### TABLE OF CONTENTS

- 1. /ThreeMeson

## /ThreeMeson [ Modules ]

NAME

module **ThreeMeson**

PURPOSE

This module implements the back reaction 3 -> 1 of mesonic decay channels

INPUTS

(none)

## ThreeMeson/DoThreeMeson [ Subroutines ]

[ Top ] [ ThreeMeson ] [ Subroutines ]

NAME

subroutine **DoThreeMeson**(time)

PURPOSE

process all the finding of possibilities for 3->1 resonance decay back reactions. Actually also do the collision.

## ThreeMeson/calcPhi3 [ Functions ]

[ Top ] [ ThreeMeson ] [ Functions ]

NAME

real function **calcPhi3**(srts,m3)

PURPOSE

Calculate the 3-particle phase space. Particle 1 and 2 are pions.

INPUTS

OUTPUT

return value in GeV^2

NOTES

there is threeBodyPhaseSpace/Integrate_3bodyPS, which does the same, but just by simply adding 100 values. This here is closer to mesonWidthVacuum/threepi

\dd\Phi_n(P;p_1,\dots,p_n) = (2\pi)^4\delta^{(4)}(P-p_1-\dots-p_n) \prod_i{\frac{\dd^3p_i}{(2\pi)^3\,2E_i}} = (2\pi)^4\delta^{(4)}(P-p_1-\dots-p_n) \prod_i{\frac{\dd^4p_i}{(2\pi)^4}} (2\pi)\delta(p_i^2-m_i^2)\Theta(p_i^0)

Here the definition of the n-body phase space is slightly (by a factor $(2\pi)^4$) modified compared to the PDG\cite{Beringer:1900zz} version.

## ThreeMeson/ThreeMeson_INIT [ Subroutines ]

[ Top ] [ ThreeMeson ] [ Subroutines ]

NAME

subroutine **ThreeMeson_INIT**()

PURPOSE

This routine initializes the 3-meson routines. It sets up internal arrays.

## ThreeMeson/ThreeMeson_DoColl [ Subroutines ]

[ Top ] [ ThreeMeson ] [ Subroutines ]

NAME

subroutine **ThreeMeson_DoColl**(Part1,Part2,Part3, ID, time)

PURPOSE

This routine does the actual collision. It replaces Part1 with the mother particle and erases Part2 and Part3