Simulation of tau decays, ambiguities and anomalous couplings

TL;DR

This paper reviews recent developments in tau decay simulations, focusing on the use of exclusive exponentiation and addressing ambiguities in new physics scenarios, with updates on simulation tools and applications at Belle II energies.

Contribution

It introduces new applications of KKMC Monte Carlo for tau pair formation, decay analysis, and ambiguity resolution in new physics contexts, enhancing simulation flexibility.

Findings

Improved tau decay simulation accuracy using exclusive exponentiation.

New tools for tau polarization and helicity attribution in event simulations.

Applications to Belle II energies for tau pair production studies.

Abstract

From the perspective of low energy tau decays and radiative corrections in decays, not much has changed since the last, Tau23 conference. Also, TAUOLA, tau decay library, and PHOTOS for radiative corrections in decays have not changed much, neither for QED nor for New Physics processes application. Progress was in the domain of flexibilities for applications and in the domain of New Physicists. There was progress with use of exclusive exponentiation (KKMC Monte Carlo) to evaluate quality of tau pair formation and decay factorization, with Collins-Soper and Mustraal frames. Ambiguities for New Physics or other processes could be thus addressed. Associated projects of KKMC f77 and KKMCee C++, are presented: (i) $\pi^+ \pi^-$ pair production at Belle II energies, interesting input for Pi_gammagamma(s), (ii) attribution of helicity like labels for taus in simulated HepMC3 format events, (iii) also tau polarimetric vectors prepared for user application of New Physics.