PoS - Proceedings of Science
Volume 310 - XVII International Conference on Hadron Spectroscopy and Structure (Hadron2017) - Session 1: Spectroscopy of mesons
Recent Results on Light-Meson Spectroscopy from COMPASS
S. Wallner*  on behalf of the COMPASS Collaboration
Full text: pdf
Pre-published on: February 16, 2018
Published on: March 20, 2018
Abstract
The main goal of the spectroscopy program at COMPASS is to explore the light-meson spectrum below about $2\,\text{GeV}/c^2$ in diffractive production. Our flagship channel is the decay into three charged pions: $p + \pi^-\to \pi^-\pi^-\pi^+ + p_\text{recoil}$, for which COMPASS has acquired the so far world's largest dataset of roughly $50\,\text{M}$ exclusive events using an $190\,\text{GeV}/c$ $\pi^-$ beam.
Based on this dataset, we performed an extensive partial-wave analysis. In order to extract the resonance parameters of the $\pi_J$ and $a_J$ states that appear in the $\pi^-\pi^-\pi^+$ system, we performed the so far largest resonance-model fit, using Breit-Wigner resonances and non-resonant contributions.

This method in combination with the high statistical precision of our measurement allows us to study ground and excited states.
We have found an evidence of the $a_1(1640)$ and $a_2(1700)$ in our data, which are the first excitations of the $a_1(1260)$ and $a_2(1320)$, respectively. The relative strength of the excited states with respect to the corresponding ground state is larger in the $f_2(1270)\,\pi$ decay mode compared to the $\rho(770)\,\pi$ decay mode.
We also study the spectrum of $\pi_2$ states in our data. Therefore, we simultaneously describe four $J^{PC}=2^{-+}$ waves in the resonance-model fit by using three $\pi_2$ resonances, the $\pi_2(1670)$, the $\pi_2(1880)$, and the $\pi_2(2005)$. Within the limits of our model, we can conclude that the $\pi_2(2005)$ is required to describe all four $2^{-+}$ waves properly.
DOI: https://doi.org/10.22323/1.310.0032
How to cite

Metadata are provided both in "article" format (very similar to INSPIRE) as this helps creating very compact bibliographies which can be beneficial to authors and readers, and in "proceeding" format which is more detailed and complete.

Open Access
Creative Commons LicenseCopyright owned by the author(s) under the term of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.