The chromomagnetic operator on the lattice

Understand

We study matrix elements of the "chromomagnetic" operator on the lattice.

• This operator is contained in the strangeness-changing effective Hamiltonian which describes electroweak effects in the Standard Model and beyond.
• Having dimension 5, the chromomagnetic operator is characterized by a rich pattern of mixing with other operators of equal and lower dimensionality, including also non gauge invariant quantities; it is thus quite a challenge to extract from lattice simulations a clear signal for the hadronic matrix elements of this operator.
• We compute all relevant mixing coefficients to one loop in lattice perturbation theory; this necessitates calculating both 2-point (quark-antiquark) and 3-point (gluon-quark-antiquark) Green's functions at nonzero quark masses.