Chiral Perturbation Theory for Neutron-Antineutron Oscillations

University essay from Lunds universitet/Institutionen för astronomi och teoretisk fysik

Abstract: This thesis treats neutron-antineutron oscillations in the framework of chiral perturbation theory. An effective Lagrangian, using mesons and nucleons as degrees of freedom, is constructed to capture the low-energy behavior of the effective six-quark operators, which is the set of higher dimensional operators that can induce neutron to antineutron transitions at the quark level. These operators have been used previously to model the oscillations using lattice QCD simulations. This Lagrangian is used to compute the neutron to antineutron transition amplitude at O(p^2) in the chiral perturbation expansion. The resulting amplitude is given as a function of the pion mass and could be of use for matching lattice simulations at unphysical quark masses to the physical situation. Furthermore, the effect that finite lattice volume has is estimated by using the difference between the known finite and infinite volume versions of chiral perturbation theory.

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