S-matrix bootstrap for resonances

N. Doroud, J. Elias Miró
2018 Journal of High Energy Physics  
We study the 2→2 S-matrix element of a generic, gapped and Lorentz invariant QFT in d=1+1 space time dimensions. We derive an analytical bound on the coupling of the asymptotic states to unstable particles (a.k.a. resonances) and its physical implications. This is achieved by exploiting the connection between the S-matrix phase-shift and the roots of the S-matrix in the physical sheet. We also develop a numerical framework to recover the analytical bound as a solution to a numerical
more » ... merical optimization problem. This later approach can be generalized to d=3+1 spacetime dimensions.
doi:10.1007/jhep09(2018)052 fatcat:byzxwbn3e5dqldnuqbh4gikz3q