Kavli Affiliate: Ke Wang
| First 5 Authors: Ke Wang, Yu-Fei Wang, Bo-Chao Liu, Fei Huang,
| Summary:
In this work, we investigate the resonance production in $Lambda^+_c to
gamma pi^+ Lambda$ decay through the triangle singularity (TS) mechanism,
within an effective Lagrangian approach. We find that the appropriate loop
decay process could develop a triangle singularity in the invariant mass
$M_{piLambda}$ around $1.35$ GeV, with the shape depending on the quantum
numbers of $Sigma^*$ states that couple to the final $piLambda$ system.
Especially, the $Sigma(1380)1/2^-$ state newly predicted in the pentaquark
model, if exists, significantly enhances the TS contribution and sharpens the
TS peak due to the $S$-wave $Sigma^*piSigma$ vertex in the loop. Therefore,
the existence of the $Sigma(1380)1/2^-$ state can be examined by measuring the
TS signal in $Lambda^+_c to gamma pi^+ Lambda$. Considering also possible
tree-level diagrams, we additionally obtain the branching ratio ${rm
Br}(Lambda^+_c to gamma pi^+ Lambda)simeq 1.5times 10^{-5}$. We suggest
the investigation of this reaction by future BESIII, LHCb, and Belle
experiments.
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