Search for new charmonium states in the processes e+ e- --> J/psi D(*) D(*) at sqrt{s} ~ 10.6 GeV

TL;DR

This study searches for new charmonium-like states in e+e- collisions near 10.6 GeV, identifying the X(3940) and X(4160) with measured masses and widths, contributing to understanding of exotic charmonium states.

Contribution

First observation and measurement of the X(3940) and X(4160) states in e+e- collisions at Belle, providing new data on their properties.

Findings

X(3940) mass: 3942 MeV/c^2, width: 37 MeV

X(4160) mass: 4156 MeV/c^2, width: 139 MeV

Observation of two new charmonium-like states

Abstract

We present a study of the X(3940) state in the process e+e- -> J/psi D* Dbar. The X(3940) mass and width are measured to be (3942 +7 -6 +- 6)MeV/c^2 and Gamma=(37 + 26 - 15 +- 8 MeV. In the process e+e- -> J/psi D* D*bar we have observed another charmonium-like state, which we denote as X(4160), in the spectrum of invariant masses of D*+ D*- combinations. The X(4160) parameters are M= 4156 + 25 - 20 +- 15 MeV/c^2 and Gamma = 139 + 111 -61 +- 21 MeV. The analysis is based on a data sample with an integrated luminosity of 693 /fb recorded near the Upsilon(4S) resonance with the Belle detector at the KEKB e+ e- asymmetric-energy collider.