## Observation of $ψ(3686) \to n\bar{n}$ and improved measurement of $ψ(3686) \to p \bar{p}$

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.

We observe the decay $ψ(3686) \to n\bar{n}$ for the first time and measure $ψ(3686) \to p \bar{p}$ with improved accuracy by using $1.07×10^8 ψ(3686)$ events collected with the BESIII detector. The measured branching fractions are $\mathcal{B}(\psi(3686) \to n \bar{n}) = (3.06 \pm 0.06 \pm 0.14)\times 10^{-4}$ and $\mathcal{B}(\psi(3686) \to p \bar{p}) = (3.05 \pm 0.02 \pm 0.12) \times 10^{-4}$. Here, the first uncertainties are statistical and the second ones systematic. With the hypothesis that the polar angular distributions of the neutron and proton in the center-of-mass system obey $1+\alpha \cos^2\theta$, we determine the α parameters to be $\alpha_{n\bar{n}} = 0.68 \pm 0.12 \pm 0.11$ and $\alpha_{p\bar{p}} = 1.03 \pm 0.06 \pm 0.03$ for $ψ(3686) \to n\bar{n}$ and $ψ(3686) \to p \bar{p}$, respectively.

Publication Date:
Aug 10 2018
Date Submitted:
Jul 01 2019
Pagination:
32006
ISSN:
2470-0010
Citation:
Physical Review D
D98
3
External Resources: