# A contribution to the discussion of the matter-antimatter asymmetry problem

Source: [A contribution to the discussion of the matter-antimatter asymmetry problem](<https://www.sota2.com/research/paper/68fa1f287a2b558e29327855>)

Collection index: [llms.txt](<https://www.sota2.com/research/llms.txt>)

Data updated: 2025-10-23T17:21:45.772Z

Authors: K. Urbanowski

Published: 1999-05-10T11:59:21.000Z

## Abstract

Using a more accurate effective Hamiltonian governing the time evolution in the particle-antiparticle subspace of states than the one obtained within the Lee-Oehme--Yang approach we show that in the case of particles created at the initial instant t = 0 only the masses of a stable particle and its antiparticle are the same at all t \> 0 in a CPT invariant system, whereas the masses of an unstable particle and its antiparticle are equal only at t = 0 and then during their time evolution they become slightly different for times t \>\> 0 if CP symmetry is violated but CPT symmetry holds. This property is used to show that if the baryon number B is not conserved then the asymmetry between numbers of unstable baryons and antibaryons can arise in a CPT invariant system at t \>\> 0 even in the thermal equilibrium state of this system.

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## Original sources and implementation

[Original paper](<https://arxiv.org/abs/hep-ph/9905279>)

[PDF](<https://arxiv.org/pdf/hep-ph/9905279.pdf>)