PT Journal
AU Debastiani, VR
   Sakai, S
   Oset, E
TI Role of a triangle singularity in the pi N(1535) contribution to gamma p -> p pi(0) eta
SO Physical Review C
JI Phys. Rev. C
PY 2017
BP 025201
EP 7pp
VL 96
IS 2
DI 10.1103/PhysRevC.96.025201
LA English
AB We have studied the gamma p -> p pi(0) eta reaction paying attention to the two main mechanisms at low energies, the gamma p ->Delta(1700) -> eta Delta(1232) and the gamma p -> Delta(1700) -> pi N(1535). Both are driven by the photoexcitation of the Delta (1700) and the second one involves a mechanism that leads to a triangle singularity. We are able to evaluate quantitatively the cross section for this process and show that it agrees with the experimental determination. Yet there are some differences with the standard partial wave analysis which does not include explicitly the triangle singularity. The exercise also shows the convenience of exploring possible triangle singularities in other reactions and how a standard partial wave analysis can be extended to accommodate them.
ER