Refining the anomalous magnetic moment of the muon in the standard model with hadronic tau decays and lattice QCD

• Grant number: 22/16553-8
• Support Opportunities: Scholarships in Brazil - Master
• Start date: March 01, 2023
• End date: January 31, 2025
• Field of knowledge: Physical Sciences and Mathematics - Physics - Elementary Particle Physics and Fields
• Principal Investigator: Diogo Rodrigues Boito
• Grantee: Lucas Morethes Mansur
• Host Institution: Instituto de Física de São Carlos (IFSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil
• Associated research grant: 21/06756-6 - Testing the standard model: precision QCD and muon g-2, AP.JP2
• Associated scholarship(s): 23/08482-6 - Improved hadronic vector-isovector spectral function from tau -decay and electroproduction data, BE.EP.MS

Abstract

The muon anomalous magnetic moment, a_mu, is one of the most precisely known quantities in physics. The measurement of a_mu in 2021 by the FNAL E989 experiment (at Fermilab) has confirmed the tension between the experimental result and the predictions based on the Standard Model of particle physics. The SM prediction relied, for a long time, on a data-based dispersion relation for the hadronic contributions. This computation shows, nowadays, a tension of 4.2 sigma with the most recent measurements. Very recently, a complete result for the hadronic contribution obtained with lattice QCD by the BMW collaboration has become available. With this result the SM-based value is only 1.5 sigma lower than the experiment. Understanding the discrepancies between experiment and theory, and between the dispersive and lattice computations, in the hadronic contributions to a_mu is one of the most crucial tasks of particle physics today. In this master project, we intend to use information from hadronic tau decay data, combined with lattice results for isospin breaking contributions, to scrutinize the SM a_mu computation. (AU)