tau Decays to Five Mesons in TAUOLA

TL;DR

This paper extends the TAUOLA library to include five-meson tau decays with realistic decay amplitudes, enabling more precise modeling of tau decay processes in high-energy physics.

Contribution

It introduces a new implementation of five-meson tau decay modes into TAUOLA with simplified resonance models and phase-space generation, improving its accuracy for current experimental data.

Findings

Monte Carlo and analytical results are in agreement for the new decay modes.

The model provides a first realistic example for five-pion decay amplitudes.

Phase-space generation includes resonance presampling, suitable for physics applications.

Abstract

The tau-decay library TAUOLA has gained popularity over the last decade. However, with the continuously increasing precision of the data, some of its functionality has become insufficient. One of the requirements is the implementation of decays into five mesons plus a neutrino with a realistic decay amplitude. This note describes a step into this direction. For the 2pi- pi+ 2pi0 mode the three decay chains tau- --> a_1- nu --> rho- (--> pi- pi0) omega (--> pi- pi+ pi0) nu, tau- --> a_1- nu --> a_1- (--> 2pi- pi+) f_0 (--> 2pi0) nu, and tau- --> a_1- nu --> a_1- (--> pi- 2pi0) f_0 (--> pi + pi-) nu are introduced with simple assumptions about the couplings and propagators of the various resonances. Similar amplitudes (without the rho omega contributions) are adopted for the pi- 4pi0 and 3pi- 2pi+ modes. The five-pion amplitude is thus based on a simple model, which, however, can be considered as a first realistic example. Phase-space generation includes the possibility of presampling the omega and a_1 resonances, in one channel only, however. This is probably sufficient for the time being, both for physics applications and for tests. The technical test of the new part of the generator is performed by comparing Monte Carlo and analytical results. To this end a non-realistic, but easy to calculate, purely scalar amplitude for the decay into five massless pions was used.