## Measurement of the matrix elements for the decays $\eta^{\prime}\rightarrow\eta\pi^+\pi^-$ and $\eta^{\prime}\rightarrow\eta\pi^0\pi^0$

Ablikim, M. ; Achasov, M. N. ; Ahmed, S. ; Albrecht, M. ; Alekseev, M. ; Amoroso, A. ; An, F. F. ; An, Q. ; Bai, J. Z. ; Bai, Y. ; Bakina, O. ; Ferroli, R. Baldini ; Ban, Y. ; Bennett, D. W. ; Bennett, J. V. ; Berger, N. ; Bertani, M. ; Bettoni, D. ; Bian, J. M. ; Bianchi, F. ; Boger, E. ; Boyko, I. ; Briere, R. A. ; Cai, H. ; Cai, X.

Based on a sample of $1.31×10^9$ $J/\psi$ events collected with the BESIII detector, the matrix elements for the decays $\eta^{\prime}\rightarrow\eta\pi^+\pi^-$ and $\eta^{\prime}\rightarrow\eta\pi^0\pi^0$ are determined using 351,016 $\eta^{\prime}\to(\eta\to\gamma\gamma)\pi^+\pi^-$ and 56,249 $\eta^{\prime}\to(\eta\to\gamma\gamma)\pi^0\pi^0$ events with background levels less than 1\%. Two commonly used representations are used to describe the Dalitz plot density. We find that an assumption of a linear amplitude does not describe the data well. A small deviation of the obtained matrix elements between $\eta^{\prime}\rightarrow\eta\pi^+\pi^-$ and $\eta^{\prime}\rightarrow\eta\pi^0\pi^0$ is probably caused by the mass difference between charged and neutral pions or radiative corrections. No cusp structure in $\eta^{\prime}\to\eta \pi^{0}\pi^{0}$ is observed.

Publication Date:
Jan 10 2018
Date Submitted:
Jul 01 2019
Pagination:
12003
ISSN:
2470-0010
Citation:
Physical Review D
D97
1
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