution of the spectator $c$-quark in the partonic decay is proportional to the absolute square of the momentum-space wave function of the $B_c$ state. It would provide, for the first time, an experimentally accessible probe of the quarkonium wave function.