First Observation of a New Narrow D_sJ Meson at 2632MeV/c^2

TL;DR

This paper reports the first observation of a new charm-strange meson D_sJ(2632) at around 2632 MeV/c^2, observed in two decay modes with specific mass peaks and a measured branching ratio, marking a significant discovery in meson spectroscopy.

Contribution

The paper presents the first experimental evidence of the D_sJ(2632) meson, including its mass, decay modes, and branching ratio, expanding the known spectrum of charm-strange mesons.

Findings

Observation of D_sJ(2632) at 2632.5 MeV/c^2

Detection in D_s eta and D^0 K^+ decay modes

Measured branching ratio of 0.14±0.06

Abstract

We report the first observation of a charm-strange meson D_sJ(2632) at a mass of 2632.5+/-1.7 MeV/c^2 in data from SELEX, the charm hadro-production experiment E781 at Fermilab. This state is seen in two decay modes, D_s eta and D^0 K^+. In the D_s eta decay mode we observe a peak with 101 events over a combinatoric background of 54.9 events at a mass of 2635.4+/-3.3 MeV/c^2. There is a corresponding peak of 21 events over a background of 6.9 at 2631.5+/-2.0 MeV/c^2 in the decay mode D^0 K^+. The relative branching ratio Gamma(D^0 K^+)/\Gamma(D_s eta) is 0.14+/-0.06. The full version of this paper has been accepted for publication in PRL (hep-ex/0406045). Here I have reproduced only the mass difference signal plots for the D_s eta and D^0 K^+ decay modes.