2016/09/14 by M. Bayar, Melahat Bayar, Francesca Aceti +4 · 2 citations
Physics and Astronomy · #Algorithm #Computer science #High-Energy Particle Collisions Research #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #hep-ph
paper · pdf · doi:10.1103/physrevd.94.074039
published as Phys. Rev. D 94, 074039 (2016) · 17 pages, 7 figures, 2 Tables
arxiv created 2016/09/14 · openalex created_date 2016/09/23 · openalex publication_date 2016/10/27 · arxiv updated 2016/11/02 · openalex updated_date 2026/08/05
We have analyzed the singularities of a triangle loop integral in detail and derived a formula for an easy evaluation of the triangle singularity on the physical boundary. It is applied to the \mathrm\ensuremathΛb\ensuremath→J/\ensuremathψK^\ensuremath-p process via \mathrm\ensuremathΛ*-charmonium-proton intermediate states. Although the evaluation of absolute rates is not possible, we identify the \ensuremathχc1 and the \ensuremathψ(2S) as the relatively most relevant states among all possible charmonia up to the \ensuremathψ(2S). The \mathrm\ensuremathΛ(1890)\ensuremathχc1p loop is very special, as its normal threshold and triangle singularities merge at about 4.45 GeV, generating a narrow and prominent peak in the amplitude in the case that the \ensuremathχc1p is in an S wave. We also see that loops with the same charmonium and other \mathrm\ensuremathΛ* hyperons produce less dramatic peaks from the threshold singularity alone. For the case of \ensuremathχc1p\ensuremath→J/\ensuremathψp and quantum numbers 3/2^\ensuremath- or 5/2+, one needs P and D waves, respectively, in the \ensuremathχc1p, which drastically reduce the strength of the contribution and smooth the threshold peak. In this case, we conclude that the singularities cannot account for the observed narrow peak. In the case of 1/2+, 3/2+ quantum numbers, where \ensuremathχc1p\ensuremath→J/\ensuremathψp can proceed in an S wave, the \mathrm\ensuremathΛ(1890)\ensuremathχc1p triangle diagram could play an important role, though neither can assert their strength without further input from experiments and lattice QCD calculations.