Improved hadronic vector-isovector spectral function from tau -decay and electroproduction data

• Grant number: 23/08482-6
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: February 01, 2024
• End date: July 31, 2024
• Field of knowledge: Physical Sciences and Mathematics - Physics - Elementary Particle Physics and Fields
• Principal Investigator: Diogo Rodrigues Boito
• Grantee: Lucas Morethes Mansur
• Supervisor: Maarten Frederik Laes Golterman
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Institution abroad: San Francisco State University, United States
• Associated to the scholarship: 22/16553-8 - Refining the anomalous magnetic moment of the muon in the standard model with hadronic tau decays and lattice QCD, BP.MS

Abstract

The determination of the Quantum Chromodynamics (QCD) coupling, alpha_s, from the theoretical description of inclusive tau in (hadrons) + nu_tau decays, dominated by perturbative QCD, is one of the most precise as extractions from experimental data. In these decays, the hadronic vector and axial vector spectral functions are experimentally accessible. Recently, we have shown that the vector spectral function can be improved, on the data side, through a combination of tau decay data for the dominant channels and the use of e+e- in hadrons cross sections, related by isospin symmetry, to describe the small contributions of higher-threshold subdominant modes. In this project, we will improve significantly over our previous work by performing a data combination on a channel-by-channel basis, which will allow for the inclusion of the high-statistics Belle data set for tau in 2pi + v_tau. Due to the presence of strong correlations and issues related with statistical bias, this will certainly require a new data-combination procedure, including novel algorithmic features, along the lines of the state-of-the-art R(s) analyses employed in the description of the anomalous magnetic moment of the muon, g- 2. With this new, highly improved, vector-isovector spectral function, we will perform a new alpha_s determination at the tau-mass scale and explore the implications of our results in applications to the description of g - 2. (AU)