Observation of the Narrow State $X(3872)\to J/ψπ^{+}π^{-}$ in $\bar{p}p$ Collisions at $\sqrt{s}=1.96 \TeV$

TL;DR

The observation of a narrow state decaying into J/psipi+pi- and produced in 220 pb(-1) of p p-bar collisions at =1.96 Tesqaure root of sV in the CDF II experiment is reported.

Abstract

We report the observation of a narrow state decaying into $J/ψπ^+π^-$ and produced in $220 pb^{-1}$ of $\bar{p} p $ collisions at $\sqrt{s}=1.96 TeV$ in the CDF II experiment. We observe $ 730 \pm 90 $ decays. The mass is measured to be $3871.3 \pm 0.7 (stat) \pm 0.4 (syst) MeV/c2$, with an observed width consistent with the detector resolution. This is in agreement with the recent observation by the Belle Collaboration of the X(3872) meson.

Figures (2)

• Figure 1: The mass distribution of $J/\psi\pi^{+}\pi^{-}$ candidates passing the selection described in the text. A large peak for the $\psi (2S)$ is seen and a signal near a mass of $3872~\mathrm{Me V\!/}c^2$ is visible (enlargement shown in the inset). The curve is a fit using two Gaussians and a quadratic background to describe the data.
• Figure 2: The mass distribution of $J/\psi\pi^+\pi^-$ candidates requiring $m(\pi^+\pi^-)>500~\mathrm{Me V\!/}c^2$. The curve is a fit with two Gaussians and a quadratic background.