[SEMINARI]: Dr. Kniehl: Decoupling relations, effective lagrangians and low-energy theorems

[Arcadi Santamaria]

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                              S E M I N A R I

            [Image]    Departament de Física Teòrica     [Image]
                          Universitat de València
                      46100 Burjassot (València) Spain

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       Decoupling relations, effective Lagrangians and low-energy theorems

                                Dr. B. Kniehl

                                (MPI, Munich)

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                     Aula de Seminaris de Física Teòrica
                  Friday 04 of September of 1998 at 12:00
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                                    Resum

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.

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