https://doi.org/10.1140/epjc/s10052-020-8014-7
Regular Article - Theoretical Physics
Triangle singularity in 
and the X(3872) mass
1
Departamento de Física Teórica, Facultad de Física, Universidad Complutense de Madrid and IPARCOS, Plaza Ciencias, 1, 28040, Madrid, Spain
2
Departamento de Física Teórica and IFIC, Centro Mixto Universidad de Valencia-CSIC, Institutos de Investigación de Paterna, Aptdo. 22085, 46071, Valencia, Spain
* e-mail: raqumoli@ucm.es
Received:
9
March
2020
Accepted:
5
May
2020
Published online:
20
May
2020
We evaluate the contribution to the X(3872) width from a triangle mechanism in which the X decays into 
, then the 
decays into 
(
) and the 
fuse to produce 
. This mechanism produces an asymmetric peak from a triangle singularity in the invariant mass with a shape very sensitive to the X mass. We evaluate the branching ratios for a reaction where this effect can be seen in the 
reaction and show that the determination of the peak in the invariant mass distribution of is all that is needed to determine the X mass. Given the present uncertainties in the X mass, which do not allow to know whether the 
state is bound or not, measurements like the one suggested here should be most welcome to clarify this issue.
© The Author(s), 2020
