Observation of an Excited Bc+/- Meson State with the ATLAS Detector

November 24, 2014

Figure 1: Invariant mass distributions of the reconstructed Bc± → J/ψπ± candidates in 7 TeV data (top) and in 8 TeV data (bottom). The data are represented by the points with error bars (statistical only). The solid line is the projection of the results of the unbinned maximum likelihood fit to all candidates in the mass range 5620–6820 MeV. The dashed line is the projection of the background component of the same fit. [From G. Aad et al. (ATLAS Collaboration), "Observation of an Excited Bc± Meson State with the ATLAS Detector," Phys. Rev. Lett. 113, 212004 – Published 21 November 2014]

The ATLAS Collaboration has observed a new excited state of the Bc± meson at 6842 MeV by reconstructing its decay. The mass and decay are consistent with QCD predictions for this excited state.

(Harvard Physics faculty participating in the ATLAS Collaboration are Professors Melissa Franklin, Joao Guimarães da Costa, John Huth, and Masahiro Morii.)