Experimental constraints on the possible J^PC quantum numbers of the X(3872)

TL;DR

This study uses angular correlations and mass distribution analysis of X(3872) decay products to constrain its quantum numbers, strongly favoring J^PC = 1++ but not excluding 2++.

Contribution

It provides experimental constraints on the J^PC quantum numbers of X(3872) using angular and mass distribution analyses in B decay data.

Findings

J^PC = 0++ and 0-+ are ruled out.

S-wave decay favors J^PC = 1++ over P-wave.

J^PC = 2++ remains a possible assignment.

Abstract

We examine possible J^PC quantum number assignments for the X(3872). Angular correlations between final state particles in X(3872) --> pi+pi- J/psi decays are used to rule out J^PC values of 0++ and 0-+. The shape of the pi+pi- mass distribution near its upper kinematic limit favors S-wave over P-wave as the relative orbital angular momentum between the final-state dipion and J/psi, which strongly disfavors 1-+ and 2-+ assignments. The accumulated evidence strongly favors a J^PC = 1++ assignment for the X(3872), although the 2++ possibility is not ruled out by tests reported here. The analysis is based on a sample of X(3872) mesons produced via the exclusive process B --> K X(3872) in a 256 fb-1 data sample collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider.