Evidence for X(3872)-->gamma J/psi and the sub-threshold decay X(3872)-->omega J/psi

TL;DR

This paper provides evidence for specific decay modes of the X(3872) particle, including gamma J/psi and omega J/psi, revealing its charge-conjugation parity and decay characteristics.

Contribution

First experimental evidence for X(3872) decaying into gamma J/psi and omega J/psi, clarifying its quantum numbers and decay mechanisms.

Findings

Evidence for X(3872) --> gamma J/psi decay with >4 sigma significance.

Evidence for X(3872) --> omega J/psi decay with >4 sigma significance.

Determination that X(3872) has positive charge-conjugation parity (C=+1).

Abstract

We report evidence for the decay modes X(3872) --> gamma J/psi and X(3872)--> pi+pi-pi0 J/psip. In the latter, the pi+pi-pi0 invariant mass distribution has a strong peak between 750 MeV and the kinematic limit of 775 MeV, suggesting that the process is dominated by the sub-threshold decay X --> omega J/psi. These results establish the charge-conjugation parity of the X(3872) as C=+1. The results are based on a study of X(3872) mesons produced via exclusive B --> K X(3872) decays in a 256 fb-1 data sample collected at the Upsilon(4S) resonance in the Belle detector at the KEKB collider. The X(3872) --> gamma J/psi signal and the pi+pi-pi0 J/psi signal each has a statistical significance that is greater than 4 sigma.