Decoupling relations, effective Lagrangians and low-energy theorems

por Dr. B. Kniehl (MPI, Munich)

viernes 4 sept. 1998 12:00 → 13:00 Europe/Madrid

Sala Seminarios (Dpto. de Fisica Teorica (UVEG))

If QCD is renormalized by minimal subtraction, at higher orders, alpha_s and m_q exhibit discontinuities at the flavour thresholds, which are controlled by so-called decoupling constants, zeta_g and zeta_m, respectively. Adopting the MS-bar scheme, we derive simple formulae which reduce the calculation of zeta_g and zeta_m to the solution of vacuum integrals. This allows us to evaluate zeta_g and zeta_m through three loops. We also establish low-energy theorems, valid to all orders, which relate the effective couplings of a CP-even Higgs boson to gluons and light quarks, due to the virtual presence of a heavy quark h, to the logarithmic derivatives w.r.t. m_h of zeta_g and zeta_m, respectively. We also consider the effective QCD interactions of a CP-odd Higgs boson and verify the Adler-Bardeen nonrenormalization theorem at three loops.