Title: Renormalization of the flavor-singlet axial-vector current and its anomaly in dimensional regularization

Speaker: Dr. Taushif Ahmed, INFN Torino, Turin, Italy

Abstract: A theoretical calculation of an observable beyond leading order in perturbative quantum field theory often suffers from the presence of ultraviolet divergences which can appear from very high values of loop momentum in a virtual Feynman diagram. In addition, the computation of a Green correlation function with the insertion of an external local operator can give rise to an additional divergence of UV origin. To understand the nature of the divergences, the theory is regulated in a regularisation scheme, among which dimensional regularisation (DR) is the most notable one. Following which we perform a suitable UV renormalisation to get rid of the divergences systematically. However, in presence of a chiral quantity, the DR encounters a serious issue - the Green correlation function violates the axial Ward identity. Through this seminar, we will see how we can consistently reconcile these two things in DR and perform a suitable UV renormalisation. In particular, we will understand the renormalisation of flavor-singlet axial-vector current at fourth order in strong coupling constant that requires a state-of-the-art four-loop calculation.